SCMRI: Study reconfirms MRI use for patients with pacemakers and defibrillators

Magnetic resonance imaging in patients with implanted pacemakers and defibrillators adds enough substantial clinical value in diagnosis and subsequent patient management to justify the risk of the procedure, according to a presentation made in a scientific session at the annual meeting of the Society of Cardiovascular MRI held in Los Angeles last month. Researchers from Allegheny General Hospital in Pittsburgh retrospectively evaluated the medical records of 157 consecutive patients with implanted cardiac devices who had MRI exams over a 10 year period.

Robert Biederman, M.D., medical director of the Cardiovascular MRI Center and one of the study’s lead researchers, explained that while multiple studies have documented the safety of MRI scans of patients with implanted devices, the diagnostic clinical value of MRI has not been established. “It was important to determine if significant life-saving or life-changing diagnoses could also be made on the results of the MRI.”

The 157 patients evaluated by the research team included 114 neurology/neurosurgery cases, 36 cardiovascular cases, and seven musculoskeletal cases. All had pacemakers. Thirty-one patients also had an automatic implantable cardioverter defibrillator (AICD). For each patient, the research team determined if the pre-MRI diagnosis was confirmed or if the primary diagnosis changed, if the MRI exam provided additional information to the existing diagnosis, and if patient management changed as a result of the findings. MRI was considered to be of value if any of these criteria were answered in the affirmative.

The MRI exams for 18% of the neurology/neurosurgery cases provided additional information and changed the original diagnosis. The findings provided additional complimentary diagnostic information for 69%, and for 88% provided value to the final diagnosis. The MRI did not provide any additional information except to confirm a patient’s diagnosis for only 12%.

All but 8% of the cardiovascular patients benefitted from the MRI scan. The MRI images of the 8% -- three patients -- had AICD artifacts which prevented the scan from being interpreted. Five patients (14%) had their original diagnosis and patient management changed, and the MRI exam provided complimentary information for 77%. For the seven musculoskeletal cases, MRI provided additional diagnostic information for six patients and changed patient management for one patient.

There were no safety issues identified or adverse effects reported. Dr. Biederman attributed this in part to careful attention to device reprogramming and scanner sequences selected.

At Allegheny General Hospital, patients who are referred for MRI undergo an extensive evaluation of their cardiovascular health and level of device dependence. Once a patient is cleared, a baseline device interrogation is performed. The patient’s pacemaker and/or defibrillator are converted to a safer mode of operation for the length of the exam. If patients are determined to be non-pacemaker dependent under baseline conditions, the device may be turned off completely.

During the procedure, a patient’s heart rhythm is monitored in real-time in the MRI suite. Dr. Biederman said that he and Moneal Shah, Ph.D., a cardiovascular medical physicist, are in attendance. When the scan has been completed, the implanted device is reprogrammed to its original settings.

“Approximately three million Americans have an implanted cardiac device, and hundreds of thousands more receive them each year. It is estimated that as many as 75% will require a MRI exam at some point in their lifetime. Our study confirms its value, and reconfirms its safety,” concluded Dr. Biederman.