HRS.15: MRI doesn’t compromise ICD’s safety, effectiveness

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MRIs and ICDs can mix, at least if MR imaging is with a 1.5 Tesla machine and the implantable cardioverter-defibrillator system is the one tested in a late-breaking clinical trial presented May 14 at the Heart Rhythm Society’s scientific session in Boston.

Michael Gold, MD, chief of cardiology and medical director at the Medical University of South Carolina in Charleston, presented results from the international, randomized clinical trial on behalf of the Evera study investigators. The findings were simultaneously published online May 14 in the Journal of the American College of Cardiology.   

The researchers noted that the FDA has not approved an MRI-compatible ICD system. Although patients with ICDs frequently have a need for diagnostic scans, MR potentially might put them at risk of injury or interfere with device functionality.

“Our goal was to truly push the limits of the ICD, in ways that other studies have not, to ensure it is able to handle the stresses of MRI scans without impacting its ability to deliver potentially life-saving therapy,” Gold said in a release.

The study evaluated the safety and efficacy of the Evera ICD system (Medtronic) in patients who underwent whole body MRIs. The Evera ICD, which has been modified to work within the MR environment, received CE mark in Europe and remains an investigational device only in the U.S. The system includes design changes such as a programmable SureScan to protect against inadvertent inactivation of the device.

Gold and his colleagues enrolled 275 patients between April and September of 2014 from 42 centers, with 263 receiving implants. Of those, 175 underwent MR imaging using 1.5 Tesla systems and 88 served as controls. At a mean follow-up of 4.5 months, there were no MRI-related complications and no significant differences in the efficacy endpoints: ventricular pacing capture threshold and sensing amplitude.

“We now show that the modifications of the ICD system employed in this trial allows for safe 1.5T MRI with <2.0 W/kg [specific absorption rate] and with no restrictions on scan location, heart rate, rhythm or pacemaker dependency,” they wrote. “Importantly, this study was performed in a large number of centers in diverse geographies with highly variable experience with such scanning.”  

The results apply only to the devices and MR scanners used in the trial and not ICD systems in general, they added. The study was funded by Medtronic.