Comparison of Radiation Exposure Among Interventional Echocardiographers, Interventional Cardiologists, and Sonographers During Percutaneous Structural Heart Interventions

Key Points Question Are interventional echocardiographers exposed to greater occupational radiation doses than interventional cardiologists and sonographers during structural heart procedures? Findings In this cross-sectional study of 60 structural heart procedures, interventional echocardiographers experienced higher head-level radiation doses than interventional cardiologists and sonographers. Meaning These comparatively higher radiation doses indicate a previously underappreciated occupational risk faced by interventional echocardiographers, which has implications for the rapidly expanding structural heart team.


Introduction
During the past decade, percutaneous procedures to treat structural heart disease have rapidly expanded.Among structural heart interventions, left atrial appendage occlusion (LAAO) and transcatheter edge-to-edge mitral valve repair (TEER) are now performed routinely at many centers and are increasing rapidly. 1,2Both LAAO and TEER are typically performed under the guidance of fluoroscopy and transesophageal echocardiography (TEE), which has resulted in the addition of an interventional echocardiographer as an integral member of the structural heart team.
Because there is a need for intermittent manipulation of the TEE probe during LAAO and TEER, the interventional echocardiographer must stand near the patient, which is the principal source of scatter radiation during fluoroscopically guided procedures.Long-term exposure to scatter radiation in the cardiac catheterization laboratory has been associated with multiple adverse health effects among interventional cardiologists, including premature cataract formation, 3,4 early carotid atherosclerosis, 5 and possibly left-sided brain malignant tumors. 6Whether interventional echocardiographers on the structural heart team are exposed to levels of radiation sufficient to pose similar adverse health risks as those faced by interventional cardiologists is not yet known.Given the rapidly increasing rates of LAAO 7 and TEER 8 procedures and progress in the field of interventional echocardiography, steps to quantify the occupational risk of interventional echocardiographers are warranted to help inform mitigation attempts.
This study aims to compare head-level radiation doses for interventional echocardiographers with those of interventional cardiologists and sonographer controls during LAAO and TEER procedures.Given the nearness of interventional echocardiographers to the radiation emission source, we hypothesized that interventional echocardiographers would be exposed to higher radiation doses compared with interventional cardiologists and sonographers.

Study Population
This single-center, prospective, investigator-initiated cross-sectional study was designed to investigate radiation doses to interventional echocardiographers during LAAO and TEER procedures.
The study was conceived, designed, and conducted by investigators of the Frederik Meijer Heart & Vascular Institute of Spectrum Health (Grand Rapids, Michigan) as previously described. 9terventional cardiologists and interventional echocardiographers were board-certified cardiologists with a mean of 10 and 3 years, respectively, of clinical practice beyond completion of their fellowship training; trainees were not involved during cases.Data on race and ethnicity were not collected as a part of this study.The institutional review board at Spectrum Health approved the protocol, and all participants provided verbal informed consent.This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
Radiation exposure data were prospectively collected on 30 consecutive LAAO procedures and 30 consecutive TEER procedures performed between July 1, 2016, and January 31, 2018.Details of implantation protocols for these commercially available devices have been previously published. 9,10ate-of-the art fluoroscopy systems (AlluraClarity, Philips) with real-time image noise reduction All LAAO procedures involved implantation of a commercially available closure device (WATCHMAN, Boston Scientific).All TEER procedures were performed using a commercially available percutaneous edge-to-edge repair device (MitraClip, Abbott Vascular).Procedures were performed using a transseptal approach and were guided by fluoroscopy and TEE.For the TEER and LAAO procedures, the measured direct-line distances from the radiation source to team member while in a neutral position were 26 cm for the interventional echocardiographer, 36 cm for the interventional cardiologist, and 250 cm for the sonographer.The procedure rooms were arranged as shown in

Radiation Monitoring
Real-time radiation exposure data were collected using a commercially available dosimetry system that contains a bedside monitor capable of displaying real-time radiation doses (RaySafe i2, Unfors RaySafe).To measure head-level radiation doses, each physician and staff member wore a dosimeter located on the left anterior side of the glasses or on the left anterior side of the thyroid collar as previously described. 11,12This system collects the cumulative head-level radiation exposure per case.
Physicians and sonographers were blinded to the radiation data collected by the dosimeters for the duration of the study.

Radiation Protection
Interventional echocardiographers, interventional cardiologists, and sonographers wore traditional lead apparel, consisting of a lead skirt, apron, and thyroid collar.A mobile, height-adjustable, accessory lead shield was positioned between the patient and interventional echocardiographer.The lead shield used in this study included a fixed lower half with a height-adjustable upper half of the shield, which provided increased shielding while the transesophageal echocardiography probe was not being manipulated but could be lowered during probe manipulation (Figure 1; see eAppendix in the Supplement for details).According to standard operating procedure at the study institution, 2 shields were positioned between the patient and interventional cardiologist in all cases: a ceilingmounted upper-body lead shield with a patient contour cutout and a lower-body lead shield attached to the side of the operating table extending from table to floor (Figure 1).The sonographer did not have a separate, dedicated mobile lead shield.

Radiation Doses
The primary measure of interest in this study was the personal dose equivalent (H p [10]) as recorded by dosimeters worn by interventional echocardiographers, interventional cardiologists, and sonographers and reported directly by the dosimetry system.In addition to reporting the personal dose equivalent per case, the frequency of a personal dose equivalent greater than 20 μSv was also reported because this dose is roughly 10-fold higher than the mean personal dose equivalent received by interventional cardiologists across a variety of procedures. 13Additional radiation metrics recorded for each case included the fluoroscopy time, air kerma (AK), and dose area product (DAP), which were automatically calculated by the fluoroscopy imaging system.Both AK and DAP are commonly used metrics to estimate patient radiation dose; AK is defined as the radiation delivered to air at a reference point located 15 cm on the x-ray tube side of isocenter, and DAP is defined as the product of AK and the x-ray field area. 14

Statistical Analysis
Data analyses were conducted between January 1, 2020, and October analysis or a Fisher exact test if the expected cell counts were below 5 in more than 20% of the cells.
Because there were 3 different groups, a Bonferroni correction was applied to these tests if needed when assessing the data across the 3 occupations.A 2-sided P < .05 was considered to be statistically significant unless otherwise noted.Odds ratios for the categorical comparisons were produced to assess the association for those that were significant.No data were imputed if missing.All statistical analyses were generated using SAS software, version 7.1 (SAS Institute Inc), and the statistical figures were generated using R statistical software, version 4.0.2(R Foundation for Statistical Computing).

Discussion
The primary results of this cross-sectional study of occupational radiation exposure indicate that interventional echocardiographers received significantly greater head-level radiation doses than interventional cardiologists during 2 commonly performed structural heart cases.In addition, in more than 25% of cases, the interventional echocardiographer received a dose that exceeded 20 μSv, which is roughly 10-fold higher than the previously reported mean personal dose equivalent received by interventional cardiologists across a variety of different procedures. 13In contrast, doses that exceeded 20 μSv were observed in 5% or fewer cases among interventional cardiologists during LAAO and TEER.Taken collectively, the findings of this study may have important occupational health implications for the rapidly expanding field of interventional echocardiography and for the structural heart team.
Despite previous work 3,4 demonstrating the occupational radiation exposure risk to interventional cardiologists performing percutaneous coronary and structural heart interventions, similar data for interventional echocardiographers are lacking.Radiation exposure for individuals procedures, including transcatheter aortic valve replacement (TAVR), LAAO, TEER, and atrial or ventricular septal defect repairs.Although differences in radiation exposure were noted based on the occupation, no statistically significant difference was found between interventional echocardiographers and interventional cardiologists in pooled procedural analyses. 16Other studies have suggested that interventional echocardiographers receive higher radiation doses than interventional cardiologists 17 and that dedicated shielding techniques for interventional echocardiographers may lower the occupational radiation exposure. 16,18,19r data build on the pioneering work of Crowhurst et al 16 and others [17][18][19] in several important ways, which may explain the higher radiation doses experienced by interventional echocardiographers in the current analyses.First, the current study focused on 2 of the most common interventional echocardiographic procedures performed in the US (LAAO and TEER), 1,2 whereas the work of Crowhurst et al 16 focused primarily on TAVR procedures.Procedural characteristics associated with TAVR vs non-TAVR procedures, including for femoral angiography and angulation of the radiation source (particularly fewer steep right anterior oblique angles), have previously been associated with different radiation doses and may account for some of the observed between-study differences. 15,16That the current study focuses on LAAO and TEER (and excluded TAVRs) is of particular importance given that many facilities have transitioned away from a dedicated intraprocedural interventional echocardiographer during TAVR procedures and toward transthoracic procedural imaging, thereby limiting the generalizability of previous studies. 15,20cond, differences in positioning and shielding techniques may explain some of the observed differences.In the current study, the interventional echocardiographer was located at the head of the bed and directly faced the patient (and the primary source of scatter radiation) (Figure 1).This position contrasted with the study by Crowhurst et al, 16 in which interventional echocardiographers were offset by approximately 45°and stood with their backs to the patient throughout the procedure.Positioning techniques in which the interventional echocardiographer has their back to the patient are not standard practice in many structural heart laboratories.Facing one's back to the patient and structural heart team may also result in workflow limitations in manipulation of the TEE probe as well as team member communication.
Third, interventional echocardiographers in our study experienced markedly reduced radiation doses than in the study by Crowhurst et al 16 -comparatively 6-fold lower doses during LAAO and 4-fold lower doses during TEER. 16The lower radiation doses in the current study may in part be attributable to the use of state-of-the art fluoroscopy equipment, including noise reduction technology, which has been shown in at least 1 randomized clinical trial 21 to reduce the operator radiation dose by 50%.Given these important positioning and procedural differences, direct comparisons in radiation doses between our study and the study by Crowhurst et al 16 are limited.
Taken collectively, the observations of the current study inform the interventional echocardiography and the structural heart communities of the substantially higher risk of head-level radiation exposure of interventional echocardiographers during structural intervention procedures.
The occupational risks depend on several factors, including the annual volume of TEE-guided fluoroscopic procedures performed, the radiation doses received during each procedure, the quality of the fluoroscopy imaging technology used, and the radiation safety practices of the institution in which the procedures take place.Additional studies are needed to determine whether thicker shields or alternative shielding configurations (such as suspended lead suits) would result in lower radiation doses than those observed.Without such technology, interventional echocardiographers may be vulnerable to even higher doses of radiation than reported herein, especially in catheterization laboratories that use older fluoroscopy equipment.We hope these data can help guide future

Table 1 .
Among the 60 structural heart interventions, the median per case radiation dose was 10.6 μSv (IQR, 4.2-22.4μSv)forinterventional echocardiographers and 2.1 μSv (IQR, 0.2-8.3μSv)forinterventional cardiologists (P < .001)(Figure2).The odds of interventional echocardiographers having a radiation dose greater than 20 μSv were 7.5 (95% CI, 2.1-27.3)times greater than interventional cardiologists (P < .001).No differences in median radiation doses between TEER and LAAO procedures were present for interventional echocardiographers (10.5 μSv [IQR, 3.1-20.5μSv] vs 10.6 μSv [IQR, 5.8-24.1 Baseline Characteristics of Patients a burden.Additional baseline characteristics of the patients are noted in Table1.Procedural radiation metrics are presented in Table2.Despite higher fluoroscopic time during TEER cases, no differences in radiation doses (AK or DAP) were observed between the LAAO and TEER procedures.a Data are presented as number (percentage) of patients unless otherwise indicated.b P values compare the LAAO and TEER groups.

Table 2 .
Radiation Metrics During Percutaneous LAAO and TEER a P values compare the LAAO and TEER groups.

Table 3 .
Personal Dose Equivalent per Case Received by Interventional Echocardiographers, Interventional Cardiologists, and Sonographers During Percutaneous Left Atrial Appendage Closures and Percutaneous Mitral Valve Repairs a P value compares interventional echocardiographer and interventional cardiologist.b P value compares interventional echocardiographer and sonographer.c P value compares interventional cardiologist and sonographer.Downloaded From: https://jamanetwork.com/

on 09/27/2023 performing
16E was initially drawn from anesthesiologists who concomitantly performed echocardiography during transcatheter aortic valve replacements.15Inone of the largest studies to date involving a dedicated interventional echocardiographer during structural heart cases, Crowhurst et al16demonstrated relatively high radiation doses across a variety of structural heart