Effects of right bundle branch block during atrioventricular nodal reentrant tachycardia B Kun-Tai Lee a,e , Shih-Huang Lee b,c,d, * , Ching-Tai Tai a,c , Pi-Chang Lee a,c , Chern-En Chiang a,c , Yenn-Jiang Lin a,c , Bien-Hsien Huang a,c , Yoga Yuniadi a,c , Wen-Ter Lai a,c , Shih-Ann Chen a,c a Cardiovascular Research Center and Division of Cardiology, Veterans General Hospital-Taipei, Taiwan, R.O.C. b Division of Cardiology, Shin Kong Wu Ho-Su Memorial Hospital, 95, Wen Chang Road, Shih Lin, Taipei, Taiwan, R.O.C. c School of Medicine, National Yang-Ming University, Taiwan, R.O.C. d School of Medicine, Fu Jen Catholic University, Taiwan, R.O.C. e School of Medicine, Kaohsiung Medical University, Taiwan, R.O.C. Received 5 February 2004; received in revised form 18 June 2004; accepted 19 June 2004 Available online 27 January 2005 Abstract 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 AVNRTand 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 (V110 ms) during sinus rhythm and AVNRT. Group II included 18 patients who had persistent RBBB (z120 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 (296F60 vs. 288F75 ms), His-ventricular (HV) interval (36F11 vs. 35F11 ms), His-atrial (HA) interval (72F24 vs. 71F28 ms), VA HRA interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of right high atrium; 34F24 vs. 37F25 ms), VA CSO interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of coronary sinus ostium; 13F28 vs. 26F23 ms) and tachycardia cycle length (TCL; 368F67 vs. 359F73 ms) during AVNRT were similar between group I and group II (all PN0.05). In group III, the AH interval (255F81 vs. 246F83 ms), HV interval (44F5 vs. 42F11 ms), HA interval (66F19 vs. 70F15 ms), VA HRA interval (27F15 vs. 29F16 ms), VA CSO interval (23F25 vs. 21F25 ms) and TCL (322F76 vs. 316F77 ms) were not significantly different between AVNRT with narrow QRS and those with transient RBBB (all PN0.05). 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. D 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Atrioventricular; Tachycardia; Bundle branch; Block 1. Introduction Functional bundle branch block is commonly encoun- tered during the course of electrophysiologic studies in patients with supraventricular tachycardia. This phenom- enon occurs much more frequently during orthodromic reentrant tachycardia than AV nodal reentrant tachycardia (AVNRT) [1–5]. To our knowledge, few studies have reported the effects of bundle branch block during AVNRT. 0167-5273/$ - see front matter D 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2004.06.010 B Supported in part by grants from the National Science Council (NSC 92-2314-B-341-006), and Shin Kong Wu Ho-Su Memorial Hospital (SKH- TMU-92-28, SKH-TMU-NSC-93-01) Taipei, Taiwan, R.O.C. * Corresponding author. Tel.: +886 2 2833 2211x2091; fax: +886 2 2834 8910. E-mail address: shlee@cm1.ethome.net.tw (S.-H. Lee). International Journal of Cardiology 101 (2005) 91 – 95 www.elsevier.com/locate/ijcard