Objective The substrates of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) had been shown involving a slow conduction zone (SCZ) and posterior Purkinje network. However, the variation of these was not understood. The purpose was to investigate the variation of the left ventricular conduction system (LVCS) and markers of successful ablation.
Methods Electroanatomical mapping was performed during sinus rhythm in 20 patients with ILVT and 20 control subjects with paroxysmal supraventricular tachycardia. LVCS and SCZ were tagged and the anatomic aspects of them were investigated.
Results According to the distribution of Purkinje potential, LVCS was distinguished into 3 types: 1: left bundle branch was divided into two discrete fascicles without interconnections; 2: was divided into three separate fascicles; 3: fanlike structure distribution over septum broadly. The length of left bundle branch and its fascicles in ILVT patients were slight longer than those of controls (P > 0.05). SCZ was located at inferoposterior septum in 17 patients with ILVT and 4 controls. The size of SCZ in the ILVT group was remarkably greater (P = 0.007) than those of the control group. Two SCZs were located at posterior and mid-septal in 2 patients, and inferior apical septum in 1 patient. At the crossover junction area with diastolic potential and Purkinje potential, with the size of 1.5 ± 0.4cm2, concealed entertainment and/or ablation were obtained successfully in all patients with patients.
Conclusions The anatomy of LVCS and SCZ is variable in human subjects in particular those with ILVT. These variabilities suggest that the electrophysiological mechanism of ILVT is complex. While exact mechanism of reentry of ILVT was not confirmed because of the lack of the activation electroanatomic mapping, the crossover junction area with Purkinje potential and diastolic potential might be a marker of radiofrequency ablation of ILVT.