ATRIAL-FIBRILLATION AFTER RADIOFREQUENCY ABLATION OF TYPE-I AERIAL FLUTTER - TIME TO ONSET, DETERMINANTS, AND CLINICAL COURSE

Background-The occurrence of atrial fibrillation after ablation of typ e I atrial nutter remains an important clinical problem. To gain furth er insight into the pathogenesis and significance of postablation atri al fibrillation, we examined the time to onset, determinants, and clin ical course of atrial fibrillation after ablation of type I nutter in a large patient cohort. Methods and Results-Of 110 consecutive patient s with ablation of type I atrial nutter, atrial fibrillation was docum ented in 28 (25%) during a mean follow-up of 20.1+/-9.2 months (cumula tive probability oi 12% at 1 month, 23% at 1 year, and 30% at 2 years) . Among 17 clinical and procedural variables,only a history of spontan eous atrial fibrillation (relative risk 3.9, 95% confidence intervals 1.8 to 8.8, P=0.001) and left ventricular ejection fraction <50% (rela tive risk 3.8, 95% confidence intervals 1.7 to 8.5, P=0.001) were sign ificant and independent predictors of subsequent atrial fibrillation. The presence of both these characteristics identified a high-risk grou p with a 74% occurrence of atrial fibrillation. Patients with only 1 o f these characteristics were at intermediate risk (20%), and those wit h neither characteristic were at lowest risk (10%). The determinants a nd clinical course of atrial fibrillation did not differ between an ea rly (less than or equal to 1 month) compared with a later onset. Atria l fibrillation was persistent and recurrent, requiring long-term thera py in 18 patients, including 12 of 19 (63%) with prior atrial fibrilla tion and left ventricular dysfunction, Conclusions-Atrial fibrillation after type I nutter ablation is primarily determined by the presence of a preexisting structural and electrophysiological substrate. These data should be considered in planning postablation management. The per sistent risk of atrial fibrillation in this population also suggests a potentially important role for atrial fibrillation as a trigger rathe r than a consequence of type I atrial flutter.