Recent study shows pacemaker, MRI compatible

Cardiovascular disease is the leading cause of death in the United States, killing approximately one million Americans each year. The good news is that the death rate is in decline, in part due to the use of pacemakers and other implantable devices designed to aid an ailing heart.

Roughly 3 million Americans currently have an implanted cardiac device. Doctors implant hundreds of thousands more each year. (Implantable cardioverter defibrillators and heart pacemakers are the first- and third-most implanted medical devices in the country.) There is no debate that these high-tech devices can save lives, but they also create a different sort of health risk for patients who seek or require use of another revolutionary medical technology: magnetic resonance imaging. Since its debut in the 1970s, the MRI has become a hugely popular method for creating detailed images of the inner body. Millions of MRIs are produced each year in this country, used to assess everything from torn ligaments to brain function.

Patients with cardiac implants, however, are frequently denied an MRI because the technology’s powerful magnets might wreak havoc upon their delicate electronic implants. Recently, Dr. Douglas Chang, chief of physical medicine and rehabilitation at the University of California San Diego School of Medicine, and colleagues published a study looking at health risks to patients with implants who undergo an MRI.

Q: Historically, what has been the concern about conducting an MRI on a patient with an implanted cardiac device like a pacemaker? Is it directly dangerous to the health of the patient or to the functioning of the device?

A: There are several concerns about performing an MRI scan on someone with an implanted cardiac electronic device. Will the strong magnetic fields damage the cardiac device? The fields potentially could reprogram or reboot the device. They could lead to inappropriate cardiac pacing activity or permanent damage to the circuitry. Another concern is for device movement. Lastly there is concern for distortion of the MR images by the device.

Q: What did your study find?

A: The study, conducted with Dr. Ulrika Birgersdotter-Green of UC San Diego, and Drs. Debra Doud and Robert Russo at Scripps Clinic, looked at patient safety and image quality in one of the largest ongoing studies of orthopedic MRI examinations. Specifically, we examined 68 cervical spine, 20 thoracic spine and 130 lumbar spine MRI tests that used a 1.5T magnet.

MRI machines are rated by the power of their magnet, using a measure called the Tesla (T). Clinical devices typically range in power from 0.5T to 3.0T; research MRIs can go as high at 60 T.

We found no adverse clinical events: death, device failure, loss of image capture. None of the MRI examinations were judged to be nondiagnostic.

Q: Are there broader ramifications to your research?

A: For patients undergoing MRI of the cervical and lumbar spine, the presence of an implanted cardiac device did not result in imaging artifacts that resulted in a nondiagnostic examination. Clinically indicated cervical and lumbar spine MRI examinations at 1.5 Tesla can be performed successfully in patients with an implanted cardiac device with appropriate programming and cardiac monitoring.


