Transient Advanced Atrioventricular Block and Left Bundle Branch Block during the Catheter Ablation of Idiopathic Ventricular Arrhythmias Originating from the Ventricular Outflow Tracts

A 68-year-old man who had undergone a prior radiofrequency catheter ablation (RFCA) of idiopathic ventricular tachycardia (IVT) originating from the right ventricle near the His bundle was referred for a RFCA of another IVT A 12-lead electrocardiogram exhibited a right bundle branch block and inferior axis QRS morphology with a tachycardia cycle length of 354 ms which suggested that the IVT originated from the left ventricular outflow tract (LVOT). The RFCA at LVOT just below the aortic valve, left coronary cusp, and right coronary cusp (RCC) failed to eliminate the IVT However, this session was taken over to the 2nd session, because left bundle branch block had occurred during the RFCA at RCC. After the IVT was successfully eliminated by the RFCA at LVOT just below the aortic valve, a sporadic premature ventricular complex (PVC) originating from the right ventricular outflow tract (RVOT) appeared. An elimination of the PVC, however, was abandoned, because the RFCA transiently caused advanced atrioventricular block. This case suggests that a proximal part of the His-Purkinje system might locate at the upper portion than usual in some case.