Obesity paradox in Korean patients undergoing primary percutaneous coronary intervention in ST-segment elevation myocardial infarction

The effect of body mass index (BMI) on outcomes after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) is not well known. In patients registered in the Korean Acute Myocardial Infarction Registry (KAMIR) between November 2005 and November 2007, 3824 STEMI patients who arrived at hospital within 12 h after onset of chest pain and underwent primary PCI were analyzed, and divided into four groups according to their BMI: underweight (BMI < 18.5 kg/m², n = 129); normal weight (18.5 ≤ BMI < 23.0 kg/m², n = 1253); overweight (23.0 ≤ BMI < 27.5 kg/m², n = 1959); and obese (BMI ≥ 27.5 kg/m², n = 483). In-hospital mortality, revascularization in 1 year, mortality in 1 year, and overall mortality were compared between groups. Overweight and obese group were significantly younger, had normal left ventricular ejection fraction, and were more likely to be men with a higher incidence of hypertension, diabetes, and hyperlipidemia. There were no significant differences in symptom-to-door time and door-to-balloon time between groups. Obese patients had significantly lower in-hospital and overall mortalities. Major adverse cardiac events showed a bimodal pattern. Obese STEMI patients treated with primary PCI were associated with lower mortality, which may be explained by better use of medical treatment, hemodynamic stability, and younger age.