Radiation-Induced DNA Damage Seen in Interventional Cardiologists

Two new studies provide more evidence of the potential risks interventional cardiologists face from occupational ionizing radiation exposure.[1,2]

These studies, once again, highlight the “concerns for the lifetime effects of high-dose exposure to ionizing radiation from fluoroscopic-guided interventions,” which “must be addressed,” Dr Charles Chambers (Heart and Vascular Institute, Penn State Hershey Medical Center, PA) writes in an editorial[3] published with the studies December 19, 2017 in Circulation.

In their study, Dr Bijan Modarai (St Thomas’ Hospital, London, UK) and colleagues studied blood samples from 15 operators performing 45 catheter-based endovascular aortic repair (EVAR) procedures.

They quantified expression of a DNA damage/repair marker, γ-H2AX, and DNA damage response marker, phosphorylated ataxia telangiectasia mutated (pATM), in circulating lymphocytes during the perioperative period of endovascular (infrarenal, branched, and fenestrated) and open aortic repair using flow cytometry. They also measured these markers while the operators wore lead leg shielding in addition to upper-body protection.

Both γ-H2AX and pATM levels increased significantly in operators immediately after branched/fenestrated EVAR (P<0.0003 for both). Only pATM levels increased after infrarenal EVAR (P<0.04). Expression of both markers returned to baseline after 24 hours. There was no change in γ-H2AX or pATM expression after open repair.

Wearing leg lead protection mitigated the DNA damage response in operators after branched and fenestrated EVAR.

“This is the first study to detect acute radiation-induced DNA damage in operators who carried out endovascular aortic repair,” Modarai and colleagues write in their report.

“We need to do more to determine the significance of this rise in markers of DNA damage and its effect on long-term health,” Modarai told theheart.org | Medscape Cardiology. “For example, large registries of radiation-exposed workers where the incidence of health problems is recorded over time to find out if there is a definitive association between exposure and cancers, cataracts, etc. What this study does show, however, is that we need to be meticulous with protection measures [and] that wearing leg shields prevents a rise in markers of DNA damage,” Modarai said.

In his view, lower leg shielding “should be standard.” His group recently did a global survey of radiation protection measures used by vascular interventionists and found that only 40% used leg lead protection.

“Since our data have been disseminated, a number of my colleagues around the world have contacted me to say that they have started to wear leg lead protection. I am hoping for much better use of leg shielding in time. Our results would suggest that leg shielding prevents DNA damage in circulating cells that were previously exposed to radiation in the lower leg,” Modarai said. Their findings were first published online October 20, 2017.

Radiation Awareness Essential  

In their separate report, Dr Maria Grazia Andreassi (CNR Institute of Clinical Physiology, Pisa, Italy) and colleagues studied plasma levels of various micro-RNAs (miRNAs) in a group of interventional cardiologists employed for more than 1 year in a catheterization laboratory and a control group of clinical cardiologists/healthcare workers not exposed to radiation. They chose to study miRNAs because these molecules have been shown to become dysregulated in many human diseases, they point out.

The researchers found significant downregulation of brain-specific miRNA-134 and miRNA-2392 in interventional cardiologists compared with controls.

Although the exact function of miRNA-2392 is currently unknown, a recent study showed that miRNA-2392 was downregulated in gastric cancer cell lines and tissues, Andreassi and colleagues note in their article.

miRNA-134 is involved in synapse development and has been directly implicated in learning and memory. It has been previously dysregulated in mesial temporal lobe epilepsy, Alzheimer’s disease, bipolar disorder, oligodendrogliomas, and glioblastomas, they add.

“Additional studies are needed to validate these findings and to further explore the existing potential of circulating miRNAs to be used clinically as novel biomarkers for identifying early, disease-related perturbations caused by long-term radiation exposure in interventional cardiologists,” they conclude.

“As the complexity of our interventional procedures increases, radiation awareness in the cath laboratory is essential now more than ever,” writes Chambers in his editorial.

“Equipment manufacturers, medical physicists, hospital administration, governing bodies, and the medical providers must work together to create a safe environment for all in the cardiac cath laboratory,” he adds. “Without this effort, unnecessary patient exposure and lost manpower from unnecessary and preventable disabilities will continue.”