Myocardial infarction and coronary pathology in severely obese people examined at autopsy

To find out the severity of coronary atherosclerosis and its relationship to body structure and adiposity in severely obese people with body mass index (BMI) > or = 35.0 kg/m(2) and to examine the incidence and characteristic features of myocardial infarction and other fatal coronary events in this population.

Autopsy reports were analyzed, including data on age, height, weight, abdominal subcutaneous fat thickness, heart weight, coronary atherosclerosis, histopathology and toxicology. Myocardial collagen and arteriolar structure were examined by computerized image analysis.

Forensic autopsy cases (n=166) with a BMI > or = 35.0 kg/m(2) examined in 1992-1998 were collected from the files of the Department of Forensic Medicine, University of Oulu, Finland.

In a large number of the severely obese individuals, the coronary arteries were either lesion-free or only fatty streaks were observed (38% of men, 44% of women) and coronary thrombosis was rare (3.8% of men and 1.6% of women). Cardiac causes of death predominated, cardiomyopathy being the commonest. Myocardial infarction was the immediate cause of death in 14.4% of men and 12.9% of the women, and it was associated with increased heart size in men. Coronary atherosclerosis without any infarction had been determined as the cause of death in 8.6% of the men and 8.1% of the women. Abdominal subcutaneous fat thickness had a significant negative association with the severity of coronary atherosclerosis in the women, and a decrease in the arteriolar media/lumen ratio with increasing BMI was observed in the men.

A considerable number of severely obese people have only fatty streaks and no marked stenosis in their coronary arteries, even at an advanced age. The large amounts of subcutaneous adipose tissue in obese women may provide some protection against coronary lesion development, which could be an estrogen effect. Myocardial infarction in severely obese men is associated with cardiac hypertrophy. The significance of the BMI-related dilatation of the myocardial arterioles in men and its relationship to a remodelling of the epicardial arteries will require future investigations.