San Francisco- According to a study presented today at Heart Rhythm 2011, the Heart Rhythm Society's 32nd Annual Scientific Sessions, a new subcutaneous implantable cardioverter defibrillator (S-ICD) accurately detected and successfully converted all episodes of ventricular fibrillation (VF) in 100% of observed patients. These promising results came out of a 98-patient, multi-center, Netherlands-based study - the largest S-ICD patient cohort study to date.
Prior to the study's observation period, S-ICDs were implanted according to international guidelines and then tested for efficacy. Following implantation, patients were observed for an average follow-up period of nine months, during which all patients were free from heart-failure related hospitalizations as well as sudden cardiac death. Investigators found the S-ICD systems to accurately detect and successfully convert all episodes of induced VF. A primary prevention indication was present in 62 patients (63 percent) and 41 percent had ischemic cardiomyopathy. Although over-sensing caused inappropriate therapy in 8 patients, after the devices were reprogrammed, no additional incidents of inappropriate therapy occurred.
Unlike existing implantable defibrillators, or ICDs, which require a wire to be placed within or on the heart, S-ICDs are minimally invasive, and do not require direct vascular access to the heart. Instead, the S-ICD is embedded under the skin, thereby reducing the complications of infections caused by the lead. Nonetheless, the study showed that 5 out of 98 patients receiving the device still developed some level of infection. Since reduction in overall infections is seen as an advantage for the device, continued work to further reduce the infection rate will be necessary. Moreover, because the S-ICD system shocks the heart externally, it is not suitable for patients who also need pacing. Since the device cannot pace continuously it will only be suitable for a select group of patients.
"This subcutaneous ICD system has proved to be a great option for many of our patients who do not require pacing," said Lara Dabiri Abkenari, MD, of ErasmusMC in Rotterdam, Netherlands. "Patients with the system have been very satisfied because it is easily implanted, easily removed if needed, and allows patients more arm movement and mobility than the conventional ICD. This S-ICD system is ideal for young adults and all those who are at risk of sudden cardiac arrest yet have no resynchronization or pacing indications."
Implanted on the left side of the body, the device sits outside of the ribs creating a "pocket" on the side of the body. This device is considerably larger than current ICD devices and is often visible externally from the body; some patients report "feeling" the device, but without any pain. The S-ICD System, manufactured by Cameron Health, received CE Mark approval in 2009 and is being used by physicians in Europe as an effective alternative to the conventional ICD system for appropriate patients. In the US, it is currently being reviewed for use by the FDA.