Necessary CTs Should Not Be Delayed in Patients with CRM Devices

March 11, 2014

Study provides no additional evidence supporting 2008 FDA advisory that warned CT scans potentially interfere with CRM devices.

The presence of a cardiac rhythm management (CRM) device should not delay a clinically indicated computed tomography (CT), according to the results of a recent study. These results provide no additional evidence in support of a 2008 advisory from the FDA that warned that radiation from CT scans could interfere with the proper functionality of these devices.

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“The exposure of a large number of cardiac rhythm management devices to direct radiation beams from CT imaging was not associated with clinically significant adverse events or alterations in programmed device settings or lead and generator parameters,” wrote Ayman Hussein, MD, an author of the study from the Maryland Arrhythmia and Cardiology Imaging Group, and colleagues.

According to the article, the FDA made its recommendations based on limited evidence that suggested that CT scans could interfere with these devices through unintended shocks to the patient, changes in pacemaker output pulse rate, resetting of the device settings or a variety of other issues.

To examine whether CTs caused significant interference with CRM devices, Hussein and colleagues evaluated data and outcomes from 516 CT scans in which CRM devices had direct radiation exposure at two major centers between 2000 and 2010. The primary outcome of the study, published in The Journal of the American College of Cardiology, was a composite of death, bradycardia or tachycardia requiring termination of the scan, or immediate intervention such as unplanned hospital admissions, reprogramming of the device, inappropriate defibrillator shocks or device replacement.

The 516 CT scans were performed in 386 patients; 241 patients had an implantable cardioverter defibrillator and 145 had a permanent pacemaker.

No outcome, as defined by the primary outcome of the study, was found in any of the patients that underwent CT imaging.

The researchers also looked at a secondary outcome of significant changes in device parameters. According to the study, potentially significant changes were found in a small group of devices, but no definitive link to the CT imaging procedure could be made.

In an accompanying editorial, Elena Arbelo, MD, PhD, and Josep Brugada, MD, PhD, of the University of Barcelona, Spain, pointed out several weaknesses with this real-world trial, including its retrospective nature, the lack of information on radiation dose and duration, and its relatively small sample size.

However, despite these weaknesses, Arbelo and Brugada wrote “the authors have validated in an everyday setting that pacemaker and ICD responses to radiation are transient and benign and that routine CT scanning on patients with cardiovascular implantable electronic devices should not be restricted.”

In fact, Arbelo and Brugada wrote that they believe that the FDA was overreacting when it issued its 2008 advisory.

“The risks associated with imaging procedures are small as compared with other risks. For instance, patients with a pacemaker or ICD, many require CT imaging for the evaluation of a lung tumor, during the evaluation of possible internal bleeding after car accident, etc,” they wrote.

“The relative risk from the natural course of any of these diseases as compared with the risk of imaging is remarkable. …For that purpose, it is of major importance that the FDA and other similar institutions work hand-in-hand with clinicians to develop a post-marketing structure that addresses new and ongoing concerns and identifies early signals of potential problems in a sensible fashion, always weighing the risk/benefit to the patient and taking into account the accumulated experience of professionals.”