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 intervention (pPCI) for STEMI and cardiac magnetic resonance was performed within 5-7 days. Patients were classified as normal weight (18.5 ≤BMI <24.0 kg/m), overweight (24.0 ≤BMI <28.0 kg/m), or obese (BMI ≥28 kg/m).

Results: Among 225 patients undergoing pPCI, 67 (30.00%) were normal weight, 113 (50.22%) were overweight, and 45 (20.00%) were obese. BMI ≥28 kg/m 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 (β = -0.252, 95% CI -20.298- -3.244, p = 0.007) and AAR, % LV mass (β = -0.331, 95% CI -0.211- -0.062, p < 0.001) than normal weight patients.

Conclusion: Obesity (BMI ≥28 kg/m) is independently associated with lower risks of MVO and a smaller AAR, % LV mass than normal weight patients among subjects undergoing pPCI for STEMI.