OBJECTIVES - The aim of this study was to examine the association between body mass index (BMI), infarct size (IS) and clinical outcomes.

BACKGROUND - The association between obesity, IS, and prognosis in patients undergoing primary percutaneous coronary intervention (pPCI) for ST-segment elevation myocardial infarction is incompletely understood.

METHODS - An individual patient-data pooled analysis was performed from 6 randomized trials of patients undergoing pPCI for ST-segment elevation myocardial infarction in which IS (percentage left ventricular mass) was assessed within 1 month (median 4 days) after randomization using either cardiac magnetic resonance (5 studies) or 99mTc sestamibi single-photon emission computed tomography (1 study). Patients were classified as normal weight (BMI <25 kg/m2), overweight (25 kg/m2 ≤BMI <30 kg/m2), or obese (BMI ≥30 kg/m2). The multivariable models were adjusted for age, sex, hypertension, hyperlipidemia, current smoking, left main or left anterior descending coronary artery infarct, baseline TIMI (Thrombolysis In Myocardial Infarction) flow grade 0 or 1, prior myocardial infarction, symptom–to–first device time, and study. 

RESULTS -  Among 2,238 patients undergoing pPCI, 644 (29%) were normal weight, 1,008 (45%) were overweight, and 586 (26%) were obese. BMI was not significantly associated with IS, microvascular obstruction, or left ventricular ejection fraction in adjusted or unadjusted analysis. BMI was also not associated with the 1-year composite risk for death or heart failure hospitalization (adjusted hazard ratio: 1.21 [95% confidence interval: 0.74 to 1.71] for overweight vs. normal [p = 0.59]; adjusted hazard ratio: 1.21 [95% confidence interval 0.74 to 1.97] for obese vs. normal [p = 0.45]) or for death or heart failure hospitalization separately. Results were consistent when BMI was modeled as a continuous variable.