New myocardial infarction definition affects incidence, mortality, hospitalization rates and prognosis.

Aims: To analyse differences in myocardial infarction incidence, mortality and hospitalization rates, 28-day case-fatality and two-year prognosis using two myocardial infarction case definitions: the classical World Health Organization definition (1994) and the European Society of Cardiology/American College of Cardiology definition (2000), which added cardiac troponin as a diagnostic biomarker.

Design: Population-based cohort of 4170 consecutive myocardial infarction patients aged 35-74 years from Girona (Spain) recruited between 2002 and 2009.

Methods: Incidence, mortality rates standardized to the European population and 28-day case-fatality were calculated. To estimate the association between case definition and prognosis, Cox models were fitted.

Results: Use of the 2000 European Society of Cardiology/American College of Cardiology definition significantly increased myocardial infarction incidence per 100,000 population (238.3 vs. 274.5 in men and 54.1 vs. 69.7 in women). Applying this definition decreased the 28-day case-fatality rate from 26.9% to 23.4% in men, and from 31.0% to 24.1% in women. In the acute phase, patients diagnosed only by increased troponins were significantly less treated with thrombolysis (34.4% vs. 2.0%), angiotensin-converting enzyme inhibitors (71.7% vs. 65.0%) and percutaneous coronary intervention (41.1% vs. 31.7%). Case-fatality at 28 days was significantly better in cases diagnosed only by troponin increase (0.2 % vs. 9.7%), but two-year cardiovascular mortality was higher (7.5% vs. 3.7%).

Conclusions: Inclusion of cardiac troponins in myocardial infarction diagnosis increased annual incidence and decreased case-fatality. Diagnosis based only on increased troponins was associated with worse outcome. This group of patients at high risk of death should receive aggressive secondary prevention therapy.