Small study: MRIs okay with pacemakers and defibrillators



VANCOUVER, B.C. – When done safely, MRI imaging has an important role to play in patients with pacemakers and implanted cardioverter defibrillators, according to a study of 32 patients who underwent the procedure without complications at Allegheny General Hospital in Pittsburgh.

"It looks like this is safe in the right situation," based on the results and ongoing research elsewhere. "There are occasions – more often than you might think – when" MRI imaging of such patients has "potentially life-saving consequences. I would suggest it is probably no longer taboo," said lead investigator Dr. Robert Biederman, director of cardiovascular MRI at Allegheny and an associate professor of medicine at Drexel University in Philadelphia.

Dr. Robert Biederman

Among the 32 patients in the study, 23 underwent neurologic MRI imaging, and 9 underwent cardiac MRI imaging.

The neurologic MRI imaging picked up a case of Creutzfeldt–Jakob disease in one with unexplained altered mental status, and a syrinx in another who had unexplained arm weakness, a finding that made a "huge difference neurosurgically." Overall, neurologic imaging made or altered diagnoses in 15 patients, and confirmed them in eight, Dr. Biederman said at the 18th World Congress on Heart Disease.

Cardiac MRI imaging picked up cardiac sarcoidosis in one, and constrictive pericarditis in another. In six cases, it simply confirmed provisional diagnoses. Even so, "there is value in confirming for surgeons, patients, and family members that they are doing the right thing," he said.

Often, in the absence of a solid diagnosis, the "patients were going to die." Imaging was only done, however, after conversations that sometimes ran more than an hour with patients and family members about the risks of MRIs with pacemakers (PM) and automated implantable cardioverter-defibrillators (AICD), including tissue cauterization, fibrosis, lethal tachycardia, and device misfire. "This was absolutely done with the patient’s full knowledge of risk," he said.

Although MRIs have caused at least 12 deaths in patients with PMs and AICDs over the last 3 decades, ongoing research with newer devices is beginning to suggest it’s safe if proper device and MRI adjustments are made; well over 1,000 patients have undergone MRIs in recent years with no complications. Even so, "assuming it is safe, no one’s asked if it makes a difference. This is the first time to my knowledge that anyone has stepped beyond the question of safety to see if results from MRIs" in these patients "warrant the risk," Dr. Biederman said (e.g., Am. Heart J. 2013;165:266-72).

Four of the patients had combination PM/AICDs, 18 had dual-chamber PMs, three dependent PMs, five AICDs, and two just single pacer leads. Only one patient had a Revo MRI SureScan Pacing System, the only pacer FDA- approved for MRI use. Scans ran an average of a half hour, plus or minus 15 minutes; a few patients were scanned twice.

The MRIs were performed in a dedicated cardiovascular MRI suite with continuous ECG, blood pressure, heart rate, and oxygen saturation monitoring. "We turned all the defibrillator technology off, and tried to turn the pacemaker off. If we couldn’t, we turned it to an asynchronous mode." Sequences were done at a specific absorption rate (SAR) of less than 2 W/kg, because "there is less radiofrequency energy being sent at a slower rate, so [it’s] less likely" to heat the device. "We try to keep the specific absorption rate as low as possible," Dr. Biederman said.

Devices were reset and tested after the procedure to ensure that impedance, thresholds, amplitudes, and shock impedances were the same as before the scans.

Dr. Biederman said he has no disclosures.

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