Largest Randomized Trial Of ICD Recipients Demonstrates Excellent Outcomes With Or Without Defibrillation Testing

Boston Scientific Shockless Implant Evaluation (SIMPLE) study results presented at Heart Rhythm 2014, the Heart Rhythm Society's 35th Annual Scientific Sessions


May 13, 2014
Boston Scientific Corp. ICD HRS 35th Annual Scientific Sessions SIMPLE Trial

May 13, 2014 — A Boston Scientific Corp. study demonstrated that outcomes for patients with the company's transvenous implantable cardioverter defibrillators (ICD) who received routine defibrillation testing (DT) at implant were similar to outcomes for those patients who did not receive defibrillation testing. TheShockless IMPLant Evaluation (SIMPLE) study is the largest randomized clinical trial of ICD recipients to date. The primary results were presented at the Heart Rhythm Society's 35th Annual Scientific Sessions in San Francisco by Jeff S. Healey, M.D., FRCPC, associate professor, Division of Cardiology and the Department of Medicine at McMaster University, Ontario, Canada.

The trial results demonstrated that routine defibrillation testing at the time of ICD implant was safe, but did not improve shock efficacy or reduce mortality compared to the no-testing strategy. Specifically, the investigators demonstrated non-inferiority for the primary endpoint of ineffective clinical shock or arrhythmic death (7.22% in the no-DT group vs. 8.30% in the DT group (PNoninferiority=0.0001)). The rate of survival from arrhythmic death was 94.8% in the no-DT group vs. 94.4% in the routine DT group (P=0.50). The primary safety endpoint, comprised of complications within 30 days of the implant, was also similar between the two patient groups (5.4% in the no-DT group vs. 6.5% in the routine DT group, p=0.25). Thus, despite questions regarding the need for routine defibrillation testing, it is generally safe and may still be suitable for certain patients at the physician's discretion.

"Defibrillation testing has long been a standard practice among electrophysiologists, but there has been little evidence suggesting it improves outcomes," said Healey. "Our findings from the SIMPLE study demonstrate that those patients who received ICDs without defibrillation testing did as well as those who underwent the standard defibrillation testing at the time of implant."

This study of Boston Scientific ICDs also demonstrated excellent efficacy in the secondary endpoint of first shock efficacy. The rate of 91 percent for first shock efficacy in the no-DT group was comparable to the findings in landmark ICD studies, such as SCD-HeFT (83 percent), as well as in the recently reported S-ICD System EFFORTLESS registry (88 percent).

ICDs are designed to provide protection to patients at risk of sudden cardiac death (SCD). Sudden cardiac death is a sudden, unexpected death caused by loss of heart function and is a leading cause of death. Nearly 400,000 out-of-hospital cardiac arrests occur annually in the United States.

The SIMPLE trial randomized 2,500 ICD recipients in 18 countries to groups either receiving or not receiving defibrillation testing, a method to test the ability of the ICD to treat an induced ventricular fibrillation during the implant procedure. Defibrillators with cardiac resynchronization therapy (CRT-D), which treat asynchronous heartbeats common in heart failure patients, were also included.  Average follow-up was over 3.1 years.

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