Physician Update - Making MRI Safe with Implanted Cardiac Devices
Making MRI Safe with Implanted Cardiac Devices
Date: June 15, 2012
Many patients who seek ablation for ventricular tachycardia have an implanted defibrillator or pacemaker—devices that once excluded them from an MRI scan. Hopkins cardiologists, however, have not only determined which implants and leads can safely go into the MRI scanner, but they also developed a protocol for programming the devices to ride out any indication, not just the heart-related.
“We have safely performed cardiac MRI scans on more than 700 patients,” says Henry Halperin, an electrophysiologist and biomedical engineer. The protocol he and his team developed—it’s now used worldwide—includes device selection, reprogramming the implants to a safe mode and carefully monitoring patients during the scan.
In a recently-published prospective study of 438 patients with implanted cardiac devices who underwent MRI scans, many of them multiple times, three people experienced a “power-on reset event” as energy from the scanner caused a return to default settings. “This is a rare occurrence that warrants close, expert monitoring during the test. Fortunately, it’s easily remedied after the test is completed,” says Saman Nazarian, lead author and co-investigator on the almost decade-long work, “and none of the three patients had device dysfunction in the months afterward.”
“With a large aging population and expanding indications for pacemakers and defibrillators, the ability to perform MRI is an increasingly important and sometimes a lifesaving issue,” Nazarian says. He’s seen patients with cardiac devices who have come to Hopkins and had tumors and other serious problems MRI-diagnosed after their problems had been missed by earlier CT or ultrasound.
When only an MRI will do
For some patients with an implanted cardiac device, MRI becomes a crucial diagnostic tool. That was the case of Ann Bigelow,* a 41-year-old New Jersey attorney. One night nine years ago, she had a grand mal seizure and awoke in a hospital bed. “I didn’t recognize my husband and had temporarily lost my short-term memory,” she says. “The memory came back, fortunately, but the following year, while pregnant, I had another seizure. I was diagnosed with epilepsy and put on an antiseizure drug.”
Despite medication, Bigelow’s seizures continued. Subsequent CT scans showed what looked to be a cyst in her brain, and her neurosurgeon in New York urged her to have an MRI. Five years earlier, however, Bigelow experienced bradycardia severe enough to need a pacemaker. And now, because of the implant, an MRI was thought unsafe.
Bigelow searched the Internet and learned about the protocol Henry Halperin (left) had tested to make things OK. “I told Dr. Halperin that I really needed the test, and he said I should come to Baltimore.” The MRI revealed a benign astrocytoma which was successfully removed in surgery. That was six years ago. Today, she has no seizures, needs no medication, and is enjoying her second child.
Twice each year, Bigelow comes back to Hopkins for follow-up MRI tests and all is going fine. “I truly believe that having the MRI saved my life.”
*not her real name.
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