Impact of overweight on myocardial infarct size in patients undergoing primary percutaneous coronary intervention: A magnetic resonance imaging study

Objective: Although obesity is a risk factor for cardiovascular disease and mortality, several studies have reported that patients with obesity who have suffered acute myocardial infarction or have undergone percutaneous coronary intervention (PCI) have better clinical outcomes than their normal weight counterparts. We evaluated the impact of overweight on myocardial infarct size in patients undergoing primary PCI for ST-segment elevation myocardial infarction (STEMI). Methods: We performed contrast-enhanced magnetic resonance imaging on 193 patients undergoing primary PCI for STEMI. Infarct size was measured with delayed-enhancement imaging and the area at risk was quantified on T2-weighted images. Results: Baseline characteristics and angiographic findings were not significantly different between the normal weight group (body mass index [BMI]<25kg/m², n=110) and the overweight group (BMI≥25kg/m², n=83). The median percent infarct volume and area at risk were significantly smaller in the overweight group than the normal weight group (17.9% [9.0-24.9%] vs. 20.8% [11.4-33.1%], p=0.04 and 29.4% [20.5-37.6%] vs. 36.0% [25.7-49.6%], p<0.01, respectively). However, the myocardial salvage index was not different between the 2 groups (overweight group vs. normal weight group, 43.2% vs. 39.2%, p=0.69). BMI≥25kg/m² was an independent predictor of smaller infarct size in multivariate analysis (Odds ratio 0.51, 95% Confidence interval 0.27-0.97, p=0.039). Conclusion: Overweight (BMI≥25kg/m²) is independently associated with smaller infarct size in patients undergoing primary PCI for STEMI.