Objectives: To examine, whether the acute myocardial infarctions (AMIs) are becoming smaller.
Design: Analysis of electrocardiogram (ECG) and enzyme findings of community-based AMI registers in three geographical areas of Finland during the 8-year period 1983-90.
Setting: In the FINMONICA AMI Register, all suspected coronary events in persons aged 25-64 years have been registered since 1983 according to the protocol of the WHO MONICA project in the provinces of North Karelia and Kuopio in eastern Finland and Turku/Loimaa area in south-western Finland.
Subjects: Each consecutive case of suspected AMI originating from the monitored populations. During the study period, 11,487 definite or possible AMIs were registered.
Main outcome measures: Trends in ECG findings classified as definite or probable, and trends in enzyme findings classified as abnormal or equivocal.
Results: Of the registered AMIs, 8439 (73.5%) reached the hospital alive and survived > or = 24 h from the beginning of the symptoms. They were included in the analyses of this report and divided further, to first ever AMIs (n = 5392) and to recurrent AMIs (3047). During the study period, the proportion of ECG findings classified as definite on the basis of the serial Minnesota coding declined in men 3.1% year-1 (P < 0.0001) on average for first AMIs and 1.9% year-1 (P = 0.004) for recurrent AMIs. In women, the corresponding declines were 1.9% year-1 (P = 0.007) and 1.6% year-1 (P = 0.02), respectively. Also, the proportion of enzymes classified as abnormal declined amongst men 2.2% year (P < 0.0001) for first AMIs and 2.8% year-1 (P < 0.0001) for recurrent AMIs. In women, the corresponding declines for abnormal enzymes was 1.3% year-1 (P = 0.13) and 3.0% year-1 (P = 0.02). These findings were consistent in all three areas with different registration teams and different laboratories. The proportion of definite ECG findings amongst patients hospitalized for AMI declined almost by half and the proportion of abnormal enzyme findings declined almost by one-third during the study period.
Conclusions: Our findings are compatible with the clinical observation that the hospitalized AMIs are becoming smaller. The timing and magnitude of the changes suggest that they are mainly caused by decreased risk-factor levels in the population. Improved treatment of coronary heart disease and changed hospital admission policy are likely to be contributing factors.