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Primary Results From the Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction (UNTOUCHED) Trial

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posted on 09.09.2021, 10:11 by Michael R Gold, Pier D Lambiase, Mikhael F El-Chami, Reinoud E Knops, Johan D Aasbo, Maria Grazia Bongiorni, Andrea M Russo, Jean-Claude Deharo, Martin C Burke, Jay Dinerman, Craig S Barr, Naushad Shaik, Nathan Carter, Thomas Stoltz, Kenneth M Stein, Amy J Brisben, Lucas VA Boersma, UNTOUCHED Investigators*

Background

The subcutaneous (S) implantable cardioverter-defibrillator (ICD) is safe and effective for sudden cardiac death prevention. However, patients in previous S-ICD studies had fewer comorbidities, had less left ventricular dysfunction, and received more inappropriate shocks (IAS) than in typical transvenous ICD trials. The UNTOUCHED trial (Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction) was designed to evaluate the IAS rate in a more typical, contemporary ICD patient population implanted with the S-ICD using standardized programming and enhanced discrimination algorithms.

Methods

Primary prevention patients with left ventricular ejection fraction ≤35% and no pacing indications were included. Generation 2 or 3 S-ICD devices were implanted and programmed with rate-based therapy delivery for rates ≥250 beats per minute and morphology discrimination for rates ≥200 and <250 beats per minute. Patients were followed for 18 months. The primary end point was the IAS-free rate compared with a 91.6% performance goal, derived from the results for the ICD-only patients in the MADIT-RIT study (Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy). Kaplan-Meier analyses were performed to evaluate event-free rates for IAS, all-cause shock, and complications. Multivariable proportional hazard analysis was performed to determine predictors of end points.

Results

S-ICD implant was attempted in 1116 patients, and 1111 patients were included in postimplant follow-up analysis. The cohort had a mean age of 55.8±12.4 years, 25.6% were women, 23.4% were Black, 53.5% had ischemic heart disease, 87.7% had symptomatic heart failure, and the mean left ventricular ejection fraction was 26.4±5.8%. Eighteen-month freedom from IAS was 95.9% (lower confidence limit, 94.8%). Predictors of reduced incidence of IAS were implanting the most recent generation of device, using the 3-incision technique, no history of atrial fibrillation, and ischemic cause. The 18-month all-cause shock-free rate was 90.6% (lower confidence limit, 89.0%), meeting the prespecified performance goal of 85.8%. Conversion success rate for appropriate, discrete episodes was 98.4%. Complication-free rate at 18 months was 92.7%.

Conclusions

This study demonstrates high efficacy and safety with contemporary S-ICD devices and programming despite the relatively high incidence of comorbidities in comparison with earlier S-ICD trials. The inappropriate shock rate (3.1% at 1 year) is the lowest reported for the S-ICD and lower than many transvenous ICD studies using contemporary programming to reduce IAS.

Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02433379.

Funding

Boston Scientific Corp

History

Citation

Circulation. 2021;143:7–17

Author affiliation

Department of Cardiovascular Sciences, University of Leicester

Version

VoR (Version of Record)

Published in

Circulation

Volume

143

Issue

1

Pagination

7 - 17

Publisher

American Heart Association

issn

0009-7322

eissn

1524-4539

Acceptance date

28/09/2020

Copyright date

2020

Available date

09/09/2021

Spatial coverage

United States

Language

eng

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