Long-term follow-up of fast pathway radiofrequency ablation in atrioventricular nodal reentrant tachycardia

Abstract

A trioventricular nodal reentrant tachycardia (AVNRT) represents one of the most common types of paroxysmal supraventricular tachycardia. It results from reentrant circuit conduction in patients with dual AV node pathway physiology. Radiofrequency catheter ablation is considered to be standard therapy in symptomatic patients with frequent episodes. Prevention of AVNRT can be achieved by radiofrequency ablation of either the slow or the fast conduction pathway. The initially introduced approach, targeting the fast pathway, is accompanied by a PR interval prolongation of varying degrees. The long-term reliability of slow pathway conduction after fast pathway ablation is unknown. It is important to know whether slow pathway conduction remains stable over time or whether progressive AV conduction disturbances occur. • • • A systematic review of the cardiac electrophysiology database at the University of Bonn was performed. A total number of 867 AVNRT radiofrequency ablations were identified between February 1990 and October 2000. All intended fast pathway ablations were performed between February 1990 and January 1994 utilizing the standard approach used at that time. Successful and persistent fast pathway ablation and/or modulation was assumed in patients with a PR interval increase of 20%, measured on the third day after fast pathway ablation. Patients with unintended complete heart block were excluded. These criteria were met by 33 patients. One patient also had coronary artery disease and another had been operated on for coarctation of the aorta 3 years before ablation. Follow-up was obtained in 30 of the 33 patients. Their ages at follow-up were 62 8 years. There were 23 women and 7 men. Fast pathway ablation in these 30 patients resulted in a PR interval increase from 153 19 to 250 45 ms ( 64%). The atrio-His interval increased from 81 17 to 152 49 ms ( 88%). Follow-up data were obtained after a mean of 8.7 years 11 months (range 81 to 128 months). Clinical events (AVNRT recurrence, repeat ablation, documented secondand third-degree AV block, syncope, pacemaker insertion) were recorded by means of a standardized questionnaire (n 30). Standard electrocardiogram for PR interval determination and 24hour electrocardiogram were obtained in 27 patients. Statistical comparisons between continuous variables were performed with Student’s t test. A p value 0.05 was considered significant. Follow-up data are shown in Figure 1. One patient (a heavy smoker) died of lung cancer 4 years after ablation. Another patient underwent repeat ablation for AVNRT recurrence, followed by pacemaker implantation for complicated complete heart block, at another hospital. Two other patients had reoccurrences that were well controlled with medication. Of the 28 patients still alive and without pacemakers, none had previous documentation of secondand third-degree AV block or syncope. At the follow-up visit, the PR interval was 233 40 ms, compared with 250 37 ms after ablation. The individual course of the PR interval before ablation, after ablation, and at follow-up is shown in Figure 1. In 5 patients, the PR interval increased further after ablation (3 patients 10 ms, 1 patient 20 ms, 1 patient 50 ms); the PR interval remained the same in 6 patients and decreased in 15 patients. One patient was in atrial fibrillation at the follow-up visit. The Holter electrocardiogram (n 27) did not show heart block in any of the patients. • • • Radiofrequency catheter ablation began to replace antiarrhythmic drugs and antitachycardia pacemakers for therapy of symptomatic recurrent AVNRT 10 years ago. The initial approach targeting the fast pathway has been abandoned in favor of slow pathway ablation, mainly because of a lower risk of inadvertent AV block. Fast pathway ablation is accompanied by varying degrees of PR interval prolongation, reported to be between 29% and 57% of baseline values. The long-term stability of slow pathway conduction after fast pathway ablation has not yet been investigated. There are a few reports regarding follow-up in patients after fast pathway ablation. The mean follow-up duration in these studies was between 6 and 33 months. Most studies did not show development of bradyarrhythmic complications during follow-up. In contrast to these studies, Fenelon et al reported on 4 patients with delayed complete heart block of 138 patients after fast pathway ablation. All 4 patients exhibited transient complete heart block during the procedure. Complete heart block was diagnosed 20 hours to 1 month after ablation. Mitrani et al From the Department of Medicine-Cardiology, University of Bonn, Bonn, Germany; the Department of Cardiology, University of Leipzig, Leipzig, Germany; and the Division of Cardiology, Johns Hopkins Hospital, Baltimore, Maryland. Dr. Lickfett’s address is: The Johns Hopkins Hospital, Division of Cardiology, 600 N. Wolfe Street/ Carnegie 592, Baltimore, Maryland 21287. E-mail: llickfe1@ jhmi.edu. Manuscript received October 25, 2001; revised manuscript received and accepted January 16, 2002.