Ablation for persistent atrial fibrillation: do we know who to turn away?

The use of catheter-based techniques for the treatment of atrial fibrillation (AF) has grown rapidly over the last decade. Once-novel strategies, focusing principally on circumferential ablation to isolate pulmonary vein (PV) ostia, have become commonplace. As ablative therapy for AF has gained wider acceptance, the indications and target patient populations referred for AF ablation have expanded accordingly. The role of ablation for patients with drug-refractory, symptomatic paroxysmal AF is generally agreed upon. Less is known, though, about the long-term success of catheter ablation in patients with persistent (and particularly long-standing persistent) AF. Large trials which have included patients with longstanding persistent AF suggest that the rate of atrial arrhythmia recurrence in this group is high. Identifying predictors of recurrence in this patient population—particularly those that pinpoint patients for whom AF ablation is truly futile—is of obvious clinical importance. McCready et al. 1 provide data on predictors of AF recurrence following ablation in patients with persistent AF. The focus of the study was long-standing persistent AF, since the large majority of the patients studied (88%) had a continuous AF duration of .1 year leading up to ablation. The authors collected data in 191 patients undergoing a total of 292 procedures. The ablation strategy used was left to the discretion of the ablating physician; typically, circumferential PV isolation was performed (100% of patients) in conjunction with a roof line (71%), and occasionally with a mitral isthmus line (44%) and complex fractionated electrogram ablation (42%). It is important to note that ablation until return of sinus rhythm was not the endpoint of the procedure; restoration of sinus rhythm during ablation was only observed in 12% of the patients. Patients were followed for an average of 13 months, with a variety of types of follow-up monitoring including clinical assessment, electrocardiograms, Holter monitoring, and device interrogation. Procedural failure was defined as recurrent AF or atrial tachycardia (AT) .30 s duration, after a 3 m blanking period on or off an antiarrhythmic medication. Sixty-seven patients underwent two or more procedures. The results presented by McCready et al. are a stark reminder of the difficulties posed by patients with long-standing persistent AF. Although PVs were isolated in 100% of the cases, operators did not succeed in terminating AF during ablation in 88% of the patients; rather, patients with AF or AT at the conclusion of the case were cardioverted. During the follow-up period, singleprocedure success occurred in 32% of the patients over 13 months. Among patients who were categorized as having a successful outcome, 30% were still taking antiarrhythmic medications. Thus, the antiarrhythmic-free single-procedure success rate in this patient population can be predicted to be ,32%. Overall success (i.e. after up to four ablation procedures and on or off antiarrhythmic drug therapy) was 64% over the same period. Importantly, the incidence of major complications was 6.2%, including cardiac tamponade in 2.4% (two patients requiring surgical repair), stroke in 1%, phrenic nerve paralysis in 0.7%, and one patient with restrictive pericarditis requiring a surgical pericardectomy. The authors found that left atrial (LA) size, measured by transthoracic echocardiography, was the sole univariate and multivariate predictor of single-procedure success. Left atrial size was also the principal predictor of overall success. Atrial fibrillation duration, procedural strategy, and other variables that one might expect to predict outcome did not do so in this series of patients. On the basis of these findings, the authors performed receiver operator characteristic analysis and found that an LA size of ,43 mm gave greatest accuracy in predicting outcome.