Collateral injury of the conduction system during catheter ablation of septal substrate in nonischemic cardiomyopathy

Introduction: In patients with nonischemic cardiomyopathy (NICM) little is known about the clinical impact of catheter ablation (CA) of septal ventricular tachycardia (VT) resulting in the collateral injury of the conduction system (CICS). Methods and Results: Ninety-five consecutive patients with NICM underwent CA of septal VT. Outcomes in patients with no baseline conduction abnormalities who developed CICS (group 1, n = 28 [29%]) were compared to patients with no CICS (group 2, n = 17 [18%]) and to patients with preexisting conduction abnormalities or biventricular pacing (group 3, n = 50 [53%]). Group-1 patients were younger, had a higher left ventricular ejection fraction and a lower prevalence of New York Heart Association III/IV class compared to group 3 while no significant differences were observed with group 2. After a median follow-up of 15 months, VT recurred in 14% of patients in group 1, 12% in group 2 (P =.94) and 32% in group 3 (P =.08) while death/transplant occurred in 14% of patients in group 1, 18% in group 2 (P =.69) and 28% in group 3 (P =.15). A worsening of left ventricular ejection fraction (LVEF) (median LVEF variation, −5%) was observed in group 1 compared to group 2 (median LVEF variation, 0%; P <.01) but not group-3 patients (median LVEF variation, −4%; P =.08) with a consequent higher need for new biventricular pacing in group 1 (43%) compared to group 2 (12%; P =.03) and group 3 (16%; P <.01). Conclusions: In patients with NICM and septal substrate, sparing the abnormal substrate harboring the conduction system provides acceptable VT control while preventing a worsening of the systolic function.