Clinical and Electrophysiologic Characteristics of Ventricular Tachycardias from the Basal Septum in Structural Heart Disease

Abstract

Background The basal septum is a common source of ventricular tachycardia (VT) in patients with structural heart disease (SHD).ObjectiveWe describe the clinical and electrophysiologic characteristics of basal septal VTs in SHD patients.MethodsData from 312 consecutive SHD patients undergoing catheter ablation of ventricular arrhythmias were reviewed.ResultsThirty-three basal-septal VTs in 31 patients (mean age 67.4{plus minus}14.2 years, left ventricular [LV] ejection fraction [EF] 42{plus minus}15%) were identified. Patients with VTs with LV basal-septal breakthrough were more likely to have ischemic cardiomyopathy and a lower LVEF; right ventricular basal-septal VT patients were more likely to have sarcoidosis or right ventricular cardiomyopathy of unknown significance, with a higher LVEF. Atrioventricular block was present in 45% and intraventricular block including persistent bi-ventricular pacing in 77%. Unipolar scar was larger than bipolar scar (area 18.8{plus minus}19.4% vs. 12.7{plus minus}14.6%, P<0.001). VTs with a right bundle branch block (BBB) morphology and S wave in V6 with positive V3/V4 polarity consistently indicated an LV basal-septal breakthrough. Inferior limb-lead discordance with a right BBB morphology and reverse pattern break in V2 were identified in LV basal infero-septal origin in 3 patients respectively. VT non-inducibility was achieved in 55% and VT recurred in 42% of patients after a single procedure, however, VT burden was significantly reduced after ablation (59 episodes pre vs. 2 episodes post, P=0.02).ConclusionBasal-septal VTs in SHD have a distinct clinical, electrocardiographic, and electrophysiologic profile depending on the breakthrough site, accompanied by a deep intramural septal substrate that limits procedural success after catheter ablation.