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  • Title: Unique electrophysiologic characteristics of atrioventricular nodal reentrant tachycardia with different ventriculoatrial block patterns: effects of slow pathway ablation and insights into the location of the reentrant circuit.
    Author: Otomo K, Okamura H, Noda T, Satomi K, Shimizu W, Suyama K, Kurita T, Aihara N, Kamakura S.
    Journal: Heart Rhythm; 2006 May; 3(5):544-54. PubMed ID: 16648059.
    Abstract:
    BACKGROUND: The electrophysiologic mechanisms of different ventriculoatrial (VA) block patterns during atrioventricular nodal reentrant tachycardia (AVNRT) are poorly understood. OBJECTIVES: The purpose of this study was to characterize AVNRTs with different VA block patterns and to assess the effects of slow pathway ablation. METHODS: Electrophysiologic data from six AVNRT patients with different VA block patterns were reviewed. RESULTS: All AVNRTs were induced after a sudden AH "jump-up" with the earliest retrograde atrial activation at the right superoparaseptum. Different VA block patterns comprised Wenckebach His-atrial (HA) block (n = 4), 2:1 HA block (n = 1), and variable HA conduction times during fixed AVNRT cycle length (CL) (n = 1). Wenckebach HA block during AVNRT was preceded by gradual HA interval prolongation with fixed His-His (HH) interval and unchanged atrial activation sequence. AVNRT with 2:1 HA block was induced after slow pathway ablation for slow-slow AVNRT with 1:1 HA conduction, and earliest atrial activation shifted from right inferoparaseptum to superoparaseptum without change in AVNRT CL. The presence of a lower common pathway was suggested by a longer HA interval during ventricular pacing at AVNRT CL than during AVNRT (n = 5) or Wenckebach HA block during ventricular pacing at AVNRT CL (n = 1). In four patients, HA interval during ventricular pacing at AVNRT CL was unusually long (188 +/- 30 ms). Ablations at the right inferoparaseptum rendered AVNRT noninducible in 5 (83%) of 6 patients. CONCLUSION: Most AVNRTs with different VA block patterns were amenable to classic slow pathway ablation. The reentrant circuit could be contained within a functionally protected region around the AV node and posterior nodal extensions, and different VA block patterns resulted from variable conduction at tissues extrinsic to the reentrant circuit.
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