The effect of revascularization procedures on myocardial infarction incidence rates and time trends: The MONICA-Brianza and CAMUNI MI registries in Northern Italy

Purpose: Clinical guidelines recommend early reperfusion treatment in myocardial infarction (MI) patients to reduce the cardiac damage. Epidemiologic definitions of MI are often based on the evolution of the cardiac lesion. We aim to study the effect of treatment on the estimates of rates and 20-year time trends of MI. Methods: A Multinational Monitoring of trends and determinants in Cardiovascular disease (MONICA) register was active between 1985 and 2004 to survey 35- to 64-year-old residents in Brianza, Northern Italy. To the well-established MONICA definite MI, we added the MONICA possible nonfatal MI receiving either myocardial revascularization or thrombolysis within 24 hours from onset. The average annual relative changes in incidence rate and 28-day case fatality percentage were estimated from log-linear models. Results: In our population, characterized by a monotonic decrease in coronary heart disease (CHD) mortality rates, the incident rate for the standard MONICA definite MI decreased yearly by 3% in both gender groups. The addition of selected revascularizations halved the downward trends in incidence rate in men and women; conversely, the decline in 28-day case fatality became steeper. Conclusions: From an epidemiologic perspective, the increasing proportion of acute events efficaciously treated with revascularization therapy affects the estimate and the interpretation of time trends in MI incidence and CHD mortality.