Safety guidelines for MRI with ICD
Date: December 26, 2011
Many patients who seek ablation for ventricular tachycardia have an implanted defibrillator or pacemaker—devices that once excluded them from having an MRI scan. Johns Hopkins cardiologists have removed that barrier by determining which devices and leads can safely go into the MRI and developing a protocol for programming the devices for the imaging test for the full range of indications, not just for heart-related issues.
“We have safely performed cardiac MRI exams for more than 700 patients,” says electrophysiologist and biomedical engineer Henry Halperin, who began researching the issue of MRI safety with implanted devices about 15 years ago. The clinical safety protocol that he and his team developed, which includes device selection, reprograming the device to a safe mode and carefully monitoring the patient during the scan, is now being adopted by institutions around the world.
In a prospective study of 438 patients with implanted cardiac devices who had 555 MRI scans, the devices in three of the patients, 1.5 percent, had a power-on reset event during an MRI scan. The energy emitted from the scanner caused the devices to revert to default settings. “This is a rare occurrence that warrants close expert monitoring during the test, but is easily remedied after the test is completed,” says Saman Nazarian, who was the lead author and co-investigator since the clinical study began in 2003. None of the three patients had device dysfunction during long-term follow-up of between 15 and 66 weeks. One completed four repeated MRI examinations during the study without any problems.
“With the advancing age of the population and the expanding indications for pacemakers and defibrillators, the capability to perform MRI in device recipients has become an increasingly important issue, and a lifesaving one for some patients,” says Nazarian. He adds that many of the patients with cardiac devices who have come to Hopkins for an MRI scan had tumors and other serious problems diagnosed and treated, whereas those problems had been missed by a previous imaging test, such as a CT or ultrasound exam.