Incidence, characteristics, and outcome of left atrial tachycardias after circumferential antral ablation of atrial fibrillation

Background: Antral pulmonary vein isolation (PVI) for treatment of atrial fibrillation may induce left atrial tachycardias (ATs).

Objective: To determine the prevalence, time course of occurrence, mechanisms, and correlation with the electrocardiogram as well as the outcome of ablation of these tachycardias.

Methods and results: Out of the 839 patients who underwent circumferential antral radiofrequency PVI guided by a circumferential pulmonary vein catheter at our institution between February 2005 and April 2011, 35 patients (4%) developed AT during follow-up. Six patients with left AT and a previous PVI at other institutions were also included. Of these 41 patients (26 men, 63%; age 59 ± 10 years), 26 (63%) had underlying paroxysmal atrial fibrillation and 15 (37%) had persistent atrial fibrillation. AT ablation was performed 47 ± 60 weeks after initial PVI, within the first 3 months in 16 patients (39%). The tachycardia mechanism was focal in 15 patients (37%), macroreentry in 25 patients (61%), and undetermined in 1 (2%). Focal tachycardias had an isoelectric line between distinct P waves in 13 of the 15 patients (87%), while only 4 (16%) with a macroreentrant mechanism had an isoelectric line (P <.001). Although difficult to measure, a P-wave width of >140 ms had the highest sensitivity and specificity to identify macroreentrant mechanism. Ablation was acutely successful in 32 patients (78%) and not successful in 4 (10%). In 5 patients, success could not be determined as the tachycardia terminated or degenerated during mapping. During a mean follow-up of 31 ± 17 months, 11 patients (27%; n = 9 [82%] with macroreentry) underwent repeat ablation procedure for AT. Eight patients had true recurrence, for example, the same AT, and 3 patients had a second mechanism of AT.

Conclusions: With the use of an identical ablation protocol, it was found that approximately 4% of the patients developed AT after mere circumferential antral PVI. The majority of ATs developed within a few months after ablation but occurred as late as several years after the initial PVI. Macroreentry was more frequent than a focal mechanism. Broad P waves and isoelectric lines between P waves help to distinguish a focal mechanism from a macroreentrant mechanism. Ablation has a high acute success rate, and AT recurrence occurs predominantly in macroreentrant AT.