Device programming
The ventricular fibrillation (VF) zone detected ventricular events faster than 185-200 beats/min and initial therapy was ≥30 joules (maximum energy of the device). The ventricular tachycardia (VT) zone detected ventricular events faster than 150-170 beats/min, and 3 sequences of ATP were initially attempted. If the arrhythmia continued, the first shock ranged from 10-20 joules and subsequent shocks with maximal energy were delivered until its termination. In cases of patients with documented slow VT, a detection zone lower than 150 beats/min was sometimes programmed. The device-related detection algorithms, such as dual chamber sensing, and the stability and sudden-onset criteria were usually employed for the discrimination of supraventricular tachycardia 10. The morphology-based algorithm for detecting ventricular tachycardia was used as a nominal setting 11. The ICD devices were manufactured by Boston Scientific (Marlborough, Massachusetts, USA), Medtronic (Minneapolis, Minnesota, USA), or Abbott/St. Jude Medical (Lake Bluff, Illinois, USA).