June 23, 2014

NICE, FRANCE – A longer-term assessment of a new subcutaneous implantable cardioverter defibrillator (ICD) (Boston Scientific) shows that just over 90% of patients are free from complications at two years.

Presenting follow-up results from a pooled analysis of the EFFORTLESS S-ICD Registry and initial investigational device exemption (IDE) study here at CardioStim 2014 , senior investigator Dr Reinoud Knops (Academic Medical Center, Amsterdam, the Netherlands) said the total complication rate, and specifically the infection and erosion rates, "were comparable to those widely recognized to accompany the conventional transvenous ICD."

The subcutaneous ICD has been available in Europe since 2008 and was approved by the US Food and Drug Administration in 2012. The subcutaneous system was developed to solve a problem "generally considered to be one of the Achilles' heels of device therapy, of ICD therapy, and that is the lead connected to the ICD tends to break over a few years," said Knops. "The idea is that a subcutaneous device would last longer and have fewer complications."

More Than 800 Patients Followed for Two Years

The IDE study was conducted at 33 sites and included 330 participants followed for a mean 22 months; the EFFORTLESS registry included mainly European centers with 1000 participants followed for five years. Investigators pooled the two cohorts in the present analysis to assess safety and effectiveness out to two years.

In total, 882 patients were included in the pooled analysis. The primary indications for the device were ischemic and nonischemic cardiomyopathy. Interestingly, approximately 13% of patients already had an ICD prior to receiving the subcutaneous ICD, with the initial transvenous device extracted for various reasons.

At two years, 90.2% of patients were free from complications, defined as the need for an invasive intervention related to the device. Most adverse events occurred within the first 120 days and were usually related to the implant procedure. "After 120 days, the complication–rate curve tends to flatten out," said Knops. "With transvenous leads, usually after one or two years, you'll see a downward curve with complication rates because the leads tend to fracture."

Regarding specific procedural complications, device infection occurred in 15 patients, device erosion in 11 patients, discomfort in eight patients, and electrode movement in five patients. The device was taken out of 14 patients because of an infection and six patients because of erosion. Session moderator Dr Michael Gold (Medical University of South Carolina, Charleston) noted that when erosions and device infections were combined they occurred together in 2.9% of patients, a rate higher than that observed with transvenous systems.

Knops acknowledged that the number of erosion/infections is slightly higher than with conventional ICDs but said the higher rate is the result of learning how to implant the new system. In the IDE study, nearly all infections occurred during early enrollment. Also, his center has had success with reducing infections by switching from a three-incision to a two-incision technique.

"From my own personal experience I can say that we've had some erosions and infections, but once you go through the learning process with the device, your procedure times will drop and complications decrease," said Knops. "Things like discomfort and erosion usually occur when you make the pockets too narrow and it's too tight around the device. These are things you learn."

For technical complications related to the device, such as inappropriate shocks, suboptimal electrode positioning, premature battery depletion, or an inability to communicate with the device, each complication occurred in less than 1% of patients. Knops noted that in the early stages, physicians explanted the device when sensing problems occurred, but as experience grows with programming, this likely won't be a reason to take out the subcutaneous ICD.

At two years, 97% of patients were alive and there were no device-related arrhythmic deaths. There were no lead fractures or systemic blood-borne infections. "The fact that the whole system is subcutaneous helps prevent larger complications," said Knops.

The EFFORTLESS registry is sponsored by Boston Scientific.

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