Radiofrequency catheter ablation in idiopathic ventricular tachycardia showing left bundle branch block and inferior axis: the significanece of morphologic variation of R wave on right precordial leads

Lee, Man Young; Shin, Woo Seung; Jin, Seung Won; Oh, Yong Seok; Huh, Min; Jung, Sung Hoon; Jang, See Jin; Lim, Min Kyung; Kim, Yeon Seong; Rho, Tai Ho

Abstract

BACKGROUND: Radiofrequency catheter ablation (RFCA) becomes an useful treatment for idiopathic ventricular tachycardia, especially right ventricular outflow tract ventricular tachycardia (RVOT VT) typically originates from "superior septal" aspect of right ventricular outflow tract. However, some of the right ventricular outflow tachycardias remain resistant despite repeated attempts of RFCA. This study was focused to search the electrocardiographic characteristics suggesting procedural success of radiofrequency ablation in RVOT VT and ventricular tachycardia that can not be ablated by conventional approach confined to right ventricular outflow tract even though to show similar electrocardiographic morphology.
METHODS
The study subjects were 25 patients who underwent RFCA with the diagnosis of RVOT VT. We classified the study subjects into 2 groups and in group 1 (N=17, Age 47.5 +/- 16.8) in those successful RFCA was possible in RVOT. In group 2 (N=8, Age 54.8 +/- 8.0), the removal of VT was not possible with the RFCA confined in RVOT. We analyzed the morphologic characteristics of QRS complex of VT or ventricular premature beats in right precordial leads; V(1-3). The QRS and R wave duration, height of R wave, depth of S wave, R/S ratio and R wave duration index were measured.
RESULTS
There was no difference of age and sex between group 1 and 2 (Group 1: N=17, Male 29.4%, Age 49.5 +/- 16.8 vs Group 2: N=8, Age 54.8 +/- 8.0, Male 37.5%). The maximal QRS duration in V(1-3) was 144.2 +/- 23.6 ms in group 1 and 136.3 +/- 25.1 ms in group 2. The R wave duration and R wave duration index were not different either between group 1 and 2. However, the R wave duration of lead V 3 in group 2 was 97.0 +/- 34.4 ms and significantly longer than 65.0 +/- 26.0 msec in Group 1 (p=0.04). R wave duration index also showed significant difference between two groups: 72.0 +/- 23.5% of group 2 vs 45.4 +/- 17.8% of group 1. In comparison of R wave height and depth of S wave in V(1-3) between two groups, the R/S ratio of lead V3 in group 2 showed the ratio of 343.4 +/- 227.7% which was significantly larger than 97.4 +/- 92.2% in group 1.
CONCLUSION
For the practice of RFCA for RVOT VT, morphologic characterstics of VT or VPC showing wide R wave and high R/S wave ratio in precordial leads, especially in V3 could be an useful electrocardiographic indicator to suspect the unusual focus of idiopathic VT showing inferior axis and LBBB pattern.