ATP challenge markedly improves ablation outcome
TOKYO, JAPAN. The average complete success rate (no AF, no antiarrhythmics) for 729 initial ablation procedures evaluated in the 2008 Ablation/Maze Survey was 50% for 15 top-ranked institutions and 21% of other institutions. After follow-up procedures the final complete success rates were 65% for top-ranked institutions (30% repeat rate) and 32% for other institutions (44% repeat rate).

Now Japanese researchers report that success rates can be markedly improved by attempting to induce atrial fibrillation 20 minutes after completing the initial procedure and then re-ablating in cases where afib recurs. It is common practice to pace the heart while infusing an isoproterenol solution when electrical isolation of the pulmonary veins from the left atrium has been achieved in order to attempt to induce AF associated with acute electrical reconnection of the veins to the atrium. Isoproterenol is a beta adrenergic agonist which can induce tachycardia and other arrhythmias. The novelty in the approach used by the Japanese researchers is that they also inject ATP (adenosine-5'-triphosphate) while pacing the heart and infusing isoproterenol. ATP is a molecule which transports energy within cells to aid in metabolism.

In the Japanese study, the combination of pacing, isoproterenol, and ATP revealed dormant reconnection in 225 pulmonary veins (24% of the 928 veins originally isolated). In comparison, pacing and isoproterenol alone only revealed dormant reconnection in 3 veins (0.3% of originally isolated veins). Thus using a combination of isoproterenol and ATP to check for acute (dormant) reconnections is substantially more effective than using isoproterenol alone.

The study involved 144 patients with paroxysmal AF, 43 with persistent AF, and 46 with permanent AF. The median age of the group was 55 years, 88% were men, and only 9% had underlying structural heart disease; so this study group consisted essentially of typical lone afibbers. All participants underwent a segmental pulmonary vein isolation procedure (PVI) using a Lasso catheter for mapping. Patients with permanent (long-lasting persistent) AF underwent additional ablation targeting complex fractionated electrograms and continuous electrical activity during ongoing afib. Those who had a history of right atrial flutter also underwent cavotricuspid isthmus ablation. Electrogram-based ablation was performed in all 46 patients with permanent AF and a right atrial flutter ablation was performed in 88 patients (37.8% of 233 patients).

At least 20 minutes after finishing the ablation and achieving electrical isolation of the targeted veins, the heart was paced and the ATP/isoproterenol infusion was begun. This procedure revealed dormant pulmonary vein conduction in 139 (59.7%) of the 233 patients. All 139 patients underwent additional ablation to close the gaps revealed by the ATP/isoproterenol infusion. During a follow-up averaging almost 3 years (903 days) 75% of paroxysmal afibbers and 46.1% of persistent and permanent afibbers remained in normal sinus rhythm (NSR) without the use of antiarrhythmic drugs (complete success) after their initial procedure. Thirty patients with paroxysmal AF and 41 with persistent or permanent AF underwent a repeat procedure (1 procedure for 65 patients and 2 for 6 patients). After the final procedure 95.1% of paroxysmal afibbers remained in NSR without the use of antiarrhythmics, while 83% of persistent and permanent afibbers achieved this enviable state. There was no difference in final outcome between patients who exhibited dormant pulmonary vein conduction after the isoproterenol/ATP challenge and those who did not. Procedure-related complications (2 strokes, 2 tamponades, and 1 peripheral arteriovenous fistula) were observed in 5 patients (1.6%).

The researchers conclude that isoproterenol/ATP administration reveals dormant PV conduction in more than 50% of ablatees and that re-ablating the lesion set gaps thus uncovered can markedly improve long-term success rates for PVI procedures.

Matsuo, S, et al. Comparison of the clinical outcome after pulmonary vein isolation based on the appearance of adenosine-induced dormant pulmonary vein conduction. American Heart Journal, Vol. 160, August 2010, pp. 337-45

Editor's comment: The finding that using an ATP/isoproterenol challenge to reveal dormant pulmonary veins reconnections and eliminating them during the ablation procedure very markedly improves success rates of ablation, both in paroxysmal and persistent afibbers, is obviously of huge importance. It is to be hoped that other ablation centers will incorporate the ATP/isoproterenol challenge as a routine measure. It is of interest to note that doing so was associated with a relatively minor increase in overall procedure time to about 3.5 hours.