Impact of Obesity on Microvascular Obstruction and Area at Risk in Patients after ST-Segment-Elevation Myocardial Infarction: A Magnetic Resonance Imaging Study.

Background: Better survival for overweight and obese patients after ST-segment elevation myocardial infarction (STEMI) has been demonstrated. The association between body mass index (BMI), microvascular obstruction (MVO), and area at risk (AAR) after STEMI was evaluated. Methods: A prospective observational study was performed to enrolled patients undergoing primary percutaneous coronary inter-vention (pPCI) for STEMI and cardiac magnetic resonance was performed within 5-7 days. Patients were classified as normal weight (18.5 & LE;BMI < 24.0 kg/m2), overweight (24.0 & LE;BMI < 28.0 kg/m2), or obese (BMI 228 kg/m2). Results: Among 225 patients undergoing pPCI, 67 (30.00%) were normal weight, 113 (50.22%) were overweight, and 45 (20.00%) were obese. BMI 228 kg/m2 was significantly associated with less risk of MVO when compared with a normal BMI after multivariable adjustment (overweight: HR 0.29, 95% CI 0.13-0.68, p = 0.004). Compared with normal weight patients, obese and overweight patients tend to have larger hearts (greater left ventricular end-diastolic volume [LVEDV] and left ventricular [LV] mass). In adjusted analysis, increased BMI was significantly associated with a smaller AAR. In addition, obese patients had a smaller AAR ([3 = -0.252, 95% CI -20.298--3.244, p = 0.007) and AAR, % LV mass ([3 = -0.331, 95% CI -0.211--0.062, p < 0.001) than normal weight patients. Conclusion: Obesity (BMI 228 kg/m2) is independently associated with lower risks of MVO and a smaller AAR, % LV mass than normal weight patients among subjects undergoing pPCI for STEMI.