MRI Tests Could Be Safe for Some People with Implanted Cardiac Devices

Researchers have developed a protocol that has proven effective in enabling patients with implanted cardiac devices to safely undergo a magnetic resonance imaging (MRI) scan, something previously not possible due to the chance of the magnetic and radiofrequency energy generated by the MRIs interfering with operation of implanted devices.

“We believe this is the largest prospective study of MRI in patients with implanted devices,” lead author Saman Nazarian, MD, a cardiac electrophysiologist and an assistant professor of medicine at the Johns Hopkins University School of Medicine, said in a statement. The study was published recently in the Annals of Internal Medicine.

Nazarian and his colleagues concluded that with a protocol based on device selection, programming, and careful patient monitoring, MRI can be performed safely in many patients who have a pacemaker or a defibrillator. “With the advancing age of the population and the expanding indications for pacemakers and defibrillators, this has become an increasingly important issue and a lifesaving one for some patients,” Nazarian said.

“The guidelines we have published can be used to make MRI more available to people who could benefit from early detection of cancer and other diseases and for guiding surgeons during procedures. MRI is considered superior to CT scans in many clinical scenarios, especially for brain and spinal cord imaging,” Nazarian added. More than 700 patients with implanted cardiac devices have safely undergone MRI exams at Johns Hopkins.

Nazarian’s prospective study followed 438 people with implanted cardiac devices that had 555 MRI scans, almost all of which were conducted at Johns Hopkins. Nazarian and his colleagues found that patients with pacemakers and defibrillators can have an MRI scan, as long as it is done with appropriate precautions, with very low risk of the device malfunctioning, moving, heating, or causing abnormal heart rhythms.

In three of the patients in the study (1.5%), implanted devices had a power-on reset event during an MRI scan, which means that the energy emitted from the scanner caused the devices to revert to default settings.

Although this is a rare occurrence that warrants close monitoring during the test, it is easily remedied after the test is completed. None of the three patients had device dysfunction during the long-term follow-up of between 15 and 66 weeks.

Newer models of pacemakers are less prone to such interference, according to Johns Hopkins cardiac electrophysiologist and biomedical engineer Henry Halperin, MD. Halperin began researching the issue of MRI safety with a range of implanted devices about 15 years ago.

“The newer pacemakers made after 1998 and defibrillators manufactured since 2000 come with electromagnetic interference protection,” said Halperin, a professor of medicine at Johns Hopkins and the study’s senior author. The Hopkins team checks the age of the device and the type and configuration of the leads attached to it. If a lead is disconnected and is not part of the device’s function, for example, an MRI would not be recommended because the tip of the wire could get very hot.

SourceHopkins Study Finds MRI Tests Safe for People with Implanted Cardiac Devices When Certain Guidelines are Followed [Johns Hopkins]