Because of the risk of burns, equipment meltdowns, and misfires, magnetic resonance imaging (MRI) is currently off-limits to people with pacemakers and implantable cardioverter defibrillators (ICDs). But that may soon change. Researchers at Johns Hopkins University Hospital have developed a set of precautions that reduce the risks for the growing number of people with implantable devices who could benefit from MRI. One precaution is to reprogram implanted devices to a specific sequence, making them "blind" to their external environment. This technique prevents a pacemaker from confusing the radiofrequency of MRI with an irregular heartbeat and firing inappropriately. Similarly, an ICD's shock function is turned off during the MRI.
Another precaution is to reduce by 50% the amount of electrical energy used during peak MRI scanning, reducing the risk of burning tissue surrounding implanted devices. The lower-energy scan still provides images of adequate quality to make an accurate diagnosis in 90% of cases, researchers report.
The Johns Hopkins team has used MRI to diagnose more than a dozen potentially life-threatening conditions in patients with implanted devices. After performing MRIs on more than 100 patients with implanted pacemakers or ICDs, researchers conclude that the test is safe and effective when performed with appropriate precautions.
Clinical utility and safety of a protocol for noncardiac and cardiac magnetic resonance imaging of patients with permanent pacemakers and implantable-cardioverter defibrillators at 1.5 tesla, Circulation, S Nazarian, et al., September 19, 2006.