Subcutaneous ICD successfully detected, converted ventricular fibrillation episodes

An entirely subcutaneous implantable cardioverter defibrillator system was found to successfully and consistently detect and convert episodes of ventricular fibrillation in a group of small, non-randomized trials.

The researchers conducted two short-term clinical trials to determine an appropriate device configuration and assess energy requirements. They evaluated four subcutaneous ICD configurations in a study population that included patients (n=78) who were candidates for ICD implantation. Subsequently, they also tested the best configuration in additional patients (n=49) to determine the subcutaneous defibrillation threshold in comparison with that of transvenous ICD. Long-term use of subcutaneous ICD use was also followed in a pilot study (n=6) and then in a larger trial (n=55).

The best device configuration, researchers found, utilized a parasternal electrode and a left lateral thoracic pulse generator, which was as effective as a transvenous ICD for terminating induced ventricular fibrillation but with a higher mean energy requirement (36.6 ± 19.8 J vs. 11.1 ± 8.5 J). Ventricular fibrillation was detected in 100% of 137 induced episodes in patients who received a permanent subcutaneous ICD. Additionally, after a mean of 10 months, the device had detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.

According to researchers, these studies cannot show whether subcutaneous ICDs are superior to conventional transvenous ICDs regarding such characteristics as lead stability or failure, but they shed light on the feasibility of an entirely subcutaneous ICD. However, “the relative benefit of subcutaneous ICDs, as compared with transvenous ICDs, will need to be shown in large, long-term, randomized, prospective, multicenter clinical trials,” they wrote.

Bardy GH. N Engl J Med. 2010;363:36-44.

Follow CardiologyToday.com on Twitter.