CT Scans Shown Not to Interfere with Heart Rhythm Devices

When the US health administrators issued an advisory in 2008 warning that computed tomography (CT) imaging might interfere with pacemakers or implantable cardioverter-defibrillators, the medical community needed more evidence to support the health agency’s recommendations. Researchers now have reported their findings of the first study to evaluate the concern in “real world,” clinical practice. The results revealed that such negative interference, if it exists, is not significant enough to merit changes in clinical practice.

The study’s findings were published online February 2014, in the Journal of the American College of Cardiology. “The presence of cardiac devices should not delay or result in cancellation of clinically indicated CT imaging procedures,” stated the study’s senior author, Timm-Michael Dickfeld, MD, PhD, associate professor of medicine at the University of Maryland School of Medicine (Baltimore, MD, USA) and chief of electrophysiology at the Baltimore Veterans Affairs (VA) Medical Center.

The original US Food and Drug Administration (FDA) advisory, which encouraged this study, recommended having a physician present during CT scans, ready to take emergency measures to manage potential adverse events, and to examine the rhythm device in the patient after CT imaging to provide correct function. An updated FDA advisory, issued in 2013, did not emphasize routine device checks but called for a physician to be available when the CT involves continuous scanning over the device for more than a few seconds. The study’s lead investigator, cardiovascular medicine fellow Ayman Hussein, MD, said, “For CT scans for diagnostic purposes, the FDA advisory may warrant further evaluation.”

The researchers retrospectively studied the records of patients who underwent over 500 CT scans between July 2000 and May 2010 performed at the University of Maryland Medical Center and the Baltimore VA Medical Center. They looked for key adverse effects such as abnormally high or low heart rate, death, an immediate intervention, hospital admission, or secondary effects such as changes in the device caused by CT imaging. The scans did not produce any of the primary outcomes, whereas several slight secondary effects were observed in a small group of devices, but there was no definitive tie to CT. Similar changes were seen in a group of devices not exposed to CT.

“Clinicians and the FDA are collectively committed to patient safety,” noted Dr. Dickfeld. “We also must rely on outcome data that helps us decide on the course of action best for our patients. This study provides what is probably the best information we will have for years to come.”

Study coauthor Jean Jeudy Jr., MD, associate professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine, stated, “At the very least, the study may provide valuable input for reevaluation of the FDA’s original advisory.”

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