Two Limitations of Subcutaneous Implantable Cardioverter Defibrillator in the Same Patient Warranting Its Explant
Unusual clinical course, Unusual or unexpected effect of treatment
Rahul Dhawan, Mansoor Ahmad, Aravdeep Jhand, Sumera Kanwal, Adeel Jamil, Faris Khan
Department of Internal Medicine, Division of Cardiovascular Medicine, University of Nebraska Medical Center, Omaha, NE, USA
Am J Case Rep 2021; 22:e928983
Available online: 2021-03-26
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.
Keywords: Cardiac Electrophysiology, Transvenous ICD, Subcutaneous ICD, Oversensing, ventricular tachycardia