Association of metabolic syndrome with non-thromboembolic adverse cardiac outcomes in patients with atrial fibrillation

Aims: Evidence suggests an excess risk of non-thromboembolic major adverse cardiac events (MACE) associated with atrial fibrillation (AF), particularly in individuals free of overt coronary artery disease (CAD). Metabolic syndrome (MetS) increases cardiovascular risk in the general population, but less is known how it influences outcomes in AF patients. We aimed to assess whether MetS affects the risk of MACE in AF patients without overt CAD. Methods and results: This prospective, observational study enrolled 843 AF patients (mean-age, 62.5 ± 12.1 years, 38.6% female) without overt CAD. Metabolic syndrome was defined according to the National Cholesterol Education Program. The 5-year composite MACE included myocardial infarction (MI), coronary revascularization, and cardiac death. Metabolic syndrome was present in 302 (35.8%) patients. At 5-year follow-up, 118 (14.0%) patients experienced MACE (2.80%/year). Metabolic syndrome conferred a multivariable adjusted hazard ratio (aHR) of 1.98 for MACE [95% confidence interval (CI), 1.23-3.16; P = 0.004], and for individual outcomes: MI (aHR, 2.00; 95% CI, 1.69-5.11; P < 0.001), revascularization (aHR, 2.33; 95% CI, 1.40-3.87; P = 0.001), and cardiac death (aHR, 2.59; 95% CI, 1.25-5.33; P = 0.011). Following the propensity score (PS)-adjustment for MetS, the association between MetS and MACE (PS-aHR, 1.87; 95% CI, 1.21-3.01; P = 0.012), MI (PS-aHR, 1.72; 95% CI, 1.54-5.00; P = 0.008), revascularization (PS-aHR, 2.18; 95% CI, 1.69-3.11; P = 0.015), and cardiac death (PS-aHR, 2.27; 95% CI, 1.14-5.11; P = 0.023) remained significant. Conclusion: Metabolic syndrome is common in AF patients without overt CAD, and confers an independent, increased risk of MACE, including MI, coronary revascularization, and cardiac death. Given its prognostic implications, prevention and treatment of MetS may reduce the burden of non-thromboembolic complications in AF.