Uncategorized

Pericardial tamponade: A comprehensive emergency medicine and echocardiography review

Journal logoUnlabelled imagePericardial tamponade: A comprehensive e”>American Journal of Emergency Medicine 58 (2022) 159-174

Contents lists available at ScienceDirect

American Journal of Emergency Medicine

journal homepage:

Pericardial tamponade: A comprehensive emergency medicine and echocardiography review

Stephen Alerhand, MD a,?, Robert James Adrian, MD a, Brit Long, MD b, Jacob Avila, MD c

a Department of Emergency Medicine, Rutgers New Jersey Medical School, 150 Bergen Street, Newark, NJ 07103, USA

b Department of Emergency Medicine, Brooke Army Medical Center, Fort Sam Houston, TX 78234, USA

c Department of Emergency Medicine, UHS Southern California Medical Education Consortium, Temecula, CA 92592, USA

a r t i c l e i n f o

Article history:

Received 7 March 2022

Accepted 3 May 2022

Keywords:

Pericardial tamponade Cardiac tamponade Pericardial effusion Pericardiocentesis Pericardial drainage Echocardiography

Point-of-care ultrasound POCUS

Pulsus paradoxus Electrical alternans

Ventricular interdependence Pericardial decompression syndrome

a b s t r a c t

Introduction: Pericardial tamponade requires Timely diagnosis and management. It carries a high mortality rate. Objective: This review incorporates available evidence to clarify misconceptions regarding the clinical presenta- tion, while providing an in-depth expert guide on Bedside echocardiography. It also details the decision-making strategy for emergency management including pericardiocentesis, along with pre- and peri-procedural pearls and pitfalls.

Discussion: Pericardial effusions causing tamponade arise from diverse etiologies across acute and sub-acute time courses. The most frequently reported symptom is dyspnea. The classically taught Beck’s triad (which includes hypotension) does not appear commonly. echocardiographic findings include: a pericardial effusion (larger size associated with tamponade), diastolic Right ventricular collapse (specific), systolic Right atrial collapse (sen- sitive), a plethoric non-collapsible inferior vena cava (sensitive), and sonographic pulsus paradoxus. Emergent pericardiocentesis is warranted by hemodynamic instability, impending deterioration, or cardiac arrest. Emer- gent surgical indications include type A aortic dissection causing hemopericardium, ventricular free wall rupture after acute myocardial infarction, severe chest trauma, and iatrogenic hemopericardium when bleeding cannot be controlled percutaneously. Pre-procedure management includes blood products for patients with traumatic hemopericardium; gentle intravenous fluids to hypotensive, hypovolemic patients with consideration for vaso- active medications; treatment of anticoagulation, coagulopathies, and anemia. Positive-pressure ventilation and intravenous sedation can lower cardiac output and should be avoided if possible. Optimal location for Echocardiography-guided pericardiocentesis is the largest, shallowest fluid pocket with no intervening vital structures. patient positioning to prevent hypoxia and liberal amounts of local anesthesia can facilitate patients remaining still. Safe needle guidance and confirmation of catheter placement is achieved using low-depth sono- graphic views, injection of agitated saline, and evaluation of initial aspirate for hemorrhage. pericardial fluid should be drained slowly to avoid pericardial decompression syndrome.

Conclusion: An understanding of the pathophysiology, clinical presentation, echocardiographic findings, and time-sensitive management of pericardial tamponade is essential for emergency physicians.

(C) 2022

  1. Introduction

Under normal circumstances, physiologic serous fluid exists within the pericardial sac and acts as lubrication for the heart. A pericardial effusion refers to when this fluid exceeds 15-50 mL [1]. Pericardial tamponade re- fers to hemodynamic instability and clinical symptoms owing directly to that effusion. This occurs when the pressure exerted on one or more car- diac chambers by the pericardial effusion (i.e. the intrapericardial pres- sure) exceeds the pressures within the cardiac chambers (i.e. the intracardiac pressure), leading to obstruction of normal chamber filling.

* Corresponding author at: 150 Bergen Street, Newark, NJ 07103, USA.

E-mail address: [email protected] (S. Alerhand).

The development of tamponade physiology is dependent on the rate of accumulation of the pericardial fluid and the pericardial compliance [2]. For example, with an acute effusion, the pericardial sac has not had time to develop compensatory compliance, so a Rapid increase in intrapericardial pressure leads to tamponade physiology. The pericar- dial stretch limit can be reached quickly, even with as little as 50 mL [3,4]. In contrast, with a chronic effusion, the pericardial sac is able to develop compliance over time, so much larger fluid volumes (up to two liters) [2,5] can be tolerated before development of tamponade physiology requiring drainage. As the pericardial compliance eventually approaches its limit, small additional increases in volume cause rela- tively larger increases in intrapericardial pressure (Fig. 1, top-center).

https://doi.org/10.1016/j.ajem.2022.05.001

0735-6757/(C) 2022

Image of Fig. 1

Fig. 1. Infographic delineating the pathophysiology and echocardiographic findings of pericardial tamponade (echocardiography graphic design by Linda Qiu MD).

As Pulmonary vascular resistance is lower than systemic vascular re- sistance, the right-sided cardiac chambers normally operate at lower pressures compared to the left-sided chambers. In pericardial tampon- ade, when the right atrium (RA) and right ventricle (RV) collapse during ventricular systole and diastole, respectively (i.e. when they are at their lowest pressures), there is decreased preload to the right side of the heart. The decrease in right ventricular stroke volume transmits along its circuit to the left side of the heart, ultimately leading to decreased cardiac output.

The spectrum of disease in pericardial tamponade ranges from slight elevations of intrapericardial pressure causing only subtle hemody- namic effects to severe Hemodynamic compromise from obstructive shock [6]. If left untreated, this pathophysiology can lead to cardiac ar- rest and death.

  1. Methods

The authors searched PubMed and Google Scholar for articles using the title keywords “cardiac tamponade” OR “pericardial tamponade.” The search was conducted from the databases’ inception to February 1, 2022. The literature search was restricted to studies published in En- glish, with a focus on the emergency medicine, critical care, and cardiol- ogy literature. Supporting citations of included articles were also reviewed. Authors decided which studies to include by consensus. When available, guidelines and systematic reviews and meta-analyses (SRMAs) were preferentially selected. These were followed sequentially by randomized controlled trials, prospective studies, retrospective stud- ies, case reports, and other narrative reviews.

  1. Discussion
    1. Demographics and outcomes

Pericardial tamponade is a rare but life-threatening condition. In a national inpatient sample database of 216 million admissions from

2008-2014, 0.05% of patients (5 cases per 10,000) were diagnosed with pericardial tamponade [7]. Emergency physicians must be aware of the various potential etiologies for a pericardial effusion causing tam- ponade and the patients who are at risk (Table 1) [5,8-21]. A meta- analysis consisting of 17,022 patients with pulmonary, infectious, car- diac, renal, or neoplastic disease found that 19.5% of patients had a peri- cardial effusion [22]. In a retrospective review of 322 patients with moderate-large effusions (> 1 cm end-diastolic diameter) (see Section 3.4.1), the etiology arose from an already known medical condi- tion in 60% of cases [11]. Similarly, in another retrospective review of 153 emergency department (ED) patients with point-of-care ultra- sound (POCUS) scans showing a pericardial effusion, 62.5% carried his- torical features suggesting the presence of an effusion [23].

Some of these effusions, especially the larger ones, eventually lead to tamponade physiology. A retrospective study of 187 hospitalized pa- tients diagnosed with a pericardial effusion found that moderate-large effusions (circumferential; >1 cm end-diastolic diameter) were more likely to develop tamponade (based on the authors’ hemodynamic criteria) or have a drainage procedure than small effusions (73% vs. 5%) [24]. These events usually occurred on the same day that the effu- sion was diagnosed. For patients with end-stage renal disease on hemo- dialysis, a larger effusion size is also predictive of tamponade and development of hemodynamic compromise [25-31]. In patients with large idiopathic chronic pericardial effusions, four separate studies of 100, 45, 28, and 22 patients found that 8 (8%), 0 (0%), 8 (29%), and 2 (9.1%) of patients developed tamponade at median follow-up of 4 years, 10 months, 7 years, and 2 years, respectively [32-35]. In the two largest studies, the effusion regressed in 39 (39%) and 2 (4.5%) of pa-

tients, respectively [32,33].

In general, short-term survival depends mostly upon early diagnosis and relief of tamponade, whereas long-term survival depends on the underlying primary illness [36]. in-hospital mortality rates for pericar- dial tamponade can be subdivided by etiology (Table 2). In a study of 78 patients with acute myocardial infarction and free wall rupture (i.e. the tamponade etiology with the highest in-hospital mortality rate),

Table 1

Table 3

Symptoms in pericardial tamponade.

Symptom

Percentage of Cases

Dyspnea

66-90%

Chest pain

12-74%

Fever

7-70%

Abdominal pain

12-61%

Orthopnea

23-51%

Lethargy/weakness

3-14%

Syncope

3-6%

Palpitations

3%

Headache

2%

Etiologies of pericardial effusions causing tamponade.

Etiology

Percentage of Cases

Malignancy

15-65%

Idiopathic

4-37%

Infectious/inflammatory

4-31%

Iatrogenic

3-35%

Metabolic

1-33%

Bleeding/anticoagulation

2-31%

Autoimmune/vasculitis

1-14%

Acute myocardial infarction

1-12%

Decompensated thyroid disease

1-10%

Aortic dissection

1-4%

Traumatic

1-2%

the majority of patients (83.3%) presented already in cardiac arrest and died in 100% of cases [37]. For those patients presenting with a sudden change in clinical condition, moderate-massive effusion (by the authors’ unspecified criteria), and pericardiocentesis showing bloody fluid (9.0%), the mortality rate was 85.7% and typically occurred within 4.5 hours. These patients may benefit from surgery within that time period. Patients with normal vital signs, moderate-massive effusion, and peri- cardiocentesis showing bloody fluid (7.7%) were found to have a 16.7% mortality rate. In the long-term, pericardial tamponade stemming from a malignant effusion (i.e. the most common effusion etiology of tamponade) carries a 1-year mortality rate between 68-89% [10,14,15,17]. The cause of death in these patients is generally from the end-stage neoplastic disease, not necessarily the effusion itself [5,13].

    1. Emergency department presentation
      1. Symptoms

Though patients will be unable to provide a history if obtunded or in cardiac arrest, a variety of Presenting complaints have been reported, most commonly dyspnea (Table 3) [21,40-46]. Clinical symptoms may appear less often in patients with low-flow tamponade, which is gener- ally attributed to hypovolemia [47]. Nevertheless, symptoms will vary depending on the etiology of the effusion itself, and there is no “classic” presentation.

The classic teaching for the diagnosis of pericardial tamponade had involved Beck’s triad. The initial data came from two cases published in 1935: an acute triad was described as “falling arterial pressure, rising venous pressure and a small quiet heart”, whereas the chronic triad was described as “ascites, high venous pressure and a quiet heart” [48]. However, a subsequent 2007 SRMA reviewed studies of patients with known tamponade or who were referred for pericardiocentesis of a known effusion [40]. Hypotension, jugular venous distention, and muf- fled heart sounds occurred in only 14-35%, 53-88%, and 24-34% of cases, respectively. In an ED-based study, the sensitivities of hypotension, jug- ular venous distention, and muffled heart sounds for a pericardial effu- sion causing tamponade (based on electronic medical record diagnosis) were 37.5%, 12.5% and 37.5%, respectively [23]. The sensitivity of one el- ement of Beck’s triad to diagnose pericardial tamponade was 50%, and no patients with tamponade had all three elements.

Table 2

in-hospital mortality rates for various etiologies of pericardial tamponade.

Etiology

In-Hospital Mortality Rate

Acute myocardial infarction

70-100% [13,17,37-39]

Aortic dissection

65% [9]

Bleeding/anticoagulation

40% [17]

Malignancy

16% [17]

Iatrogenic

10% [17]

Infectious/inflammatory

8% [17]

Although pericardial tamponade represents an acutely dangerous condition, patients (especially those with Malignant effusions) may present with symptoms that have been ongoing for up to one week [17,49,50]. The variations and subtleties in the patient presentation can lead to early failure in making the diagnosis. Moreover, the pericar- dial effusion may be found by an echocardiogram performed for reasons other than a clinical suspicion for tamponade [49]. Nevertheless, the re- ported frequency of non-specific symptoms and physical examination findings prior to making the diagnosis has decreased over time, which one study’s authors attribute to an improvement in cardiovascular im- aging and a high index of suspicion [49].

      1. Vital signs
        1. Blood pressure. Hypotension is traditionally taught as being pres- ent in patients with pericardial tamponade. However, a systolic blood pressure (SBP) < 100 mmHg only occurs in 14-35% of patients with non-traumatic pericardial tamponade [19,42-44]. In a retrospective re- view of 342 patients who underwent pericardiocentesis for a clinically significant pericardial effusion, only 9.6% had SBP <= 90 mmHg [45].

An assessment of six studies comprising 235 patients with pericar-

dial tamponade found that SBP ranged between 127-144 mmHg [51]. In an ED-based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation (ex- cluding trauma patients and those who received cardiopulmonary re- suscitation), the mean SBP was 106 mmHg [21]. In the ED-based study of 153 patients with a pericardial effusion, the sensitivity of hypotension for tamponade (based on electronic medical record diagnosis) was 37.5% [23]. Another retrospective study of 46 patients who underwent percutaneous pericardiocentesis found that hypotension was 24% sensi- tive and 83% specific for tamponade (based on the presence of diastolic chamber collapse) [42].

Hypotension is especially uncommon when the effusion develops over days to weeks [40,41,51,52]. Increased sympathetic tone can main- tain SBP even as cardiac output decreases [53]. High levels of circulating catecholamines in response to hemodynamic stress can even produce hypertensive tamponade [52,54]. The previously mentioned assess- ment of six studies reported that 27-43% of patients with pericardial tamponade had SBP >= 140 mmHg [51].

        1. Heart rate. Since cardiac compression by a pericardial effusion limits diastolic filling and stroke volume, a compensatory tachycardia develops in an attempt to maintain cardiac output. The 2007 SRMA found that a heart rate > 100 beats per minute occurred in 65-88% of pa- tients with pericardial tamponade [40]. In the ED-based study of 205 pa- tients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, the mean heart rate was 100 beats per minute [21]. In the ED-based study of 153 patients with a peri- cardial effusion, a heart rate > 100 beats per minute was 69% sensitive for a pericardial effusion causing tamponade (based on electronic med- ical record diagnosis) [23]. Lastly, the retrospective study of 46 patients who underwent percutaneous pericardiocentesis found that a heart rate

> 100 beats per minute was 88% sensitive and 67% specific for

point-of-care echocardiography“>tamponade (based on the presence of diastolic chamber collapse) [42]. Of note, tachycardia may be blunted by beta-blockade or Conduction system disease.

Table 5

Electrocardiogram findings in patients with pericardial tamponade. Electrocardiogram Findings Percentage of Cases (%)

based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, the mean respi- ratory rate was 21 breaths per minute [21]. Of note, tachypnea may not be present late in the disease course if there is respiratory muscle fa- tigue.

      1. Physical examination

Physical examination findings in patients with pericardial tampon- ade vary widely and are poorly predictive (Table 4). The assessment and interpretation of some findings (e.g. jugular venous distention) can differ even amongst experienced physicians [55,56].

    1. Emergency department evaluation
      1. Electrocardiogram

Electrocardiogram (ECG) findings vary in pericardial tamponade, with tachycardia being the most common finding (Table 5).

      1. Chest radiography

The 2007 SRMA included four studies in which an enlarged cardiac contour was present on chest radiograph in 68-100% of cases with peri- cardial tamponade [19,42,44,57]. In patients with hemodynamic insta- bility or concerning symptoms for whom transport poses a risk, only a portable chest radiograph will be feasible.

    1. Point-of-care echocardiography

Suspicion for pericardial tamponade is raised by clinical evaluation, with confirmation by bedside echocardiography [59]. Guidelines from the American Heart Association, American College of Cardiology, American Society of Echocardiography (ASE), and European Society of Cardiology (ESC) posit echocardiography as the first-level diagnostic tool in the evaluation of suspected pericardial disease [60,61]. There are certain echocardiographic findings suggesting tamponade physiol- ogy of which emergency physicians should be aware (Fig. 1) [59]. Since these findings are reflective of hemodynamic compromise, their presence even in Hemodynamically stable patients can help identify those who are at risk for Disease progression. Of note, the predictive values of these echocardiographic findings for tamponade are heavily influenced by the disease prevalence in a given population [62]. There- fore, they must be interpreted in the context of the patient’s pretest probability based on clinical history, symptoms, vital signs, and physical examination.

In the ED-based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, patients who underwent the procedure within 12 hours had had a

PR-segment depression 18% [43]

Atrial arrhythmias 0-9% [19,43,58]

3.2.2.3. Respiratory rate. Only one study included in the 2007 SRMA re-

Tachycardia

Low-voltage QRS complexes

47-88% [40,41,45]

22-56% [19,42-45,57]

ported statistics for respiratory rate. It found that tachypnea was pres-

ST-segment elevation

18-30% [19,57]

ent in 80% of patients with pericardial tamponade [40]. In the ED-

Electrical alternans

3-21% [19,43,45]

[40] is an SRMA that obtained statistics for heart rate based on physical examination (i.e. a tachycardic patient would presumably show tachycardia on ECG).

shorter time to POCUS than those who did so within 12-24 hours (48 vs. 78 minutes, respectively) [21]. Three other separate retrospective re- views have evaluated patients with clinically significant pericardial ef- fusions (non-iatrogenic, non-traumatic, and Penetrating cardiac injury proven at operation or autopsy, respectively) [45,63,64]. They all also found that use of POCUS was associated with lower time-to-diagnosis and time-to-pericardiocentesis. In the first study (n = 263), there was no statistical difference in hemodynamic profile between the POCUS and departmental echocardiography groups [45]. In the second study (n = 73), the POCUS group had a lower average SBP than the other- imaging group (117.6 mmHg vs. 134.6 mmHg), but this difference would not be clinically significant on its own to raise concern for tam- ponade [63]. Studies assessing POCUS in penetrating cardiac injury have also shown improved outcomes such as survival rate and neurolo- gic outcome (as per the Glasgow Outcome Score) [64-68].

      1. Pericardial effusion

ASE recommendations and an American College of Emergency Phy- sicians (ACEP) position statement support the use of emergency physician-performed POCUS to visualize a pericardial effusion (of only 15-35 mL) in both the medical and trauma settings [1,69]. In a prospec- tive ED-based study of 515 patients with high-risk medical and trau- matic criteria for the diagnosis of pericardial effusion, POCUS scans by trained emergency physicians were 96% sensitive, 98% specific, and 97.5% accurate for the presence of an effusion against the reference standard of one cardiologist’s review [70]. In another prospective obser- vational study that included 67 Cardiac PoCUS scans (8 with an effu- sion), emergency physicians with no prior POCUS experience who underwent a 4-hour training program performed scans with 88% sensi- tivity and 98% specificity for pericardial effusion, also compared to the reference interpretation of one blinded cardiologist [71].

A pericardial effusion should be classified by its hemodynamic im- pact, size, distribution, onset, and composition (Table 6). ASE and European Association of Cardiovascular imaging (EACVI) guidelines rec- ommend estimating effusion size by the end-diastolic diameter be- tween the visceral and parietal pericardium (i.e. the parietal separation distance) (Table 7) [1,72]. Seeing an evenly distributed effu- sion from multiple sonographic views increases the predictive value of this size estimation [1]. In the ED-based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, 58% of effusions were large, 35% were moderate, and

Table 4

Physical Examination Test Characteristics in Patients with Pericardial Effusions Causing Tamponade.

Physical Examination Finding

Percentage of Cases (%)

Sensitivity (%)

Specificity (%)

Elevated jugular venous pressure

41-88 [4245]

13-88 [23,42]

83 [42]

Muffled heart sounds

3-34 [19,43]

24-38 [23,42]

100 [42]

Pulsus paradoxus

36-98 [19,43,44,45,57,58]

80-98 [42, 57]

40-100 [42, 57]

-[19,43,44,57,58] were described in an SRMA [40]. To determine the presence or absence of tamponade, three studies based their designation upon the clinical and Hemodynamic response to pericardiocentesis, one study upon both clinical findings and a pericardial effusion diagnosed by echocardiography, and one study upon echocardiographic findings alone.

-[23] determined the presence of tamponade based on electronic medical record diagnosis.

-[42] determined the presence of tamponade based on diastolic chamber collapse.

-[45] evaluated patients with symptomatic pericardial effusions. Echocardiography found that 90% were circumferential, 67% had 2 cm end-diastolic diameter between the visceral and parietal pericardium, 64% had systolic right atrial collapse, 58% had diastolic right ventricular collapse, and 29% had sonographic pulsus paradoxus.

Table 6

Classification model for pericardial effusions.

locations outside and within the pericardium, respectively (Fig. 5) (Video 5). Acquiring other abdominal views of ascites can further

Hemodynamic Impact

Hemodynamically

Size Distribution Onset Composition

Localized adjacent to

point to that diagnosis. Lastly, cardiac tumors can appear as echo-free spaces along the epicardium [81]. Similar to a pericardial fat pad, these tumors will move in concert with the myocardium throughout the car-

stable Trivial

specific chamber(s) Acute Blood

diac cycle.

Hemodynamically unstable

Small Circumferential Subacute Transudate

Moderate Chronic Exudate Large Air

Gas

      1. Diastolic right ventricular collapse

When the intrapericardial pressure exceeds the right ventricular in- tracardiac pressure, the RV will collapse. Intrapericardial pressure (P) is proportional to pericardial fluid volume (V) multiplied by the stiffness of the pericardial sac (?P/?V) [59]. In early tamponade, the RV might

7% were small (based on a board-certified cardiologist’s report) [21]. In- terestingly, in the retrospective review of 342 patients who underwent pericardiocentesis for a clinically significant pericardial effusion, larger effusions (> 2 cm end-diastolic diameter) were found more often from a non-procedural etiology than from an iatrogenic and procedural etiology (78% vs. 30%) [45].

Due to the time-sensitive management and potentially suboptimal sonographic views in often-distressed patients with pericardial tam- ponade, a simple and more practical size categorization can also be de- termined qualitatively (Fig. 2) (Video 1) (Table 7) [1-3,59,73,74]. For determining the presence, size, and distribution of a pericardial effusion, it is important to acquire multiple cardiac views. An effusion may ap- pear in one cardiac view but not in another, and what can appear as a small effusion in one view could actually appear large in another, and vice versa (Video 2). Pericardial fluid generally appears first posteriorly to the Left ventricle , moves apically and anteriorly as the fluid vol- ume increases, and finally progresses laterally and posteriorly to the left atrium (LA) [75]. Compared to simple serous fluid that appears an- echoic, hemorrhagic or purulent contents may appear more echogenic [76]. Of note, the pulmonary expansion associated with deep inspiration in dyspneic patients will decrease the amount of cardiac tissue lying close to the chest [77], as well as cause posterior displacement and rota- tion of the heart [78]. Whereas the parasternal views thus appear less pronounced during inspiration, downward movement of the dia- phragm improves access to the subxiphoid views [77].

Caution is needed to distinguish a pericardial fat pad from a pericar- dial effusion (Fig. 3) (Video 3) [59]. The former will generally have a “stippled” appearance and be located in the anterior atrioventricular groove, best visualized in the parasternal long-axis (PLAX) and subxiphoid long-axis (SXLA) views [79]. In contrast, an effusion (usually anechoic) will typically collect in the most dependent pericardial loca- tion. Moreover, a pericardial fat pad adheres to the myocardium and thus moves in synchrony with the heart throughout the cardiac cycle [79]. Conversely, an effusion will alternatingly appear smaller and larger as the adjacent cardiac chamber expands and contracts within the peri- cardium whose space they share.

Another masquerade of a pericardial effusion is a left-sided pleural effusion [59] (Fig. 4a) (Video 4a). In the PLAX view, a pericardial effu- sion will appear anterior to the descending aorta, whereas a pleural ef- fusion will appear posterior to it [80]. Additionally, whereas a pericardial effusion may appear circumferentially around the heart, a pleural effusion will not cross the midline. As confirmation, the left lung base should also be assessed for the presence of the pleural effusion (Fig. 4b) (Video 4b). Thirdly, in the SXLA view, abdominal ascites may mimic a pericardial effusion, but they can be differentiated by their

only collapse during expiration, when positive intrathoracic pressure decreases preload to the right side of the heart (i.e. with resultant de- creased intracardiac pressure). Even with disease progression, collapse of the RV may occur over a shorter duration during inspiration (i.e. neg- ative intrathoracic pressure, increased venous return, and increased in- tracardiac pressure) than during expiration. In general, the longer the duration of right ventricular collapse, the more severe the tamponade [82,83]. The outflow region of the RV generally compresses earlier than does the basal portion.

This finding has been shown to be 48-60% sensitive and 75-90% spe- cific for pericardial tamponade, though the determination of what con- stitutes tamponade has varied between studies [57,84-88]. In the ED- based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, diastolic right ventricular collapse was found in 85% of patients [21]. In the 342 pa- tients who underwent pericardiocentesis for a clinically significant peri- cardial effusion, right ventricular collapse was found more often from a non-procedural etiology than from an iatrogenic and procedural etiol- ogy (62% vs. 33%) [45]. Moreover, in the retrospective study of 187 hos- pitalized patients diagnosed with a pericardial effusion, 64% of patients having a moderate-large effusion (circumferential; >1 cm end-diastolic diameter) showed diastolic right ventricular collapse compared to only 4% in small effusions (seen only posteriorly) [24].

It is critical to determine the timing of right ventricular collapse in the cardiac cycle. Whereas right ventricular free wall contraction would be normal if occurring during systole (i.e. when the atrioventric- ular valves are closed), its collapse during diastole (i.e. when the atrio- ventricular valves are open) suggests tamponade. This assessment is best performed in the Apical 4-chamber (A4C) and SXLA views that pro- vide optimal simultaneous visualization of the atrioventricular valves and entire right ventricular free wall (Fig. 6) (Video 7). The PLAX view, as well as the parasternal short-axis (PSAX) and subxiphoid short-axis (SXSA) views (particularly at the aortic valve level), visualize mostly the outflow region.

Unfortunately, patients with pericardial tamponade often present

with tachycardia [23,40,42], making it difficult to determine if the atrio- ventricular valve opening and right ventricular free wall collapse are oc- curring simultaneously. The easy solution is to use the ultrasound cine loop to cycle between consecutive still frames from a frozen image or saved 6-second clip. Furthermore, in the A4C and SXLA views, the tri- cuspid valve (TV) and right ventricular free wall are located close to- gether and can usually be visualized simultaneously. Similar proximity relationships exist between the PSAX and SXSA views (which only visu- alize a portion of the right ventricular free wall) and the mitral valve (MV). Alternatively, in the PLAX view, the MV and right ventricular

Table 7

Quantitative and qualitative size categorization of pericardial effusions.

Size

Estimated Volume

Appearance

End-Diastolic Diameter Between Visceral and Parietal Pericardium

Trivial

< 50 mL

Only in systole

0 cm

Small

50-100 mL

Systole and diastole

< 1 cm

Moderate

100-500 mL

Circumferential

1-2 cm

Large

> 500 mL

Qualitatively large

> 2 cm

Image of Fig. 2

Fig. 2. A trivial, small, moderate, and large pericardial effusion in the parasternal long-axis view. For the large effusion, a dotted line delineates the end-diastolic diameter between the visceral and parietal pericardium. Using the baseline scale along the right side of the image as reference, this distance qualitatively appears to be > 2 cm.

outflow tract (RVOT) are located further apart. A helpful strategy for this view entails using M-mode due to its higher temporal resolution, with the beam directed through the center of the RVOT free wall and the tip of the anterior MV leaflet (Fig. 7). The movement of these two struc- tures will be depicted on the y-axis over time (i.e. the x-axis), allowing determination of whether the RVOT’s collapse is truly occurring during diastole.

The RV will be less likely to demonstrate diastolic collapse (and thus, tamponade physiology) in the presence of a higher baseline intrapericardial pressure (Video 6). This would be the case for cor pulmonale and pulmonary hypertension (PH) (in whom 30% of patients develop a pericardial effusion [89,90]), severe left ventricular failure, or

Image of Fig. 3

Fig. 3. A pericardial effusion and pericardial fat pad in the subxiphoid long-axis view (PEff

= pericardial effusion, PF = pericardial fat pad, RVFW = right ventricular free wall, RV = right ventricle).

other etiologies of Right ventricular hypertrophy [58,82,83,91-96]. Alter- natively, right ventricular collapse will occur more readily if the cham- ber’s intracardiac pressures are lower, such as with hypovolemia [83,97,98].

      1. Systolic right atrial collapse

When the intrapericardial pressure exceeds the right atrial intracar- diac pressure, the thin-walled RA will collapse. The right atrial pressure has the lowest pressure during systole than does any other chamber of the heart during systole or diastole. Therefore, its collapse is the earliest echocardiographic sign of tamponade [99]. Though the determination of what constituted tamponade varied between studies, this finding has been shown to be 50% sensitive for tamponade early in the disease pro- cess, but up to 100% sensitive with its progression [84,85,100,101]. Its specificity ranges from 33-100% [84,85,100-102]. These values trend higher when the duration of right atrial collapse lasts > 1/3 of the cardiac cycle [57,101,103,104]. Otherwise, collapse during < 1/3 of the cardiac cycle may simply reflect normal atrial contraction in diastole [85,101]. In the ED-based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, systolic right atrial collapse was found in 70% of patients [21]. In the 342 patients who underwent pericardiocentesis for a clinically significant pericardial effusion, right atrial collapse was found more often with non-procedural than iatrogenic and procedure-related effusions (71% vs. 41%) [45]. Moreover, in the retrospective study of 187 hospitalized patients diagnosed with a pericardial effusion, systolic right atrial col- lapse was found in 86% of patients having moderate-large effusions (cir- cumferential; >1 cm end-diastolic diameter) compared to only 10%

with small effusions (seen only posteriorly) [24].

Systolic right atrial collapse is best assessed in the A4C and SXLA views that provide optimal visualization of the TV and entire right atrial free wall (the PSAX and SXSA views at the aortic valve level visualize less of the free wall) (Image 8) (Video 8). Use of an offline software that provided field-by-field analysis to determine a quantitative right atrial inversion time index (i.e. number of video fields showing right

Image of Fig. 4

Fig. 4. PLAX) A small pericardial and a left-sided pleural effusion in the parasternal long-axis view (* = pericardial effusion, Ao = descending aorta). Left mid-axilla) A left-sided pleural effusion at the mid-axillary lung base. Rather than being filled with air and subject to sonographic artifacts, the lung tissue is actually visualized in this patient due to compressive atelec- tasis.

atrial collapse divided by the total number of video fields per cardiac cycle) > 0.34 was shown to improve specificity and predictive value for tamponade [101]. A similar albeit less precise evaluation can con- ceivably be derived on standard ultrasound machines using the ultra- sound cine loop.

Compared to their left-sided counterparts, the RA and RV will col- lapse more readily from elevated intrapericardial pressure due to their lower baseline intracardiac pressures (3-5 mmHg and 15-25 mmHg, re- spectively). The lack of any right-sided chamber collapse carries a 90% negative predictive value for tamponade [85]. Some exceptions include infectious and/or loculated pericardial effusions [105-108], post- surgical complications [109-112] leading to a compressive pericardial blood clot [113], and large left-sided Pleural effusions [114-118]. For in- stance, a loculated effusion or blood clot adjacent only to the LV would lead to the LV’s collapse, thereby decreasing preload and resultant car- diac output without any right-sided heart compression. In the 342 pa- tients who underwent pericardiocentesis for a clinically significant pericardial effusion, a regional effusion was found more often with iatrogenic and procedure-related compared to non-procedural effu- sions (16% vs. 2%) [45]. Post-surgical regional tamponade may occur early (within 24 hours, due to surgical bleeding or cardiopulmonary

Image of Fig. 5

Fig. 5. Both ascites (denoted “A”) and a circumferential pericardial effusion (the anterior portion denoted “P”) visualized within the same subxiphoid long-axis view. The ascites lies outside the hyperechoic pericardium, whereas the effusion lies within it (adapted with permission from Abhilash Koratala MD, NephroPOCUS.com).

bypass-induced coagulopathy) or late (up to 5-7 days after cardiac surgery due to excessive mediastinal drainage or post-pericardiotomy syndrome) [1]. Nevertheless, a retrospective survey of 4,561 postopera- tive patients found that only 48 (1%) had moderate-large effusions (by unspecified criteria), with 36 of those causing tamponade [119].

      1. Plethoric and non-collapsible inferior vena cava

When compressed by the elevated intrapericardial pressure from a pericardial effusion, the RA is unable to accommodate incoming preload from the Inferior vena cava . Hence, analogous to the sensitivity of systolic right atrial collapse, a plethoric IVC with minimal respirophasic variation is 95-97% sensitive for tamponade, though the definition of tamponade has varied between studies [1,84,93,120,121]. Exceptions include patients with low-pressure tamponade, who do not have signif- icant venous congestion yet still benefit from Pericardial aspiration [122]. In the ED-based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, a plethoric IVC was found in 70% of patients [21]. In the retrospective study of 187 hospitalized patients diagnosed with a pericardial effusion, a plethoric IVC with blunted respirophasic variation was present in 75% of patients having a moderate-large effusion (circumferential; >1 cm end-diastolic diameter), compared to only 32% when the effusion was small (seen only posteriorly) [24].

The long-axis of the IVC can be visualized inferior to the xiphoid pro- cess in the sagittal plane (Fig. 9) (Video 9). The diameter is evaluated just proximal to the hepatic vein inflow that lies between 0.5-3.0 cm from the IVC-RA junction [123]. The use of M-mode is not recom- mended, because inadvertently placing the beam obliquely to the long-axis of the IVC (versus perpendicularly) will overestimate IVC di- ameter and underestimate its collapsibility. The opposite will occur (i.e. an underestimated diameter and overestimated collapsibility) if the transducer is not placed (or does not remain) along the IVC’s long- axis during the evaluation [123].

ASE guidelines define a plethoric IVC as having diameter > 2.1 cm with < 50% respirophasic variation [1,123]. However, in the time- sensitive context of evaluating symptomatic patients, a qualitative bi- nary assessment of plethoric and non-collapsible versus thin or collaps- ible is sufficient [59].

      1. Respirophasic variation in mitral and tricuspid inflow velocities as a surrogate for pulsus paradoxus

Under normal circumstances, spontaneous inspiration and associ- ated chest cavity expansion draw air into the lungs due to the negative intrathoracic pressure. Increased lung oxygen content leads to a de- crease in pulmonary vascular resistance, thereby facilitating increased

Image of Fig. 6

Fig. 6. Diastolic right ventricular collapse from large pericardial effusions in the parasternal long-axis, parasternal short-axis, apical 4-chamber, and subxiphoid long-axis views.

blood flow through the right side of the heart to the pulmonary arterial system. As the two ventricles occupy the same space within the pericar- dial sac, an increase in filling of the RV is normally associated with a minimal (< 5%) decrease in filling of the LV [92].

With pericardial tamponade from an evenly distributed effusion, an elevation in intrapericardial pressure (generally > 15 mmHg when se- vere) leads to equalization of the right and left ventricular end-diastolic pressures (i.e. within 5 mmHg) [1]. Since the ventricles now also compete with the effusion for space within the pericardial sac, the effects of ven- tricular interdependence are more pronounced. An increase or decrease

in the diastolic volume of one ventricle will have the opposite effect on the volume of the other ventricle. Accordingly, with the increased right- sided cardiac filling associated with inspiration, the RV cannot fully ex- pand due to the effusion, and there will be further bulging of the interven- tricular septum towards the LV than normal. As a result, there will be decreased blood flow through the left side of the heart, with a resultant drop in stroke volume. This manifests as the abnormally large decrease in inspiratory SBP > 10 mmHg seen with pulsus paradoxus.

An echocardiographic surrogate for the changes in blood flow through the left and right sides of the heart is the measurement of

Image of Fig. 7

Fig. 7. A) M-mode of diastolic right ventricular collapse in the parasternal long-axis view. Note how the inward movement of the Right ventricular outflow tract free wall corresponds with the timing of the mitral valve opening (i.e. diastole). B) No diastolic right ventricular collapse. Note how the right ventricular outflow tract free wall does not bow inwards when the an- terior mitral valve leaflet is open.

Image of Fig. 8

Fig. 8. Systolic right atrial collapse from large pericardial effusions in the apical 4-chamber and subxiphoid long-axis views. Note the invagination of the right atrial free wall when the Tricuspid valve is closed (i.e. during systole).

blood flow velocities through the MV and TV, respectively [124,125]. These velocities, along with their variation over several heartbeats be- tween inspiration and expiration, can be obtained using pulsed wave Doppler in the A4C view (Fig. 10). In this orientation, blood through the atrioventricular valves will flow roughly in the same direction as the sound waves emitted from the transducer, providing the largest ob- tainable Doppler shift (i.e. Doppler shift FD ? cos(?); cos(0?) = 1).

Under normal circumstances, the peak respirophasic variation in E-

wave mitral inflow velocity is approximately 5% [125]. In spontaneously breathing patients with pericardial tamponade, there will be an approxi- mately > 30% inspiratory decrease in blood flow velocity through the MV and > 60% inspiratory increase through the TV [1,46,59,61, 85,124,126,127]. The magnitude of this Respiratory variation is not predic- tive of pericardial pressure or severity of hemodynamic compromise [128]. This finding may also appear with marked dyspnea, severe chronic ob- structive pulmonary disease, and pulmonary embolism [129]. In the ED- based study of 205 patients diagnosed with tamponade who underwent pericardiocentesis within 24 hours of ED presentation, exaggerated mitral inflow velocity variability was found in 78% of patients [21]. In the 342 pa- tients who underwent pericardiocentesis for a clinically significant pericar- dial effusion, respirophasic transvalvular flow variation was found more often with non-procedural than with iatrogenic and procedure-related ef- fusions (33% vs. 15%) [45]. Of note, for patients receiving positive-pressure ventilation, sonographic pulsus paradoxus is not as useful for determining

Image of Fig. 9

Fig. 9. A plethoric and non-collapsible inferior vena cava visualized draining into the right atrium in the subxiphoid long-axis plane.

whether an effusion is causing tamponade. In an experimental study of subjects receiving positive-pressure ventilation, respirophasic variation in MV inflow velocity was greater than normal (36%), decreased with a peri- cardial effusion (29%), and decreased even further with tamponade (16%) [130]. Since the left ventricular filling gradient in pericardial tamponade is already compromised by cardiac compression, the respiratory variations in pleural and pericardial pressures due to positive-pressure ventilation have minimal effect.

    1. Emergency department management

The ultimate management of pericardial tamponade is drainage of the effusion. Just as even a small amount of additional fluid can push the intrapericardial pressure above the intracardiac pressure (i.e. caus- ing tamponade), drainage of a small amount of fluid can relieve tam- ponade due to the steep pericardial pressure-volume relationship (Fig. 1, top-center). After drainage, the cardiac chambers can fully ex- pand, allow incoming preload, and thereby produce sufficient stroke volume and cardiac output. The procedure’s timing (i.e. emergent, ur- gent, or elective) and technique (i.e. percutaneous pericardiocentesis or surgical drainage) depend on certain considerations.

Image of Fig. 10

Fig. 10. Exaggerated respirophasic variation of mitral valve inflow velocity as a surrogate for pulsus paradoxus.

Table 8

Indications for emergent [8,127,131,132] and urgent (while admitted) [8,132-140] peri- cardiocentesis.

Emergent Urgent

Purulent, tuberculous, or neoplastic

heart failure. Echocardiographic parameters included pericardial effu- sion etiology, size, and findings suggestive of hemodynamic compro- mise. The following year, the same author group retrospectively evaluated this tool in hospitalized patients with moderate-large effu-

sions (>= 1 cm end-diastolic diameter) and no hemodynamic compro-

hemodynamic shock

effusion

mise on admission [152]. The pericardial effusion scoring index

Impending cardiac arrest Human immunodeficiency virus or other immunosuppression

Cardiac arrest Loculated effusion not amenable to percutaneous drainage

obtained from the initial presentation (i.e. initial medical contact lead- ing to evaluation for pericardial effusion) showed a high accuracy in identifying patients who required pericardial drainage at a mean

Rapidly deteriorating patients with iatrogenic hemopericardium

      1. To drain or not to drain

Symptomatic despite medical treatment

follow-up of 2.5 days later.

For patients with moderate-large effusions (>= 1 cm end-diastolic di- ameter), another author group in 2021 retrospectively derived and in- ternally validated a simplified tool to predict the risk of pericardial drainage or death attributed to tamponade within 24 hours [46]. Vari-

For a patient with a pericardial effusion, the emergency physician must decide whether the effusion requires drainage, and if so, whether the procedure must be performed emergently versus urgently (within 12-48 hours while admitted) (Table 8). These decisions depend on the clinical presentation, changes in hemodynamic status over time, risk- benefit ratio of the procedure, and echocardiographic findings [8]. In brief, the emergency physician must perform the pericardiocentesis in the ED when any delay could lead to the patient’s hemodynamic col- lapse and death.

For those patients with tamponade but not in hemodynamic shock, the ESC published a triage strategy in 2014 that provides a numerical score corresponding to the risk and likelihood of developing obstructive shock and hemodynamic compromise [8]. First, the etiology is assessed for its association with large effusions (e.g. malignancy). Second, the clinical presentation is assessed for highly symptomatic patients (e.g. orthopnea without rales) who are acutely worsening, and with con- cerning vital signs or physical examination findings. Third, bedside echocardiography is assessed for a circumferential pericardial effusion and other sonographic signs of tamponade. Suggestive ECG (e.g. low voltage) and chest radiograph (e.g. cardiomegaly) findings fall under this step as well. Higher scores call for immediate drainage, whereas lower scores allow delay for up to 12-48 hours. If the hospital has lim- Management considerations precedi”>ited experience with pericardial drainage, transfer to a specialized insti- tution is indicated so long as the patient is clinically stable [8].

Regardless of this numerical score, the ESC advocates that certain in- dications warrant urgent surgical management (Table 9) [8,141]. For patients with aortic dissection or myocardial rupture, pericardiocentesis may cause an increase in SBP from a temporary rise in cardiac output. This can lead to worsening of the dissection with potential aortic rup- ture and recurrent pericardial bleeding, respectively [142-145]. How- ever, if surgical management is not promptly available for an aortic dissection or the patient is unlikely to survive transfer to the operating room, controlled percutaneous drainage of very small amounts of hemopericardium (raising the SBP to the lowest acceptable level ~ 90 mmHg) can be attempted as a stabilizing measure [146-150].

In hemodynamically stable patients with pericardial effusions, an- other author group previously developed a stepwise pathway-based al- gorithm in 2011 for quantifying the need for pericardial drainage [151]. They used the CHASER mnemonic for entry into this pathway: Chest pain, Hypotension or Arrest, Shortness of breath, Echocardiographic or other imaging finding of pericardial effusion, and Right-predominant

ables incorporated into a numerical score included SBP < 100 mmHg, pericardial effusion diameter, diastolic right ventricular collapse, and

> 25% respirophasic variation of the mitral inflow velocity. The need for drainage within 24 hours was risk-stratified as low (8.1%), interme- diate (63.8%), or high (93.7%), respectively.

Though emergent drainage of a large pericardial effusion without hemodynamic compromise is not indicated in the ED, these patients nonetheless warrant coordination with consulting services (i.e. cardiol- ogy) for conservative management and monitoring over time, or per- haps elective drainage [132,134,135,153].

      1. Contraindications to pericardiocentesis

There are no absolute contraindications to pericardiocentesis in the setting of pericardial tamponade causing hemodynamic shock. How- ever, several relative contraindications exist (Table 10) [8,154]. Never- theless, two such examples–thrombocytopenia (< 50,000 103 cells/ uL) and coagulopathy (INR >= 1.5)–did not demonstrate an association

with major Bleeding complications in a retrospective review of 1,196

echocardiography-guided pericardiocentesis procedures performed by experienced cardiologists [155]. Moreover, platelet transfusion in thrombocytopenic patients does not appear to modify the risks of peri- cardial drainage [156,157].

      1. Management considerations preceding emergent pericardiocentesis

First, in the brief time interval between diagnosis and emergent drainage, hemodynamics and end-organ perfusion should be optimized. For a patient with penetrating injury to the chest causing cardiac rup- ture and hemorrhagic shock, blood products should be administered emergently [158]. For patients with non-traumatic tamponade, admin- istration of 250-500 mL intravenous fluids (IVF) over 10 minutes should be considered in dehydrated hypovolemic patients with an SBP < 100 mmHg [141,159-163]. In these patients, volume expansion may lead to a rise (albeit modest) in arterial pressure and cardiac output. An increase in cardiac output from receiving IVF has also been predicted by a resting heart rate > 109 beats per minute, but not by a larger peri- cardial effusion size, presence of right atrial or ventricular collapse, or raised jugular venous pressure [159,160].

As a caution against liberal IVF administration, an increase in arterial pressure could be offset by an increase in left ventricular end-diastolic pressure causing pulmonary edema [160,164]. Moreover, in a reflection of increased ventricular interdependence occurring with pericardial

Table 9

Indications for urgent surgical mnagement regardless of pericardial effusion etiology, patient presentation, and echocardiographic findings

Indications for Urgent Surgical Management of Pericardial Tamponade Type A aortic dissection causing hemopericardium

Ventricular free wall rupture after acute myocardial infarction Severe chest trauma

Iatrogenic hemopericardium when bleeding cannot be controlled percutaneously

Table 10

Relative contraindications to pericardiocentesis

Relative Contraindications to Pericardiocentesis Uncorrected coagulopathy

Ongoing anticoagulant therapy with INR > 1.5 Thrombocytopenia < 50,000 cells/uL

Posterior pericardial effusion Loculated pericardial effusion

Effusion responding to anti-inflammatory treatment

tamponade, volume expansion of the right-sided chambers may lead to compression of the left-sided chambers with a corresponding drop in cardiac output [161]. Therefore, volume expansion above 500 mL is not recommended unless the patient clearly remains hypovolemic.

Furthermore, due to a decreased stroke volume in pericardial tam- ponade, cardiac output becomes dependent on compensatory tachycar- dia. If the heart rate fails to increase appropriately, the use of inotropy for inducing tachycardia can be considered [165]. Experimental studies have examined the potential role of various inotropes and vasopressors in tamponade [166,167], with some supporting the use of the ?– adrenergic agent isoproterenol due to its positive inotropy (via ?1 receptors), peripheral vasodilation to reduce systemic vascular resistance (via ?2 receptors), and positive chronotropic effects [168- 171]. Unfortunately, isoproterenol may not be readily available in all ED’s. A more widely available and better option may be low-dose epi- nephrine (0.01-0.5 mcg/kg/min), which works more specifically as an inotrope (via ?1 receptors) with some vasoconstrictive effects (via ?1 receptors), which minimizes potential hypotension.

Second, anticoagulation, coagulopathies, and anemia must be treated as quickly as possible, preferably prior to pericardial drainage [8]. Third, Elevated blood pressure readings should not be treated ag- gressively. A medication-induced decrease in blood pressure, along with relief of the sympathetic surge following pericardial drainage, may together contribute to Significant hypotension and hemodynamic compromise [51,172].

Fourth, it may be tempting to place a dyspneic patient on positive- pressure non-invasive ventilation. However, when the associated in- crease in intrathoracic pressure decreases preload to the right heart, it also decreases intracardiac pressures and renders those chambers more susceptible to collapse from the elevated intrapericardial pressure. This leads to a further decrease in cardiac output than would be ex- pected from just positive-pressure ventilation. The positive end- expiratory pressure (PEEP) also compresses the heart, vena cavae, and pulmonary vasculature, which leads to reduced filling of both right- and left-sided cardiac chambers [167,173]. Furthermore, endotracheal intubation and invasive ventilation pose even greater risks, as the cardiovascular-depressing induction and sedation agents contribute to hypotension and decreased cardiac output [174]. Therefore, mainte- nance of spontaneous ventilation is recommended [173,175,176], with dissociative agents such as ketamine of potential use for performing the pericardiocentesis [177]. During this time, hypercarbia should be avoided, as it increases pericardial pressure and (through respiratory acidosis) decreases cardiac performance [178].

If non-invasive or invasive ventilation cannot be avoided, drainage of pericardial fluid should ideally be performed beforehand [173,179]. Otherwise, initiation of positive-pressure ventilation should at least be delayed until pericardial drainage is imminent [173,175,176,179]. For the intubation itself, an awake intubation ( i.e. airway topicalization followed by gently-induced sedation and analgesia) can be used to avoid the deleterious effects on cardiac output by the typical dosing for induction and sedation agents [176,179]. Once intubated, higher re- spiratory rates (and therefore smaller tidal volumes) can help avoid the high-inspiratory airway pressures associated with decreased cardiac output in tamponade [167].

      1. Where to drain the effusion

The optimal location for a pericardiocentesis is the site at which the visualized fluid pocket is largest and shallowest, with no intervening or- gans or vital structures. Multiple echocardiographic views should be ob- tained in order to determine this site. Pushing too hard with the transducer and indenting the skin will provide falsely shorter estimated distances to the effusion. Prior studies have varied in their support for the PLAX, A4C, and SXLA approaches [180-184]. One ED-based retro- spective study of 166 pericardial effusions diagnosed by POCUS found that the skin-to-effusion distance the needle must travel was least in the A4C (2.5 cm) and PLAX (2.7 cm) views, as compared to the SXLA

view (5.6 cm) [185]. As determined by Clinical Ultrasound Fellowship- trained physicians, they also found a lower predicted complication rate for the PLAX (20.2%) and A4C (31.9%) views, as compared to the SXLA view (79.7%). The most frequently predicted complications for each of the views were poor Image quality precluding a safe procedure (30.0%), inability to access the fluid collection (26%), and liver puncture (83.7%), respectively.

Using the PLAX or A4C approaches may raise concern for needle puncture of the lung and an iatrogenic pneumothorax. However, if the lung lies in the proposed needle path, this will be made clear by the sonographic artifacts of lung tissue such as A-lines. Encountering lung tissue will be more likely in patients with chronic obstructive pulmo- nary disease in whom lung hyperinflation obscures the parasternal views, in which case the SXLA approach would be warranted. Moreover, for the parasternal approach, care must be taken to avoid the internal thoracic artery (also known as the internal mammary artery) that runs approximately 1-3 cm lateral to the left sternal border [154]. The needle should also enter at the superior border of the rib to avoid injur- ing the neurovascular bundle inferiorly. As an interesting caveat, though the A4C approach risks ventricular puncture due to proximity to the LV, this chamber’s thicker wall is more likely to self-seal after inadvertent puncture than will other chambers.

Though thrombocytopenia and coagulopathy are only relative con- traindications to pericardiocentesis, the SXLA approach should ideally be avoided in these patients so as to avoid liver injury and associated bleeding. For patients in cardiac arrest, the PLAX approach may be pre- cluded by ongoing chest compressions, defibrillation pads, and other re- suscitative activities. The SXLA approach may thus be a safer and more realistic option in cardiac arrest [186].

      1. Pearls and pitfalls for the pericardiocentesis procedure

Pericardiocentesis in the ED has classically been performed with the subxiphoid approach using anatomical landmarks, with a long needle directed towards the left shoulder at a 30? angle to the skin [141]. How- ever, echocardiography can reveal the location and depth of the effu- sion, intervening structures, and therefore, the ideal entry site. In the echocardiography-assisted method, the operator plots the needle tra- jectory first and then separately advances the needle along this path. In the echocardiography-guided method, the needle is visualized throughout the entire process of puncturing the skin, advancing to- wards the effusion, and draining it. The complication rate for pericardio- centesis is much lower when using ultrasound assistance or guidance (0.5-3.7%) as compared to blind or using electrocardiogram assistance (15-20%) [180,187-195].

There are several key considerations when setting up the pericardio- centesis procedure [144,154,196-198]. First, elevating the head of the bed to the semi-reclined position prevents pericardial fluid from gravi- tating posteriorly, as it would in a Supine patient. Secondly, this position may also prevent hypoxia and respiratory distress, which facilitates the safety of the procedure by helping the patient remain still. That will also be supported by injecting liberal amounts of local anesthesia (without epinephrine) along the planned needle tract. Third, intravenous seda- tion should be avoided in hemodynamically unstable patients, as re- moving the patient’s sympathetic drive can lead to a precipitous drop in SBP.

Fourth, decreasing the depth of the visual field increases the pulse repetition frequency (and thereby the frame rate), which enhances nee- dle visualization. Whereas diagnosis and characterization of a pericar- dial effusion call for echocardiographic visualization of all cardiac structures, safe needle guidance requires only seeing the desired effu- sion pocket, which is optimized with less depth in a given view (Fig. 11) (Video 10). If the fluid pocket is superficial enough (within ap- proximately 5 cm depth), the high-frequency linear transducer can be used to provide the optimal resolution. This transducer is already com- monly used for other ED procedural skills requiring needle guidance

Image of Fig. 11

Fig. 11. Pericardiocentesis of an anterior pericardial effusion at low depth (providing optimal needle visualization) using the linear (adapted with permission from Ahad Alhassan MD) and curvilinear transducers.

such as peripheral [199,200] and central line placement [201], arthrocentesis [202], and abscess drainage [203].

Of note, the phased array transducer used for echocardiography is not well-suited for needle guidance. Whereas the piezoelectric crystals of single-element transducers (e.g. linear and curvilinear) are lined up to emit sound waves in a fixed direction (i.e. towards the needle), the scan lines of the phased array transducer emanate in a fan-like forma- tion from the narrow beam point in the center of the transducer face. A differential timed excitation of these piezoelectric crystals causes the beam to be electronically steered and swept through tissue without movement of the transducer itself. Therefore, a smaller proportion of these sound waves encounter the needle directly to be reflected back to the transducer. Instead, the visual “slice” depicted on the screen in- corporates all the views insonated from the fan-like emanation of sound waves, and not just those structures to which the transducer is physically pointing.

The next critical safety checkpoint is proper advancement of the pericardiocentesis needle into the pericardial space. First, the plastic cannula tip sits approximately 1 mm proximal to the needle tip visual- ized under ultrasound guidance. Therefore, the needle should be ad- vanced into the effusion by that amount prior to advancing the cannula. Second, the needle or catheter location should be confirmed prior to attempted aspiration of the effusion. This is best achieved by vi- sualizing the needle or catheter within the effusion using multiple

echocardiographic views. A supplementary confirmation technique en- tails injecting up to 10 mL of agitated saline and visualizing the bubbles within the pericardial space (Fig. 12) (Video 11) [196,204,205]. In the event that a cardiac chamber is inadvertently perforated, the catheter should not be removed until another drainage catheter is properly placed into the pericardial space. If the bleeding persists, Surgical repair is needed. Third, if the needle is not long enough or cannot reach the ef- fusion for other reasons, or aspiration through the narrow catheter does not seem feasible (e.g. purulent or clotted material), then surgical drain- age is indicated [8].

Once aspiration begins, a hemorrhagic appearance to the fluid war- rants that 5-10 mL be expelled onto a gauze pad to examine for small Blood clots. If there are no clots, the blood is likely from the pericardial space, as the pericardial mesothelium carries intrinsic fibrinolytic and anti-clotting properties [206]. Conversely, if clots are present, this indi- cates that either the needle is intracardiac from an inadvertent puncture (blood carries a higher hemoglobin and hematocrit than pericardial fluid), or the clots occurred due to fresh bleeding from an aortic dissec- tion, myocardial rupture, or traumatic hemopericardium (Fig. 13) (Video 12) [207]. In either case, aspiration must be ceased immediately. In the latter scenario, further drainage will allow SBP to rise and pro- mote worsening of the aortic dissection (with potential rupture) or ven- tricular rupture. As a caveat, aspirated effusion contents can be falsely negative for hemorrhage due to clotted blood products impeding

Image of Fig. 12

Image of Fig. 13Fig. 12. Administration of agitated saline to confirm pericardiocentesis catheter placement in the pericardial space. In this apical 4-chamber view using the phased array transducer, bubbles produced by the agitated saline appear outside and lateral to the left-sided heart

chambers (adapted with permission from Robert Jones DO). Fig. 13. Traumatic hemopericardium in the subxiphoid long-axis view. Note the hyper-

echoic clotted blood adjacent to the apex of the heart.

aspiration through the catheter. Additionally, in anticoagulated pa- tients, the aspirated contents may take a longer time to coagulate into clots. Lastly, a myocardial or coronary artery puncture may initially re- main clinically silent and later present with delayed hemopericardium. As aspiration continues, the pericardial fluid should be drained slowly. Though more often associated with surgical drainage, a rapid evacuation of > 1 L of fluid can lead to pericardial decompression syn- drome [8,184,208-212]. With a mortality of 29% in 35 cases found be- tween 1983-2013 [208], this condition manifests immediately or up to within 48 hours as cardiogenic pulmonary edema and left-, right-, or biventricular heart failure. It may occur with up to 5% of all pericardio- centesis procedures and is likely underreported [184]. A theorized mechanism is that increased right ventricular preload and chamber en- largement (from removal of the compressive pericardial fluid) distends the muscle fibers and thereby reduces right ventricular systolic func- tion. In conjunction with a persistent catecholaminergic peripheral va- soconstriction, right ventricular compression upon the LV leads to acute left ventricular pressure overload [209]. Patients with chronic PH and right ventricular dysfunction have a particularly high risk for mortality after pericardial drainage [213]. The already pressure- overloaded RV can now enlarge even further, resulting in further septal bowing into the LV and decreased left ventricular preload. Additionally, the reduction in diastolic Coronary blood flow associated with right ven- tricular overdistention leads to chamber ischemia. Treatment for this

condition is supportive.

Finally, once initial drainage is completed, the catheter should ide- ally be left in place (or guided in using Seldinger technique if only a nee- dle was used initially) while it continues to drain > 25 mL per day [8,73,134,196,214]. This will help achieve complete pericardial drain- age, as well as facilitate adherence between the visceral and parietal pericardial layers to prevent the effusion from reaccumulating [134]. In- termittent drainage is recommended, with saline left within the cathe- ter to prevent its occlusion [197]. The pericardial effusion recurrence rate for extended drainage is 12-24% compared to 27-55% after simple pericardiocentesis [215,216].

  1. Conclusions

Pericardial tamponade is a life-threatening condition requiring timely diagnosis and management. Effusions arise from varying etiolo- gies and can develop into tamponade acutely or sub-acutely. The clinical presentation most often includes dyspnea. Though classically taught, Beck’s triad does not actually appear commonly. Echocardiographic findings consist of a pericardial effusion (larger size more often associ- ated with tamponade), diastolic right ventricular collapse (specific), systolic right atrial collapse (sensitive), a plethoric and non-collapsible IVC (sensitive), and respirophasic changes in the mitral and tricuspid in- flow velocities that reflect pulsus paradoxus. The decision and timing for performing a pericardiocentesis depend on clinical presentation, patient hemodynamics, effusion etiology, and Sonographic findings. Patients with hemodynamic instability, impending deterioration, or car- diac arrest warrant emergent ED pericardiocentesis. Emergent surgical indications include type A aortic dissection causing hemopericardium, ventricular free wall rupture after acute myocardial infarction, severe chest trauma, and iatrogenic hemopericardium when bleeding cannot be controlled percutaneously.

Certain management considerations leading up to the procedure include administration of blood products to patients with traumatic hemopericardium; gentle IVF administration to hypotensive, hypovole- mic patients with consideration for Vasoactive medications such as epinephrine; and treatment of anticoagulation, coagulopathies, and anemia. Positive-pressure ventilation will decrease cardiac output, and intravenous sedation can remove the patient’s sympathetic drive main- taining their blood pressure. Both of those interventions should be avoided if possible. The optimal location for echocardiography-guided pericardiocentesis is the largest and shallowest fluid pocket with as

few intervening organs and vital structures as possible. For the proce- dure itself, elevating the head of the bed to the semi-reclined position to prevent hypoxia, as well as using liberal amounts of local anesthesia, will help the patient remain comfortable and still. Safe needle guidance and confirmation of proper catheter placement should be undertaken using low-depth sonographic views, injection of agitated saline, and evaluation of the initial aspirate for a hemorrhagic appearance. Finally, the pericardial fluid should be drained slowly over time to prevent peri- cardial decompression syndrome.

Disclosures

JA serves as consultant for Butterfly, Vave, and Echonous. SA, RJA, and BL have no declarations of interest.

Sources of support

N/a

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2022.05.001.

References

  1. Klein AL, Abbara S, Agler DA, et al. American Society of Echocardiography clinical recommendations for multimodality cardiovascular imaging of patients with peri- cardial disease: endorsed by the Society for Cardiovascular Magnetic Resonance and Society of Cardiovascular Computed Tomography. J Am Soc Echocardiogr. 2013;26(9):965-1012 e15.
  2. Spodick DH. Acute cardiac tamponade. N Engl J Med. 2003;349(7):684-90.
  3. Tsang TS, Oh JK, Seward JB. Diagnosis and management of cardiac tamponade in the era of echocardiography. Clin Cardiol. 1999;22(7):446-52.
  4. Saito Y, Donohue A, Attai S, et al. The syndrome of cardiac tamponade with “small”

pericardial effusion. Echocardiography. 2008;25(3):321-7.

  1. Kabukcu M, Demircioglu F, Yanik E, et al. Pericardial tamponade and large pericar- dial effusions: causal factors and efficacy of percutaneous catheter drainage in 50 patients. Tex Heart Inst J. 2004;31(4):398-403.
  2. Reddy PS, Curtiss EI, Uretsky BF. Spectrum of hemodynamic changes in cardiac tamponade. Am J Cardiol. 1990;66(20):1487-91.
  3. Al-Ogaili A, Ayoub A, Fugar S, et al. Cardiac tamponade incidence, demographics and in-hospital outcomes: analysis of the national inpatient sample database. J Am Coll Cardiol. 2018;71(11).
  4. Ristic AD, Imazio M, Adler Y, et al. Triage strategy for urgent management of cardiac tamponade: a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2014;35(34):2279-84.
  5. Nakai C, Izumi S, Haraguchi T, et al. Acute type A aortic dissection with cardiopul- monary arrest at presentation. Ann Thorac Surg. 2021;112(4):1210-6.
  6. Kiziltunc E, Unlu S, Yakici IE, et al. Clinical characteristics and prognosis of cardiac tamponade patients: 5year experience at a tertiary center. Herz. 2020;45(7): 676-83.
  7. Sagrista-Sauleda J, Merce J, Permanyer-Miralda G, et al. Clinical clues to the causes of large pericardial effusions. Am J Med. 2000;109(2):95-101.
  8. Levy PY, Corey R, Berger P, et al. Etiologic diagnosis of 204 pericardial effusions. Medicine (Baltimore). 2003;82(6):385-91.
  9. Ma W, Liu J, Zeng Y, et al. Causes of moderate to large pericardial effusion requiring pericardiocentesis in 140 Han Chinese patients. Herz. 2012;37(2):183-7.
  10. Sanchez-Enrique C, Nunez-Gil IJ, Viana-Tejedor A, et al. Cause and long-term out- come of cardiac tamponade. Am J Cardiol. 2016;117(4):664-9.
  11. Cornily JC, Pennec PY, Castellant P, et al. Cardiac tamponade in Medical patients: a 10-year follow-up survey. Cardiology. 2008;111(3):197-201.
  12. Levy PY, Fournier PE, Charrel R, et al. Molecular analysis of pericardial fluid: a 7- year experience. Eur Heart J. 2006;27(16):1942-6.
  13. Orbach A, Schliamser JE, Flugelman MY, et al. Contemporary evaluation of the causes of cardiac tamponade: acute and long-term outcomes. Cardiol J. 2016;23 (1):57-63.
  14. Pennacchioni A, Nanni G, Sgura FA, et al. Percutaneous pericardiocentesis for peri- cardial effusion: predictors of mortality and outcomes. Intern Emerg Med. 2021;16 (7):1771-7.
  15. Guberman BA, Fowler NO, Engel PJ, et al. Cardiac tamponade in medical patients. Circulation. 1981;64(3):633-40.
  16. Colombo A, Olson HG, Egan J, et al. Etiology and prognostic implications of a large pericardial effusion in men. Clin Cardiol. 1988;11(6):389-94.
  17. Eke OF, Selame L, Gullikson J, et al. Timing of pericardiocentesis and clinical out- comes: Is earlier pericardiocentesis better? Am J Emerg Med. 2022;54:202-7.
  18. De Filippo O, Gatti P, Rettegno S, et al. Is pericardial effusion a negative prognostic marker? Meta-analysis of outcomes of pericardial effusion. J Cardiovasc Med (Ha- gerstown). 2019;20(1):39-45.
  19. Stolz L, Valenzuela J, Situ-LaCasse E, et al. Clinical and historical features of emer- gency department patients with pericardial effusions. World J Emerg Med. 2017; 8(1):29-33.
  20. Eisenberg MJ, Oken K, Guerrero S, et al. Prognostic value of echocardiography in hospitalized patients with pericardial effusion. Am J Cardiol. 1992;70(9):934-9.
  21. Leehey DJ, Daugirdas JT, Popli S, et al. Predicting need for surgical drainage of peri- cardial effusion in patients with end-stage renal disease. Int J Artif Organs. 1989;12 (10):618-25.
  22. Luft FC, Gilman JK, Weyman AE. Pericarditis in the patient with uremia: clinical and echocardiographic evaluation. Nephron. 1980;25(4):160-6.
  23. Peraino RA. Pericardial effusion in patients treated with maintenance dialysis. Am J Nephrol. 1983;3(6):319-22.
  24. Ribot S, Frankel HJ, Gielchinsky I, et al. Treatment of uremic pericarditis. Clin Nephrol. 1974;2(4):127-30.
  25. Kramer P, Wigger W, Scheler F. Management of uraemic pericarditis. Br Med J. 1975;4(5996):564-6.
  26. De Pace NL, Nestico PF, Schwartz AB, et al. Predicting success of intensive dialysis in the treatment of uremic pericarditis. Am J Med. 1984;76(1):38-46.
  27. Renfrew R, Buselmeier TJ, Kjellstrand CM. Pericarditis and renal failure. Annu Rev Med. 1980;31:345-60.
  28. Imazio M, Lazaros G, Valenti A, et al. Outcomes of idiopathic chronic large pericar- dial effusion. Heart. 2019;105(6):477-81.
  29. Merce J, Sagrista-Sauleda J, Permanyer-Miralda G, et al. Should pericardial drainage be performed routinely in patients who have a large pericardial effusion without tamponade? Am J Med. 1998;105(2):106-9.
  30. Sagrista-Sauleda J, Angel J, Permanyer-Miralda G, et al. Long-term follow-up of id- iopathic chronic pericardial effusion. N Engl J Med. 1999;341(27):2054-9.
  31. Lazaros G, Antonopoulos AS, Lazarou E, et al. Long-term outcome of pericardial drainage in cases of chronic, large, hemodynamically insignificant, C-reactive pro- tein negative, idiopathic pericardial effusions. Am J Cardiol. 2020;126:89-93.
  32. Markiewicz W, Borovik R, Ecker S. Cardiac tamponade in medical patients: treat- ment and prognosis in the echocardiographic era. Am Heart J. 1986;111(6): 1138-42.
  33. Gong W, Nie S. New clinical classification for ventricular free wall rupture following acute myocardial infarction. Cardiovasc Ther. 2021;2021:1716546.
  34. Sanmartin-Fernandez M, Raposeiras-Roubin S, Anguita-Sanchez M, et al. In- hospital outcomes of mechanical complications in acute myocardial infarction: analysis from a nationwide Spanish database. Cardiol J. 2021;28(4):589-97.
  35. Lopez-Sendon J, Gurfinkel EP, Lopez de Sa E, et al. Factors related to heart rupture in acute coronary syndromes in the Global Registry of Acute coronary events. Eur Heart J. 2010;31(12):1449-56.
  36. Roy CL, Minor MA, Brookhart MA, et al. Does this patient with a pericardial effusion have cardiac tamponade? JAMA. 2007;297(16):1810-8.
  37. Kapoor T, Locurto M, Farina GA, et al. Hypotension is uncommon in patients pre- senting to the emergency department with non-traumatic cardiac tamponade. J Emerg Med. 2012;42(2):220-6.
  38. Gibbs CR, Watson RD, Singh SP, et al. Management of pericardial effusion by drain- age: a survey of 10 years’ experience in a city centre general hospital serving a mul- tiracial population. Postgrad Med J. 2000;76(902):809-13.
  39. Levine MJ, Lorell BH, Diver DJ, et al. Implications of echocardiographically assisted diagnosis of pericardial tamponade in contemporary medical patients: detection before hemodynamic embarrassment. J Am Coll Cardiol. 1991;17(1):59-65.
  40. Cooper JP, Oliver RM, Currie P, et al. How do the clinical findings in patients with pericardial effusions influence the success of aspiration? Br Heart J. 1995;73(4): 351-4.
  41. Hanson MG, Chan B. The role of point-of-care ultrasound in the diagnosis of peri- cardial effusion: a single academic center retrospective study. Ultrasound J. 2021; 13(1):2.
  42. Duanmu Y, Choi DS, Tracy S, et al. Development and validation of a novel prediction score for cardiac tamponade in emergency department patients with pericardial ef- fusion. Eur Heart J Acute Cardiovasc Care. 2021;10(5):542-9.
  43. Sagrista-Sauleda J, Angel J, Sambola A, et al. Low-pressure cardiac tamponade: clin- ical and hemodynamic profile. Circulation. 2006;114(9):945-52.
  44. Beck C. Two cardiac compression triads. JAMA. 1935;104(9):714-6.
  45. Gandhi S, Schneider A, Mohiuddin S, et al. Has the clinical presentation and clini- cian’s index of suspicion of cardiac tamponade changed over the past decade? Echocardiography. 2008;25(3):237-41.
  46. Larose E, Ducharme A, Mercier LA, et al. Prolonged distress and clinical deteriora- tion before pericardial drainage in patients with cardiac tamponade. Can J Cardiol. 2000;16(3):331-6.
  47. Argulian E, Herzog E, Halpern DG, et al. Paradoxical hypertension with cardiac tam- ponade. Am J Cardiol. 2012;110(7):1066-9.
  48. Brown J, MacKinnon D, King A, et al. Elevated arterial blood pressure in cardiac tamponade. N Engl J Med. 1992;327(7):463-6.
  49. Cogswell TL, Bernath GA, Raff H, et al. Total peripheral resistance during cardiac tamponade: adrenergic and angiotensin roles. Am J Phys. 1986;251(5 Pt 2): R916-22.
  50. Kaszaki J, Nagy S, Tarnoky K, et al. Humoral changes in shock induced by cardiac tamponade. Circ Shock. 1989;29(2):143-53.
  51. Cook DJ. Clinical assessment of central venous pressure in the critically ill. Am J Med Sci. 1990;299(3):175-8.
  52. Davison R, Cannon R. Estimation of central venous pressure by examination of jug- ular veins. Am Heart J. 1974;87(3):279-82.
  53. Singh S, Wann LS, Schuchard GH, et al. right ventricular and right atrial collapse in patients with cardiac tamponade-a combined echocardiographic and hemody- namic study. Circulation. 1984;70(6):966-71.
  54. Reddy PS, Curtiss EI, O’Toole JD, et al. Cardiac tamponade: hemodynamic observa- tions in man. Circulation. 1978;58(2):265-72.
  55. Alerhand S, Carter JM. What echocardiographic findings suggest a pericardial effu- sion is causing tamponade? Am J Emerg Med. 2019;37(2):321-6.
  56. Cheitlin MD, Armstrong WF, Aurigemma GP, et al. ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to Update the 1997 Guidelines for the Clinical Application of Echocardiography). Circulation. 2003;108(9):1146-62.
  57. Adler Y, Charron P, Imazio M, et al. 2015 ESC Guidelines for the diagnosis and man- agement of pericardial diseases: The Task Force for the Diagnosis and Management of Pericardial Diseases of the European Society of Cardiology (ESC)Endorsed by: The European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2015; 36(42):2921-64.
  58. Eisenberg MJ, Schiller NB. Bayes’ theorem and the echocardiographic diagnosis of cardiac tamponade. Am J Cardiol. 1991;68(11):1242-4.
  59. Alpert EA, Amit U, Guranda L, et al. Emergency department point-of-care ultraso- nography improves time to pericardiocentesis for clinically significant effusions. Clin Exp Emerg Med. 2017;4(3):128-32.
  60. Plummer D, Brunette D, Asinger R, et al. Emergency department echocardiography improves outcome in penetrating cardiac injury. Ann Emerg Med. 1992;21(6): 709-12.
  61. Nagy KK, Lohmann C, Kim DO, et al. Role of echocardiography in the diagnosis of occult penetrating cardiac injury. J Trauma. 1995;38(6):859-62.
  62. Aaland MO, Bryan 3rd FC, Sherman R. Two-dimensional echocardiogram in hemo- dynamically stable victims of penetrating precordial trauma. Am Surg. 1994;60(6): 412-5.
  63. Freshman SP, Wisner DH, Weber CJ. 2-D echocardiography: emergent use in the evaluation of penetrating precordial trauma. J Trauma. 1991;31(7):902-5. discus- sion 905-6.
  64. Jimenez E, Martin M, Krukenkamp I, et al. Subxiphoid pericardiotomy versus echo- cardiography: a prospective evaluation of the diagnosis of occult penetrating car- diac injury. Surgery. 1990;108(4):676-9. discussion 679-80.
  65. Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and American College of Emergency Physicians. J Am Soc Echocardiogr. 2010;23(12): 1225-30.
  66. Mandavia DP, Hoffner RJ, Mahaney K, et al. Bedside echocardiography by emer- gency physicians. Ann Emerg Med. 2001;38(4):377-82.
  67. Lanoix R, Leak LV, Gaeta T, et al. A preliminary evaluation of emergency ultrasound in the setting of an emergency medicine training program. Am J Emerg Med. 2000; 18(1):41-5.
  68. Cosyns B, Plein S, Nihoyanopoulos P, et al. European Association of Cardiovascular Imaging (EACVI) position paper: Multimodality imaging in pericardial disease. Eur Heart J Cardiovasc Imaging. 2015;16(1):12-31.
  69. Adler Y, Charron P. The 2015 ESC Guidelines on the diagnosis and management of pericardial diseases. Eur Heart J. 2015;36(42):2873-4.
  70. Imazio M, Brucato A, Trinchero R, et al. Diagnosis and management of pericardial diseases. Nat Rev Cardiol. 2009;6(12):743-51.
  71. Hoit BD. Pericardial disease and pericardial tamponade. Crit Care Med. 2007;35(8 Suppl):S355-64.
  72. Wann S, Passen E. Echocardiography in pericardial disease. J Am Soc Echocardiogr. 2008;21(1):7-13.
  73. Ginghina C, Beladan CC, Iancu M, et al. Respiratory maneuvers in echocardiogra- phy: a review of clinical applications. Cardiovasc Ultrasound. 2009;7:42.
  74. Fenichel NM, Arora J, Khan R, et al. The effect of respiratory motion on the echocar-

diogram. Chest. 1976;65(5):655.

  1. Rifkin RD, Isner JM, Carter BL, et al. Combined posteroanterior subepicardial fat simulating the echocardiographic diagnosis of pericardial effusion. J Am Coll Cardiol. 1984;3(5):1333-9.
  2. Haaz WS, Mintz GS, Kotler MN, et al. Two dimensional echocardiographic recogni- tion of the descending thoracic aorta: value in differentiating pericardial from pleu- ral effusions. Am J Cardiol. 1980;46(5):739-43.
  3. Come PC, Riley MF, Fortuin NJ, et al. Echocardiographic mimicry of pericardial effusion. Am J Cardiol. 1981;47(2):365-70.
  4. Leimgruber PP, Klopfenstein HS, Wann LS, et al. The hemodynamic derangement associated with right ventricular diastolic collapse in cardiac tamponade: an exper- imental echocardiographic study. Circulation. 1983;68(3):612-20.
  5. Gaffney FA, Keller AM, Peshock RM, et al. Pathophysiologic mechanisms of cardiac tamponade and pulsus alternans shown by echocardiography. Am J Cardiol. 1984; 53(11):1662-6.
  6. Guntheroth WG. Sensitivity and specificity of echocardiographic evidence of tam- ponade: implications for ventricular interdependence and pulsus paradoxus. Pediatr Cardiol. 2007;28(5):358-62.
  7. Merce J, Sagrista-Sauleda J, Permanyer-Miralda G, et al. Correlation between clini- cal and Doppler echocardiographic findings in patients with moderate and large pericardial effusion: implications for the diagnosis of cardiac tamponade. Am Heart J. 1999;138(4 Pt 1):759-64.
  8. Armstrong WF, Schilt BF, Helper DJ, et al. Diastolic collapse of the right ventricle with cardiac tamponade: an echocardiographic study. Circulation. 1982;65(7): 1491-6.
  9. Engel PJ, Hon H, Fowler NO, et al. Echocardiographic study of right ventricular wall motion in cardiac tamponade. Am J Cardiol. 1982;50(5):1018-21.
  10. Singh S, Wann LS, Klopfenstein HS, et al. Usefulness of right ventricular diastolic collapse in diagnosing cardiac tamponade and comparison to pulsus paradoxus. Am J Cardiol. 1986;57(8):652-6.
  11. Shimony A, Fox BD, Langleben D, et al. Incidence and significance of pericardial ef- fusion in patients with pulmonary Arterial hypertension. Can J Cardiol. 2013;29(6): 678-82.
  12. Natanzon A, Kronzon I. Pericardial and pleural effusions in congestive heart failure- anatomical, pathophysiologic, and clinical considerations. Am J Med Sci. 2009;338 (3):211-6.
  13. Hoit BD, Fowler NO. Influence of acute right ventricular dysfunction on cardiac tamponade. J Am Coll Cardiol. 1991;18(7):1787-93.
  14. Santamore WP, Heckman JL, Bove AA. Right and left ventricular pressure-volume response to elevated pericardial pressure. Am Rev Respir Dis. 1986;134(1):101-7.
  15. Ceriani E, Cogliati C. Update on bedside ultrasound diagnosis of pericardial effusion. Intern Emerg Med. 2016;11(3):477-80.
  16. Mahmud E, Raisinghani A, Hassankhani A, et al. Correlation of left ventricular dia- stolic filling characteristics with right ventricular overload and pulmonary artery pressure in chronic thromboembolic pulmonary hypertension. J Am Coll Cardiol. 2002;40(2):318-24.
  17. Plotnick GD, Rubin DC, Feliciano Z, et al. Pulmonary hypertension decreases the predictive accuracy of echocardiographic clues for cardiac tamponade. Chest. 1995;107(4):919-24.
  18. Sahay S, Tonelli AR. Pericardial effusion in Pulmonary arterial hypertension. Pulm Circ. 2013;3(3):467-77.
  19. Klopfenstein HS, Cogswell TL, Bernath GA, et al. Alterations in intravascular volume affect the relation between right ventricular diastolic collapse and the hemody- namic severity of cardiac tamponade. J Am Coll Cardiol. 1985;6(5):1057-63.
  20. Antman EM, Cargill V, Grossman W. Low-pressure cardiac tamponade. Ann Intern Med. 1979;91(3):403-6.
  21. Perez-Casares A, Cesar S, Brunet-Garcia L, et al. Echocardiographic evaluation of pericardial effusion and cardiac tamponade. Front Pediatr. 2017;5:79.
  22. Kronzon I, Cohen ML, Winer HE. Diastolic atrial compression: a sensitive echocar- diographic sign of cardiac tamponade. J Am Coll Cardiol. 1983;2(4):770-5.
  23. Gillam LD, Guyer DE, Gibson TC, et al. Hydrodynamic compression of the right atrium: a new echocardiographic sign of cardiac tamponade. Circulation. 1983;68 (2):294-301.
  24. Materazzo C, Piotti P, Meazza R, et al. respiratory changes in transvalvular flow ve- locities versus two-dimensional echocardiographic findings in the diagnosis of car- diac tamponade. Ital Heart J. 2003;4(3):186-92.
  25. Fast J, Wielenga RP, Jansen E, et al. Abnormal wall movements of the right ventricle and both atria in patients with pericardial effusion as indicators of cardiac tampon- ade. Eur Heart J. 1986;7(5):431-6.
  26. Field LC, Guldan 3rd GJ, Finley AC. Echocardiography in the intensive care unit. Semin Cardiothorac Vasc Anesth. 2011;15(1-2):25-39.
  27. Elavunkal J, Bright L, Stone MB. Emergency ultrasound identification of loculated pericardial effusion: the importance of multiple cardiac views. Acad Emerg Med. 2011;18(3):e29.
  28. Kronzon I, Cohen ML, Winer HE. Cardiac tamponade by loculated pericardial hema- toma: limitations of M-mode echocardiography. J Am Coll Cardiol. 1983;1(3): 913-5.
  29. Berge KH, Lanier WL, Reeder GS. Occult cardiac tamponade detected by trans- esophageal echocardiography. Mayo Clin Proc. 1992;67(7):667-70.
  30. Fusman B, Schwinger ME, Charney R, et al. Isolated collapse of left-sided heart chambers in cardiac tamponade: demonstration by two-dimensional echocardiog- raphy. Am Heart J. 1991;121(2 Pt 1):613-6.
  31. Bommer WJ, Follette D, Pollock M, et al. Tamponade in patients undergoing cardiac surgery: a clinical-echocardiographic diagnosis. Am Heart J. 1995;130(6):1216-23.
  32. Chuttani K, Tischler MD, Pandian NG, et al. Diagnosis of cardiac tamponade after cardiac surgery: relative value of clinical, echocardiographic, and hemodynamic signs. Am Heart J. 1994;127(4 Pt 1):913-8.
  33. Chuttani K, Pandian NG, Mohanty PK, et al. Left ventricular diastolic collapse. An echocardiographic sign of regional cardiac tamponade. Circulation. 1991;83(6): 1999-2006.
  34. Aqel RA, Aljaroudi W, Hage FG, et al. Left ventricular collapse secondary to pericar- dial effusion treated with pericardicentesis and percutaneous pericardiotomy in se- vere pulmonary hypertension. Echocardiography. 2008;25(6):658-61.
  35. D’Cruz IA, Kensey K, Campbell C, et al. Two-dimensional echocardiography in car- diac tamponade occurring after cardiac surgery. J Am Coll Cardiol. 1985;5(5): 1250-2.
  36. Gowani SA, Danielian A, Villaneuva J, et al. Large pleural effusions causing cardiac tamponade: a case report and review of the literature. Conn Med. 2014;78(3): 149-52.
  37. Bilku RS, Bilku DK, Rosin MD, et al. Left ventricular diastolic collapse and late re- gional cardiac tamponade postcardiac surgery caused by large left pleural effusion. J Am Soc Echocardiogr. 2008.;21(8) p. 978 e9-11.
  38. Kopterides P, Lignos M, Papanikolaou S, et al. Pleural effusion causing cardiac tam- ponade: report of two cases and review of the literature. Heart Lung. 2006;35(1): 66-7.
  39. Kaplan LM, Epstein SK, Schwartz SL, et al. Clinical, echocardiographic, and hemody- namic evidence of cardiac tamponade caused by large pleural effusions. Am J Respir Crit Care Med. 1995;151(3 Pt 1):904-8.
  40. Kisanuki A, Shono H, Kiyonaga K, et al. Two-dimensional echocardiographic dem- onstration of left ventricular diastolic collapse due to compression by pleural effu- sion. Am Heart J. 1991;122(4 Pt 1):1173-5.
  41. Kuvin JT, Harati NA, Pandian NG, et al. Postoperative cardiac tamponade in the modern surgical era. Ann Thorac Surg. 2002;74(4):1148-53.
  42. Himelman RB, Kircher B, Rockey DC, et al. Inferior vena cava plethora with blunted respiratory response: a sensitive echocardiographic sign of cardiac tamponade. J Am Coll Cardiol. 1988;12(6):1470-7.
  43. Settle HP, Adolph RJ, Fowler NO, et al. Echocardiographic study of cardiac tampon- ade. Circulation. 1977;56(6):951-9.
  44. Walsh BM, Tobias LA. Low-pressure pericardial tamponade: case report and review of the literature. J Emerg Med. 2017;52(4):516-22.
  45. Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiogra- phy endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocar- diography. J Am Soc Echocardiogr. 2010;23(7):685-713. quiz 786-8.
  46. Leeman DE, Levine MJ, Come PC. Doppler echocardiography in cardiac tamponade: exaggerated respiratory variation in transvalvular blood flow velocity integrals. J Am Coll Cardiol. 1988;11(3):572-8.
  47. Appleton CP, Hatle LK, Popp RL. Cardiac tamponade and pericardial effusion: respi- ratory variation in transvalvular flow velocities studied by Doppler echocardiogra- phy. J Am Coll Cardiol. 1988;11(5):1020-30.
  48. Hoit BD, Gabel M, Fowler NO. Cardiac tamponade in left ventricular dysfunction. Circulation. 1990;82(4):1370-6.
  49. Imazio M, De Ferrari GM. Cardiac tamponade: an educational review. Eur Heart J Acute Cardiovasc Care. 2020..
  50. Gonzalez MS, Basnight MA, Appleton CP. Experimental pericardial effusion: rela- tion of abnormal respiratory variation in mitral flow velocity to hemodynamics and diastolic right heart collapse. J Am Coll Cardiol. 1991;17(1):239-48.
  51. Hoit BD, Shaw D. The paradoxical pulse in tamponade: mechanisms and echocardi- ographic correlates. Echocardiography. 1994;11(5):477-87.
  52. Faehnrich JA, Noone Jr RB, White WD, et al. Effects of positive-pressure ventilation, pericardial effusion, and cardiac tamponade on respiratory variation in transmitral flow velocities. J Cardiothorac Vasc Anesth. 2003;17(1):45-50.
  53. Goldstein JA. Cardiac tamponade in the interventional era: a paradigm shift in eti- ology and outcomes. Catheter Cardiovasc Interv. 2020;95(3):387-8.
  54. Soler-Soler J, Sagrista-Sauleda J, Permanyer-Miralda G. Management of pericardial effusion. Heart. 2001;86(2):235-40.
  55. Imazio M, Adler Y. Management of pericardial effusion. Eur Heart J. 2013;34(16): 1186-97.
  56. Sagrista-Sauleda J, Merce AS, Soler-Soler J. Diagnosis and management of pericar- dial effusion. World J Cardiol. 2011;3(5):135-43.
  57. Imazio M, Spodick DH, Brucato A, et al. Controversial issues in the management of pericardial diseases. Circulation. 2010;121(7):916-28.
  58. Imazio M, Mayosi BM, Brucato A, et al. Triage and management of pericardial effu- sion. J Cardiovasc Med (Hagerstown). 2010;11(12):928-35.
  59. Maisch B, Ristic A, Pankuweit S. Evaluation and management of pericardial effusion in patients with neoplastic disease. Prog Cardiovasc Dis. 2010;53(2):157-63.
  60. Imazio M, Cecchi E, Demichelis B, et al. Indicators of poor prognosis of acute peri- carditis. Circulation. 2007;115(21):2739-44.
  61. Gowda RM, Khan IA, Mehta NJ, et al. Cardiac tamponade in patients with human immunodeficiency virus disease. Angiology. 2003;54(4):469-74.
  62. Chen Y, Brennessel D, Walters J, et al. Human immunodeficiency virus-associated pericardial effusion: report of 40 cases and review of the literature. Am Heart J. 1999;137(3):516-21.
  63. Maisch B, Seferovic PM, Ristic AD, et al. Guidelines on the diagnosis and manage- ment of pericardial diseases executive summary; The Task force on the diagnosis and management of pericardial diseases of the European society of cardiology. Eur Heart J. 2004;25(7):587-610.
  64. Isselbacher EM, Cigarroa JE, Eagle KA. Cardiac tamponade complicating proximal aortic dissection. Is pericardiocentesis harmful? Circulation. 1994;90(5):2375-8.
  65. Coplan NL, Goldman B, Mechanic G, et al. Sudden Hemodynamic collapse following relief of cardiac tamponade in aortic dissection. Am Heart J. 1986;111(2):405-6.
  66. Flint N, Siegel RJ. Echo-guided pericardiocentesis: when and how should it be per- formed? Curr Cardiol Rep. 2020;22(8):71.
  67. Silvestry FE, Kerber RE, Brook MM, et al. Echocardiography-guided interventions. J Am Soc Echocardiogr. 2009;22(3):213-31. quiz 316-7.
  68. Kitamura T, Miyaji K. Emergency pericardial drainage without Aortic repair for type A intramural haematoma complicated by cardiac tamponade. Interact Cardiovasc Thorac Surg. 2021;32(6):953-5.
  69. Cruz I, Stuart B, Caldeira D, et al. Controlled pericardiocentesis in patients with car- diac tamponade complicating aortic dissection: experience of a centre without car- diothoracic surgery. Eur Heart J Acute Cardiovasc Care. 2015;4(2):124-8.
  70. Hayashi T, Tsukube T, Yamashita T, et al. Impact of controlled pericardial drainage on critical cardiac tamponade with acute type A aortic dissection. Circulation. 2012; 126(11 Suppl 1):S97-S101.
  71. Garcia-Jimenez A, Peraza Torres A, Martinez Lopez G, et al. Cardiac tamponade by aortic dissection in a hospital without cardiothoracic surgery. Chest. 1993;104 (1):290-1.
  72. Aravot DJ, Vidne BA. Prevention of hemodynamic collapse after relief of cardiac tamponade in aortic dissection. Am Heart J. 1987;113(6):1537-8.
  73. Argulian E, Halpern DG, Aziz EF, et al. Novel “CHASER” pathway for the manage- ment of pericardial disease. Crit Pathw Cardiol. 2011;10(2):57-63.
  74. Halpern DG, Argulian E, Briasoulis A, et al. A novel pericardial effusion scoring index to guide decision for drainage. Crit Pathw Cardiol. 2012;11(2):85-8.
  75. Little WC, Freeman GL. Pericardial disease. Circulation. 2006;113(12):1622-32.
  76. Luis SA, Kane GC, Luis CR, et al. Overview of optimal techniques for pericardiocen- tesis in Contemporary practice. Curr Cardiol Rep. 2020;22(8):60.
  77. Ryu AJ, Kane GC, Pislaru SV, et al. bleeding complications of ultrasound-guided pericardiocentesis in the presence of coagulopathy or thrombocytopenia. J Am Soc Echocardiogr. 2020;33(3):399-401.
  78. Iliescu C, Khair T, Marmagkiolis K, et al. Echocardiography and fluoroscopy-guided pericardiocentesis for cancer patients with cardiac tamponade and thrombocyto- penia. J Am Coll Cardiol. 2016;68(7):771-3.
  79. Warner MA, Woodrum D, Hanson A, et al. Preprocedural platelet transfusion for patients with thrombocytopenia undergoing interventional radiology procedures is not associated with reduced bleeding complications. Transfusion. 2017;57(4): 890-8.
  80. Cooper FW, Stead EA, Warren JV. The beneficial effect of intravenous infusions in acute pericardial temponade. Ann Surg. 1944;120(6):822-5.
  81. Singh V, Dwivedi SK, Chandra S, et al. Optimal fluid amount for haemodynamic benefit in cardiac tamponade. Eur Heart J Acute Cardiovasc Care. 2014;3(2): 158-64.
  82. Sagrista-Sauleda J, Angel J, Sambola A, et al. hemodynamic effects of volume ex- pansion in patients with cardiac tamponade. Circulation. 2008;117(12):1545-9.
  83. Imazio M. Volume expansion as temporizing measure for cardiac tamponade: when and how? Eur Heart J Acute Cardiovasc Care. 2014;3(2):165-6.
  84. Kerber RE, Gascho JA, Litchfield R, et al. Hemodynamic effects of volume expansion and nitroprusside compared with pericardiocentesis in patients with acute cardiac tamponade. N Engl J Med. 1982;307(15):929-31.
  85. Gascho JA, Martins JB, Marcus ML, et al. Effects of volume expansion and vasodila- tors in acute pericardial tamponade. Am J Phys. 1981;240(1):H49-53.
  86. Isaacs JP, Berglund E, Sarnoff SJ. Ventricular function. III. The pathologic physiology of acute cardiac tamponade studied by means of ventricular function curves. Am Heart J. 1954;48(1):66-76.
  87. Kearns MJ, Walley KR. Tamponade: hemodynamic and echocardiographic diagno- sis. Chest. 2018;153(5):1266-75.
  88. Martins JB, Manuel WJ, Marcus ML, et al. Comparative effects of catecholamines in cardiac tamponade: experimental and clinical studies. Am J Cardiol. 1980;46(1): 59-66.
  89. Mattila I, Takkunen O, Mattila P, et al. Cardiac tamponade and different modes of artificial ventilation. Acta Anaesthesiol Scand. 1984;28(2):236-40.
  90. Finegan RE, Schroll M, Robison S, et al. Action of pharmacologic agents in experi- mental cardiac tamponade. Am Heart J. 1971;81(2):220-6.
  91. Fowler NO, Holmes JC. Hemodynamic effects of isoproterenol and norepinephrine in acute cardiac tamponade. J Clin Invest. 1969;48(3):502-7.
  92. Treister B, Gianelly RE, Cohn KE, et al. The circulatory effects of isoproterenol, acetylstrophanthidin, and volume loading in acute pericardial tamponade. Cardiovasc Res. 1969;3(3):299-305.
  93. Millard RW, Fowler NO, Gabel M. Hemodynamic and regional blood flow distribu- tion responses to dextran, hydralazine, isoproterenol and amrinone during exper- imental cardiac tamponade. J Am Coll Cardiol. 1983;1(6):1461-70.
  94. Rowan SB, Krantz MJ. Paradoxical decrease in blood pressure after relief of cardiac tamponade: the role of Sympathetic activity. Med Sci Monit. 2006.;12(2) p. CS16-9.
  95. Moller CT, Schoonbee CG, Rosendorff C. Haemodynamics of cardiac tamponade during various modes of ventilation. Br J Anaesth. 1979;51(5):409-15.
  96. Stanley TH, Weidauer HE. Anesthesia for the patient with cardiac tamponade. Anesth Analg. 1973;52(1):110-4.
  97. Lake CL. Anesthesia and pericardial disease. Anesth Analg. 1983;62(4):431-43.
  98. Webster JA, Self DD. Anesthesia for pericardial window in a pregnant patient with cardiac tamponade and Mediastinal mass. Can J Anaesth. 2003;50(8):815-8.
  99. Aye T, Milne B. Ketamine anesthesia for pericardial window in a patient with peri- cardial tamponade and severe COPD. Can J Anaesth. 2002;49(3):283-6.
  100. Koller ME, Smith RB, Sjostrand U, et al. Effects of hypo-, normo-, and hypercarbia in dogs with acute cardiac tamponade. Anesth Analg. 1983;62(2):181-5.
  101. Breen PH, MacVay MA. Pericardial tamponade: a case for awake endotracheal intu- bation. Anesth Analg. 1996;83(3):658.
  102. Tsang TS, Enriquez-Sarano M, Freeman WK, et al. Consecutive 1127 therapeutic echocardiographically guided pericardiocenteses: clinical profile, practice patterns, and outcomes spanning 21 years. Mayo Clin Proc. 2002;77(5):429-36.
  103. Law MA, Borasino S, Kalra Y, et al. Novel, long-axis in-plane ultrasound-guided pericardiocentesis for postoperative pericardial effusion drainage. Pediatr Cardiol. 2016;37(7):1328-33.
  104. Cho BC, Kang SM, Kim DH, et al. Clinical and echocardiographic characteristics of pericardial effusion in patients who underwent echocardiographically guided peri- cardiocentesis: Yonsei Cardiovascular Center experience, 1993-2003. Yonsei Med J. 2004;45(3):462-8.
  105. Hanaki Y, Kamiya H, Todoroki H, et al. New two-dimensional, echocardiographically directed pericardiocentesis in cardiac tamponade. Crit Care Med. 1990;18(7):750-3.
  106. Sinnaeve PR, Adriaenssens T. A contemporary look at pericardiocentesis. Trends Cardiovasc Med. 2019;29(7):375-83.
  107. Stolz L, Situ-LaCasse E, Acuna J, et al. What is the ideal approach for emergent peri- cardiocentesis using point-of-care ultrasound guidance? World J Emerg Med. 2021;12(3):169-73.
  108. Flower L, Olusanya O, Madhivathanan PR. The use of critical care echocardiography in peri-arrest and Cardiac arrest scenarios: Pros, cons and what the future holds. J Intensive Care Soc. 2021;22(3):230-40.
  109. Akyuz S, Zengin A, Arugaslan E, et al. Echo-guided pericardiocentesis in patients with clinically significant pericardial effusion. Outcomes over a 10-year period. Herz. 2015;40(Suppl. 2):153-9.
  110. Callahan JA, Seward JB, Nishimura RA, et al. Two-dimensional echocardiographically guided pericardiocentesis: experience in 117 consecutive patients. Am J Cardiol. 1985;55(4):476-9.
  111. Maggiolini S, Gentile G, Farina A, et al. Safety, efficacy, and complications of pericar- diocentesis by real-time echo-monitored procedure. Am J Cardiol. 2016;117(8): 1369-74.
  112. Duvernoy O, Borowiec J, Helmius G, et al. Complications of percutaneous pericar- diocentesis under fluoroscopic guidance. Acta Radiol. 1992;33(4):309-13.
  113. Tsang TS, Barnes ME, Hayes SN, et al. Clinical and echocardiographic characteristics

of significant pericardial effusions following cardiothoracic surgery and outcomes of echo-guided pericardiocentesis for management: Mayo Clinic experience, 1979-1998. Chest. 1999;116(2):322-31.

  1. Bastian A, Meissner A, Lins M, et al. Pericardiocentesis: differential aspects of a common procedure. Intensive Care Med. 2000;26(5):572-6.
  2. Ho MY, Wang JL, Lin YS, et al. Pericardiocentesis adverse event risk factors: a na- tionwide population-based cohort study. Cardiology. 2015;130(1):37-45.
  3. Wong B, Murphy J, Chang CJ, et al. The risk of pericardiocentesis. Am J Cardiol. 1979;44(6):1110-4.
  4. Bishop Jr LH, Estes Jr EH, McIntosh HD. The electrocardiogram as a safeguard in pericardiocentesis. J Am Med Assoc. 1956;162(4):264-5.
  5. Tsang TS, Freeman WK, Sinak LJ, et al. Echocardiographically guided pericardiocen- tesis: evolution and state-of-the-art technique. Mayo Clin Proc. 1998;73(7): 647-52.
  6. Callahan JA, Seward JB, Tajik AJ, et al. Pericardiocentesis assisted by two- dimensional echocardiography. J Thorac Cardiovasc Surg. 1983;85(6):877-9.
  7. Loukas M, Walters A, Boon JM, et al. Pericardiocentesis: a clinical anatomy review. Clin Anat. 2012;25(7):872-81.
  8. Stolz LA, Stolz U, Howe C, et al. Ultrasound-guided Peripheral venous access: a meta-analysis and systematic review. J Vasc Access. 2015;16(4):321-6.
  9. Egan G, Healy D, O’Neill H, et al. Ultrasound guidance for difficult peripheral venous access: systematic review and meta-analysis. Emerg Med J. 2013;30(7):521-6.
  10. Saugel B, Scheeren TWL, Teboul JL. Ultrasound-guided central venous catheter placement: a structured review and recommendations for clinical practice. Crit Care. 2017;21(1):225.
  11. Gottlieb M, Alerhand S. Ultrasound should be considered for all arthrocentesis. Ann

Emerg Med. 2020;75(2):261-2.

  1. Gottlieb M, Avila J, Chottiner M, et al. Point-of-care ultrasonography for the diagno- sis of skin and soft tissue abscesses: a systematic review and meta-analysis. Ann Emerg Med. 2020;76(1):67-77.
  2. Ainsworth CD, Salehian O. Echo-guided pericardiocentesis: let the bubbles show the way. Circulation. 2011;123(4):e210-1.
  3. Chiang HT, Lin M. Pericardiocentesis guided by two-dimensional contrast echocar- diography. Echocardiography. 1993;10(5):465-9.
  4. Spodick DH. Macrophysiology, microphysiology, and anatomy of the pericardium: a synopsis. Am Heart J. 1992;124(4):1046-51.
  5. Spodick DH, Worcester. Bloody pericardial effusion: clinically significant without intrinsic Diagnostic specificity. Chest. 1999;116(6):1506-7.
  6. Pradhan R, Okabe T, Yoshida K, et al. Patient characteristics and predictors of mor- tality associated with pericardial decompression syndrome: a comprehensive anal- ysis of published cases. Eur Heart J Acute Cardiovasc Care. 2015;4(2):113-20.
  7. Imazio M. Pericardial decompression syndrome: a rare but potentially fatal compli- cation of pericardial drainage to be recognized and prevented. Eur Heart J Acute Cardiovasc Care. 2015;4(2):121-3.
  8. Angouras DC, Dosios T. Pericardial decompression syndrome: a term for a well- defined but rather underreported complication of pericardial drainage. Ann Thorac Surg. 2010;89(5):1702-3. author reply 1703.
  9. Karamichalis JM, Gursky A, Valaulikar G, et al. acute pulmonary edema after peri- cardial drainage for cardiac tamponade. Ann Thorac Surg. 2009;88(2):675-7.
  10. Ligero C, Leta R, Bayes-Genis A. Transient biventricular dysfunction following peri- cardiocentesis. Eur J Heart Fail. 2006;8(1):102-4.
  11. Hemnes AR, Gaine SP, Wiener CM. Poor outcomes associated with drainage of peri- cardial effusions in patients with pulmonary arterial hypertension. South Med J. 2008;101(5):490-4.
  12. Kopecky SL, Callahan JA, Tajik AJ, et al. Percutaneous pericardial catheter drainage: report of 42 consecutive cases. Am J Cardiol. 1986;58(7):633-5.
  13. Rafique AM, Patel N, Biner S, et al. Frequency of recurrence of pericardial tampon- ade in patients with extended versus nonextended pericardial catheter drainage. Am J Cardiol. 2011;108(12):1820-5.
  14. Buchanan CL, Sullivan VV, Lampman R, et al. Pericardiocentesis with extended catheter drainage: an effective therapy. Ann Thorac Surg. 2003;76(3):817-20.