EAST PALO ALTO. CALIFORNIA. The �official� (Heart Rhythm Society) definition of ablation failure is the occurrence of a single arrhythmia (atrial fibrillation, atrial flutter, atrial tachycardia) episode lasting longer than 30 seconds, usually following a post-ablation blanking period of 3 months. This definition is quite arbitrary, and far stricter than the criterion used to define failure of treatment with antiarrhythmic drugs. It is also totally unrealistic from the patient�s point of view.

A group of electrophysiologists at Silicon Valley Cardiology now suggests that a better definition of ablation failure would be an AF burden (episode frequency multiplied by duration) of more than 0.5% when measured over a longer term (7 days of event monitoring, or 1 year of pacemaker interrogation). Their recommendation for the change in ablation failure definition is based on a study carried out to determine the actual incidence of AF in a group of 203 patients who had undergone a successful catheter ablation as defined as being clinically free of AF 1 year after the procedure without the use of antiarrhythmic drugs. An average of 3.1 years following the last ablation, 186 of the patients underwent 7-day event monitoring. The remaining 17 patients had pacemakers, the records of which were analyzed for the most recent year.

The 7-day event monitoring showed that 95.7% of the patients had no AF recurrence at all. Amongst the 8 patients with recurrence, 1 was found to have persistent AF. For the other 7, AF burden varied between 0.0075% (45 seconds/week) and 3.34% (5.6 hours/week) with 3 patients out of 7 having a burden of 0.037% (4 minutes or less/week). In the pacemaker group, 76.5% were totally AF-free during the 1-year analysis period. The AF burden amongst the 4 patients with recurrence ranged from 0.0037% (22 seconds/week) to 0.16% (16 minutes/week).

The authors conclude that the AF burden (silent and symptomatic) experienced 3 years post-ablation by patients whose last ablation was clinically successful at 1-year post-ablation is very low. They suggest that an AF burden of more than 0.5% on long-term monitoring may be a more realistic definition of ablation failure than a single arrhythmia recurrence lasting longer than 30 seconds. They also noted that the only variable directly correlated with ablation failure was AF duration. In other words, the longer a patient had suffered from AF prior to the ablation, the greater the chance of failure.
Winkle, RA, et al. Atrial arrhythmia burden on long-term monitoring in asymptomatic patients late after atrial fibrillation ablation. American Journal of Cardiology, May 31, 2012 [Epub ahead of print]

Editor�s comment: I wholeheartedly concur with the above conclusion. To suggest that one 31-second arrhythmia episode, following a suitable blanking period, would classify an ablation as a failure is just not realistic in the real world. Most afibbers who have suffered frequent and/or protracted symptomatic episodes prior to their ablation would not consider it a failure, even if they should experience a few short episodes lasting longer than 30 seconds. NOTE: Only 2% of the 203 patients involved in the study actually had an AF burden exceeding 0.5% (50 minutes/week) on long-term monitoring.