No lack of news on the implantable cardiac devices front these days. A team of researchers from all over the world have published their experience with a completely subcutaneous ICD from Cameron Health (San Clemente, CA) in this week’s New England Journal of Medicine. The researchers eliminated the transvenous pacing lead, implanting the lead subcutaneously and tested various configurations for their effectiveness. The pacing lead is a major source of complications of ICDs due to problems during insertion and long-term failure. In the end clinicians found a parasternal electrode and a left lateral thoracic pulse generator to be the optimal configuration, as effective as transvenous ICD for terminating induced ventricular fibrillation. In addition, the device successfully detected and treated 12 episodes of spontaneous ventricular tachyarrhythmia in patients enrolled in the study. One issue to consider is that the energy required for the shock was significantly higher than traditional ICDs. Additional disadvantages of the device is that it cannot perform long-term pacing and cannot treat ventricular tachycardias of less than 170 beats per minute.
From the article abstract in The New England Journal of Medicine:
Methods First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients.
Results The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (±SD) energy requirement (36.6±19.8 J vs. 11.1±8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10±1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.
Conclusions In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.
Press release: Research Published in the New England Journal of Medicine Highlights Potential Benefits of Cameron Health’s S-ICD System…
Product page: Cameron Health S-ICD System…
Full article in NEJM: An Entirely Subcutaneous Implantable Cardioverter-Defibrillator
Flashbacks: EU Issues OK for Minimally Invasive Subcutaneous Implantable Defibrillator; Subcutaneous Implantable Cardiac Defibrillators