Under-the-Skin ICD Holds Up Over Time

SAN FRANCISCO -- The subcutaneous implantable cardioverter-defibrillator (S-ICD) appears to be holding up in longer-term outcomes, a largely European registry showed.

At 1 year, 98.0% of recipients remained free from infections, failure of the parasternal lead, and other device-caused complications, Lucas Boersma, MD, PhD, of the St. Antonius Hospital in Nieuwegein, the Netherlands, and colleagues reported here at the Heart Rhythm Society meeting.

That rate was 99.0% at 6 months, compared with the 79% performance goal specified by the FDA for the device's pivotal trial, based on historical transvenous ICD data.

"It exceeds the expectations, so it's actually pretty good; and it was almost the same as in the IDE [investigational device exemption] trial, so it seems to be pretty safe," Boersma said, adding that safety appeared to be improving with operator experience, suggested by a nonsignificant trend (P=0.06).

Most of the complications occurred early in follow-up, with infections and device removal being most common. There were no lead-related complications and no late infections.

For the 994 patients who received the device at 42 sites in Europe and one site in New Zealand in the EFFORTLESS registry with an average 3.1 years of follow-up, a device change was prompted to implant a pacemaker in 10 patients, because left ventricular function improved sufficiently to not require an ICD in two, and because of inability to program the device for ventricular tachycardia (VT) of less than 170 bpm in one.

The rate of inappropriate shocks in the first year was 1.5%, which Boersma noted has been reduced with newer programming on T-wave oversensing.

The rate of failed acute conversion testing for ventricular tachycardia or fibrillation was 0.5%.

The rate of appropriate shocks was 5.8% at 1 year, with a 97.4% shock conversion rate in non-storm episodes and 92.3% for the 11 patients with storm episodes. None of the non-storm patients died; one died due to bradycardia in a storm event that was not converted, which Boersma noted was a challenging patient with the rare Loeffler's syndrome.

In terms of how to select appropriate patients, Thomas Deering, MD, of Piedmont Hospital in Atlanta, said at a press conference he co-chaired discussing the late-breaking trials:

"This is a sub-selected group of patients who have either a primary or secondary prevention indication for a device, do not have a pacing need, or they probably won't in the short-term life of the device have a pacing need, who are at relatively low risk for ATP (so an ischemic cardiomyopathy with lots of non-sustained VT [ventricular tachycardia] may not be an ideal choice patient perhaps because of that potential possibility), and people whom you don't think you need to monitor a lot of atrial tachyarrhythmias that are present. The technological improvements in the device mean that it would be a lot easier. So you are trading off a little bit long term as the device gets older having to upgrade to a CRT-D as LV dysfunction worsens, QRS widens, etc. It's that balancing act wherein for high-risk patients -- the high infection risk patients; patients who are at high risk of pneumothorax -- you can move in that direction."

Boersma told attendees his strategy:

"In my hospital, my approach is this patient can have an S-ICD unless there is a need for CRT [cardiac resynchronization therapy], unless this patient has a history of more VT then they benefit from ATP [antitachycardia pacing], or there is a bradycardia indication. In all other indications, a patient could receive an S-ICD. So then patient factors like stature or patient preferences also are taken into account and discussed with patients. We have been implanting the device since 2009, so for us it is part of routine decision making."

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