Lack of association between left bundle-branch block and acute myocardial infarction in symptomatic ED patients☆
Received 9 May 2008; received in revised form 18 June 2008; accepted 16 July 2008.
Abstract
Objective
Guidelines recommend treating patients with a new or presumed new left bundle-branch block (LBBB) similar to those with an acute ST-segment elevation myocardial infarction. It is often unclear which emergency department (ED) patients with potentially ischemic symptoms actually have an acute myocardial infarction (AMI), even in the setting of LBBB. Our null hypothesis was that in ED patients with potential AMI, the presence of a new or presumed new LBBB would not predict an increased likelihood of AMI.
Methods
This was an observational cohort study. Patients older than 30 years who presented with chest pain or other ischemic equivalent and had an electrocardiogram (ECG) to evaluate potential acute coronary syndrome (ACS) were enrolled. Data collected include demographics, history, ECG, and cardiac markers. Electrocardiograms were classified according to the standardized guidelines, including LBBB not known to be old (new or presumed new LBBB), LBBB known to be old, or no LBBB. The hospital course was followed, and 30-day follow-up was performed on all patients. Our main outcome was AMI.
Results
There were 7937 visits (mean age, 54.3 ± 15 years, 57% female, 68% black): 55 had new or presumed new LBBB, 136 had old LBBB, and 7746 had no LBBB. The rate of AMI was not significantly different between the 3 groups (7.3% vs 5.2% vs 6.1%; P = .75). Revascularization (7.8% vs old 5.2% vs 4.3%; P = .04) and coronary artery disease were more common in patients with new or presumed new LBBB (19.2% vs 11.9% vs 10.1%; P = .0004).
Conclusions
Despite guideline recommendations that patients with potential ACS and new or presumed new LBBB should be treated similar to STEMI, ED patients with a new or presumed new LBBB are not at increased risk of AMI. In fact, the presence of LBBB, whether new or old, did not predict AMI. Caution should be used in applying recommendations derived from patients with definite AMI to ED patients with potential ACS that may or may not be sustaining an AMI.
aDepartment of Emergency Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA 19104-4283, USA
bDivision of Emergency Services, Department of Medicine, San Francisco General Hospital, University of California–San Francisco, San Francisco, CA 94143, USA
cDepartment of Emergency Medicine, University of Colorado Health Sciences Center, Denver, CO 80045, USA
Corresponding author. Department of Emergency Medicine, University of Pennsylvania. Philadelphia, PA 19104-4283, USA. Tel.: +1 215 421 4120.
☆ Presented at the Society for Academic Emergency Medicine annual meeting, Washington, DC, May 2008.
ABSTRACT