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Two different MRI-safe ICDs show safety, efficacy

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MRI-safe ICDs offer a welcome option

MRI-safe implantable cardioverter defibrillators will become the standard of care. They are especially appropriate for patients who are younger when they receive their device and hence more likely to need an MRI at sometime in their future, as well as for older patients who are known to need an MRI in the foreseeable future.

Dr. Fred M. Kusumoto

MRI-safe implanted pacemakers have been routinely available in the United States for a few years, and since their U.S. introduction they have gradually increased their market share and have become the dominant device for younger patients and for patients with a scheduled, upcoming MRI.

Now that MRI-safe pacemakers and implantable cardioverter defibrillators exist, the next step will be to create an MRI-compatible cardiac resynchronization therapy device, but their more complicated design and lead placements will mean further design and engineering challenges.

Dr. Fred M. Kusumoto is a professor of medicine and an electrophysiologist at the Mayo Clinic in Jacksonville, Fla. He had no relevant financial disclosures. He made these comments in an interview.




BOSTON – An implantable cardioverter defibrillator device that can safely undergo magnetic resonance imaging may soon be a commercial reality as two different models from two different manufacturers showed safety and mostly uncompromised efficacy during and after MRI in two separate studies reported at the annual scientific sessions of the Heart Rhythm Society.

The impending availability of two different brands of implantable cardioverter defibrillators (ICDs) that allow patients to safely undergo MRI “will hopefully open a new era when most [ICDs] are designed” to be MRI safe, said Dr. Khaled A. Awad, an electrophysiologist at the University of Alabama at Birmingham, and lead investigator for one of the new studies.

“Within 10 years, all ICDs getting implanted will be MRI compatible,” predicted Dr. Michael R. Gold, chief of cardiology and medical director of the heart and vascular center at the Medical University of South Carolina in Charleston and lead investigator for the second study.

Until now, having an ICD in a patient created a contraindication for using MRI on the patient, a situation that would change once MRI-safe ICDs become routinely available, noted Dr. Gold. MRI-compatible implanted pacemakers have been on the U.S. market since 2011; ICDs able to safely undergo MRI exposure became the next frontier for creating implanted cardiovascular devices that allow MRIs. Both studies used MRI performed with a 1.5-T magnetic field, a strength commonly used in routine practice today.

Dr. Khaled A. Awad

Dr. Khaled A. Awad

The ProMRI study reported by Dr. Awad enrolled patients at 39 U.S. centers who at least 5 weeks previously had received an Iforia ICD made by Biotronik along with commercially available leads believed to be MRI safe. The researchers performed MRIs of the heart or thoracic spine on 154 patients, and then ran follow-up examinations on 150 patients 1 month after the MRI, and a second, 3-month follow-up on 92 of the enrolled patients. The study did not include any control patients who received the ICD and did not undergo MRI.

No patient had an adverse event related or possibly related to their ICD either at the time of the MRI or at follow-up, Dr. Awad reported. In addition, no patients had a significant change in their ICD’s ventricular capture threshold, and one patient had a significant change in the ICD’s ventricular sensing. During follow-up, the ICDs of enrolled patients detected a total of 403 ventricular arrhythmias in 39 patients, with all these episodes appropriately detected and treated.

Dr. Michael R. Gold

Dr. Michael R. Gold

The study reported by Dr. Gold enrolled patients at 42 centers in 13 countries including the United States. The investigators implanted ICDs into 263 patients using commercially available leads, and then 9-12 weeks after placement, they randomized patients at a 2:1 rate to either undergo MRI or receive no MRI and serve as controls. Of the 175 patients randomized to undergo MRI, 156 actually received the examination, a full-body examination, and 147 participated in follow-up to at least 1 month and were part of the safety analysis.

Patient follow-up showed no complications, no episodes of a significant change in ventricular-pacing sensing threshold, and one episode of a significant change in ventricular-sensing amplitude, Dr. Gold reported, showing safety and efficacy outcomes identical to those in the trial of the Biotronik device. During follow-up 34 episodes of ventricular tachycardia or fibrillation occurred in 24 patients in the MRI group, and the implanted ICDs detected and treated all episodes appropriately. Concurrent with Dr. Gold’s report, the results also appeared in an article published online (J. Am. Coll. Cardiol. 2015 [doi:10.1016/j.jacc.2015.04.047]).

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