Harvard Heart Letter

Follow-up: Pacemakers and MRIs

Follow-up

Pacemakers and MRIs. In the April 2006 Harvard Heart Letter, we described how MRIs can damage pacemakers and implantable cardioverter/defibrillators (ICDs). A team from Johns Hopkins Hospital says that people with certain makes and models of pacemakers and ICDs can safely have an MRI as long as proper precautions are taken. The safety protocol the Hopkins team tested included temporarily reprogramming implanted devices for the duration of the MRI, turning off defibrillators' shock function, reducing the energy of the MRI, continuous monitoring with an electrocardiogram during the scan, and making sure that equipment for restarting the heart and performing CPR were immediately available. The researchers can vouch only for the 24 pacemaker and ICD models they tested. (A list of the models is available at health.harvard.edu/109.) The Hopkins researchers also said that MRIs are appropriate only for people with newer pacemakers (made after 1996) or defibrillators (made after 2000) since they are smaller, have better protection against MRI energy, and contain less magnetic metal.

An editorial on the study by two FDA experts on pacemakers and MRIs indicated that the benefits of a scan may outweigh the risks to the pacemaker or ICD for people in urgent need of an MRI for diagnosing brain cancer, detecting stroke, or planning surgery. But they stressed that this study does not give a green light for MRIs in everyone with a pacemaker or ICD. (Circulation, September 19, 2006)

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