Interventional Imagers Take on Central Role, and More Radiation Interventional Imagers Take on Central Role, and More Radiation

Interventional echocardiographers have become an increasingly critical part of the structural heart team but may be paying the price in terms of radiation exposure, a new study suggests.

Results showed that interventional echocardiographers receive threefold higher head-level radiation doses than interventional cardiologists during left atrial appendage occlusion (LAAO) closures and 11-fold higher doses during mitral valve transcatheter edge-to-edge repair (TEER).

“Over the last five to 10 years there’s been exponential growth in these two procedures, TEER and LAAO, and while that’s been very exciting, I think there hasn’t been as much research into how to protect these individuals,” lead author David A. McNamara, MD, MPH, Spectrum Health, Grand Rapids, Michigan, told theheart.org | Medscape Cardiology. The study was published July 7 in JAMA Network Open.

Previous studies have focused largely on radiation exposure and mitigation efforts during coronary interventions, but the room set-up for LAAO and TEER and shielding techniques to mitigate radiation exposure are vastly different, he noted.

A 2017 study reported that radiation exposure was significantly higher for imaging specialists than structural heart specialists and varied by procedure type.

For the current study, McNamara, an echocardiographer by training, and colleagues collected data from 30 consecutive LAAO and 30 consecutive TEER procedures performed at their institution between July 2016 and January 2018.

Interventional imagers, interventional cardiologists, and sonographers all wore a lead skirt, apron, and thyroid collar, as well as a dosimeter to collect radiation data.

Interventional cardiologists stood immediately adjacent to the procedure table and used a ceiling-mounted, upper-body lead shield and a lower-body shield extending from the table to the floor. The echocardiographer stood at the patient’s head and used a mobile accessory shield raised to a height that allowed the imager to extend their arms over the shield to manipulate a transesophageal echocardiogram probe throughout the case.

The median fluoroscopy time was 9.2 minutes for LAAO and 20.9 minutes for TEER. The median air kerma was 164 mGy and 109 mGy, respectively.

Interventional echocardiographers received a median per case radiation dose of 10.6 µSv compared with 2.1 µSv for interventional cardiologists. The result was similar for TEER (10.5 µSv vs 0.9 µSv) and LAAO (10.6 v 3.5 µSv; P < .001 for all).

The odds of interventional echocardiographers having a radiation dose greater than 20 µSV were 7.5 times greater than for interventional cardiologists (P < .001).

“It’s not the direction of the association, but really the magnitude is what surprised us,” observed McNamara.

The team was pleasantly surprised, he said, that sonographers, a “vastly understudied group,” received significantly lower median radiation doses than interventional imagers during LAAO (0.2 µSV) and TEER procedures (0.0 µSv; P < .001 for both).

The average distances from the radiation source were 26 cm (10.2 inches) for the echocardiographer, 36 cm (14.2 inches) for the interventional cardiologist, and 250 cm (8.2 feet) for the sonographer.

“These folks [sonographers] were much further away than both the physicians performing these cases and that is what we hypothesize drove their very low rates, but that should also help inform our mitigation techniques for physicians and for all other cath lab members in the room,” McNamara said.

He noted that Spectrum Health has been at the forefront in terms of research into radiation exposure and mitigation, has good institutional radiation safety education, and used dose-lowering fluoroscopy systems (AlluraClarity, Philips) with real-time image noise reduction technology and a frame rate of 15 frames per second for the study. “So we’re hopeful that this actually represents a somewhat best-case scenario for what is being done at multiple institutions throughout the nation.”

Nevertheless, there is a huge amount of variability in radiation exposure, McNamara observed. “First and foremost, we really just have to identify our problem and highlight that this is something that needs some advocacy from our [professional] groups.”

Sunil Rao, MD, the newly minted president of the Society of Cardiovascular Angiography and Interventions (SCAI), said, “This is a really important study because it expands the potential occupational hazards outside of what we traditionally think of as the team that does interventional procedures…we have to recognize that the procedures we’re doing in the cath lab have changed.”

“Showing that our colleagues are getting 3 to 10 times radiation exposure is a really important piece of information to have out there. I think it’s really sort of a call to action,” Rao, professor of medicine at Duke University in Durham, North Carolina, told theheart.org | Medscape Cardiology.

Nevertheless, he observed that practices have shifted somewhat since the study and that interventional cardiologists working with imaging physicians are more cognizant of radiation exposure issues.

“When I talk with our folks here that are doing structural heart procedures, they’re making sure that they’re not stepping on the fluoro pedal while the echocardiographer is manipulating the TE probe,” Rao said. “The echocardiographer is oftentimes using a much bigger shield than what was described in the study, and remember there’s an exponential decrease in the radiation exposure by distance, so they’re stepping back during the fluoroscopy time.”

Although the volume of TEER and LAAO procedures, as well as tricuspid interventions, will continue to climb, Rao said he expects radiation exposure to the imaging cardiologist will fall thanks to greater use of newer-generation imaging systems with dose-reduction features and better shielding strategies.

He noted that several of SCAI’s best practices documents call attention to radiation safety and that SCAI is creating a pathway where imaging cardiologists can become fellows of the society, which was traditionally reserved for interventionalists.

Still, imaging and cardiovascular societies have yet to endorse standardized safety procedures for interventional imagers, nor is information routinely collected on radiation exposure in national registries.

“We just don’t have the budgets or the interest nationally to do that kind of thing, so it has to be done locally,” Rao said. “And the person who I think is responsible for that is really the cath lab director and the cath lab nurse manager, who really should work hand-in-glove to make sure that radiation safety is at the top of the priority list.”

The study was funded by the Frederik Meijer Heart & Vascular Institute, Spectrum Health, and by Corindus. The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, approval of the manuscript; and the decision to submit the manuscript for publication. Senior author Ryan Madder, MD, reports receiving research support, speaker honoraria, and grants, and serving on the advisory board of Corindus. No other disclosures were reported.

JAMA Network Open. Published online July 7, 2022. Full text

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