Traditional wisdom and regulatory agencies say that patients with heart devices can't safely undergo magnetic resonance imaging (MRI). But that seems to be changing as doctors give MRIs to more of these patients successfully and safely.
Yale specialists are providing the option to patients who join the Magnasafe Registry, the only registry, or observational study, at multiple sites that is providing MRIs to patients with devices such as pacemakers or defibrillators who meet the eligibility criteria. The registry has already resulted in MRIs for the first third of a planned 1,500-patient enrollment for the study, aimed at clarifying cautions and hazards.
"This is a very important study, because there are millions of patients with pacemakers in the United States who at some point in their lives are going to need and MRI," says Jeffrey Weinreb, MD, chief of MRI for Yale Medical Group. "Frankly, for some patients, MRI is the only way to make the diagnosis."
"It's a very exciting protocol that will improve quality of care for patients, because now they will be able to get the test that is most important for them," says electrophysiologist Rachel Lampert, MD. She says patients outside of the registry often have to settle for an imaging test that may not provide the most accurate result in their situation.
New reports change old concerns
Since MRI became available in the early 1980s, doctors cautioned that giving the test to patients with implanted cardiac devices would put them at risk for serious injury or even death. The fear was that the strong magnetic field would damage the device or cause it to malfunction, and this could cause an arrhythmia in the patient. Another concern was that the lead wires that connect the pacemaker's power source to the heart could burn. "This has been pretty much dogma for all these years," says Dr. Weinreb.
More recently there have been documented reports and small studies in which the procedure was successful and safe for patients with devices, Patients who enroll in the registry must still meet certain criteria, which include having a device that was implanted after 2002, and needing medical imaging that can't be gotten through a CT scan or other tests. They must undergo the test in a carefully controlled environment.
"This protocol requires a very close collaboration between cardiology and radiology," Dr. Weinreb says. "This is not something the radiologist should do alone, or that the cardiologist should do alone." Electrophysiology evaluation is essential for documenting what sort of pacemaker the patient has and when it was implanted, and that they have no abandoned lead wires left from previous devices. Radiologists make sure the study is medically necessary and that the same information couldn't be gotten with an ultrasound, CT scan or other imaging test. The registry does not include MRI of the chest.
On the day of the scan, an electrophysiology team must be available to reprogram the pacemaker or turn off the defibrillator, and monitor the patient during the procedure.
Results are promising, but not definitive
While some patients have recently-approved devices that were designed to be MRI-compatible, the registry is designed for the vast population of patients with standard devices. There have been no imaging-associated deaths, device failures or other serious side effects among the registry's first 530 patients, most of whom had scans of the brain and spine. "So far it appears that it's safe with recent devices," Dr. Lampert says.
But both Dr. Lampert and Dr. Weinreb say that while results so far are promising, they are not yet definitive."The reason that these studies are going on is to see if there is any risk to patients. We can't say at this point that there is zero risk."
For questions about the Magnasafe Registry or how to enroll patients, contact Dr. Lampert at 203-785-4126, Dr. Weinreb at 203-785-5913 or study coordinator Renee James at 203-737-1330.