Abstract 18100: Comparative Analysis of Right Ventricular (RV) Apical Pacing versus Physiologic Left Bundle Branch Area Pacing (LBBAP) in Hypertrophic Cardiomyopathy With Left Ventricular Outflow Tract Obstruction (LVOTO): A Case Study

Introduction: AV dyssynchrony is considered advantageous in HoCM patients requiring pacemaker therapy. The impact of physiologic pacing, particularly LBBAP, on LVOTO in HoCM remains unexplored. We present a patient highlighting the effect of LBBAP on LVOTO. Case: A 69-year-old female with HoCM (resting gradient ~130mmHg) and asymmetric septal hypertrophy (17mm), managed conservatively due to high surgical risk. She had persistent AF, accompanied by debilitating fatigue and palpitations. Due to unsuccessful treatment with sotalol, dofetilide, and 5 DCCV procedures, other treatment options were discussed. She opted for LBBA pacing and AV node ablation. Dual chamber device was implanted utilizing a Medtronic 3830 lead. Within 48 hours of discharge, she came to the ER with exertional dyspnea and lightheadedness, indicating ambulatory cardiogenic shock (BP: 78/66 mmHg). A stat echo showed LVEF of 75%, severe SAM, LVOT gradient of 179 mmHg, and severe MR. No pericardial effusion. Phenylephrine was initiated, and VVIR rate was decreased from 90 bpm to 60 bpm, but no BP improvement. Obstructive cardiogenic shock from worsened LVOTO was likely caused by physiologic LBBAP. To objectively demonstrate this, she underwent a brief study in the lab after informed consent. We inserted a temporary RV apical pacing lead and assessed LVOT gradients at rest and during exercise for both physiologic pacing and RV apical pacing. RV apical pacing had lower LVOT gradient at rest and exercise compared to LBBA pacing (Figure 1). LBBA lead was extracted and a CRT-P device implanted and programmed for optimal dyssynchrony. Discussion: Traditional RV apical pacing is superior to physiologic LBBAP in HoCM. Limited studies suggest biventricular pacing reduces LVOT gradient, but CRT is not superior to RV pacing. LBBA pacing may be contraindicated in LVOTO patients. Conclusion: In HCM patients with LVOTO, RV apical pacing appears superior to LBBAP, reducing LVOT gradient at rest and during exercise.