June 9th, 2014

Wide Range of Radiation Dose in Children Undergoing Cardiac Procedures

Children with heart disease are at increased risk for developing cancer later in life due to their exposure to radiation during imaging procedures. Since an ever-growing number of children with heart disease now reach adulthood, this may become an increasingly important public health issue.

A new study published in Circulation offers some reassurance in finding that for most children the increased risk is low or negligible. But for some children who undergo more complex procedures, the increased risk is significant.

Jason Johnson and colleagues calculated the radiation dose received by 337 children who underwent 1 of 7 cardiac surgery procedures at Duke University. The median number of radiation-producing imaging procedures received by the children was 17. The median cumulative effective dose was 2.7 mSv, less than the annual background exposure of 3.0–3.5 mSv in the U.S.

There was a wide variation in radiation exposure. For 5 of the 7 procedures (atrial septal defect, ventricular septal defect, arterial switch operation, tetralogy of Fallot, and atrioventricular canal defect), the median annual dose ranged from 0.9 to 0. 29 mSv, which the authors said was “reassuringly low.” But children who underwent the most complex operations received much higher levels of radiation: the median dose was 20.08 mSv for children who underwent the Norwood operation and 42.54 for those who underwent cardiac transplantation.

Although cardiac catheterization represented only a small percentage (1.5%) of all imaging procedures, it was responsible for a majority (60%) of the total radiation exposure.

The lifetime attributable risk for cancer due to radiation was small for the less complex procedures, ranging from a median of 6-20 cases per 100,000 exposed. But the risk was much more elevated for the Norwood procedure (799 cases per 100,000) and cardiac transplantation (1677 per 100,000). Because of the expected impact of radiation on breast and thyroid cancer, girls had a significantly higher increase in risk than boys.

The authors write that their findings can be used in clinical practice: “To reduce long-term cancer risk, providers should target reducing radiation exposure in the highest-risk cohorts, including those children who will require repetitive high-exposure imaging and females because of their increased cancer risk. Providers can consider our relative exposure estimates when choosing between various radiation-producing imaging modalities.”



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