Received on May 11, 2006
Accepted on August 17, 2006

Evidence-Based Laboratory Medicine and Test Utilization

Health Outcomes Categorized by Current and Previous Definitions of Acute Myocardial Infarction in an Unselected Cohort of Troponin-Naïve Emergency Department Patients

¹ Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
² Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
³ Department of Pathology, Women and Infants Hospital of Rhode Island, Providence, RI
⁴ Institute for Clinical Evaluative Sciences, University of Toronto, Toronto, ON, Canada
⁵ Cardiovascular Division and Division of Laboratory Medicine, Mayo Clinic, Rochester, MN

^* To whom correspondence should be addressed. E-mail: kavsakp{at}mcmaster.ca.

Background: New European Society of Cardiology/American College of Cardiology (ESC/ACC) criteria defining acute myocardial infarction (AMI) rely more substantially on measurements of cardiac troponin (cTn). We used the ESC/ACC AMI definition with cTnI concentrations to retrospectively reclassified a population with AMI classified by the WHO definition and compared health outcomes that were based on the WHO definition and occurred before the use of cTn biomarkers.

Methods: For 448 patients who presented to the emergency department with symptoms suggestive of cardiac ischemia in 1996, we obtained data for all-cause mortality and recurrent AMI for up to 1 year after the initial presentation. We performed retrospective analysis of the patients' frozen plasma samples to measure cTnI (AccuTnI^®, Beckman Coulter).

Results: At 30, 120, and 360 days, the risk for AMI/death in patients positive for AMI by only the ESC/ACC criteria was significantly lower than the risk in patients positive by both ESC/ACC and WHO criteria, and significantly higher than in patients negative according to both criteria. In a separate analysis, patients with a peak cTnI 0.10 µg/L were at greater risk for AMI/death than patients with cTnI concentrations of 0.04-0.10 µg/L. Patients negative by both definitions or with peak cTnI concentrations <0.04 µg/L had the highest event-free survival rates (92% and 94%, respectively) at 1 year.

Conclusion: In a troponin-naïve population, patients classified as positive for AMI by only the ESC/ACC criteria have a prognosis that appears to be intermediate between those classified positive by both the WHO and ESC/ACC definitions and those who meet neither criteria.