THE "SILENT CORONARY": THE FREQUENCY AND CLINICAL CHARACTERISTICS OF UNRECOGNIZED MYOCARDIAL INFARCTION IN THE FRAMINGHAM STUDY

Abstract

The incidence of painless myocardial infarction was studied in a group of 5209 subjects between 30 and 59 years of age through periodic cardiovascular examinations at the Heart Disease Epidemiology Study, Framingham, Massachusetts. All of the subjects had complete cardiovascular examinations every 2 years including a 12-lead ecg. The usual criteria for myocardial infarction on ecg were used. A myocardial infarction was considered as recognized if in the course of an acute interim illness the subject consulted a physician who established the diagnosis. Otherwise it was considered as unrecognized. Between June, 1950 and April, 1957, 49 subjects sustained recognized myocardial infarctions and 15 subjects sustained unrecognized infarctions. Among the unrecognized group, 8 of the 15 were completely asymptomatic. Further analysis revealed that the prevalence of angina pectoris following myocardial infarction was less common in the clinically unrecognized group and that most of the "silent" coronaries were anteroseptal or posterior.