Two Limitations of Subcutaneous Implantable Cardioverter Defibrillator in the Same Patient Warranting Its Explant

BACKGROUND A subcutaneous implantable cardioverter defibrillator (S-ICD) is preferred over a transvenous implantable cardioverter defibrillator (TV-ICD) in selected cases owing to a lower rate of lead-related complications such as infections and venous thrombosis. However, the S-ICD has its own limitations, including inappropriate shocks due to oversensed events, and the inability to treat ventricular tachycardia (VT) below a heart rate of 170 beats per minutes (bpm). We present a patient case which showed manifestations of both of these limitations, warranting explant of the device. CASE REPORT A 50-year-old man with a history of nonischemic cardiomyopathy and VT had a S-ICD placed at an outside facility. However, he continued to have VT despite on anti-arrhythmic drugs and required recurrent S-ICD shocks. Device interrogation showed that he was intermittently receiving appropriate shocks for slower VT (with a heart rate ranging from 150 bpm to 160 bpm) due to oversensing of T waves. However, treatment was delayed for other VT episodes owing to appropriate sensing and the patient's heart rate being below the lowest detection zone for S-ICD. Due to slower VT cycle length and frequent oversensed events, the S-ICD was ultimately replaced by a TV-ICD system. CONCLUSIONS This case report emphasizes the importance of S-ICD pre-implant vector screening and the need for paying attention to VT cycle length to prevent inappropriate device shocks and/or delayed therapies.