Candidacy and long-term outcomes of subcutaneous implantable cardioverter-defibrillators in current practice in patients with hypertrophic cardiomyopathy.

Background: In patients with Hypertrophic Cardiomyopathy (HCM) S-ICD is usually the preferred option as pacing is generally not indicated. However, limited data are available on its current practice adoption and long-term follow-up.
Methods: Consecutive HCM patients with S-ICD implanted between 2013 and 2021 in 3 international centers were enrolled in this observational study. Baseline, procedural and follow-up data were regularly collected. Efficacy and safety were compared with a cohort of HCM patients implanted with a tv-ICD.
Results: Seventy patients (64% males) were implanted with S-ICD at 41 ± 15 years, whereas 168 patients with tv-ICD at 49 ± 16 years. For S-ICD patients, mean ESC SCD risk score was 4,5 ± 1.9%: 25 (40%) at low-risk, 17 (27%) at intermediate and 20 (33%) at high-risk. Patients were followed-up for 5.1 ± 2.3 years. Two patients (0.6 per 100-person-years, vs 0.4 per 100 person-years with tv-ICD, p = 0.45) received an appropriate shock on VF, 17 (24%) were diagnosed with de-novo AF. Inappropriate shocks occurred in 4 patients (1.2 per 100-person-years, vs 0.9 per 100 person-years with tv-ICD, p = 0.74), all before Smart-Pass algorithm implementation. Four patients experienced device-related adverse events (1.2 per 100-person-years, vs 1 per 100 person-years with tv-ICD, p = 0.35%).
Conclusions: S-ICDs were often implanted in patients with an overall low-intermediate ESC SCD risk, reflecting both the inclusion of additional risk markers and a lower decision threshold. S-ICDs in HCM patients followed for over 5 years showed to be effective in conversion of VF and safe. Greater scrutiny may be required to avoid overtreatment in patients with milder risk profiles.
Competing Interests: Conflict of interest The authors report no conflict of interest regarding the topic discussed in the present manuscript. The study was supported by an educational grant from Boston Scientific, USA. Disclosures: Dr. I. Olivotto has received grants from Brystol Myers Squibb, Cytokinetics, Amicus, Genzyme, Shire, Bayer, Boston Scientific, Menarini International, and fees (honoraria or consulting) from Bristol Myers Squibb, Cytokinetics, Amicus, Genzyme, Shire, Boston Scientific, and served or currently serving as PI on EXPLORER-HCM, MAVA-LTE, REDWOOD-HCM, REDWOOD-OLE, and SEQUOIA-HCM trial. Dr. F. Cecchi received consultancy fees from Pfizer and Bristol Myers Squibb. Dr. L. Crotti and Dr. N. Maurizi received consultancy fees from Bristol Myers Squibb.
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