Safety update: What we know about performing MR exams on patients with implantable cardiac devices

Recent research has shown MRIs are safe for patients with implantable cardiac devices such as pacemakers and cardioverter defibrillators. However, according to a recent analysis published by Radiology, there’s still a lot of information for radiologists, cardiologists and electrophysiologists to know about this important topic

The authors began by reviewing the large number of complications that could occur if physicians and imaging providers don’t pay close attention and follow protocols as recommended.

“Potential consequences of MRI on cardiac implantable electronic devices include movement of the device, heating of the leads and surrounding tissues (causing subsequent tissue damage), altered capture and sensing thresholds, current induction within leads, and other unpredictable pacing behaviors,” wrote author Saman Nazarian, MD, PhD, from the Hospital of the University of Pennsylvania in Philadelphia, and colleagues. “Additionally, radiofrequency noise detected by implantable cardioverter defibrillators has the potential to cause inappropriate inhibition of pacing, activation of pacing because of tracking, or activation of tachycardia therapies including defibrillation."

The authors also reviewed some of the more recent research on this topic, noting that two of them also worked on a study published by the New England Journal of Medicine in December 2017 that “demonstrated the safety of 1.5-T MR examinations in patients with legacy cardiac devices by using a standardized protocol for programming and monitoring during the examination with infrequent changes in device parameters and no long-term clinically significant adverse effects.”

Nazarian and colleagues emphasized that the use of that standardized protocol is vital to understanding the safety of these imaging services.

“It is important to recognize that this protocol requires a programmed asynchronous pacing mode for pacing-dependent patients because electromagnetic interference can cause inappropriate inhibition of pacing,” the authors wrote. “It is also critical that all tachyarrhythmia therapies are deactivated to avoid inappropriate sensing and attempted delivery of unnecessary therapy. For both reasons, it is essential that patients are monitored by providers with experience in cardiac life support and that equipment for potential defibrillation or external pacing be present.”

The authors also noted that additional research is necessary to study the safety of imaging patients with implantable cardiac devices with more powerful MRI equipment.

“Thin-section 3-T MR examinations have not been established to be safe with legacy cardiac implantable electronic devices, which is an area of future research as these imagers become more common,” they wrote. “Because cardiac implantable electronic devices are constantly evolving, it will also be important to continue to monitor for evidence that future systems may have unexpected interactions with the MRI environment.”

Nazarian and colleagues added that, back in January, CMS proposed covering MRI scans for Medicare beneficiaries with implantable cardiac devices. In April, CMS published a decision memo finalizing that proposal, emphasizing that the MRI field strength must be 1.5 Tesla when in “Normal Operating Mode” and the device must have “no fractured, epicardial or abandoned leads.”