Device improvements boost performance
The low 1-year and 18-month rates of inappropriate shocks likely occurred because of new filtering and programming incorporated into the tested device. “By changing the filter, we could make it more like a transvenous device” that is not fooled by T wave over sensing. The programing also included a high beat threshold, with a conditional zone above 200 beats per minute and an “aggressive shock zone” of 250 bpm, Dr. Gold said. This helped make the tested S-ICD more immune to inappropriately shocking a supraventricular arrhythmia; the study recorded no inappropriate shocks of this type, he reported.
The UNTOUCHED study enrolled 1,116 patients at any of 110 sites in the United States and elsewhere who had a need for primary prevention of sudden cardiac death, a left ventricular ejection fraction of 35% or less, no need for pacing, and had successfully passed an S-ICD screening test. The investigators were able to include 1,111 of these patients in their endpoint analysis. Patients averaged 56 years of age, a quarter were women, and their average ejection fraction was 26%.
In addition to the primary endpoint and the 1-year inappropriate-shock rate, the results also showed an all-cause shock-free rate of 90.6% during 18-months’ follow-up, which significantly surpassed the prespecified performance goal for this metric of 85.8%. The tested device also appeared to successfully apply appropriate shocks when needed, delivering a total of 64 of these with just 1 shock failure, a case where the patient spontaneously reverted to normal rhythm. During the study period, 53 patients died (5%), including 3 arrhythmia-related deaths: 1 caused by asystole and 2 from pulseless electrical activity.
“The data show that in a standard ICD population, the device worked well, and was safe and effective,” Dr. Russo said. “These data say, at least consider this device along with a transvenous device” for appropriate patients. “It’s a great option for some patients. I’ve seen so may lead problems, and this avoids them.”
UNTOUCHED was sponsored by Boston Scientific, the company that markets the tested S-ICD. Dr. Gold has been a consultant to Boston Scientific and Medtronic and has been an investigator for trials sponsored by each of these companies. Dr. Russo served on the steering committee for UNTOUCHED but received no compensation and has no financial disclosures.