Thromboembolism in chronic atrial flutter: is the risk underestimated?

OBJECTIVES: We sought to evaluate the risk of thromboembolic events in the presence of chronic atrial flutter and to determine the impact of anticoagulation therapy, if any, on this risk. BACKGROUND: Thromboembolic events are thought to be rare after cardioversion of atrial flutter. METHODS: This study was a retrospective analysis of 110 consecutive patients referred to the electrophysiology laboratory for cardioversion of chronic atrial flutter from 1986 to 1996. Atrial flutter was present for at least 6 months. Of the 110 patients reviewed, 100 had adequate information available regarding the effectiveness of anticoagulation (mean age 64 years, range 27 to 86; 75 men, 25 women; mean left ventricular ejection fraction 42%). RESULTS: Thirteen patients (13%) had a thromboembolic event. Of these, seven were attributable to causes other than atrial flutter. In the remaining six patients (6%), thromboembolic events occurred during a rhythm of atrial flutter or after cardioversion to sinus rhythm. Other causes of thromboembolism were excluded. Effective anticoagulation was associated with a decreased risk of thromboembolism (p = 0.026). CONCLUSIONS: Patients with chronic atrial flutter are at an increased risk of thromboembolic events. Effective anticoagulation may decrease this risk.