Risk factors for thromboembolism in patients with paroxysmal atrial fibrillation

There is some controversy concerning which clinical characteristics predict thromboembolism and whether treatment with class I antiarrhythmic drugs reduces thromboembolim in patients with paroxysmal atrial fibrillation (AF). This retrospective, multicenter study was undertaken to determine risk factor or factors for thromboembolism in patients with paroxysmal AF. Seven hundred forty patients with paroxysmal AF (mean age 56 years) without prior thromboembolic events were followed retrospectively. Cerebral thromboembolism, including transient ischemic attack and embolism of peripheral arteries, were selected as primary end points. Independent risk factors were determined with multivariate analysis, and event-free survival curves were estimated. During 3.4-year follow-up period, primary end points occurred in 55 patients (2.2% per year). Patients with thromboembolism had a higher prevalence of underlying heart disease (p <0.01), less frequent treatment with antiarrhythmic drugs (p <0.01), and received diuretics more often (p <0.01) compared with patients without thromboembolism. Age (>/=65 years, RR 3.33, p = 0.0001) and gender (male, RR = 2, p = 0.0291) emerged as predictors of thromboembolism by multivariate analysis with Cox's proportional hazard model. Treatment with antiarrhythmic drugs (RR = 0.57, p = 0.0578) and aspirin (RR = 0.52, p = 0.1094) showed trends toward reducing thromboembolic risks. It is suggested that elderly men (>/=65 years) with paroxysmal AF are at risk for thromboembolism, but the risk tended to be reduced by treatment with antiarrhythmic drugs and aspirin.