PracticeUpdate Cardiology Best of 2018

EDITOR’S PICKS 9

MRI Appears Safe in Patients With Cardiac Devices The New England Journal of Medicine Take-home message

COMMENT By Clare M. C. Tempany-Afdhal MB, BAO, BCh, FISMRM T his is an important article that prospectively documents the safety of 1.5 Tesla MR scanning in 1509 patients with implanted cardiac legacy devices. All patients were scanned in a single center under very tightly controlled proto- cols and real-time physiological monitoring before, during, and after the MR exams. No long-term adverse events were iden- tified. In the past, all cardiac implanted devices were a major contraindication to MR scanning. However, driven by the recog- nition of the clinical need and value of MRI exams, many device manufacturers have redesigned their implants, which are now classified by the FDA as non-hazardous or “MRI-conditional.” As a word of caution, the careful monitoring of the patients in this study was resource-intensive, unlikely to be generaliza- ble and, importantly, the results are only relevant to 1.5 Telsa imaging. As this readership will know, we generally prefer 3 Tesla for prostate MR examinations. It is likely that these results combined with earlier ones from the MagnaSafe registry will lead to a modification of current safety guidelines for legacy

• Patients with a pacemaker or an ICD not meeting the FDA criteria as suitable for MRI underwent clinically necessary MRI and were followed to evaluate potential adverse effects. There were no reports of any long-term clinically significant adverse events in 1509 patients. Overall, nine devices required a reset to a backup mode; in eight of these cases, the reset was transient and, in a single case, there was insuffi- cient battery life to allow reprogramming and the pacemaker was replaced. Around 1% of patients demonstrated a reduc- tion in P-wave amplitude immediately after MRI. Common long-term changes included decreases in P-wave amplitude from baseline (4%), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%), but these changes were not clinically significant. • MRI with the use of a prespecified safety protocol was found to be safe for individuals with a legacy pacemaker or a legacy ICD system. Abstract BACKGROUND Patients who have pacemakers or defibrillators are often denied the opportunity to undergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria speci- fied by the Food and Drug Administration (termed “MRI-conditional” devices). METHODS We performed a prospective, nonrandomized study to assess the safety of MRI at a magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter–defibrillator (42%) that was not considered to be MRI-conditional (termed a “legacy” device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters). RESULTS No long-term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patient’s device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) imme- diately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients. At long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in 4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture thresh- old (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming. CONCLUSIONS We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter– defibrillator system. No long-term clinically significant adverse events were reported. Safety of Magnetic Resonance Imaging in Patients With Cardiac Devices. N Engl J Med 2017 Dec 28;377(26)2555-64, S Nazarian, R Hansford, AA Rahsepar, et al. www.practiceupdate.com/c/62465

devices. 1 Reference

1. Russo RJ, Costa HS, Silva PD, et al. Assessing the risks associated with MRI in patients with a pacemaker or defibrillator. N Engl J Med 2017;376(8):755-764.

Dr. Tempany-Afdhal is the Ferenc Jolesz MD Professor of Radiology at Harvard Medical School, Vice-Chair of Radiology Research at Brigham & Women’s Hospital, and Director of the Ferenc Jolesz National Center for Image-Guided Therapy in Boston, Massachusetts.

By Minesh P. Mehta MD, FASTRO People have been concerned about the use of MRI in patients who have cardiac devices, and this has led to some patients actually not having MRI scans performed. This paper in a large number of patients (over 1500) shows that patients with either pacemakers or implanted cardioverter defibrillator systems did not experience any clinically significant adverse events. In a long-term analysis of a large database of patients with cardiac devices, no significant adverse events linked to the perfor- mance of MRI scans were observed, implying that it is safe to proceed with MRI in these patients as clinically necessary and indicated. And this would now allow appropriate use of MRI without undue concern about its toxicity.

Dr. Mehta is Deputy Director and Chief of Radiation Oncology at Miami Cancer Institute in Miami, Florida.

VOL. 3 • NO. 4 • 2018