Subcutaneous Implantable Cardioverter Defibrillator in Patients With Hypertrophic Cardiomyopathy: An Initial Experience

Abstract

BackgroundThe subcutaneous implantable cardioverter defibrillator (S‐ICD) has been developed to avert risks associated with transvenous defibrillator leads. The technology is attractive for younger patients, such as those with hypertrophic cardiomyopathy (HCM). However, there are limited data on S‐ICD use in HCM.Methods and Results HCM patients identified at risk for sudden death were considered for S‐ICD implantation. Patients were screened for potential oversensing by surface electrocardiography (ECG). At implant, defibrillation threshold (DFT) testing was performed at 65, 50, and 35 joules (J). Twenty‐seven patients were considered for S‐ICD implantation, and after screening, 23 (85%) remained eligible. The presence of a bundle branch block was associated with screening failure, whereas elevated body mass index (BMI) showed a trend toward association. One patient passed screening at rest, but failed with an ECG obtained after exercise. At implant, the S‐ICD terminated ventricular fibrillation (VF) with a 65J shock in all 15 implanted patients and a 50J shock was successful in 12 of 15. A 35J shock terminated VF in 10 of 12 patients. DFT failure at 50 J was associated with a higher BMI. There were no appropriate shocks after a median follow‐up of 17.5 (3–35) months, and 1 patient received an inappropriate shock attributable to a temporary reduction in QRS amplitude while bending forward, resulting in oversensing, despite successful screening.ConclusionsIn a high‐risk HCM cohort without a pacing indication referred for consideration of an ICD, the majority were eligible for S‐ICD. The S‐ICD is effective at recognizing and terminating VF at implant with a wide safety margin.

Implantable cardioverter defibrillator therapy in hypertrophic cardiomyopathy: an updated systematic review and meta-analysis of outcomes and complications

“…The majority of the patients were given an ICD for primary prevention (83%) compared to secondary prevention (17%). Three of the studies used a subcutaneous ICD (18,22,34). Left ventricular (LV) thickness ≥30 mm, family history of SCD, non-sustained VT, syncope and abnormal blood pressure response to exercise were present in 10%, 26%, 25%, 7% and 22% of the patients respectively ( Table S1).…”

“…Subcutaneous ICDs pose a major advantage of less serious complications from lead failure and infection, because removal of subcutaneous ICD is a lower risk procedure compared to the removal of transvenous leads. Furthermore, the absence of a lumen in the subcutaneous leads may theoretically reduce the risk of lead failure (34). However, a subcutaneous ICD provides neither bradycardia pacing nor anti-tachycardia pacing capabilities, which limits the suitability of subcutaneous devices for certain patients who require pacing.…”

Pacing for hypertrophic obstructive cardiomyopathy: an update and future directions

“…When a single-chamber ICD is implantedcurrent clinical evidence indicate the S-ICD is safe and effective in patients with HCM [34][35][36] and support the 2014 ESC / HCM guidelines proposal that S-ICD may be considered in HCM patients who do not have an indication for pacing (Class IIb, level of evidence C) 15 .…”

ICD Therapy for Primary Prevention in Hypertrophic Cardiomyopathy

“…67 The advent of the fully subcutaneous ICD (S-ICD), see was the only baseline characteristic that was associated with an unsuccessful 50 J shock. 69 This early success led to long-term followup studies that also appear promising. 70 A recent publication of a large pooled S-ICD cohort of 872 patients, including 100 patients with HCM, indicates that the S-ICD can effectively terminate spontaneous life-threatening arrhythmias.…”