Author + information
- Received September 21, 2018
- Revision received November 30, 2018
- Accepted December 3, 2018
- Published online May 20, 2019.
- Anthony Aizer, MD, MSc∗ (, )
- Jessica K. Qiu, BS,
- Austin V. Cheng, BS,
- Patrick B. Wu, MD,
- Douglas S. Holmes, MD,
- Steven R. Wagner, MS,
- Scott A. Bernstein, MD,
- David S. Park, MD, PhD,
- Barbara Cartolano, RN,
- Chirag R. Barbhaiya, MD and
- Larry A. Chinitz, MD
- New York University Cardiac Electrophysiology Service, New York University School of Medicine, New York University Langone Medical Center, New York, New York
- ↵∗Address for correspondence:
Dr. Anthony Aizer, New York University Heart Rhythm Center, New York University Langone Medical Center, Tisch Hospital, Electrophysiology Laboratory, 560 First Avenue, 5th Floor, New York, New York 10016.
Objectives This study sought to determine whether a radiation safety time-out reduces radiation exposure in electrophysiology procedures.
Background Time-outs are integral to improving quality and safety. The authors hypothesized that a radiation safety time-out would reduce radiation exposure levels for patients and the health care team members.
Methods The study was performed at the New York University Langone Health Electrophysiology Lab. Baseline data were collected for 6 months prior to the time-out. On implementation of the time-out, data were collected prospectively with analyses to be performed every 3 months. The primary endpoint was dose area product. The secondary endpoints included reference point dose, fluoroscopy time, use of additional shielding, and use of alternative imaging such as intracardiac and intravascular ultrasound.
Results A total of 1,040 patient cases were included. The median dose area product prior to time-out was 18.7 Gy∙cm2, and the median during the time-out was 14.7 Gy∙cm2, representing a 21% reduction (p = 0.007). The median reference point dose prior to time-out was 163 mGy, and during the time-out was 122 mGy (p = 0.011). The use of sterile disposable protective shields and ultrasound imaging for access increased significantly during the time-out.
Conclusions A radiation safety time-out significantly reduces radiation exposure in electrophysiology procedures. Electrophysiology laboratories, as well as other areas of cardiovascular medicine using fluoroscopy, should strongly consider the use of radiation safety time-outs to reduce radiation exposure and improve safety.
Surgical pre-procedure checklists reduce patient morbidity and mortality (1–7). Although radiation exposure increases the risk of a number of adverse outcomes, including skin burns, cataracts, malignancies, and death, there are few data on the use of pre-procedure checklists with regard to fluoroscopy-based radiation exposure. We hypothesized that a radiation safety time-out implemented before all electrophysiology procedures would reduce patient and operator radiation exposure. To analyze this, we designed a sequential intervention study comparing radiation exposure prior to versus during implementation of a radiation safety time-out.
The Institutional Review Board reviewed the study and deemed it a clinical quality improvement initiative. A prospective cohort study of radiation usage was conducted for all procedures performed in the New York University Langone Medical Center Electrophysiology Lab between October 19, 2015 and June 30, 2017. Patients under the age of 18 years were excluded. Data were collected for 6 months prior to the radiation safety time-out, during which operators were unaware of the planned intervention.
The radiation safety time-out is a novel 7-item checklist using the concepts of “as low as reasonably achievable” (ALARA), review of best practices, and in consultation with the medical center’ director of radiation safety (Table 1) (8–10). Prior to and during radiation safety time-out implementation, all participating physicians were educated annually with the medical center mandatory video, “Radiation Safety for Fluoroscopically Guided Interventional Medical Procedures,” outlining optimal techniques to reduce radiation exposure.
Radiation safety time-out implementation included a 10-min education for attending physicians, fellows, and registered nurses on how to perform the time-out before starting all electrophysiology procedures. The radiation safety time-out was printed on a standardized “time-out card” present in each procedure room. This card was attached to and used after the medical center procedural time-out card.
The primary endpoint of the study was dose area product (DAP). DAP quantifies patient radiation exposure. It reflects both radiation dose and area irradiated. DAP strongly correlates with patient stochastic risk, that is, cancer induction (11). DAP was to be assessed every 3 months until a statistically significant difference from baseline was found or 12 months elapsed. If the time-out reduced the DAP, it was to be withdrawn and DAP was to be followed monthly, up to 12 months. If post time-out DAP increased compared with DAP during the time-out, the analyses would be terminated.
A secondary endpoint was reference point dose. This measurement is associated with peak skin dose; critical for deterministic effects (skin injuries, hair loss, and cataracts). To better understand how changes in the primary endpoint may have occurred, additional secondary endpoints included median fluoroscopy time and median total procedure time. Finally, use of optional protective equipment and techniques were analyzed as secondary endpoints, specifically use of sterile disposable protective shields (X-drapes, AADCO Medical, Randolph, Vermont), ultrasound for vascular access, and intracardiac ultrasound for procedural guidance (SOUNDSTAR, Biosense Webster, Baldwin Park, California).
After all radiation usage data was collected, a survey was administered individually to attending physicians, fellows, and physician assistants to assess which aspects of the time-out were still practiced. The survey included a free-response section in which participants listed the steps regularly taken to minimize radiation exposure. This was followed with the time-out list. Participants indicated which ones they regularly implemented. To evaluate how practitioners learned to minimize radiation exposure, participants indicated all methods by which they learned to take those steps: the radiation safety time-out; observation or discussion with an attending physician; observation or discussion with a fellow; and observation or discussion with a physician assistant.
Patient demographics and case characteristics were collected. Age, sex, and body mass index were collected from electronic medical records. Case characteristics (fluoroscopy equipment, operator, procedure, disposable protective drape use, ultrasound for vascular access, intracardiac ultrasound use, and total case time) were collected from procedure logs. Procedures were categorized as ablations, devices, or other with further subcategorization (Table 2). Fluoroscopy equipment included the following fixed x-ray systems: Allura Xper FD 10, Allura Xper FD 10/10, and Allura Xper FD 20 (Philips, Amsterdam, the Netherlands); and Axiom Artis dFC (Siemens, Munich, Germany). DAP, reference point dose, and fluoroscopy time were collected from the fluoroscopy equipment.
Unadjusted analyses of the effect of the radiation safety time-out on median DAP, reference point dose, fluoroscopy time, and total case time were performed. Additionally, the effect of the radiation safety time-out was assessed after adjusting for all known potentially confounding variables. These included patient age, sex, body mass index, radiation equipment, operator, and procedure type.
Continuous variables were reported as mean ± SD if normally distributed, median if non-normally distributed, and number (percentage) if categorical. Comparisons were made using the Student’s t-test for normal, continuous variables and Fisher exact test or Pearson chi-square test for categorical variables. Nonparametric data were analyzed using the Mann-Whitney U test. Adjusted analyses were performed using either linear regression for continuous normally distributed data or logistic regression for binary outcomes. Nonparametric continuous data (DAP, reference dose, fluoroscopy time, and total procedure time) were defined as a dichotomous outcome comparing the highest quartile to the lowest 3 quartiles of radiation exposure. A p value of <0.05 was considered significant. SPSS version 21 (IBM, Armonk, New York) was used for all statistical analyses.
Demographics and characteristics of patient cases
Baseline characteristics of each study group are presented in Table 2 (N = 1,040). There were no significant differences in the patient demographics or fluoroscopy equipment utilized between study groups.
Unadjusted radiation use from time-out implementation
The quantity of absolute x-radiation per patient case, measured by DAP and reference point dose, was significantly reduced during the radiation safety time-out. The median DAP of cases prior to the time-out was 18.7 Gy∙cm2. The median DAP for the first 3 months after radiation safety time-out incorporation was 14.7 Gy∙cm2, a 21% decrease from pre-time-out baseline (p = 0.007). A rapid and consistent reduction occurred with a leveling of the reduction during the third month of the intervention (Figure 1). The median DAP of the third intervention month was 12.5 Gy∙cm2, a 33% reduction in DAP compared with the pre-intervention arm (p = 0.008).
Similar to DAP, median reference point dose of cases prior to the time-out was 163 mGy, whereas median reference point dose during the first 3 months of the time-out was 122 mGy (p = 0.011). In contrast, median fluoroscopy time prior to time-out was 8.8 min, and median fluoroscopy time during the time-out was 8.7 min (p = 0.96). There was no significant difference in median total procedure time between groups (118 min vs. 121 min [p = 0.70]).
Adjusted analyses for effect of time-out on radiation use
When adjusted for patient age, sex, body mass index, fluoroscopy equipment, operators, and procedure type, the time-out remained associated with decreased DAP (p = 0.021) and decreased reference point dose (p = 0.024) (Table 3). DAP prior to versus during the time-out was examined after stratification by operators performing 40 or more procedures in each study arm (Figure 2). All operators had a reduction in DAP with time-out implementation.
Additional imaging techniques and protective measures
Disposable protective shields were used in 53.4% of cases pre-time-out and in 61.6% of cases during the time-out (p = 0.009) (Table 3). In the maximally adjusted model, the use of the time-out remained associated with increased use of disposable protective drapes (p < 0.001). Ultrasound for vascular access was used in 63.7% of nondevice cases prior to the radiation safety time-out and in 81.0% of cases during implementation of the time-out (p < 0.001 in univariate and maximally adjusted models). In contrast, intracardiac ultrasound use occurred in 26.7% of nondevice cases prior to time-out and in 29.8% of cases during time-out implementation (p = 0.40 in unadjusted and p = 0.45 in maximally adjusted models).
Radiation levels after time-out withdrawal
Because of the significant reduction in the primary endpoint 3 months after time-out implementation, the radiation safety time-out was subsequently withdrawn. Comparison of baseline demographics and potential confounding variables between cases during the time-out and cases after time-out withdrawal revealed no significant differences (Supplemental Table 1). Median DAP rose modestly in the first month following time-out withdrawal, but over the next 11 months, median DAP experienced a net negative trend (Figure 3). DAP for the 12 months after time-out withdrawal was 13.1 Gy∙cm2, which was not significantly different from the DAP during the time-out (univariate p = 0.18; maximally adjusted p = 0.81), whereas post-time-out DAP remained significantly reduced compared with DAP before time-out implementation for both unadjusted (18.7 vs. 13.1 Gy∙cm2 [p < 0.001]) and maximally adjusted models (standardized B = −0.179; p = 0.001).
Similarly, there was no significant difference between reference point dose after time-out withdrawal and during the time-out in unadjusted (p = 0.48) and maximally adjusted models (p = 0.81). Like DAP, reference point dose after time-out withdrawal remained significantly reduced compared with the reference point dose prior to the time-out for unadjusted (121 mGy vs. 163 mGy [p < 0.001]) and maximally adjusted models (standardized B = −0.152; p = 0.006).
Fluoroscopy time after time-out withdrawal (median 8.0 min) was not significantly different from the fluoroscopy time either during the time-out implementation for univariate (p = 0.23) and maximally adjusted (p = 0.20) models, or prior to the time-out in univariate (p = 0.16) and maximally adjusted models (p = 0.60).
Post-radiation safety time-out survey
Attending physicians (n = 7), fellows (n = 3), and physician assistants (n = 6) completed a post-radiation safety time-out survey 12 months after time-out withdrawal. Over one-half of participants reported regularly ensuring the lowest acceptable frame rate is programmed (81%), the bed height is elevated as close as possible to the image intensifier (62%), magnification is set as low as possible (69%), and all shields and drapes are in place (75%). Fewer than one-half reported regularly ensuring the beam is collimated (25%), all team members are wearing dosimeter badges (6%), or fluoroscopy images are saved over fluorography when possible (19%). Over one-half reported learning to take these steps to minimize radiation exposure from the time-out card (56%) or from either observation of or conversation with an attending physician (69%). Less than one-half reported learning these steps from observation of or conversation with a fellow (19%) or physician assistant (25%).
This is the first study to design, implement, and demonstrate that a radiation safety time-out reduces radiation exposure levels in the electrophysiology lab. The radiation safety time-out also increased use of protective equipment, including protective drapes and non-radiation-based vascular access imaging. These changes occurred independently of operator, procedure type, and patient demographics. It resulted in no significant increase in procedure time or complications.
The decrease in radiation levels occurred independently of total fluoroscopy time, for which there was no difference between groups. In addition, intracardiac ultrasound use did not increase. This suggests that the time-out did not influence the operators’ choices in how often or how long to use fluoroscopy. The radiation exposure levels decreased likely because the time-out led operators to optimize fluoroscopy equipment programming to minimize output while maintaining image fidelity.
Recently, pre-procedural time-outs with checklists have been widely adopted. Described in To Err Is Human: Building a Safer Health System, published in 1999, checklists in medicine could improve medical care by reducing human error (12). Surgery was an area that could be improved, and as such, utilization of surgical time-outs with checklists was studied comprehensively (1–7). Subsequently, it was confirmed that time-outs reduced surgical morbidity and mortality. The World Health Organization published a standardized surgical checklist and recommends its use for procedures (13).
Cardiac electrophysiology procedures using fluoroscopy expose patients and health care teams to x-radiation, carrying a risk of immediate and long-term consequences. The harmful effects of radiation can be divided into 2 categories, deterministic and stochastic. Deterministic effects occur predictably with a minimum threshold of radiation exposure, such as cataracts, hair loss, skin burns, or death (14). Stochastic effects, however, can occur randomly from any level of radiation; these injuries include fatal and nonfatal malignancies (15). Stochastic effects are more important to consider for electrophysiology procedures, as the levels of x-radiation rarely are high enough to cause deterministic effects (15,16). The risks of low-dose radiation exposure are not well defined. In 1 review, fluoroscopy in electrophysiology procedures can yield effective dose radiation exposures from 1 to 60 mS (16). The lifetime risk of adult, fatal cancer increases by 0.005% for every millisievert of exposure (17). Given this, at its worst, electrophysiology fluoroscopy can increase the risk of fatal cancer for the patient by 1 event for every 333 procedures (18).
Recently, radiation risks have been found for interventionalists that regularly use radiation. Deoxyribonucleic acid response/repair markers (γ–H2AX and phosphorylated ataxia telangiectasia mutated) were immediately up-regulated post-radiation exposure during endovascular aortic repair, implicating radiation-induced deoxyribonucleic acid damage (19). Brain-specific micro ribonucleic acid (microRNA)-134 and microRNA-2392 were down-regulated in interventional cardiologists compared with control subjects. MicroRNA-134 dysregulation is associated with epilepsy, Alzheimer’s disease, bipolar disorder, and brain malignancies. MicroRNA-2392 down-regulation has been linked to gastric cancer (11).
Epidemiologic studies support these molecular findings. Interventional cardiologists have a mean lifetime excess cancer risk of 1 in 192, higher than that of radiologists and nuclear physicians (20). These risks could be specifically for brain and neck tumors (21). Cataracts developed for 1 of 2 interventional cardiologists without protective equipment (22). Given the dangers for both patients and operators, it is imperative that radiation exposures be maximally reduced.
To reduce radiation exposure in all parts of health care, the Nuclear Regulatory Commission implemented the concept of ALARA (23). The National Research Council notes that there is no threshold below which there is no tumor-induction risk (24). ALARA protocols do not mandate time-out checklists to reduce exposure. Editorials within the vascular surgery publications and the recently published “2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging” have proposed checklists to reduce exposure (25,26). However, there has been little direct evidence to support their use. Limited data are available from the pediatric publications. Because of increased use of x-radiation and the increased radiation absorption rates in children, the Alliance for Radiation Safety in Pediatric Imaging was established with the goal of reducing pediatric radiation exposure. The alliance initiated the Image Gently, Step Lightly Campaign, which includes a checklist to reduce x-radiation exposure (27). In a small pediatric study with 37 control and 32 intervention patients, use of a checklist during ureteroscopy reduced total fluoroscopy time and mean entrance skin dose (28). An additional study investigated the use of a pre-procedural fluoroscopy checklist for first-year radiology residents performing gastrointestinal/genitourinary imaging (29). Implementation of the checklist reduced mean fluoroscopy time by 41.1 s. Though intriguing, these studies are limited. They lack any assessment of permanence of the time-out intervention, efficacy of the checklist for nontrainees, or utility of the intervention in other areas of medicine. However, in light of the findings in our study with over 1,000 patients, expansion of a pre-procedure radiation safety time-out to additional areas of medicine should be considered.
In our analyses, 1 year after the radiation safety time-out was withdrawn, radiation levels remained reduced, suggesting that the time-out was not only effective, but also educational. Practitioners likely learned methods of minimizing radiation exposure from repeatedly practicing the time-out during the 3-month implementation. Repetition has long been associated with learning. Message repetition can positively affect an individual’s attitude toward advocated measures (30). The World Health Organization Surgical Safety Checklist implementation increased awareness and perceived importance of the checklist’s beneficial effects (31–33). In our study, over 50% of attending physicians, fellows, and physician assistants reported learning from the time-out steps to minimize radiation exposure, and over 80% of practitioners report regularly implementing at least 3 of 7 radiation safety time-out items.
However, there were a number of radiation safety measures that were no longer regularly implemented since time-out withdrawal. Based on survey responses, few practitioners checked to save fluoroscopy images over fluorography/cine images, and only attending physicians checked for beam collimation. Furthermore, reported compliance can overestimate actual implementation rates (34). Occasional omissions of any of these actions can have significant impact on patient and physician exposure. Of note, frame rate has a nearly linear relationship to patient exposure. Similarly, there is a nearly linear reduction in exposure with reduction in surface area via collimation. Fluorography images typically expose patients to 10× fluoroscopy radiation levels (16). Doubling the distance between patient and image intensifier can result in up to a 17-fold dose increase (35). Magnification increases radiation dose by a factor of the square of the ratio of the original and magnified image intensifier diameters (36). Perhaps most importantly, shielding can reduce operator exposure up to 20-fold (37,38).
Although radiation output levels remained low after withdrawal of the time-out despite reduced adherence, this should not be interpreted as a diminished requirement for diligent utilization of radiation safety techniques. Failure to implement all time-out items may be undetectable by the gross means of this study’s primary and secondary endpoints, but any additional radiation exposure poses dangers to patients and practitioners. Given the risks and benefits, we recommend other electrophysiology laboratories explore the option of pre-procedural time-outs to reduce radiation exposure. Furthermore, radiation safety time-outs for other areas of medicine that involve regular use of fluoroscopy may also yield decreases in radiation exposure, improving safety for patients and health care teams.
This study was performed at a single center. Further studies are necessary to assess efficacy of a radiation safety time-out across other institutions and during non-electrophysiology-based procedures. DAP and reference point dose were used as measurements of radiation exposure for health care workers in procedure rooms. Corroboration with an analysis of staff radiation dosimeter badges would add further support to the study findings. However, because staff wore dosimeter badges inconsistently prior to the time-out, any analyses would have been at risk of significant observation bias. Further study is warranted to determine whether the effects of the time-out would be beneficial in laboratories utilizing radiation technicians. Direct observation was not used to determine which items from the radiation safety time-out were still being implemented after time-out withdrawal. Instead, attending physicians, fellows, and physician assistants completed post-radiation safety time-out surveys. The post-time-out survey relied on participant self-report, which has the potential of introducing social desirability response bias (39).
A mandated pre-procedural radiation safety time-out significantly reduces fluoroscopy radiation levels in electrophysiology procedures. Furthermore, protective equipment use, such as disposable protective drapes, as well as ultrasound for vascular access use, increased with the time-out. Electrophysiology laboratories, as well as other areas of medicine that regularly use fluoroscopy, should strongly consider the use of radiation safety time-outs to reduce radiation exposure and improve safety.
COMPETENCY IN MEDICAL KNOWLEDGE: A radiation safety time-out significantly reduces radiation exposure during electrophysiologic procedures. As radiation exposure occurs across a wide array of medical specialties, it is imperative that every practitioner recognize the dangers of radiation exposure and mitigate risk by limiting exposure to ALARA. A radiation safety time-out can assist ALARA goals. Utilization of a radiation safety time-out created a repetitive, clinically driven education regarding how to reduce radiation exposure. The success of this practice-based educational approach was evident when despite time-out withdrawal, radiation exposure remained reduced, indicating a significant change in physician practice.
TRANSLATIONAL OUTLOOK: The reduction in radiation exposure in the electrophysiology lab raises the question whether a radiation safety time-out can be applied across the myriad domains of medicine to reduce radiation exposure for multiple patient populations. Further investigation in the fields of cardiac catheterization, peripheral vascular intervention, vascular surgery, gastroenterology, neurointervention, and radiology are warranted to determine whether we can better protect the vast majority of patients being exposed to x-radiation. This study also highlights the importance of the time-out as a mechanism across many disciplines within medicine to optimize patient care and reduce adverse outcomes. Time-outs should not be limited to procedures. Rather, time-outs may benefit patients at many points along their care.
Dr. Aizer has served as a consultant for Biosense Webster; received research support from Abbott and SentreHEART; and received fellowship support from Abbott, Biotronic, Boston Scientific, and Medtronic. Dr. Park has received grant support from the National Institutes of Health (R01 HL132073). Dr. Barbhaiya has received speaking fees/honoraria from Abbott, Biotronic, Medtronic, and Zoll; and received research support from Biotronic. Dr. Chinitz has received speaking fees/honoraria from Abbott, Biosense Webster, Biotronik, Boston Scientific, and Medtronic; and served as a consultant for Abbott, Biosense Webster, Biotronik, Medtronic, and Pfizer. All other authors have reported that they have no relationships relevant to the contents of this paper.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Abbreviations and Acronyms
- as low as reasonably achievable
- dose area product
- micro ribonucleic acid
- Received September 21, 2018.
- Revision received November 30, 2018.
- Accepted December 3, 2018.
- 2019 American College of Cardiology Foundation
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