title: Subcutaneous Implantable Cardioverter Defibrillator in Patients With Hypertrophic Cardiomyopathy: An Initial Experience.
abstract: BACKGROUND
  The 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.
  
  
  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.
  
  
  CONCLUSIONS
  In 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.
authors.affiliation: Cardiac Arrhythmia Center and The Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA jweinstock1@tuftsmedicalcenter.org.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Weinstock
authors.affiliation: Cardiac Arrhythmia Center and The Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA.
authors.forename: Yousef H
authors.initials: YH
authors.lastname: Bader
authors.affiliation: Cardiac Arrhythmia Center and The Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Maron
authors.affiliation: Cardiac Arrhythmia Center and The Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA.
authors.forename: Ethan J
authors.initials: EJ
authors.lastname: Rowin
authors.affiliation: Cardiac Arrhythmia Center and The Hypertrophic Cardiomyopathy Center, Tufts Medical Center, Boston, MA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Link
mesh_terms: D000293:Adolescent; D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation*; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D004868:Equipment Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D055815:Young Adult
keywords: defibrillation; hypertrophic cardiomyopathy; implantable defibrillator; sudden death