Atrioventricular Nodal Reentrant Tachycardia in Patients with Atrial Fibrillation
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Synopsis: Ablation of AVNRT in patients with AF was associated with improved outcomes compared with those with other triggers of AF.
Source: Sauer WH, et al. Atrioventricular Nodal Reentrant Tachycardia in Patients Referred for Atrial Fibrillation Ablation: Response to Ablation that Incorporates Slow-Pathway Modification. Circulation. 2006;114:191-195.
In this report, sauer and colleagues from the University of Pennsylvania describe the prevalence, significance, and management strategy for patients who have AV node reentrant tachycardia (AVNRT) in association with atrial fibrillation (AF). Sauer et al reviewed their database of patients undergoing trigger-guided ablation of AF. When possible, standard programmed stimulation in the atrium and ventricle was used to exclude the presence of AV node reentry or an accessory AV pathway before Sauer et al proceeded to transseptal puncture for the AF ablation. Patients also underwent a search for AF triggers that included isoproterenol infusions and burst pacing in association with recordings from inside the pulmonary veins. In patients in whom AVNRT was identified and there were no ectopy or left atrial AF triggers, only an AV nodal slow pathway modification was performed. In patients who had both AV nodal reentrant tachycardia and either pulmonary vein ectopy or other left atrial AF triggers, both a slow pathway modification and trigger-guided ablations were performed. After their initial procedure, patients were followed-up for between 6 weeks and 6 months on antiarrhythmic medications (flecainide, propafenone, or sotalol). Transtelephonic monitoring was used in conjunction with clinic visits at 6 to 8 weeks, 6 months, and every 6 months thereafter. Arrhythmia recurrence during the first 6 weeks after ablation was censored.
The entire trigger-guided AF ablation cohort consisted of 629 patients. Of these, 27 (4.3%) had AV node reentry tachycardia identified as a potential trigger for AF. None of these patients had a documented regular narrow complex tachycardia prior to the procedure. In comparison to the patients without AVNRT, the patients with that arrhythmia were younger and had less concomitant heart or vascular disease.
At the electrophysiologic study, 13 of the 27 patients with inducible AVNRT had no other trigger for AF identified and, therefore, they underwent only slow pathway modifications. In the other 14 patients, pulmonary vein triggers were identified, and these patients underwent isolation of from 1 to 4 pulmonary veins. Three of these patients also had nonpulmonary vein, left atrial sites triggering AF that were also ablated. Three of the patients who had AVNRT identified had the diagnosis made only at a second AF ablation attempt. For a variety of reasons, a complete programmed atrial stimulation protocol was not possible at the initial study, and it was only at a repeat study that the AV node reentry was identified in association with other left sided atrial AF triggers.
The mean follow-up duration for the entire cohort was 21.4 ± 9 months. Freedom from AF was achieved in 21 of 24 patients who had AVNRT identified at the time of their initial procedure. Among the 13 patients who had only AVNRT identified as the trigger for AF and had only a slow pathway modification, 12 remained AF free. The single recurrence in this group was due to a recurrence of AV node reentry. In the remaining 14 patients who also had left atrial or pulmonary vein triggers, 9 of 11 had success with their initial procedure. The 3 patients, in whom the AV node reentry was identified only at a second procedure, also did well. When the results of up to 2 procedures were combined, 26 of the 27 patients with AVNRT achieved long-term maintenance of sinus rhythm. In comparison, the success rate for prevention of AF after a single procedure was 54.7% among the 602 patients without AVNRT identified at the time of study.
Sauer et al conclude that AVNRT is a possible trigger for AF that is seen more frequently in patients with presentations early in life. Ablation of AVNRT, and of any associated left atrial triggers, is associated with a high success rate.
The paper by Sauer et al points out the need for careful electrophysiologic studies in patients who present as candidates for AF ablation. Electrophysiologists have long known that ablation of the accessory pathway conduction in patients with Wolff-Parkinson-White syndrome who present with both SVT and AF usually, but not always, eliminate the tendency for AF. It has also been previously recognized that patients who present predominantly with AV node reentry tachycardia may occasionally develop AF as a result of that rhythm. In this paper, we learn that even patients who have only documentation of AF may have AV node reentry either as the sole or as a contributing cause for their AF.
Since the development of the slow pathway modification technique for patients with AV node reentry, it has been possible to eliminate that rhythm in a fairly simple and safe procedure. Success rates in this paper, as in most laboratories, are above 90%. Therefore, electrophysiologists performing AF ablation procedures should make sure they do not miss this important and easily treatable cause of AF.
Sauer et al had a difficult job when they tried to compare results in the AVNRT patients with the rest of their AF ablation cohort. During the period in which the cohort was collected, the techniques for AF ablation have changed substantially, and the patients to whom the procedure is offered have also become more complicated. These changes have made it difficult for the contemporary results of AF ablation procedures to be quantitated, and this makes it difficult to compare AF ablation to other forms of therapy.