Effect of Low Body Mass Index on the Clinical Outcomes of Japanese Patients With Acute Myocardial Infarction　- Results From the Prospective Japan Acute Myocardial Infarction Registry (JAMIR).

BACKGROUND: Acute myocardial infarction (AMI) patients with low body mass index (BMI) exhibit worse clinical outcomes than obese patients; however, to our knowledge, no prospective, nationwide study has assessed the effect of BMI on the clinical outcomes of AMI patients.Methods and Results:In this multi-center, prospective, nationwide Japanese trial, 2,373 AMI patients who underwent emergent percutaneous coronary intervention within 12 h of onset from the Japanese AMI Registry (JAMIR) were identified. Patients were divided into the following 4 groups based on their BMI at admission: Q1 group (BMI <18.5 kg/m2, n=133), Q2 group (18.5≤BMI<25.0 kg/m2, n=1,424), Q3 group (25.0≤BMI<30.0 kg/m2, n=672), and Q4 group (30.0 kg/m2≤BMI, n=144). The primary endpoint was all-cause death, and the secondary endpoint was a composite of cardiovascular death, non-fatal myocardial infarction (MI), and non-fatal stroke. The median follow-up period was 358 days. Q1 patients were older and had lower prevalence of coronary risk factors. Q1 patients also had higher all-cause mortality and higher incidence of secondary endpoints than normal-weight or obese AMI patients. Multivariate analysis showed that low BMI (Q1 group) was an independent predictor for primary endpoint. CONCLUSIONS: AMI patients with low BMI had fewer coronary risk factors but worse clinical outcomes than normal-weight or obese patients.