Safe MRI Scans for Patients with Defibrillators and Pacemakers

Ivanhoe Newswire
Thursday, September 21, 2006; 12:00 AM

(Ivanhoe Newswire) -- Patients with implantable defibrillators and pacemakers may soon be able to safely have magnetic resonance imaging (MRI). This would let them get images critical for early diagnosis of certain cancers of the brain, head and neck, as well as help guide doctors during invasive procedures.

Doctors once thought using an MRI on a patient with these devices to be impossible. The electromagnetic field of the scanner could cause a defibrillator to unnecessarily shock a patient, for example.

Researchers from Johns Hopkins Hospital in Baltimore have developed several techniques to reduce the risk of complications an MRI can cause. One thing they have done is reprogram the devices to make them blind to their external environment -- this reduces their chances of mistaking the radiofrequency the MRI generates as an irregular heartbeat and therefore prevents misfires. Another technique is to turn off the defibrillators' shocking function during the 30-minute to 60-minute MRI scan.

Researchers also reduced the amount of electrical energy an MRI uses at peak scanning in half. They found the lower-energy scan still provides images good enough to make an accurate diagnosis in more than 90 percent of the cases they studied.

"The risk to patients of burning heart tissue or misfiring is still there," cautions Henry Halperin, M.D. of Johns Hopkins University School of Medicine. "But our results show that with appropriate precautions, MRI is a safe and effective diagnostic tool to use for those with modern implanted heart devices."

In the study, 31 patients had a pacemaker and 24 patients had an implantable defibrillator. MRI helped plan artery-opening procedures for 13 study participants, detect abnormalities in the blood vessels of nine, and diagnose and treat tumors in nine. All the devices were functioning properly after MRI.

MRI is currently unavailable for millions of patients because the Food and Drug Administration does not authorize any implanted device for MRI testing except for research purposes.

This article was reported by Ivanhoe.com, who offers Medical Alerts by e-mail every day of the week. To subscribe, go to: http://www.ivanhoe.com/newsalert/.

SOURCE: Circulation, 2006;114:1277-1284