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CT imaging did not interfere with cardiac rhythm management devices
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The presence of cardiac rhythm management devices should not delay or cancel clinically indicated CT imaging procedures, researchers reported in a new study.
The study demonstrated no clinical consequences related to CT imaging of patients with cardiac rhythm devices.
The findings call into question whether an FDA advisory issued in 2008 is warranted, according to Ayman Hussein, MD, from University of Maryland, and colleagues. The advisory recommended the presence of a physician to take emergency measures to manage adverse events and checking the cardiac device after imaging to assure proper functioning.
The researchers studied 516 CT scans of 386 patients (mean age, 63.7 years; 81% men) involving direct radiation exposure to cardiac rhythm management devices at the University of Maryland Medical Center and Baltimore Veterans Administration Medical Center from July 2000 to May 2010. Of the devices, 332 were pacemakers and 184 were defibrillators.
The primary outcome was a composite of death; bradycardia or tachycardia requiring termination of the scan or an immediate intervention; unplanned hospital admission; device reprogramming; inappropriate shocks from a defibrillator; or device replacement/revision related to CT imaging. The primary outcome did not occur in any patient and no clinically evident device malfunction during CT imaging was documented. The researchers also found no difference in arrhythmic events between post-CT interrogations and pre-CT interrogations (32% vs. 33.1%; P=.69).
The secondary outcome of the study was the occurrence of significant changes in device parameters with potential clinical significance, such as an unexpected decrease in battery power, lead failure to pace/sense or change in lead impedance by ≥50%. For the secondary outcome, the researchers studied a control group; one control device was studied for every four exposed to CT scans. The goal was to better assess small changes in device parameters, which can occur over time under normal circumstances, the researchers wrote.
Significant changes in device parameters were observed in a very small number of CT-exposed and control devices. However, the researchers could not confirm a definitive link between changes and CT imaging, and they found no associated clinical consequences.
“The findings suggest that the presence of cardiac devices should not delay or result in cancellation of clinically indicated CT imaging procedures, and provide evidence which would be helpful when the FDA advisory is reevaluated,” Hussein and colleagues wrote. “Incorporating [the FDA’s] recommendations into clinical practice would be logistically challenging and would require a significant amount of resources given the exponential growth of CT use in the past 2 decades.”
Disclosure: One researcher reports financial ties with Biosense Webster and General Electric. The other researchers report no relevant financial disclosures.
Perspective
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Judith Mackall, MD
The study by Hussein et al assessed the safety of CT in patients with cardiac rhythm management devices. In the study, the researchers retrospectively evaluated the clinical records including device interrogations before and after CT scans in 516 patients with pacemakers and implantable cardioverter defibrillators. Adverse clinical events or changes in device programming, lead sensitivity, pacing threshold, lead impedance or arrhythmias that could be attributed to the CT scan were evaluated. Significantly, there were no demonstrable long-term effects of the CT scan on the cardiac device programming or lead function. In addition, no patient experienced an adverse event during scan.
Does this mean that the radiation received during a CT scan has no effect on cardiac devices? There are very limited data about the effect of CT scanning on the device during the scan. One previous study suggested that pacemakers programmed in a unipolar mode and exposed to a higher radiation dose could experience inhibition for a few seconds.
In clinical practice, CT scans are routinely performed in patients with implanted cardiac devices, both pacemakers and ICDs. Device interrogation or reprogramming is not performed because it is not considered necessary. New-generation CT scanners are using lower doses of radiation and most cardiac devices are programmed in bipolar sensing mode, making any device effect less likely.
The lack of any permanent device effect or adverse clinical event as a result of the CT scan in the large cohort of patients studied certainly supports current clinical practice. It may be time for the FDA to re-evaluate their recommendations.
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