Shock or no shock - a question of philosophy or should intraoperative implantable cardioverter defibrillator testing...

Implantation of implantable cardioverter defibrillators (ICDs) in patients with a high risk for life-threatening ventricular arrhythmias is a standard therapy. The development of new ICD leads, shock algorithms, high-energy defibrillators and rapid energy supply has improved the devices. Nevertheless, the discussion regarding 'shock or no shock' to test the system intraoperatively has not silenced yet.

In this study, all 718 patients (60.0 ± 14.2 years old, 570 male) who were treated with a first ICD at our institution since 2005 were analysed. The indication for implantation was primarily prophylactic in 511 patients (71.3%). Underlying diseases included ischaemic cardiomyopathy (358 patients, 50%), dilated cardiomyopathy (270 patients, 37.7%) and others (12.3%). Mean ejection fraction was 27.4 ± 11.8%. Intraoperative ventricular fibrillation was induced with a T-wave shock or burst stimulation. The primary end-point was failing the initial intraoperative testing.

During the initial testing, 28 patients (3.9%) had a defibrillation threshold (DFT) >21 J. The mean age of these patients was 51 ± 14 years, ranging from 22 to 71 years, 20 were male, and the ejection fraction was 23.8 ± 11.8%. The indication for ICD implantation was prophylactic in 13 patients. Twenty-one of the 28 patients suffered from dilated cardiomyopathy, whereas seven patients had ischaemic cardiomyopathy. Twenty-four ICDs were implanted on the left side and four on the right side. None of the patients had been treated with amiodarone at the time of implantation. All patients achieved a sufficient DFT ≤ 21 J by changing the ICD leads, device repositioning and/or optimizing the shock configuration.

The standard of care intraoperative ICD testing remains necessary.