JEREMY R. BURT, MD
Having been involved with research in the field of MRI and pacemakers/defibrillators (P/Ds) for many years, I'm very excited to announce that many patients with these devices can now safely undergo MRI. Our initial concern was that P/D patients placed in the magnetic field created by the MRI scanner would develop dangerous arrhythmias, leading to symptoms such as chest pain, shortness of breath, palpitations, or loss of consciousness. For this reason, P/Ds have been regarded as a near absolute contraindication for MRI. Over 2 million patients in the United States have implanted devices, including P/Ds. Estimates show that more than 50 percent of these patients will need an MRI while the device is in place.
Many clinicians need their patients to undergo MRI and cannot order another exam because of concerns related to radiation exposure, allergy to iodinated contrast or require MRI to answer a specific question that cannot be resolved with other imaging modalities. An example would be a patient needing a cardiac MRI to evaluate for a potential cardiomyopathy.
Other modalities such as echocardiography or cardiac CT angiography are generally insufficient for evaluating patients with cardiomyopathy. In the past, a patient with P/D in this situation would not be able to undergo MRI. In 2016, two companies received approval from the Federal Drug Administration (FDA) for safe MRI of P/D patients. The devices are made by Medtronic and Biotronic (SureScan™ Revo MRI™ and Advisa MRI™; ProMRI®). Initially, only pacemakers were approved, and only under very controlled circumstances. For example, patients with defibrillators or those needing a cardiac MRI were not deemed as safe to undergo MRI by the FDA with these devices. Additional research in this arena led to removal of many of these restrictions.
The current imaging protocol for MRI performed in these patients includes continuous monitoring of vital signs (heart rate, blood pressure, SpO2, single lead electrocardiogram), visual monitoring of the patient during the exam by an ACLS trained nurse or physician, and monitoring of the MRI machine and patient by the MRI technician. All P/D patients with MR conditional devices must be evaluated by a cardiovascular health care professional prior to and after the MRI with interrogation of the device and switching to "MR safe mode" during the MRI.
Other makers of pacemakers and defibrillators are hoping to follow suit. Many implantable device companies are also evaluating the safety of performing MRI in patients with non-MRI conditional P/Ds. A few investigators have published smaller studies to determine the safety of these devices (Nazarian 2011 and Russo 2014). Patients with nonMRI conditional P/Ds must be closely monitored before, during and after the MRI by cardiovascular nurses, radiologists, and/or cardiologists and have interrogation of the P/Ds prior to and after the MRI.
Many of these research projects are currently enrolling P/D patients as part of the MRI Diagnostic Imaging Registry. These trials are being performed at many centers in the country including Florida Hospital. Investigators are evaluating the safety, image quality, clinical impact and diagnostic utility of MRI in patients implanted with certain types of implantable devices. These studies are accepting eligible patients who have certain brands of implantable devices who require MRI imaging of the head, cervical spine, lumbar spine, pelvis, or extremities.
Although the research protocols may vary depending on the device being imaged, in most cases, a cardiac radiologist and/or electrophysiologist are on site to monitor patients who participate in the project before, during and after the MRI. ACLS certified nursing personnel are also present throughout each MRI to provide cardiac monitoring of the patient. Finally, the patient's devices are interrogated before and after the MRI to monitor for any significant changes. Patients are followed by research personnel at a follow up visit to check the device and assess for any adverse events.
Researchers in the field are actively trying to safely extend the unique diagnostic power of MRI to more patients, including those with pacemakers and defibrillators. Please reach out to your local radiologist to determine the appropriateness of MRI in your pacemaker and defibrillator patients.
Jeremy R. Burt, MD, is a diagnostic radiologists sub-specialized in body imaging for Radiology Specialists of Florida/Florida Hospital, Orlando. His expertise ranges from MRI, CT, Oncology, Cardiovascular to Genitourinary Imaging. He is currently the medical director of Radiology Research, the medical director of MRI Safety, GI/GU Imaging, and the Co-Chair of Radiology Residency, at Florida Hospital. He is also the Adjunct Professor of Research, Adventist University of Health Sciences, Orlando, the Assistant Professor of Radiology, at Florida State University, and the Assistant Professor of Radiology, at the University of Central Florida.