A Subcutaneous Implantable Cardioverter-Defibrillator Inches Toward Prime Time

Randomized controlled trials have demonstrated the superiority of implantable cardioverter-defibrillators (ICDs) to antiarrhythmic drugs in preventing sudden cardiac death. However, ICDs are not without problems, including both device and lead malfunction. Many ICD manufacturers are pursuing systems that would avoid some of these problems. In a new report, investigators present findings from two feasibility trials and two short-term clinical follow-up trials of a subcutaneous ICD, all sponsored by the device manufacturer.

Of four device configurations tested in 78 patients, the best performer was a high-energy (80-J generator placed in the left lateral chest wall and attached to a lead placed immediately to the left of the sternum. In a subsequent trial, this device effectively sensed induced ventricular fibrillation (VF) in 49 patients. The mean defibrillation threshold was 36.6 joules, although the device failed to terminate VF at maximal energy in one patient, in whom the lead was found to have been incorrectly placed. During a pilot trial in six patients (mean follow-up, 488 days) and a clinical trial in 55 patients (mean follow-up, 10 months), patient survival and device performance were excellent, although oversensing of muscle noise occurred in three patients in the latter trial.