1180 Evidence-Based Medicine [ 1 5 4 # 5 C H E S T N O V E M B E R 2 0 1 8 ] Atrial Flutter The risk of thromboembolism and stroke in patients with atrial utter has been evaluated in relatively few studies compared with AF. However, patients with atrial utter frequently present phases of AF alternated with phases of classical utter or regular atrial rhythm.392-394 A systematic review on the thromboembolic risk associated with atrial utter, including 52 articles, found that thromboembolic event rates after cardioversion varied from 0% to 6% with a follow-up from 1 week to 6 Echocardiographic studies reported prevalence of intra-atrial thrombi from 0% to 38% and a prevalence of spontaneous echo contrast up One ablation study in non-anticoagulated patients with atrial utter reported thromboembolic events in 13.9% of cases.416 The differences in patient selection, type of study, and, importantly, use of oral anticoagulation explain the heterogeneity of reported data regarding echo ndings and thromboembolic complications. Observational studies demonstrated an increased risk of stroke (RR, compared with control subjects at long-term follow-up. A report from the Danish nationwide registry on patients undergoing an atrial utter ablation or an AF ablation procedure between 2000 and 2013 found that the rate of thromboembolic events for atrial utter patients was 0.46 per 100 person-years, not signi cantly different from that of patients presenting with AF (HR adjusted for several variables including The role of anticoagulant therapy for patients with atrial utter has not been evaluated in large randomized clinical trials, but because these patients often have concomitant AF or are at increased risk of developing AF, it is reasonable to base decisions regarding antithrombotic therapy on the same risk strati cation schemes and scores used for AF.3 Recommendation 44. 