Outcomes associated with small changes in normal-range cardiac markers
Received 10 June 2009; received in revised form 22 July 2009; accepted 18 August 2009. published online 10 March 2010. Corrected Proof
Abstract
Introduction
Troponin concentrations rising above an institutional cutpoint are used to define acute myocardial necrosis, yet it is uncertain what outcomes are associated with fluctuations in troponin that do not exceed this level. We evaluate the association between troponin fluctuations below an institutional upper limit of normal and acute coronary syndrome (ACS).
Materials and methods
This was a post hoc analysis of the Internet tracking registry of ACS (i*trACS), which describes patients presenting to emergency departments (EDs) with suspected ACS across the spectrum of risk. Patients were included in this registry if they were at least 18 years old and had suspected ACS at the time of their ED visit. Inclusions in this analysis required that patients had at least 1 cardiac marker (creatine kinase-MB [CK-MB], troponin T, or troponin I) drawn twice within 6 hours of presentation, with both measures being below the institution's upper limit of normal. A marker change was defined as either an increase or decrease that exceeded 15% of the institutional upper limit of normal. Acute coronary syndrome was defined as a positive stress test, documented myocardial infarction, coronary revascularization, or death within 30 days of their ED admission.
Results
Of 17 713 patient visits, 2162 met inclusion and exclusion criteria. There were 1872 patient visits with 2 troponin results and 1312 with 2 CK-MB results. Patient visits with increasing troponin had increased odds of ACS compared with those with stable troponin levels (odds ratio, 3.6; 95% confidence interval, 1.4-9.2). Changing CK-MB and decreasing troponin were not associated with increased odds of ACS.
Conclusions
Small increases in troponin concentration below the upper limit of normal are associated with increased odds of ACS.
ABSTRACT