Abstract 13503: Efficacy of Subcutaneous Implantable Cardioverter Defibrillator Defibrillation Testing in Hypertrophic Cardiomyopathy Patients at High Risk of Sudden Cardiac Death

Abstract

Introduction: Subcutaneous ICD (S-ICD) is a promising option for Hypertrophic Cardiomyopathy (HCM) patients at high-risk of Sudden Cardiac Death (SCD). However, its efficacy in terminating ventricular arrhythmias in HCM is yet unresolved. Hypothesis: To determine the efficacy of post-implantation S-ICD defibrillation testing (DT) of Ventricular Fibrillation (VF) in HCM patients and assess possible predictors of failure. Methods: Consecutive HCM patients referred for S-ICD implantation at seven Italian Centers from June 2014 to May 2016 were prospectively enrolled. At S-ICD implantation, patients underwent one or two attempts of VF induction by programmed electrical stimulation. Successful conversion was defined as any 65j shock that terminated VF and did not require rescue shocks. Clinical, ECG and Echocardiographic findings were analyzed to study potential predictors of conversion failure. Results: We evaluated 50 HCM patients (34 males, mean age 40±16) with a mean BMI of 25.2±4.4 kg/m 2 [18.1-36]. Two patients (4%) had a history of cardiac arrest, whereas 48 (96%) were implanted in primary prevention. Mean calculated risk of SCD at 5 years by the ESC score was 6.5±3.9% and all patients had at least one major risk factor. Maximal LV wall thickness (LVMWT) was >25 mm in 19 (38%) patients and ≥ 30 mm in 13 (26 %). In 2/50 patients (4%) no arrhythmias were inducible, while in 7 (14%) only polymorphic sustained ventricular tachycardia (SVT) was induced and correctly cardioverted by the S-ICD. In the remaining 41 (82%) patients, 70 VF episodes were induced (2 VF in 29 and 1 VF in 12 patients), all correctly recognized by the device. Of the 70 VFs, 4 (6%) spontaneously converted into sinus rhythm. In 65/66 (98%) the S-ICD performed successful conversions, but failed in 1 (2%) patient, who needed rescue defibrillation. This patient was severely obese, with a BMI 36 kg/m 2 and LVMWT of 25 mm. VF was induced again and successfully converted by 80j shock with inverted polarity. Conclusions: Acute defibrillation testing at 65j shows the efficacy of S-ICD in terminating VF or polymorphic SVT in HCM patients, despite the presence of extreme LV hypertrophy. Severe obesity was possibly responsible for the single failure observed at 65j in our series.