Deep septal pacing and subsequent individualized interventricular electrical optimization in HCM with preserved...

Management of patients with hypertrophic cardiomyopathy (HCM), preserved left ventricular ejection fraction, and high anticipated ventricular pacing burden remains challenging because current pacing guidelines provide limited direction for this clinical scenario. A 68-year-old man with non-obstructive HCM, symptomatic 2:1 atrioventricular block, and nonsustained ventricular tachycardia underwent implantation of a cardiac resynchronization therapy-defibrillator (CRT-D) system using a lumenless septal pacing lead connected to the LV port. Lead implantation proved technically challenging owing to marked septal hypertrophy (31 mm) with increased tissue resistance during lead advancement; despite repeated attempts at different septal sites, further lead advancement could not be achieved, and the final lead position remained within the deep interventricular septum. Stepwise lead advancement resulted in progressive shortening of the V6 R-wave peak time from 114 ms to 87 ms and paced QRS narrowing from 168 ms to 143 ms with deep septal pacing alone. Although the clinical trajectory was favorable, electrical assessment at the two-week follow-up demonstrated a residual 39-ms V6-to-V1 activation delay with deep septal pacing alone. Individualized ECG-guided VV optimization was therefore performed using coordinated deep septal and right ventricular pacing, bringing V6-to-V1 activation timing toward near-equalization with septal pre-excitation of 20 ms and further reducing QRS duration from 143 ms to 134 ms. At one month, NYHA functional class improved from III to I-II and NT-proBNP decreased from 1,868 to 369 pg/mL, with both remaining stable at one year. The clinical improvement was likely multifactorial; the specific contribution of VV optimization to this outcome could not be determined from a single case. This case highlights the potential value of device configurations that enable systematic post-implant interventricular electrical optimization as part of individualized programming in patients with structurally complex substrates and high anticipated pacing burden.