​Undergoing magnetic resonance imaging (MRI) with a legacy cardiac device is not associated with any long-term clinically significant adverse events, according to a December 28, 2017, study in the New England Journal of Medicine. The authors conducted a prospective study of MRI safety among 1,509 patients who had either a pacemaker (58% of the patients) or implantable cardioverter-defibrillator (ICD; 42% of the patients) considered to be MRI-conditional (meaning the device has been shown to pose no hazard, under specified conditions, to patients undergoing MRI) by the U.S. Food and Drug Administration. Using a prespecified safety protocol, imaging was performed on each patient using MRI scanners with a strength of 1.5 Tesla. The implanted devices were adjusted for the MRI environment before the scans. The authors measured for device-related events including generator failure, power-on reset, changes in pacing threshold, battery depletion, cardiac arrhythmia, inhibition of pacing, and inappropriate delivery of pacing or shock, as well as patient-report events such as pain, warm sensations from the device, and palpitations. The most important event reported, the authors said, was the occurrence of power-on reset in about 1 out of every 200 observations. Power-on reset is when a device's settings automatically reset to a backup mode, as if the power had been shut on and off. Of the nine examinations in which power-on reset occurred, one was associated with mild physical symptoms and one was associated with transient inhibition of patient. One power-on reset event resulted in the inability to reprogram the device; however, this occurred when the battery was nearing the end of its life, the authors said. This was the only event that resulted in a need to replace the device. The authors were able to conduct long-term follow-up with 63% of the patients and found the most common notable changes from baseline to be decreases in P-wave amplitude (4% of participants), increase in atrial capture threshold (4%), and increase in right ventricular capture threshold (3%). None of these were clinically significant, the authors said. The authors acknowledged several limitations of their study including that it occurred at a single facility, all MRIs used the same field strength, and that technology is constantly evolving and so future interactions cannot be predicted.

HRC Recommends: Use of MRI can cause adverse events under certain circumstances. Even though this study did not show long-term clinically significant adverse events related to legacy cardiac devises, risk managers need to be alert to limitations of this or any study's findings. HRC recommends implementation of precautions to mitigate MRI risks. For example: Establish and routinely review MRI policies and procedures and assess staff compliance. Identify with clear signage zones in the MRI suite and surrounding rooms (including adjacent floors) where the magnetic field strength exceeds 5 T. Ensure that these signs are visible. Define this area as the MRI environment, and restrict access to this area. Provide formal training on safety considerations in the MRI environment to all MRI staff and to other personnel who would have an opportunity to enter the MRI environment. This might include surgical, transport, security, housekeeping, and maintenance personnel, as well as emergency response personnel (e.g., firefighters). Install an intercom system between the MRI scan room and the control room, and check its operation regularly. Finally, provide the patient with an MRI-safe alarm device to alert staff in case of emergency. At a minimum, superconductive MRI scan rooms should be equipped with a low-oxygen monitor/alarm to alert MRI personnel to magnet quenches. Ideally, the monitor/alarm would be configured to automatically activate scan-room ventilation.​