Abstract 17689: Distal Ventricular Pacing for Drug-Refractory Mid-Cavity Obstructive Hypertrophic Cardiomyopathy: A Randomized, Placebo-Controlled Trial of Personalized Pacing

Abstract

Introduction: Patients with refractory symptomatic left ventricular (LV) mid-cavity obstructive (LVMCO) hypertrophic cardiomyopathy (HCM) have extremely limited therapeutic options. Hypothesis: We hypothesized that site-specific-pacing would induce regionalized contractile dyssynchrony to reduce LVMCO gradients and improve symptoms. Methods: Symptomatic-drug-refractory LVMCO patients were recruited for a randomized blinded trial of personalized prescription of pacing (PPoP). Multiple LV and apical RV pacing sites were assessed during invasive hemodynamic study. Patient-specific optimal pacing site and atrioventricular (AV) delays were selected on basis of LVMCO gradient reduction and pacing parameters. Patients were randomized to 6 months active or back-up pacing in cross-over design. Primary outcome examined invasive gradient change with PPoP. Secondary outcomes assessed quality of life and exercise. Results: A total of 17 patients were recruited; 16 met primary endpoints. Baseline NYHA was 3±0.6 despite medical therapy. Hemodynamic effects were assessed during pacing at RV apex and a mean of 8 LV sites (range 4-16). Optimal PPoP was achieved via LV pacing in 14 (88%) patients and RV apex in 2. Mean baseline gradient 80±29 mmHg fell to 31±21 mmHg with PPoP (p<0.0001). Cardiac vein perforation occurred in one case, and 15 patients entered into cross-over; 2 withdrawals occurred during cross-over (myocardial infarction, persistent atrial fibrillation). Of the 13 completing cross-over, 9 (69%) chose active pacing as their preferred setting. PPoP was associated with better 6-minute walking test performance (329±100 vs 286±106 meters, p=0.018); other outcome measures also indicated benefit with PPoP. Conclusions: In a randomized placebo-controlled trial, PPoP reduces obstruction and improves exercise performance in severely symptomatic LVMCO patients. A personalized approach to pacing site selection is a key component of this novel therapy.