Ventricular Fibrillation Terminated by the Seventh Shock

A 49-year-old man consulted our department 3 months after having several implantable cardioverter-defibrillator (ICD) shocks with subsequent syncope. A CRT-D device (Boston Scientific, Cognis 100-D) and a single-element subcutaneous array (Medtronic, model 6996 SQ) had been implanted 2 years previously for primary prevention of sudden cardiac death caused by symptomatic (New York Heart Association class III) nonischemic dilated cardiomyopathy with severely impaired left ventricular function (left ventricular ejection fraction, 10%) and a left bundle-branch block (QRS width, 176 ms). ICD interrogation revealed a prolonged episode of tachyarrhythmia starting with a fast monomorphic ventricular tachycardia (VT cycle length, 230 ms). Antitachycardia pacing (ATP) during charging led to discrete VT acceleration, followed by degeneration into ventricular fibrillation (VF) caused by the first 41-J shock. Another 5 ineffective ICD shocks were delivered. Eventually, the seventh shock was able to terminate VF (Figure 1). Chest radiographic examination revealed a dislodged SQ array requiring surgical revision (Figure 2). After positioning of a new SQ array, the intraoperative defibrillation threshold (DFT) was determined at 21 J. No perioperative complications occurred, and the patient could be discharged home after recovery. On follow-up 6 weeks later, the patient remained in stable condition with no arrhythmia recurrence.