VENTRICULOATRIAL NODAL CONDUCTION IN PATIENTS WITH ATRIOVENTRICULAR REENTRANT TACHYCARDIAS

Background:  Character of ventriculoatrial (VA) nodal conduction in patients with accessory pathways may play a role in initiating AV re-entrant tachycardia by ventricular premature beats (VPBs).
Methods: We compared the VA nodal conduction in 3 groups of: a) patients with accessory pathway, b) patients with typical atrioventricular nodal reentrant tachycardia (AVNRT), and c) control subjects. Present VA nodal conduction was defined as a loss of 1:1 conduction during incremental ventricular pacing > 100 bpm.
Results: Digital recordings of stimulation protocols were retrospectively analyzed in age-matched groups of patients: after successful ablation of accessory pathway (Group 1, n =50, 33 M, 46 ± 15 yrs); before the slow pathway ablation for AVNRT (Group 2, n= 47, 12 M, 49 ± 16 yrs); and during completely negative EP study performed for suspected arrhythmia (Group 3, n = 42, 17 M, 50 ± 17 yrs).  Retrograde VA nodal conduction was present in 32/50 pts (64%), 46/47 pts (98%), and 35/42 pts (83%) in Groups 1-3, respectively (all percentage differences significant p < 0.05).
Conclusions: While well-preserved VA nodal conduction may be assumed prerequisite in AVNRT patients, significantly lower occurrence of VA nodal conduction in patients with accessory pathways has probably no physiological background. This finding presumably reflects selection (referral) bias as patients with impaired VA nodal conduction might have more symptoms due to AV reentrant tachycardias easily induced by spontaneous VPBs.