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SIMPLE: Defibrillation testing safe, but did not improve outcomes
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SAN FRANCISCO — Routine defibrillation testing appears to be safe, but does not improve outcomes in patients with implantable cardioverter defibrillators to detect and treat ventricular fibrillation, according to study results presented at the Heart Rhythm Society Annual Scientific Sessions.
In clinical trials, it is protocol to include defibrillation testing as part of ICD implantation, but it had never been shown to improve outcomes, Jeffrey S. Healey, MD, FHRS, from Population Health Research Institute in Ontario, Canada, said at a press conference.
Jeffrey S. Healey
In fact, Healey said, cohort studies have identified serious complications related to defibrillation testing, secondary analyses from randomized trials have indicated possible harm from ICD shocks and recent registry data have shown that defibrillation testing is on the decline. However, there had not been a definitive trial on the subject.
Continued use questioned
“Many electrophysiologists around the world have begun to question whether this type of procedure was still necessary,” especially because improvements in ICD technology have led to lower failure rates, Healey said.
The SIMPLE investigators enrolled 2,500 patients in 18 countries undergoing their first ICD implant. Patients were randomly assigned on a 1:1 basis to receive defibrillation testing or no testing. Median follow-up was 3.1 years. During this time, only a small percentage of patients were lost to follow-up, Healey said.
The primary outcome was a composite of failed appropriate shock or arrhythmic death.
“We thought this was an important clinical outcome because that’s what the testing is meant to do; it’s meant to improve the likelihood that the device will successfully terminate an episode of ventricular tachycardia or ventricular fibrillation,” Healey said.
A key secondary outcome was all-cause mortality. The researchers also evaluated 30-day safety, including a composite of death, MI, stroke, anoxic brain injury, systemic or pulmonary embolism, HF, need for chest compressions or aortic balloon pump, need for intra-operative vasoconstrictors of more than 15 minutes, non-elective intubation, pneumothorax, cardiac perforation, ICD infection, arterial line complication, aspiration pneumonia or unplanned ICU stay.
Noninferiority proved
For the primary outcome, ICD implantation without defibrillation testing was noninferior to ICD implantation with defibrillation testing (P for noninferiority<.0001), Healey said. The primary outcome occurred at an annual rate of 7.2% of patients in the no-testing arm vs. 8.3% of patients in the testing arm (HR=0.86; 95% CI, 0.65-1.14).
“We hypothesized that an implant without testing would be noninferior to an implant with testing, and we very much succeeded in showing that was the case,” Healey said. “Actually, the point estimate fell in favor of no testing. We were very happy that we proved it in a very robust way.”
There was no difference between the groups in rates of all-cause mortality (HR=1.04; 95% CI, 0.86-1.26) or the 30-day safety composite outcome, he said.
“We think that the ICD without routine testing should be the preferred approach now,” Healey said. – by Erik Swain
For more information:
Healey JS. Abstract LB01-01. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 7-10, 2014; San Francisco.
Disclosure: The SIMPLE study was funded by Boston Scientific. Healey reports receiving research grants and consulting fees from Boston Scientific, Medtronic and St. Jude Medical.
Perspective
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Paul A. Friedman, MD, FHRS
We can now safely stop testing in the majority of patients. That is a big step because testing has been very controversial with strong opinions and proponents in both directions due to the absence of compelling data. Every single pivotal trial that has informed the use of ICDs that have demonstrated their superiority to other therapies has used some form of testing. For most patients receiving a new left-sided transvenous implant, defibrillation threshold testing and consequent general anesthesia can safely be avoided.
This study also confirmed that when testing is needed it is safe, with an extremely low rate of complications. In patients with right-sided systems, amiodarone use or subcutaneous systems, testing should be strongly considered, as [these groups] were not well represented in or were excluded from the study, and their defibrillation efficacy may be lower.
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