For patients with symptomatic obstructive hypertrophic cardiomyopathy (oHCM), the net effect of right ventricular pacing (RVP) has been variable, as it can reduce the left ventricular outflow tract gradient (LVOTg) but may also decrease cardiac output.¹ The EMORI-HCM trial investigated whether electromechanically optimising the atrio-ventricular delay (AVD) could allow RVP to achieve a consistent benefit on symptoms.²

Methodology

EMORI-HCM (Electromechanically Optimized Right Ventricular Pacing in Obstructive Hypertrophic Cardiomyopathy) was a multicenter, blinded, randomized, crossover trial. The study enrolled 60 patients with symptomatic oHCM who had existing dual-chamber devices and a resting or provoked LVOTg of at least 30 mm Hg.²

Participants were randomized to one of two sequences: 3 months of continuous AVD-optimized RVP followed by 3 months of backup-only RVP (control), or the reverse order. The AVD was individually optimized for each patient using a high-precision protocol that assessed acute, beat-by-beat changes in blood pressure while varying the AVD setting.²

The primary outcome was symptom burden, measured by the Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS). Secondary outcomes included daily symptom scores collected via a smartphone app, patient preference, EQ-5D, exercise capacity, and LVOTg.²

Results

Compared with backup-only pacing, AVD-optimized RVP led to a significant improvement in the primary outcome, with the KCCQ-CSS increasing by 4.5 points (95% credible interval [CrI]: 1.3–8.1; probability of benefit [Pr(benefit)] = 0.997).²

Significant improvements were also seen in key secondary outcomes. Daily symptom scores improved (OR: 1.29; 95% CrI: 0.98–1.68; Pr(benefit): 0.969), and exercise capacity increased by 1.0 mL/kg/min (95% CrI: 0.1–2.0; Pr(benefit): 0.984). Furthermore, the LVOTg was reduced by a mean of 7.3 mm Hg (95% CrI: −13.5 to −1.1; Pr(benefit): 0.010). The intervention had no effect on B-type natriuretic peptide, and ejection fraction was preserved.²

In Practice/Interpretation

The findings from EMORI-HCM suggest that personalising the AVD setting is a key factor in unlocking the therapeutic potential of RVP for patients with oHCM. By optimising the pacing parameters based on individual haemodynamics, this approach can provide meaningful improvements in symptoms and functional capacity. “In patients with oHCM, RVP delivered at electromechanically optimized AVD improves symptoms and exercise capacity,” the study authors concluded.²

This study was funded by Imperial College London.

References

1. Makavos G, Κairis C, Tselegkidi ME, et al. Hypertrophic cardiomyopathy: an updated review on diagnosis, prognosis, and treatment. Heart Fail Rev. 2019;24:439-459. https://doi.org/10.1007/s10741-019-09775-4

2. Mohal JS, Whinnett ZI, Mohiddin SA, et al. Electromechanically Optimized Right Ventricular Pacing for Obstructive Hypertrophic Cardiomyopathy: The EMORI-HCM Trial. J Am Coll Cardiol. 2026;87(2):124-139. https://doi.org/10.1016/j.jacc.2025.08.050

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