Study finds common test of ICD patients to be unnecessary

The largest ever randomized clinical trial of 2,500 implantable cardioverter defibrillator patients has determined that routine defibrillation testing during the implant procedure does not improve efficacy or mortality, and may even be harmful.

Patients in the global, nearly 5-year Shockless Implant Evaluation study who received the testing were more likely to suffer fromineffective clinical shock or arrhythmic death than those who did not. Among those in the no-test control group, 7.22% suffered from those complications, compared to 8.3% in the defibrillation test group, according to study collaborator Boston Scientific ($BSX).

The other endpoints were similar between the two groups. Both had a rate of survival fromarrhythmic death of nearly 95%. Patients in the no-test group were less likely to report complications within 30 days than those in the test group (5.4% vs. 6.5% of those in the defibrillation test group), but the difference is not statistically significant.

Defibrillation testing involves putting the patient into cardiac arrest during the implant to determine if the ICD can recognize and correct cardiac complications like ventricular tachycardia and ventricular fibrillation. Seventy percent of the 300,000 patients worldwide who receive an ICD every year get defibrillation testing, according to principal investigator, Dr. Jeff Healey of McMaster University in Ontario, Canada.

"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," Boston Scientific concluded in a statement.

Healey was far less equivocal. "Without the testing we can save a significant amount of time, money and more importantly, avoid potentially serious complications in patients who are receiving an ICD," he said. "Over the last 10 years, there has been an important shift in practice around the world towards ICD implantation without the test. However, until now, there has been no scientific evidence to support this change in practice. Our study now provides clear and robust evidence to guide practice."

- read the Boston Scientific release
- read the McMaster University release

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