Personalized permanent pacing guided by hemodynamic study as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) patients with left ventricular outflow tract obstruction (LVOTO) often experience severe drug refractory symptoms. Overall, studies on gradient reduction by electrostimulation have led to contradictory results, possibly due to the heterogeneity of stimulation sites and intervals. Based on these conflicting data, current guidelines assign a class IIb indication for DDD pacing in HOCM patients without a bradycardia indication.

We sought to validate the hypothesis that acute hemodynamic testing might be used to select the optimal right ventricular (RV), left (LV) or biventricular pacing site in order to achieve the maximum reduction in gradient and functional capacity improvement, in patients whose optimal medical therapy had failed.

Between 2016 and 2024, patients with obstructive HCM have been included if 1) symptomatic, 2) refractory to optimized medical therapy and 3) not or poorly eligible for septal myectomy or with an indication to implant a pacing device (pacemaker or ICD). Cardiac catheterization and temporary pacing were performed to identify the pacing site(s) among RV apex and suitable branches of the coronary sinus (CS) and the best configuration (RV only, LV only or biventricular) associated to the maximum reduction of LVOT gradient. Thereafter, all patients were implanted, regardless the results of acute stimulation test.

The study population consisted of 10 patients with obstructive HCM (50% male) who underwent cardiac device implantation guided by haemodynamic testing. Mean age at implant was 76 ± 9 years. Of the 10 patients, 2 (20%) were referred for primary prevention ICD and 4 (40%) had pacing indication for bradycardia. Of those, 6 patients had resting obstruction documented by simultaneous LV apical and aortic pressure assessment > 30 mmHg, whereas 4 patients required gradient provocation via isoprenaline infusion. The mean pre-treatment invasive gradient was 111 ± 31 mmHg, versus 45 ± 20 mmHg during pacing from the optimal ventricular site (p < 0.0001) (Table 1). In 5 (50%) of 10 patients, this was obtained from an anterior or apical position of the LV, whereas in 3 (30%) it was from the right ventricle. The postero-lateral LV position resulted to be the worst configuration in the majority of patients (50%). In 2 of 10 patients, it proved impossible to deliver a lead with stable or satisfactory pacing parameters at the best LV position. All 10 subjects underwent successful device implantation with uncomplicated insertion (Figure 1).

Notwithstanding the upcoming therapy with myosin inhibitors, in drug-refractory symptomatic obstructive HCM, a personalized permanent pacing can reduce LVOT obstruction in patients with limited treatment options and device indication. A haemodynamic pacing study is an effective strategy for identifying optimal pacing site and configuration which is often an antero-distal LV position.