CT Scans May Disrupt Pacemakers, Other Medical Devices

The notice is available at www.fda.gov/cdrh/safety/071408-ctscanning.htmlwww.fda.gov/MedWatch/report.htm

The Food and Drug Administration is alerting health care professionals about reports of malfunctions in pacemakers and other electronic medical devices worn by patients during computed tomography scanning.

The agency has received a “small number” of adverse event reports “in which CT scans may have interfered with electronic medical devices, including pacemakers, defibrillators, neurostimulators, and implanted or externally worn drug infusion pumps,” according to a public health notification issued by the FDA.

The adverse events that were likely caused by CT scans were unintended “shocks” (such as stimuli) from neurostimulators, malfunctions of insulin infusion pumps, and transient changes in the output pulse rate of pacemakers.

To date, no deaths have been reported.

These malfunctions can result from direct exposure of the medical device to the high radiation dose rates generated by some CT equipment and are different from the malfunctions related to magnetic resonance imaging, which are caused by strong electric and magnetic fields, the alert says.

The FDA has not received any reports of CT interference with cochlear implants or retinal implants, but says such interference is “theoretically possible.” Problems that “might” be caused by CT scanner interference include resetting or reprogramming of devices and generation of spurious signals, including cardiac defibrillation pulses.

The alert recommends moving external devices out of the range of the scan, if possible, and asking patients with neurostimulators to shut off the device during a scan.

When a CT procedure requires scanning over the device continuously for more than a few seconds, such as during an interventional exam, “attending staff should be ready to take emergency measures to treat adverse reactions if they occur,” the alert emphasized.

Patients should be advised to check their devices for function even if they turned them off during the procedure, and to contact their health care providers if they suspect malfunctioning of their device.

The increase in these reports may be related to greater use of CT scans, the higher dose capability of new CT machines, the larger number of patients wearing devices, and improvements in reporting, according to the FDA, which is continuing to investigate this issue.