Aims: The aim of this study is to evaluate the impact of metabolic syndrome (MetS) on clinical severity and long-term prognosis in patients with myocardial infarction with ST-segment elevation (STEMI). Methods: We examined 507 patients with STEMI, who were admitted for primary percutaneous coronary intervention classified according to the presence of MetS using American Heart Association and the National Heart, Lung, and Blood Institute definition. After applying these criteria, the patients were categorized into groups as patients with MetS and without MetS. We compared baseline characteristics, clinical findings, and outcomes between these groups. During the 48-month follow-up, we collected data about major adverse cardiac events (MACE) and mortality. Results: The MetS group comprised 217 patients with MetS (mean age = 60.71 ± 11.52 years; 59 females), while the control group comprised 290 subjects (mean age = 57.50 ± 10.95 years; 54 females). The patients with and without MetS had similar parameters of clinical severity of STEMI but differed in severe coronary artery disease. During the follow-up period, a significantly higher percentage of myocardial infarction (6.91% vs 2.06%) and new revascularization (16.59% vs 8.97%) was recorded in the MetS group. On multivariate analysis, MetS was independently associated with MACE (HR = 1.834, 95% CI = 1.162-2.896, p = 0.009) but not with mortality (HR = 1.603, 95% CI = 0.864-2.973, p = 0.134). Among cardiovascular events that compose MACE, MetS was associated with new revascularization (HR = 2.204, 95% CI = 1.273-3.815, p=0.005). Conclusion: The presence of MetS in patients with STEMI is an independent risk factor for MACE, and this syndrome is strongly associated with new revascularization. Keywords: Metabolic syndrome, Myocardial Infarction, Clinical severity, Long-term prognosis
