ICD Study Says Defibrillation Testing Safe But Unneccessary

This week has seen the Heart Rhythm Society’s 35th Annual Scientific Sessions in San Francisco. Boston Scientific’s SIMPLE study results were presented at the event and showed 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.


Routine defibrillation testing at implantation of your Implantable Cardioverter/Debrillator (ICD) has been brought into question by the newly presented study, tagged SIMPLE (Shockless IMPLant Evaluation). SIMPLE is the largest randomized clinical trial of ICD recipients to date and its primary results were presented at the HRS event by Jeff S. Healey, M.D., FRCPC, associate professor, Division of Cardiology and the Department of Medicine at McMaster University, Ontario, Canada.

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 heart beats common in heart failure patients, were also included. Average follow-up was over 3.1 years.

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).

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).

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. 

Investigator comments

“Defibrillation testing has long been a standard practice among electrophysiologists, but there has been little evidence suggesting it improves outcomes,” said Jeff S. Healey, M.D., FRCPC, associate professor, Division of Cardiology and the Department of Medicine at McMaster University, Ontario, Canada. “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.”

Company comments

“We are proud to have exclusively sponsored the investigators in the largest randomized trial of ICD recipients to date, and are now able to address a key clinical question that has been debated since we pioneered ICD therapy 30 years ago,” said Kenneth Stein, M.D., chief medical officer, Rhythm Management, Boston Scientific. “While the study challenges the value of routine defibrillation testing, physicians and their patients should be comforted by the safety and efficacy of our ICD devices with either approach.”

Source:Boston Scientific Corporation 


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