Protocol slashes radiation dose but not cath lab volume

Operators reduced radiation dose 48 percent with no loss in volumes or interventions using a novel algorithm in the catheterization laboratory, researchers reported online April 16 in the Journal of the American College of Cardiology: Cardiovascular Interventions.

Anthony W. A. Wassef, MD, and colleagues at St. Boniface General Hospital in Winnipeg, Manitoba, Canada, conducted a retrospective study that compared radiation dose for diagnostic angiography and PCIs two months before and two months after the hospital upgraded its cardiac cath lab with a dose reduction protocol (Philips Allura Xper, Royal Philips Electronics). Their goal was to assess radiation dose reduction (air kerma) under the new protocol and measure changes in throughput of cath lab cases.

The new system allowed x-ray parameters to be calibrated to examination and patient size; setting a default fluoroscopy dose mode from normal to low or a combination; and included the option to reduce frame rates from 15 frames per second (FPS) to 7.5 FPS.

They enrolled 605 consecutive patients who underwent diagnostic angiography or PCI for the evaluation; 309 patients from March 1-April 30, 2012, before implementation; and 296 patients from May 18-July 22, 2012, after implementation. Lab personnel did not change throughout the two periods. In the after-implementation segment, operators chose the FPS; 160 patients received traditional 15 FPS and 136 received 7.5 FPS.  

Patient baseline characteristics were similar in the before and after groups, with the exception of a higher percentage of men in the after group. There was no significant difference between the 15 FPS and 7.5 FPS subgroups.

The mean dose reduction in the post-intervention group was 48 percent compared with the before group. Compared with the before group, the 15 FPS and 7.5 FPS subgroups had dose reductions of 35 percent and 62 percent, respectively. The dose reduction benefit was maintained in both angiography and PCI procedures.      

There were no differences in fluoroscopy times, although there was a trend toward a higher number of cine runs after implementation of the protocol. The relative proportion of patients undergoing PCI stayed the same before and after, but the mean number of stents placed was higher in the after group (1.84 vs. 2.05). The number of vessels intervened on per procedure remained unchanged.  

The increase in cine runs post-implementation may be due to “increased laxity” when operators saw lower air kerma on their monitors, or to reduced image quality that required more cine runs, Wassef and colleagues speculated. They recommended a larger, multicenter study to validate their results and further explore image quality questions.