MRI Scans Now Safely Done

MRI Scans Now Safely Done on Selected Pacemaker and ICD Patients

By Peter Ott, MD, associate professor of medicine, Division of Cardiology

Magnetic resonance imaging (MRI) is a powerful diagnostic tool that can produce highly detailed, images of virtually any area in the body. Unlike other diagnostic imaging tools, such as X-ray or CT scans, it does not use radiation. MRI uses a powerful magnetic field and delivers strong radiofrequency energy pulses to generate its images.

It is, however, exactly these energy sources that can create a problem for patients with implanted pacemakers or implantable cardioverter defibrillators (ICDs). In particular, the radiofrequency energy pulses can be picked up by the pacing leads (akin to an antenna) and transferred into the generator (altering or destroying its controlling software) or be transferred towards the heart muscle, potentially rendering the pacing lead inoperative or generating abnormally fast heart rhythms. The magnetic energy field also may affect device function.

Therefore, MRI scans typically are not done on patients with pacemakers or ICDs.

However, Sarver Heart Center members at University of Arizona Medical Center – University Campus, who are part of the electrophysiology group and the MRI imaging group, built on the experiences of other medical centers and initiated a protocol that allows MRI scanning in carefully selected and supervised patients with implanted pacemakers or ICDs whose medical conditions require an MRI.

An estimated 50 to 75 percent of patients with implanted devices may at some point need MRI scans, so all pacemaker and ICD companies are developing “MRI safe” devices. These devices contain lower ferrous content of the hardware, filters and lead design in an effort to protect the device software from the radiofrequency energy.

A careful review of current medical diagnosis and available pacemaker or ICD technology is required to choose the correct device for each individual patient. This discussion should be led by a cardiac electrophysiologist (specialist trained in pacemaker and ICD technology), in close cooperation with the patient’s primary physician or cardiologist.

Dr. Peter Ott, electrophysiology cardiology specialist, teamed up with cardiology imaging specialists to establish protocols to safely use magnetic resonance imaging on patients with pacemakers or implantable cardioverter defibrillators (ICDs).

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