Electrophysiological and clinical characteristics of atrioventricular nodal reentrant tachycardia and longterm success of radiofrequency catheter ablation

Abstract

Background: Diff erent reentry circuits within A-V node region are able to sustain A-V nodal reentrant tachycardia (AVNRT). On this basis, electrophysiological criteria for at least three AVNRT types – slow/fast, fast/slow, and slow/ slow–have been proposed. Th e aim was to reevaluate these criteria in a group of our patients. In addition, clinical profi le and long-term success rate of catheter ablation procedure were studied. Methods: All consecutive patients referred for catheter ablation of AVNRT from September 2004 to December 2006 were prospectively recruited. Th e informed consent was signed by all and the study had been approved by the competent state’s ethics committee. A standard electrophysiological study with programmed single or double extrastimuli or high-rate electrostimulation until the development of refractoriness or tachycardia induction was performed. Orciprenaline i.v. was used to facilitate AVNRT induction and to test the ablation result. Slow-pathway electrograms at inferoposteroseptal right atrium and ablation-induced nodal rhythm were ablation targets. Th e radiofrequency energy of 30–50 W for a duration of at least 20 seconds was used. Non-inducibility of AVNRT and of echo-beats was the procedure end point. In addition, antegrade and retrograde A-V junction conduction times were measured and analysed manually. Patients underwent a detailed re-evaluation aft er at least 1 year of follow-up. Th e descriptive statistic was used to present the data. Results: One hundred and four patients, 72 % female, mean age 53 years, were included. Th ey had their fi rst tachycardia episode at a mean age of 35 years with an average recurrence rate of 1- to 3-times a year. Syncope was experienced in 9.5 % of patients. Familial tachycardias were reported in 4 % of patients. One third (34 %) were hypertensive (≥ 140/90 mmHg). In majority, slow/fast AVNRT type (98/104–94 %) was induced. Th e fast/slow and slow/slow types were rare (3/104 each). Th e mean heart rate of induced AVNRT was 166 beats/min. Measurements were available for 92 patients. Our best diagnostic criteria were: V-A’interval ( 150 fast/slow, 70–120 slow/slow), H-A’interval ( 200 fast/slow; 120–170 slow/ slow), and A’-H/H-A’ ratio (> 2,3 slow/fast, < 1 fast/slow, 1–2,3 slow/slow). Th e slow/fast type was generally induced from the atrium, while the fast/slow and slow/slow also from the ventricle. In the slow/fast type, the earliest retrograde atrial activation was recorded from the His bundle position in 95 % (proximal coronary sinus (CS) in 5 %). Th e earliest retrograde atrial activation was recorded from proximal CS in the fast/slow type, but from CS or His in the slow/slow. A transient A-V block was documented in 6 patients during ablation procedure. None of them needed a permanent pacemaker implantation. Aft er 16 months of follow-up, 96 % of our patients were free of tachycardia recurrences. Conclusions: Electophysiologic criteria for three AVNRT types, clinical characteristics, and AVNRT long-term radiofrequency catheter ablation success rate are consistent with data reported in the literature.