Background 

Transcoronary ablation of septal hypertrophy (TASH) to relieve left ventricular outflow tract obstruction (LVOT) is an established treatment for selected patients with hypertrophic obstructive cardiomyopathy (HOCM) who remain symptomatic despite optimal medical therapy. Alcohol is the medium of choice, while the safety and efficacy of microsphere embolization have not yet been studied.

Aim

To investigate the safety and efficacy of septal microsphere embolization (SME) for targeted occlusion of the septal perforator of interest.

Methods

We conducted a retrospective analysis of SME procedures performed at our center from 2006 to 2021 using75 µm microspheres (Embozene®, Boston Scientific). The primary endpoint was in-hospital mortality. Secondary endpoints were major adverse cardiovascular events and the reduction of the LVOT gradient. 

Results

The study population comprised 76 patients with HOCM with a mean age of 61.5 ± 16.0 years at the time of the procedure. Males constituted almost half of the population (n = 33, 43.4 %). Severe dyspnoea NYHA ≥ 3 was present in n = 65, 86 % of the study patients, whereas non-sustained/sustained ventricular tachycardia and previous syncope were described in n = 8, 11 % and n = 14, 18% of patients, respectively. Approximately a fifth of the patients had already undergone a defibrillator or pacemaker implantation (n = 16, 21 %). The median duration of hospitalisation was 13.5 (IQR 7.2 – 19.9) days, and the median time to the first follow-up was four months. SME resulted in a significant reduction in resting and provoked LVOT gradients at follow-up (42 vs. 21mmHg, p < 0.001 and 95 vs. 43 mmHg, p < 0.001, respectively). The observed mean ΔGradients at rest and with Valsalva provocation were -25.2 mmHg and -60.3 mmHg, respectively. Intraprocedural death due to a therapy refractory cardiogenic shock occurred in one case of urgent SME in an acutely decompensated patient directly after transcatheter aortic valve replacement. A complete atrioventricular block following the ablation procedure was observed in n = 4, 5.3 % of the population. Post-procedural left bundle branch block of new-onset was diagnosed in n = 1, 1.3 %, and a right bundle branch block in n = 3, 4.1 %. Access site complications were described in n = 3, 5.2 % of the patients. No further major or minor cardiovascular events were observed up to discharge from the index hospitalization.

Conclusion

In this seminal study, we demonstrate that SME is a safe and effective alternative to alcohol-based TASH for the treatment of patients with HOCM who remain refractory to pharmacologic treatments. Any potential benefits of this technique over alcohol and the sustainability of the achieved reduction in the LVOT gradients are still to be investigated in further studies with longer follow-up.