Cardiac Implants and MRI Safety

Because of safety concerns, magnetic resonance imaging (MRI) scans are avoided in most of the 2 million people in the U.S. who have an implanted pacemaker or defibrillator (ICD). In fact, both the FDA and manufacturers of the devices have considered that MRIs should not be done in patients with any ICD or with the great majority of those people who have implanted pacemakers. But a new research study shows that it can be safe.

Potential Dangers of MRIs and Cardiac Implants

The potential danger is that the magnetic field produced during an MRI scan could interfere with the function of the devices. However, MRI scans are such an invaluable diagnostic test for abnormalities of the brain, spine, joints, liver, and other organs that estimates suggest at least up to 75 percent of those with an implanted cardiac device could benefit from an MRI scan at some future time.

Switching Devices to Safe Mode

A report on October 4 in the journal Annals of Internal Medicine described the largest prospective study yet done on MRI scans in patients with implanted cardiac devices. The study was carried out mostly at Johns Hopkins as well as at a medical center in Haifa, Israel. The 438 patients with certain pacemakers or ICDs underwent 555 MRI scans. The pacemakers and ICDs were manufactured after 1998 and 2000, respectively, and not all such devices were tested.

Key to this procedure is that the devices were reprogrammed to a safe mode for the scan and patients were carefully monitored. After the scan, the device was again reprogrammed and checked for function. The only significant clinical event, which caused a change in the settings of a device, occurred during the scans in 1.5 percent of the patients and was easily corrected after the scan was completed.

More Studies are Needed

The editors of the journal concluded, “Some patients with certain cardiac devices can safely undergo MRI with appropriate monitoring.” These findings promise more accurate diagnostic evaluations when CT scans and/or ultrasound fail to provide important information. Even larger studies with more devices will be needed, however, to make MRI scans feasible in most patients with implanted cardiac devices.