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MagnaSafe published: MRI safe for patients with pacemakers, ICDs, regardless of labeling
With appropriate device reprogramming and screening, patients with a non-MRI-conditional pacemaker or implantable cardioverter defibrillator can undergo MRI with no device or lead failure, according to results from the MagnaSafe Registry published in The New England Journal of Medicine.
Results from the MagnaSafe Registry were first presented at the American Heart Association Scientific Sessions in November 2014.
“There are about 2 million people in the U.S., probably about 6 million people worldwide outside the U.S., with an MRI-non-conditional pacemaker or defibrillator and about half of them are thought to need a clinically indicated MRI at some time in their life after the device has been implanted,” Robert J. Russo, MD, PhD, from the department of cardiovascular medicine at Scripps Clinic in La Jolla, California and the department of molecular and experimental medicine at Scripps Research Institute, told Cardiology Today. “That means for a fair number of people who require an MRI diagnostically, they now have a protocol to follow so that they can have it done safely.”
Study parameters and protocol
Russo and colleagues evaluated adult participants who had a non-conditional-MRI pacemaker or ICD generator from any manufacturer implanted after 2001. Participants were included for study if they had a clinically indicated nonthoracic MRI at 1.5 T.
Participants were excluded if they were pacing-dependent, if their device’s battery was near the end of its battery life or if there was an abandoned or inactive lead that could not be interrogated.
Device interrogation was performed pre-scan according to a standardized protocol. Asymptomatic patients with at least 40 bpm had their device programed to a nonpacing mode (ODO or OVO). If a patient was symptomatic or had and intrinsic heart rate of < 40 bpm, their device was reprogrammed to an asynchronous pacing mode (DOO or VOO). Nonpacing-dependent patients with an ICD had all bradycardia and tachycardia therapies inactivated pre-scan. Pacing-dependent ICD patients were excluded.
After MRI, baseline settings were restored, device interrogation was repeated and, if needed, the device was reprogrammed.
Results
The primary outcomes included death, generator or lead failure requiring immediate replacement, loss of capture, new-onset arrhythmia and partial or full generator electrical outset. Secondary outcomes included clinically relevant changes in battery voltage, lead impedance, lead threshold and P- and R-wave amplitude.
From April 2009 to April 2014, 1,000 MRI scans were performed in 818 patients with pacemakers and 500 scans were performed in 428 patients with ICDs. Follow-up data was available for 1,395 cases.
I. There were almost no cases presenting with primary outcomes. In one case, the ICD had not been reprogrammed appropriately before the MRI. After the scan, the generator could not be interrogated and required immediate replacement.
The researchers observed six cases of atrial fibrillation or flutter, all of which self-corrected. Five of these patients had a history of paroxysmal AF. In six cases (five patients), partial generator electrical reset occurred; in all cases, the pacemakers had been implanted more than 5 years before the scan. Settings that were reset included identification information.
Changes in secondary outcomes were limited to a small number of cases. Small decreases in battery voltage were measured post-MRI. All pacemaker decreases of 0.04 V or more had resolved at the last follow-up; however, some ICD voltage decreases had not.
Repeat MRI was no associated with an increased number of adverse events.
“What we were trying to do in MagnaSafe was to determine if there really were risks to the patient or to the device if they needed MRI,” Russo said. “What we succeeded in doing in a large enough number of patients is to show that there doesn’t seem to be a risk to the patient or the device if you follow the protocol that we laid out. The fear across many disciplines of medicine — cardiology, general medicine, radiology — were that the radiofrequency energy from the MRI scan would create heating in the lead that would damage the myocardium of the heart or that the device itself would be damaged. What we showed was that those fears, for the most part, were not founded clinically and that patients were not at significant risk when this was done appropriately.”
Russo said he and his colleagues are now seeking to alter Medicare coverage to allow patients with devices that are MRI nonconditional to have a scan covered. They are also working on a study of nonthoracic 3 T scans and 1.5 T thoracic scans on patients with nonconditional pacemakers or ICDs. – by Cassie Homer
For more information:
Robert J. Russo, MD, PhD, can be reached at Department of Molecular and Experimental Medicine, Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037; email: russo@scripps.edu.
Disclosure: The MagnaSafe Registry is supported by grants from Biotronik, Boston Scientific/Guidant, the Hewitt Medical Research Foundation, St. Jude Medical and other philanthropic sources. Russo reports receiving grant support from Biotronik, Boston Scientific and St. Jude Medical and personal fees from St. Jude Medical. Please see the full study for a list of the other researchers’ relevant financial disclosures.