Life-span of First-Generation S-ICD Is 5 Years, Study Reports

Marlene Busko

July 14, 2015

ROTTERDAM, THE NETHERLANDS — Researchers have determined that on average, the first-generation subcutaneous implantable cardioverter defibrillator S-ICD (Boston Scientific and formerly Cameron Health) needs to be replaced after 5 years, exactly what the manufacturer estimated and slightly less than the life-span of single-chamber or dual-chamber transvenous ICD systems (5.5 years and 5.8 years, respectively)[1].

These findings, by Dr Dominic AMJ Theuns (Erasmus University Medical Center, Rotterdam, the Netherlands) and colleagues, based on an analysis of the 55 patients in the European Registry Trial, were published July 6, 2015 in Circulation: Arrhythmia and Electrophysiology.

Commenting to heartwire from Medscape, Theuns said that the two other notable findings in this study are that the "longevity of the S-ICD is not affected by delivered shock therapy" and that "the need [to replace the S-ICD system with] a transvenous ICD system . . . due to bradycardia therapy, cardiac resynchronization therapy, or need for antitachycardia pacing therapy is low."

However, a new, longer-lasting, second-generation S-ICD is available in Europe and coming soon to the US, he noted.

Does Battery Life or Number of Shocks Predict Device Replacement?

The S-ICD system was designed to reduce mortality in patients at high risk of sudden cardiac death from ventricular arrhythmia and eliminate complications associated with transvenous leads. The reported complication rate with surgery to implant or remove a transvenous ICD is almost 10%, according to Theuns.

The investigational-device-exemption (IDE) trial proved that the S-ICD system is safe and effective, and a recent interim analysis of the EFFORTLESS registry presented "real-world" data, but the longevity of the S-ICD has not been investigated, the researchers write.

Theuns and colleagues examined data from 55 patients who had these devices implanted between December 2008 and February 2009 in Europe and New Zealand. None of the patients had an indication for bradycardia pacing, cardiac resynchronization therapy, or ventricular tachycardia that could be terminated by antitachycardia pacing.

Device longevity was defined as the time from device implantation to surgical replacement. Reasons for replacement included elective replacement, excessive battery drainage (leading to premature replacement within 36 months), device malfunction, and infection.

An "indication for elective replacement" represents "a point in the battery life of cardiac implantable electronic devices where replacement is voluntary, but the devices will continue to operate normally for a maximum of 3 months," Theuns explained. Patients have the battery life of their devices checked regularly when they come to the clinic, and S-ICDs also emit an audible tone to alert patients that they need to promptly consult their physicians about their devices.

The trial patients had a mean age of 56 and were mostly men (80%). About two-thirds of patients had underlying ischemic heart disease, and most patients (78%) had the device implanted for primary prevention.

At 5 years of follow-up, 71% of the devices were still in service.

During a median follow-up of 5.8 years, five patients (9%) had had the device explanted, 26 patients (47%) had received replacement devices, eight patients had died (15%; three from cardiac causes and five from noncardiac causes), and the remaining 16 patients (26%) still retained their original device.

In most of the patients who had their devices replaced (25 of 26 patients; 92%), this was prompted by battery depletion.

"Unexpected" premature replacement of the device due to rapid battery depletion was observed in five devices (9%) with a mean service time of 1.5 years, "which is similar to rates observed with transvenous ICD systems," Theuns said.

The device was explanted and replaced with a transvenous ICD system in four patients (7%)—due to a need for effective defibrillation (one patient), resynchronization therapy (two patients), and antibradycardia pacing (one patient). One patient of the 55 had the device explanted due to infection, which is an acceptable, low rate, Theuns noted.

During follow-up, 16 patients (29%) received 119 shocks from the S-ICD devices; most patients (69%) received fewer than five shocks. There was no association between the number of shocks and elective device replacement (HR 1.01; 95% CI 0.98–1.04, P=0.29).

Second-Generation S-ICD Coming Soon to the US

Further insights into S-ICD are expected to come from ongoing follow-up of the EFFORTLESS registry and from the randomized PRAETOREAN trial (comparing S-ICD vs transvenous ICD), which is still enrolling patients.

Meanwhile, on March 17, 2015, Boston Scientific announced that it had received US Food and Drug Administration (FDA) approval and CE Mark approval for a second-generation S-ICD, EMBLEM, which is 20% thinner and estimated to last 40% longer than the first-generation S-ICD system[2].

"The projected longevity of the second-generation S-ICD is 7.3 years," Theuns specified. "After a limited and controlled release in a small number of European centers, a broad launch started in May 2015 for European centers and a subsequent launch in the US is planned for [the third quarter of] 2015," he said.

Theuns has received institutional grants and consulting fees from Boston Scientific. Disclosures for the coauthors are listed in the article.

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