A protocol in which patients’ pacemakers or defibrillators are reprogrammed to a “safe mode” before an MRI exam and then programmed back to their normal operating mode afterward—along with close monitoring during the exam—allowed MRI to be safely used in some patients with an implantable device.
“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,” says Saman Nazarian, MD, an assistant professor of medicine at the Johns Hopkins University School of Medicine. “MRI is considered superior to CT scans in many clinical scenarios, especially for brain and spinal cord imaging.”
More than 700 patients with implanted cardiac devices have safely undergone MRI exams at Johns Hopkins.
“We believe this is the largest prospective study of MRI in patients with implanted devices,” Nazarian says.
The prospective study followed 438 people with implanted cardiac devices who had 555 MRI scans. Most exams (94%) were conducted at The Johns Hopkins Hospital. The researchers found that with appropriate precautions, patients with pacemakers and defibrillators can have an MRI scan with very low risk of the device malfunctioning, moving, heating, or causing abnormal heart rhythms due to the magnetic and radio-frequency energy generated by the test.
The devices implanted in three of the patients in the study (1.5%) had a power-on reset, which means the energy emitted from the scanner caused the devices to revert to default settings during the exam. This is a rare occurrence that warrants close expert monitoring during the test but is easily remedied after the test is completed. None of the three had device dysfunction during the long-term follow-up of between 15 and 66 weeks. One of those patients completed four repeated MRI examinations during the study without any problems.
In addition to considering the age of a device, the researchers checked the type and configuration of the leads attached to the devices. If a lead is disconnected and is not part of a device’s function, an MRI would not be recommended because the tip of the wire could get very hot.
“The newer pacemakers made after 1998 and defibrillators manufactured since 2000 come with electromagnetic interference protection,” says Henry Halperin, MD, a professor of medicine at the Johns Hopkins University School of Medicine and senior author of the study.
“We reprogram the device to a safe mode while the patient is having the MRI scan,” says Rozann Hansford, RN, MPH, a study coauthor. “We carefully monitor the patient’s blood pressure, electrical activity of the heart, and oxygen saturation and look for any unusual symptoms. After the test, we reprogram the device and carefully check its function.”
The patients’ devices were checked again in three to six months.
“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 says.
—Source: Johns Hopkins University Hospital