Harvard Heart Letter

MRI and pacemakers: A risky mix

Unless you have an MRI-friendly pacemaker, a CT scan may be safer.

If you have an implanted cardiac device such as a pacemaker or defibrillator, you have likely been told you cannot undergo magnetic resonance imaging (MRI). In multiple studies, the powerful magnets in MRI units have caused pacemakers to change their settings and the leads in both types of devices to become superheated. Some deaths have occurred during inadvertent, unmonitored scanning of patients with pacemakers, although the exact reasons are unknown.

Computed tomography (CT) is often recommended as an alternative imaging test. However, MRI remains the gold standard for diagnosing certain diseases of the brain and spinal cord. This has prompted several medical centers to develop protocols that allow people with cardiac devices to undergo MRI scanning with reasonable safety. But until these protocols have been perfected, or MRI-friendly devices become the norm, Harvard hospitals prefer to err on the side of caution.

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