HRS.15: No adverse outcomes in patients with ICD system undergoing MRIs

BOSTON—Patients with the Iforia ProMRI implantable cardiac device (ICD) system had no adverse outcomes related to the device and no significant changes to pacing or sensing parameters after undergoing a thoracic spine or cardiac MRI, according to a multicenter, nonrandomized trial.

All episodes of life-threatening ventricular arrhythmias were appropriately detected and treated. The MRI had no impact on the ICD’s main function of detecting and treating arrhythmias.

Lead researcher Khaled Awad, MD, of the University of Alabama at Birmingham,  presented results of the study on May 15 during a late-breaking clinical trials session at Heart Rhythm 2015. Biotronik, the device’s manufacturer, funded the study.

No ICD systems currently have an FDA labeling indicating they are safe for use in MRIs, according to Awad. He said patients with ICDs typically do not undergo an MRI because of potential adverse outcomes, including interactions between the ICD system and the electromagnetic fields generated by the MRI machine.

However, he added that some pacemakers are designed to work in collaboration with MRIs, although the successful interaction between ICDs and MRIs is unknown. Biotronik initiated the ProMRI trials to investigate the safety and efficacy of ICD platforms in MRIs.

Five weeks after patients underwent ICD implantation for various clinical indications, they were assessed for eligibility to participate in this study. Patients were required to be at least 18 years old and have stable lead parameters for five weeks. They were excluded if they had a planned cardiac surgery within three months of enrollment, were pregnant, had a life expectancy of less than three months, had abandoned ICD or pacemaker leads or had implanted prostheses or medical devices that could complicate MRI studies.

Of the 170 patients who were provisionally enrolled at 39 centers in the U.S., 154 met the eligibility criteria. The mean age was 60, and 57.1 percent of patients had a primary prevention indication for their ICDs. All but six patients underwent a cardiac or thoracic MRI with a standard 1.5T scanner.

The scanning protocol was predefined and standardized between patients and centers.

“The design of the protocol was aimed at stressing the device and the whole system as much as possible and increasing the magnitude of the magnetic fields to probably the highest levels that you could encounter in a clinical scan,” Awad said.

The researchers found there were 43 adverse events, but most were not serious and none were related to the ICD or MRI. The most common events were incidental MRI findings and heart failure exacerbation.