Ablation of persistent atrial fibrillation

BORDEAUX, FRANCE. The success rate (no afib, no medications) for radiofrequency (RF) ablation of paroxysmal (intermittent) atrial fibrillation now approaches 90% in top centers. However, successfully ablating persistent AF (episodes lasting longer than 7 days or lasting less than 7 days, but requiring cardioversion), or long-lasting (permanent) persistent AF (continuous AF of greater than 1 year duration) is quite a different matter with success rates often being 50% or less. Paroxysmal AF is triggered from areas in or around the entrance of the pulmonary veins into the left atrium and therefore can be eliminated by isolating the pulmonary veins electrically from the left atrium through a relatively simple PVI procedure. However, in the case of persistent and permanent afib, other areas of both the left and right atrium are involved in initiating, propagating and maintaining persistent AF.

An increasingly popular approach to dealing with persistent afib involves substrate ablation. This procedure, pioneered by Dr. Koonlawee Nademanee, involves locating sites with complex fractionated electrograms recorded during AF and then ablating them. An electrogram is a picture of the electrical activity of the heart as sensed from within the heart as opposed to an ECG which senses the activity from outside the heart. Fractionated electrograms are characterized by abnormalities in the baseline or a very short cycle length.

Linear ablation involving the roof of the left atrium and the mitral isthmus may also be involved in performing a successful ablation for persistent AF.

The Bordeaux team of Prof. Haissaguerre and colleagues now report the outcome of RF ablation in 71 patients with persistent AF and 82 patients with permanent AF. The average age of the patients was 56 years and 85% were male. Almost half (48%) of the 153 patients had structural heart disease. All underwent a standard, segmental PVI followed by substrate ablation, and linear ablation as required. Spontaneous termination of AF was achieved in 9% after the PVI, in 58% after substrate ablation, and in 18% after linear ablation. The remaining 15% could not be terminated by ablation and required pharmacological and/or electrical cardioversion. The average total procedure time was 4 hrs. 15 min. with fluoroscopy time of 86 minutes and RF energy delivery duration of 88 minutes.

Of the patients in whom AF terminated during the procedure, 83% terminated via atrial tachycardia (AT) which needed ablation, and 17% converted directly to normal sinus rhythm (NSR). The Bordeaux team observed that the chances of AF termination during the procedure was better with a smaller left atrium diameter, a shorter duration of persistent AF, and a longer atrial fibrillation cycle length (AFCL) at baseline. AF and/or AT recurrence was common among all study participants with half the patients who experienced AF termination during the initial procedure requiring repeat ablation(s) – 58 for AT and 6 for AF. In the non-termination group 16 out of 23 patients (70%) required repeat procedures – 9 for AF and 7 for AT.

After a follow-up ranging between 28 months and 40 months, 95% of patients whose AF terminated during the initial procedure were still in NSR as compared to only 52% in the group whose AF could not be terminated during the initial procedure. No asymptomatic episodes were detected in a subgroup of patients undergoing continuous, long-term monitoring. Prof. Haissaguerre and colleagues conclude that long-lasting persistent AF is a complex arrhythmia (what an understatement!) and that termination of AF during the initial procedure is associated with a better long-term outcome.

O’Neill, MD, et al. Long-term follow-up of persistent atrial fibrillation ablation using termination as a procedural endpoint. European Heart Journal, Vol. 30, 2009, pp. 1105-12

Editor’s comment: This report vividly illustrates the enormous challenge in successfully dealing with persistent and permanent afib. It also reveals, as many afibbers themselves have observed, that atrial tachycardia is common following an otherwise successful AF ablation and, in many cases, needs an additional ablation to resolve. Realistically, anyone with persistent or permanent afib should be psychologically and financially prepared to undergo at least two ablation procedures. This provides a strong incentive to deal with afib while it is still paroxysmal.