Failed Maximal Defibrillation Threshold Testing in the Subcutaneous Implantable Cardioverter Defibrillator

The subcutaneous implantable cardioverter defibrillator (S-ICD) registry included very few patients with a body mass index (BMI) greater than 40. We present a case of a 40-year-old male with a BMI of 44 and ejection fraction of 25% who underwent S-ICD implantation for primary prevention of sudden cardiac death in the setting of a nonischemic cardiomyopathy. Defibrillation threshold (DFT) testing failed at high output. A posterior to anterior radiograph demonstrated migration of the components despite positioning under fluoroscopy. After repositioning, repeat DFT testing showed an inconsistent efficacy. We discuss the probabilistic nature of DFT testing, clinical factors affecting the S-ICD implant in the obese population and offer a novel insight from this specific experience.