Radiation-Induced DNA Damage in Operators Performing Endovascular Aortic Repair

Abstract

Background: Radiation exposure during fluoroscopically guided interventions such as endovascular aortic repair (EVAR) is a growing concern for operators. This study aimed to measure DNA damage/repair markers in operators perfoming EVAR.

Methods: Expression of the DNA damage/repair marker, γ-H2AX and DNA damage response marker, phosphorylated ataxia telangiectasia mutated (pATM), were quantified in circulating lymphocytes in operators during the peri-operative period of endovascular (infrarenal, branched, and fenestrated) and open aortic repair using flow cytometry. These markers were separately measured in the same operators but this time wearing leg lead shielding in addition to upper body protection and compared with those operating with unprotected legs. Susceptibility to radiation damage was determined by irradiating operators' blood in vitro.

Results: γ-H2AX and pATM levels increased significantly in operators immediately after branched endovascular aortic repair/fenestrated endovascular aortic repair (P<0.0003 for both). Only pATM levels increased after infrarenal endovascular aortic repair (P<0.04). Expression of both markers fell to baseline in operators after 24 hours (P<0.003 for both). There was no change in γ-H2AX or pATM expression after open repair. Leg protection abrogated γ-H2AX and pATM response after branched endovascular aortic repair/fenestrated endovascular aortic repair. The expression of γ-H2AX varied significantly when operators' blood was exposed to the same radiation dose in vitro (P<0.0001).

Conclusions: This is the first study to detect an acute DNA damage response in operators performing fluoroscopically guided aortic procedures and highlights the protective effect of leg shielding. Defining the relationship between this response and cancer risk may better inform safe levels of chronic low-dose radiation exposure.

Keywords: DNA damage; aortic aneurysm; endovascular; occupational exposure; radiation.

Figure 1.

Radiation exposure to operators during EVAR procedures. A, Screening time during BEVAR/FEVAR was significantly longer than IEVAR (P<0.0001). B, DAP during BEVAR/FEVAR was higher than IEVAR (P<0.0001). C, Readings from personal dosimeters placed over operators’ chest under the lead, over the lead, and at the left leg. Leg doses were significantly higher during BEVAR/FEVAR compared with IEVAR (P<0.05). BEVAR indicates branched endovascular aortic repair; DAP, dose area product (mGy cm²); EVAR, endovascular aortic repair; FEVAR, fenestrated endovascular aortic repair; horizontal line, median; and IEVAR, infrarenal endovascular aortic repair.

Figure 2.

Flow cytometric and immunohistochemistry analysis of γ-H2AX and pATM expression in operators’ lymphocytes during the peri-operative period of EVAR. Flow cytometric dot plots of lysed, fixed, and permeabilized cells from whole blood collected from an operator before, immediately after, and 24 hours after FEVAR. A, Lymphocytes are identified according to forward and side scatter profile and gated according to the expression of CD3. B, Example flow cytometric dot plots showing that γ-H2AX expression in CD3⁺ lymphocytes increases in an operator immediately after a FEVAR and falls to preoperative levels after 24 hours. This response is also seen with lymphocyte expression of pATM. C, Immunohistochemical staining of lymphocytes (DAPI, blue) isolated from an operator shows, compared with the preoperative sample, an increase in γ-H2AX expression (purple foci) on these cells immediately after FEVAR. γ-H2AX indicates gamma H2AX; DAPI, 4’,6-diamidino-2-phenylindole dihydrochloride; EVAR, endovascular aortic repair; FEVAR, fenestrated endovascular aortic repair; and pATM, phosphorylated ataxia telangiectasia mutated protein (scale bar=10 µm).

Figure 3.

Changes in expression of γ-H2AX and pATM in operators’ lymphocytes in response to radiation exposure during EVAR. A, Expression of γ-H2AX in operators’ lymphocytes before, immediately after, and 24 hours after open aortic repair (n=14) and EVAR (all IEVAR and BEVAR/FEVAR procedures grouped together [n=31]). B, Expression of pATM in operators’ lymphocytes before, immediately after, and 24 hours after open aortic repair (n=14) and EVAR (n=31). C, γ-H2AX expression during the peri-operative period of BEVAR/FEVAR (n=16) compared with IEVAR (n=15). D, pATM expression during the peri-operative period of BEVAR/FEVAR (n=16) compared with IEVAR (n=15). E, Correlation between fold change increase in γ-H2AX expression and DAP (n=31). F, Correlation between fold change increase in pATM levels and DAP (n=31). G, Correlation between fold change increase in γ-H2AX levels and fluoroscopy time (n=31). H, Correlation between fold change increase in pATM levels and fluoroscopy time (n=31). None of the operators studied wore leg shielding during these procedures. γ-H2AX indicates gamma H2AX; BEVAR, branched endovascular aortic repair; EVAR, endovascular aortic repair; FEVAR, fenestrated endovascular aortic repair; IEVAR, infrarenal endovascular aortic repair; and pATM, phosphorylated ataxia telangiectasia mutated protein. *P<0.05.

Figure 4.

Factors affecting γ-H2AX expression in operators.A, Variation in γ-H2AX levels in operators’ lymphocytes after in vitro irradiation of their blood samples on 3 separate occasions (bars represent standard error of means, n=6, P<0.0001). B, An operator wearing lower leg shielding (red arrows). C, γ-H2AX and pATM expression in operators’ lymphocytes with (black bars, n=9) and without (red bars, n=16) the use of leg protection during BEVAR/FEVAR procedures (P<0.05). D, Radiation exposure measured by DAP and personal dosimeters worn at leg levels during procedures with (n=9) and without (n=16) leg shielding. γ-H2AX indicates gamma H2AX; BEVAR, branched endovascular aortic repair; DAP, dose area product; FEVAR, fenestrated endovascular aortic repair; pATM, phosphorylated ataxia telangiectasia mutated protein. *P<0.05.