Congenital heart program nips radiation dose by 61 percent

Initiating a radiation safety protocol in their congenital heart center reduced the cumulative radiation dose in patients undergoing catheterizations by 61 percent, cardiologists reported in the November issue of Catheterization and Cardiovascular Interventions.

Daniel Mauriello, MD, and colleagues at the Mayo Clinic in Rochester, Minn., developed a two-pronged approach in an effort to lower radiation exposure to patients with congenital heart disease. Those patients now live longer, typically undergo numerous procedures that expose them to ionizing radiation and consequently have a greater lifetime risk of developing radiation-induced cancer.

The Mayo team instituted practice and technical changes between 2008 and 2010. Practice changes included creating a radiation safety commission for the cardiovascular invasive laboratories; intraprocedurally notifying physicians when a 3,000 mGy threshold was reached; internally reporting case doses exceeding 6,000 mGy; including cumulative air kerma in final reports; and compulsory training for fellows.

For technical changes, they increased spectral filtration for acquisition imaging; changed the default fluoroscopy setting to low; decreased the fluoroscopy frame rate from 15 to 7.5 frames per second; reduced the detector target dose; and removed the antiscatter grid for patients weighing less than 20 kg (and, at the provider’s discretion, for patients between 20 kg and 60 kg).

They reviewed records for pediatric and adult patients from June 2008 to March 2012. Cases were divided by age group, weight group and procedure type (noninterventional, a simple intervention or a complex intervention). They used phantoms to measure representative air kerma rates for reference.

They analyzed 1,082 procedures by four experienced cardiologists and 43 fellows. Median air kerma decreased from 424 mGy the first year to 200 mGy the last year, for a 61 percent reduction. Mean fluoroscopy time remained the same.

The simple intervention group experienced the biggest reduction (74 percent) followed by the noninterventional group (71 percent). There was no change with complex interventions, whose fluoroscopy times increased by seven minutes between the first and last years of the study.

Mauriello et al explained that after the start of the study period, they began performing complex and sometimes lengthy Melody valve implantations. They suggested that may have been a factor, citing the 28 percent hike in fluoroscopy time.  

Cumulative dose dropped 74 percent for patients between 10 and 17 years old and 67 percent in adults. Infants had no change and they reported a nonsignificant decrease in children between 1 and 9 years old.

By weight, the 20 to 60 kg and more than 60 kg groups fared the best, with reductions of 74 percent and 64 percent. The 0 to 20 kg group included one patient who underwent four complex procedures. Excluding him, the group had an air kerma reduction of 67 percent.