Electromechanically Optimized Right Ventricular Pacing for Obstructive Hypertrophic Cardiomyopathy: The EMORI-HCM Trial.
Mohal JS., Whinnett ZI., Mohiddin SA., Malcolmson J., Elliott P., Ormerod JOM., Prasad S., Ware JS., Cooper RM., Tanner MA., Khalique Z., Shah JS., Keene D., Tangkongpanich P., Lewis EC., Sharma C., Reddy RK., Naraen A., Saleh K., Samways JW., Howard JP., Artico J., Kanagaratnam P., Francis DP., Al-Lamee RK., Varnava A., Shun-Shin MJ., Arnold AD.
BACKGROUND: Many patients with symptomatic obstructive hypertrophic cardiomyopathy (oHCM) have devices capable of right ventricular pacing (RVP). Although pacing can reduce left ventricular outflow tract gradient (LVOTg), it can also reduce cardiac output, so its net effect is variable. OBJECTIVES: We tested whether electromechanical optimization of the programmed atrio-ventricular delay (AVD) allows RVP to achieve a net benefit on symptoms. METHODS: EMORI-HCM (Electromechanically Optimized Right Ventricular Pacing in Obstructive Hypertrophic Cardiomyopathy) is a multicenter, blinded, randomized, crossover trial of AVD-optimized RVP in patients with symptomatic oHCM with resting or provoked gradient of at least 30 mm Hg. Patients with existing dual-chamber devices were randomized to either 3 months of continuous AVD-optimized RVP (intervention) followed by 3 months of backup-only RVP (control), or vice versa. AVD was optimized using a high-precision multiple-alternation protocol assessing acute change in beat-by-beat blood pressure while varying AVD. The primary outcome was symptoms measured by the Kansas City Cardiomyopathy Questionnaire Clinical Summary Score. Secondary outcomes include patient-reported daily symptom data collected using a dedicated smartphone application (ORBITA-app), dichotomous patient preference, EQ-5D, exercise capacity, and LVOTg. Patients were blinded to treatment allocation. Symptom assessments were self-administered. Outcome measures were recorded at baseline, crossover, and completion. Analysis was by Bayesian ordinal mixed modeling. RESULTS: Between October 2021 and October 2024, 117 screened patients met the inclusion criteria, of whom 60 were randomized. AVD-optimized RVP improved Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (+4.5; 95% credible interval [CrI]: 1.3-8.1; probability of benefit [Prbenefit] = 0.997) and daily symptom scores (OR: 1.29; 95% CrI: 0.98-1.68; Prbenefit: 0.969) compared with backup-only pacing. AVD-optimized RVP improved exercise capacity (+1.0 mL/kg/min; 95% CrI: 0.1-2.0; Prbenefit: 0.984) and LVOTg (-7.3 mm Hg; 95% CrI: -13.5 to -1.1; Prbenefit: 0.010). It had no effect on B-type natriuretic peptide (Prbenefit: 0.893) and ejection fraction was preserved (Prbenefit: 0.409). CONCLUSIONS: In patients with oHCM, RVP delivered at electromechanically optimized AVD improves symptoms and exercise capacity. (Electromechanically Optimized Right Ventricular Pacing in Obstructive Hypertrophic Cardiomyopathy [EMORI-HCM], NCT05257772).