Timing essential in ablation for persistent AF
TOKYO, JAPAN. Persistent atrial fibrillation (AF) is defined as episodes lasting longer than seven days but amenable to cardioversion to normal sinus rhythm. Persistent AF is notoriously more difficult to eliminate than is paroxysmal (intermittent) AF because the foci precipitating the fibrillation are not exclusively or almost exclusively located in the pulmonary veins as is the case in paroxysmal AF.

A group of researchers from the Tokyo Medical University treated a group of persistent afibbers and observed that the chance of a successful outcome was substantially higher the shorter the time the patients had suffered from persistent AF. In other words, if an afibber develops the persistent variety, an early ablation would be in order. The study included 93 patients (85% male) with an average age of 58 years and the median duration of persistent AF being one year. Average left ventricular ejection fraction was 60%, and 85% of participants had lone AF (no underlying heart disease).

The first procedure included anatomically-guided pulmonary vein isolation (PVI), electrogram-based ablation in the left atrium and coronary sinus, left atrium linear ablation, superior vena cava (SVC) isolation, and cavotricuspid isthmus linear ablation (right atrial flutter ablation). The pulmonary veins were isolated in all patients, but this part of the procedure only terminated the AF in two patients, clearly indicating that the triggers for persistent AF are not primarily located in the pulmonary veins. Following ablation of other targets, AF was terminated in 25 patients (27%), while the remaining 68 patients (73%) had their arrhythmia terminated by cardioversion.

After a mean follow-up of 1.8 years, only 38% of patients remained in normal sinus rhythm (NSR), 33% had experienced recurrence of AF, while the remaining 29% were found to have atrial tachycardia (AT). Twenty-eight of the 31 patients who had recurrence of AF (21 persistent and 7 paroxysmal) underwent a second procedure involving re-isolation of the pulmonary veins and electrogram-based ablation. This terminated AF in two patients. Further ablation in the right atrium added another five patients to the AF-free group. All of the patients with AT after the first procedure underwent a second procedure specifically aimed at curing the AT. This was successful in 66% of cases. Finally, 19 patients underwent a third procedure – 6 patients for AF and 13 for AT.

After an average 1.3 years from the last procedure, 76 patients (82%) were in NSR, but five of them (5%) only with the aid of antiarrhythmics. Patients who had only had their persistent AF for a relatively short time were significantly more likely to have a successful outcome as were those whose arrhythmia stopped on its own during the first ablation. The researchers also observed substantial benefits of having an extensive right atrium ablation. Of the 26 patients who underwent this additional procedure, 62% achieved NSR.

The researchers speculate that the fibrillatory substrate progressively extends from the left atrium to the right atrium over time, and conclude that right atrial ablation may improve outcome in patients whose left atrial ablation was unsuccessful. They also point out that patients with shorter duration of persistent AF are more likely to have a successful left atrial ablation.

Takahashi, Y, et al. Clinical characteristics of patients with persistent atrial fibrillation successfully treated by left atrial ablation. Circulation Arrhythmia and Electrophysiology, Vol. 3, October 2010, pp. 465-71

Editor's comment: The take-home message of this study is not to wait too long to undergo an ablation once it is established that the AF is of the persistent nature