HRS: More data lean in favor of S-ICD system

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Subcutaneous implantable cardioverter defibrillator - 87.86 Kb
Locations of the components of a subcutaneous implantable cardioverter–defibrillator in situ Source: New England Journal of Medicine

BOSTON—Adding to the recent positive data from the FDA regarding Cameron Health’s subcutaneous implantable cardioverter-defibrillator (S-ICD) system, a study presented May 10 at the late-breaking clinical trial section at the 33rd annual scientific sessions of the Heart Rhythm Society found the device to be safe and effective.

“The S-ICD system detects, senses and treats ventricular tachyarrhythmias with a device that is completely under the skin,” said Martin C. Burke, DO, interim chief of the section of cardiology and director of the Heart Rhythm Center at the University of Chicago Medicine, during a morning press briefing. The prospective, nonrandomized, multicenter trial evaluated 330 patients who were enrolled at 33 clinical sites. Fifteen percent of enrollment was outside of the U.S., with the remaining 85 percent from the U.S., Burke said.

The researchers used effectiveness, which was defined as induced ventricular fibrillation (VF) conversion rate, as the study's primary endpoint. This was defined as two consecutive successful conversions out of a possible four attempts at 65 joules. The safety endpoint used was the 180-day S-ICD system complication-free rate. 

Burke said that the performance goal criteria, obtained from a review of prior literature, was deemed to be 88 percent for the effectiveness endpoint and 79 percent for the safety endpoint.

S-ICD device implantation was attempted in 321 of the 330 patients enrolled. Patients had a mean age of 52 (younger than those usually enrolled in transvenous ICD studies), 74 percent were male and patients within the study had a mean ejection fraction of 36 percent.

“In both cases … the primary endpoint was met,” Burke said. Of the patients enrolled 80 percent had a primary indication for an ICD implant, 41 percent had a prior MI and 11 percent had a channelopathy.

Burke added that 304 patients met the effectiveness event rate. “That means a 100 percent success rate was seen, which was well above the 88 percent performance criterion that was set prior to the trial.”

The trial’s safety endpoint was also met. In fact, the type 1 complication-free rate at 180 days was reported to be 99 percent, where the performance criterion set at the start of the trial was 79 percent. 

Infections were seen in four implants, which resulted in explantation of the device. The 180-day major complication rate was reported to be 7.9 percent. Burke said that initial implantation techniques were altered during the early stages of the trial after the infection rates seen in the first patient implantations. After alteration of the technique by operators, none of the last two-thirds of patients experienced device explants due to infection.

During the study, 7.2 percent of patients required 26 repeat surgeries. Five patients underwent repeat surgery for suboptimal position, three for electrode movement, one for incomplete electrode connection, one for device movement, nine for discomfort, two for premature battery depletion, two for communication failure and three for oversensing.

“In summary, the process of this particular trial demonstrates that both these primary endpoints were met,” Burke said. “We saw spontaneous episodes that were very successfully treated 100 percent of the time.” During the trial, 109 episodes occurred in 16 patients.

The researchers reported 68 incidences of ventricular tachycardia of ventricular fibrillation and 39 patients received an inappropriate shock.

“The most interesting thing that I can tell you from our data points is that 13 percent of the patients actually had a previous transvenous ICD system,” Burke said. He added that when these patients were presented with the option of receiving a transvenous system again or entering a trial and receiving the S-ICD device, all patients chose the S-ICD device.

“This is not a niche device,” Burke said. “We actually implanted the device in anyone who presented with an indication for ICD implantation that met the guidelines indication for enrollment.”

Compared with traditional transvenous ICD trials, the S-ICD trial included a patient subset that was much younger (average age of 52). Burke said that recently data have shown that lead problems with long-term utilization in transvenous lead systems have occurred in younger patients.

“I think this has made referring doctors