The obesity paradox and myocardial infarct size

Obese subjects have a risk of death from cardiovascular disease higher than those with normal body weight. Obese patients, however, have a better outcome when undergoing coronary revascularisation, and when suffering from heart failure or chronic kidney disease. The term 'obesity paradox' underlines the divergence between increased risk and better outcome in sick obese patients. We tested the hypothesis that the obesity paradox could also occur in myocardial infarction.

A group of 89 patients (mean age 62 +/- 11 years) with previous myocardial infarction (Q-wave in 72 patients) underwent contrast-enhanced MRI.

Areas of delayed contrast enhancement (which reflects myocardial necrosis) were present in 15 +/- 9% of left ventricular myocardium. Infarct size was not influenced by patient age, gender, history of arterial hypertension, hypercholesterolaemia, hypertriglyceridaemia nor tobacco smoking. Infarct size, however, was larger in insulin-dependent diabetic patients (P = 0.06) and in those with a family history of premature coronary artery disease (P = 0.06). Surprisingly, infarct size was smaller in obese patients (11 +/- 4% of left ventricular myocardium) than in those with normal body weight (16 +/- 9% of left ventricular myocardium, P = 0.03). Insulin-dependent diabetes mellitus, obesity and family history of coronary artery disease were the only independent predictors of infarct size at multiple linear regression analysis.

Owing to its limitations (small sample size and exclusion of extremely obese patients), this study generates a working hypothesis, which should be tested in larger prospective studies, that the obesity paradox could also occur in myocardial infarction.