Supraventricular extrasystole due to 1:2 atrioventricular conduction: procedural characteristics and long term follow-up of slow pathway modulation

Background: Dual atrioventricular nodal physiology can cause atrioventricular nodal reentrant tachycardia (ANVRT). However, dual AVN physiology can sometimes also cause atrial extrasystole by 1:2 separate AV conduction via the fast and the slow pathway. This arrhythmia may be treated by radiofrequency modulation of the slow pathway (SPM). So far, only case reports have been published. We here present procedural characteristics and long-term follow-up in a series of five patients who underwent SPM for the treatment of 1:2 AVN conduction. Outcome: A population of 2927 patients who underwent SPM in our institution between 1994 and 2012 was screened for 1:2 AVN conduction. Five patients (2 male; mean age 55±14 yrs) were identified. All patients were highly symptomatic with palpitations. ECG documentation of 1:2 supraventricular extrasystole had been obtained in all patients. During electrophysiological study dual AVN physiology with separate AV nodal conduction via the fast and slow pathway in a 1:2 pattern was revealed in four patients. Mean fast pathway conduction measured as the AH interval was 149±70 ms while mean slow pathway conduction was 536±99 ms. In none of the 5 patients AVNRT was inducible. SPM was performed in all patients with the endpoint of absence of 1:2 conduction, which was tested by programmed atrial stimulation including orciprenaline challenge. In one patient, no dual AVN physiology was inducible despite extensive programmed stimulation and application of chatecholamines. On the ground of typical ECG documentation and severe symptoms, empirical SPM was performed in this case. There were no complications in any of the patients. Long term follow up (69.6±54.8 months) was performed by a telephone questionnaire. 4 patients were free of symptoms. The patient with empirical SPM remained symptomatic; however, he also reported improvement of clinical symptoms due to lower frequency of occurrence and shorter duration of episodes. Conclusion: 1:2 AVN conduction is a rhythm disorder that can be highly symptomatic. Although rare, this diagnosis should be considered in patients with palpitations and ECG documentation compatible with 1:2 AV conduction. Our data show that in this clinical setting catheter ablation is an effective and safe therapy with good long term outcome.