National Impact of the Troponin Diagnostic Standard on the Prevalence and Prognosis of Acute Myocardial Infarction in Older Persons

BACKGROUND: Consensus guidelines from the American College of Cardiology, the American Heart Association, and the European Society of Cardiology have made cardiac troponin central to the diagnosis of acute myocardial infarction (AMI). Although multiple studies have shown that the troponin diagnostic standard facilitates the identification of new AMI cases in the general population, and that elevations of troponin are associated with poor prognosis, questions remain regarding the impact of the troponin diagnostic standard on the prevalence and prognosis of AMI in older persons. METHODS: Nationwide samples of eligible Medicare beneficiaries aged > or =65 years who were hospitalized (n = 71,120) with a primary discharge diagnosis of AMI between April 1998 and March 1999 (baseline cohort) or July 2000 and June 2001 (remeasurement cohort) were evaluated. The analysis was restricted to patients with clinically confirmed AMI who underwent testing for both CK-MB and troponin. RESULTS: The majority of these patients (71.0%) were both CK-MB- and troponin-positive, but 17.8% were diagnosed with AMI based solely on positive troponin levels. Combining the CK-MB or both groups as a reference and troponin as a design variable to fit Cox proportional hazards models, troponin-only-positive patients had an unadjusted risk ratio (RR) of 1.14 (95% confidence interval [CI], 1.07-1.22) for the 30-day mortality and RR of 1.09 (95% CI, 1.03-1.15) for the 3-year mortality. However, after adjusting for patient demographics, clinical characteristics, physician specialties, and hospitals characteristics, troponin-only-positive patients had similar risk for early- and long-term mortality as the other 2 groups; the risk-adjusted RR for 30-day mortality was 0.96 (95% CI, 0.89-1.02) and for 3-year mortality was 0.95 (95% CI, 0.90-1.00). CONCLUSION: The widespread application of cardiac troponins results in a substantial increase in AMI diagnoses in older patients. Contrary to the prevailing wisdom that troponin-only-positive AMIs are smaller "infarctlets" and likely to have better prognosis, older persons with troponin-only AMIs are at similar risk for early and long-term mortality compared with those with CK-MB-positive AMIs. Therefore, nationwide efforts should focus on the unique characteristics of this emerging patient population so as to improve quality of care provided to this high-risk cohort of patients with AMI.