Unrecognized myocardial infarction: five-year incidence, mortality, and risk factors.

In the course of 5 years, 9509 healthy adult subjects had an average annual incidence of 3.6 unrecognized infarcts per 1000 persons and 5.3 clinical ones per 1000 persons. A multivariate analysis showed that the most significant risk factors were age, left axis deviation, left ventricular hypertrophy, cigarette smoking, systolic or diastolic blood pressure, and peripheral vascular disease. Some of the known risk factors of clinical infarct, or angina pectoris or both, such as cholesterol, diabetes, anxiety, and psychosocial problems, do not play a significant role in unrecognized infarcts. Subjects whose electrocardiograms were initially interpreted by cardiologists as noninfarcts but by the computer as infarcts developed a high rate of unrecognized infarcts in the subsequent 5 years. A 7-year mortality follow-up showed a markedly higher rate among the unrecognized infarct group as compared with the noninfarct population, but significantly lower than those who developed a clinical infarct.