Safety of MRI in patients with implantable cardiac devices


Clinical question: Is MRI safe for patients who have implanted ICD or pacemakers that have not been deemed to be “MRI conditional” by the Food and Drug Administration?

Background: The majority of patients with implantable cardiac devices have a clinical indication for MRI within 10 years. Devices that meet certain criteria specified by the Food and Drug Administration are not felt to pose any safety hazards and are deemed “MRI conditional.” Those that do not meet these criteria are referred to as “legacy” devices and are considered to be a contraindication to MRI by the FDA and device manufacturers. The majority of ICDs and pacemakers currently in use are legacy devices and access to MRI for patients who have these devices has been very limited. This study is the first large prospective study to evaluate the safety of an MRI protocol in patients with legacy ICDs and pacemakers.

Study design: Prospective nonrandomized study.

Setting: Single academic medical center.

Synopsis: During 2003-2015, 1,509 patients with ICDs (629 patients) and pacemakers (880 patients) were enrolled and underwent 2,103 MRI examinations supervised by either an electrophysiologist or a registered nurse with cardiac device programming experience.

Study outcomes included safety and device function immediately after MRI and change in device parameters both immediately after MRI and at long-term follow-up. The most important clinical adverse event that occurred was a reset of device to backup settings referred to as “power on reset” that occurred in nine examinations. Of these nine events, one was associated with mild physical discomfort, one led to device replacement, and one was associated with transient inhibition of pacing. Small changes in P- or R-wave amplitude and atrial or ventricular capture were noted at long-term follow-up. However, none of these were large enough to result in lead revision or device reprogramming. Notable limitations of this study include that it is a single-center study limiting its ability to be generalized and that nearly 20% of patients were lost to long term follow up.

Bottom line: When performed at an institution with an established safety protocol, MRI examinations in patients with legacy devices are not associated with clinically significant adverse safety events or changes in device function that require reprogramming. Multicenter studies are necessary to determine if these results can be generalizable.

Citation: Nazarian S et al. Safety of magnetic resonance imaging in patients with cardiac devices. N Engl J Med. 2017 Dec 28;377(26):2555-64.

Dr. Scaletta is a hospitalist at Denver Health Medical Center and an assistant professor of medicine at the University of Colorado at Denver, Aurora.

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