Effects of right bundle branch block during atrioventricular nodal reentrant tachycardia

Background: The significant role of bundle branch block during atrioventricular nodal reentrant tachycardia (AVNRT) is not clear. The purposes of this study were to study the effects of complete right bundle branch block (RBBB) on electrophysiological parameters during AVNRT and to define the significance of complete RBBB during AVNRT. Methods and results: According to characteristics of electrocardiogram during sinus rhythm and AVNRT, 50 patients who underwent catheter ablation for slow-fast AVNRT were divided into three groups. Group I included 20 patients who had narrow QRS (≤110 ms) during sinus rhythm and AVNRT. Group II included 18 patients who had persistent RBBB (≥120 ms) during sinus rhythm and AVNRT. Group III included 12 patients who had narrow QRS during sinus rhythm, but they had narrow QRS and transient RBBB during AVNRT. The atrio-His (AH) interval (296±60 vs. 288±75 ms), His-ventricular (HV) interval (36±11 vs. 35±11 ms), His-atrial (HA) interval (72±24 vs. 71±28 ms), VA_HRA interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of right high atrium; 34±24 vs. 37±25 ms), VA_CSO interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of coronary sinus ostium; 13±28 vs. 26±23 ms) and tachycardia cycle length (TCL; 368±67 vs. 359±73 ms) during AVNRT were similar between group I and group II (all P>0.05). In group III, the AH interval (255±81 vs. 246±83 ms), HV interval (44±5 vs. 42±11 ms), HA interval (66±19 vs. 70±15 ms), VA_HRA interval (27±15 vs. 29±16 ms), VA_CSO interval (23±25 vs. 21±25 ms) and TCL (322±76 vs. 316±77 ms) were not significantly different between AVNRT with narrow QRS and those with transient RBBB (all P>0.05). Conclusions: Persistent RBBB and transient RBBB have no significant effects on the electrophysiological parameters during AVNRT. These findings suggest that RBBB might not influence the conduction of lower common pathway or the circuit of AVNRT.