Impact of a Disposable Sterile Radiation Shield on Operator Radiation Exposure During Percutaneous Coronary Intervention of Chronic Total Occlusions

Abstract: Background. Daily radiation exposure over many years can adversely impact the health of medical professionals. Methods. Operator radiation exposure was recorded for 124 percutaneous coronary interventions (PCIs) performed at our institution between August 2011 and May 2013: 69 were chronic total occlusion (CTO)-PCIs and 55 were non-CTO PCIs. A disposable radiation protection sterile drape (Radpad; Worldwide Innovations & Technologies, Inc) was used in all CTO-PCI cases vs none of the non-CTO PCI cases. Operator radiation exposure was compared between CTO and non-CTO PCIs. Results. Mean age was 64.6 ± 6.2 years and 99.2% of the patients were men. Compared with non-CTO PCI, patients undergoing CTO-PCI were more likely to have congestive heart failure, to be current smokers, and to have longer lesions, and less likely to have prior PCI and a saphenous vein graft target lesion. CTO-PCI cases had longer procedural time (median: 123 minutes (IQR, 85-192 minutes] vs 27 minutes [IQR, 20-44 minutes]; P<.001), fluoroscopy time (35 minutes [IQR, 19-54 minutes] vs 8 minutes [IQR, 5-16 minutes]; P<.001), number of stents placed (2.4 ± 1.5 vs 1.7 ± 0.9; P<.001), and patient air kerma radiation exposure (3.92 Gray [IQR, 2.48-5.86 Gray] vs 1.22 Gray [IQR, 0.74-1.90 Gray]; P<.001), as well as dose area product (267 Gray•cm² [IQR, 163-4.25 Gray•cm²] vs 84 Gray•cm² [IQR, 48-138 Gray•cm²]; P<.001). In spite of higher patient radiation exposure, operator radiation exposure was similar between the two groups (20 µSv [IQR, 9.5-31 µSv] vs 15 µSv [IQR, 7-23 µSv]; P=.07). Conclusions. Operator radiation exposure during CTO-PCI can be reduced to levels similar to less complicated cases with the use of a disposable sterile radiation protection shield. 

J INVASIVE CARDIOL 2015;27(7):313-316

Key words: percutaneous coronary intervention, chronic total occlusion, radiation exposure

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Interventional cardiologists and the cardiac catheterization laboratory staff are exposed to ionizing radiation on a daily basis over many years, which predisposes to cancer,¹ cataract formation, and comorbidities associated with protective garments.^2,3 Operator radiation exposure is mostly due to scatter, highlighting the importance of shielding.⁴ The Radpad (Worldwide Innovations & Technologies, Inc) is a disposable sterile surgical drape that contains bismuth and barium. When positioned on the abdomen of the patient, it attenuates scatter radiation to the operator, as demonstrated in electrophysiologic procedures^5,6 and complex percutaneous coronary interventions (PCIs).⁴ Since 2011, Radpad has been routinely utilized in all chronic total occlusion (CTO)-PCIs (but not in non-CTO PCIs) at our institution. The goal of the present study was to assess the impact of the Radpad shield on operator radiation exposure.

Methods

Patient population. We retrospectively identified all CTO and non-CTO PCIs in which operator radiation exposure was recorded between August 2011 and May 2013. A Radpad sterile drape was used in all CTO-PCI cases (Figure 1) vs none of non-CTO PCI cases. The drape was placed on the patient’s inguinal region and lower abdomen after arterial access was obtained. The study was approved by the Institutional Review Board. 

Operator radiation exposure. Operator radiation exposure was measured with a real-time radiation monitoring device (Bleeper Sv; Vertec Scientific, Inc), which was worn outside the lead apron in the front pocket of the radiation vest. The device was zeroed at the beginning of the case and the device reading was recorded at the end of the case.

Patient radiation exposure. Two measurements of patient radiation exposure were obtained for each procedure: air kerma (AK, measured in Gray) and dose area product (DAP, measured in Gray•cm²). Total air kerma (kinetic energy released in matter) is the procedural cumulative x-ray energy delivered to air at the interventional reference point, ie, 15 cm on the x-ray tube side of isocenter — the point at which the primary x-ray beam intersects with the rotational axis of the c-arm gantry.⁷ The AK dose directly correlates with the risk of radiation skin injury.³ DAP is the product of AK and the x-ray field size, and correlates best with the risk of developing stochastic complications, such as cancer.

Definitions. Coronary CTOs were defined as coronary lesions with Thrombolysis in Myocardial Infarction (TIMI) grade-0 flow for a duration of at least 3 months. Estimation of the occlusion duration was based on first onset of angina symptoms, prior history of myocardial infarction (MI) in the target vessel territory, or comparison with a prior angiogram. 

Technical success of CTO-PCI was defined as successful CTO revascularization with achievement of <30% residual diameter stenosis within the treated segment and restoration of TIMI grade-3 antegrade flow. Technical success of non-CTO PCI was defined as revascularization of TIMI grade-3 antegrade flow with <10% residual diameter stenosis.⁸Procedural success was defined as achievement of technical success with no in-hospital major adverse cardiac event (MACE), which was defined as a composite of death, clinical MI, stroke, or urgent coronary revascularization. 

Statistical analysis. Continuous data were summarized as mean ± standard deviation (for normally distributed data) or median and interquartile range (for non-normally distributed data) and compared using t-test or Wilcoxon rank-sum test, as appropriate. Categorical data were presented as frequencies or percentages and compared using chi square or Fisher’s exact test, as appropriate.

The distribution of the operator radiation exposure was extremely positively skewed. The data, therefore, were converted into ordinal variables (0-.99 = 1; 1.0-1.99 = 2; 2.0-3.5 = 3; 3.51-13 = 4). Ordinal regression on the recoded operator radiation exposure was performed using the negative log-log function (to reflect the naturally positively skewed distribution). A P-value of <.05 was considered statistically significant. Statistical analyses were performed using JMP v. 11.0 (SAS Institute).

Results

Patient characteristics. A total of 124 PCI procedures performed by the same primary operator were included in the present study (69 CTO-PCIs and 55 non-CTO PCIs). The clinical characteristics of the study patients are shown in Table 1. Mean age was 64.6 ± 6.2 years and all patients were men. Patients undergoing CTO-PCI were more likely to be current smokers, to have low left ventricular ejection fraction, and to undergo PCI of the right coronary artery, and less likely to have prior PCI or prior coronary artery bypass graft surgery. As expected, the CTO-PCI target lesions were longer.

Procedural characteristics and outcomes. CTO-PCI was associated with a significantly higher use of dual injection and 8 Fr sheaths and lower use of the radial approach (Table 2). CTO-PCI required use of more guidewires and more stents, and was often accomplished using the retrograde approach. Technical success and the incidence of MACE were similar in the two groups. One patient had post-PCI MI, 1 patient had a stroke, and 1 patient underwent emergency PCI due to acute stent thrombosis causing cardiac arrest and requiring cardiopulmonary resuscitation and intubation. CTO-PCI resulted in more than three-fold higher patient AK (3.92 Gray [IQR, 2.48-5.86 Gray] vs 1.22 Gray [IQR, 0.74-1.90 Gray]; P<.001) and DAP (267 Gray•cm² [IQR, 163-425 Gray•cm²] vs 84 Gray•cm² [48-138 Gray•cm²]; P<.001) radiation dose. However, there was no significant difference in first operator radiation exposure between the CTO and non-CTO groups (20 µSv [IQR, 9.5-31 µSv] vs 15 µSv [IQR, 7-23 µSv]; P=.07) (Table 2, Figure 2).

Ordinal regression on the recoded first operator radiation exposure revealed a significant interaction between patient AK values and CTO vs non-CTO PCI groups (P=.02; Nagelkerke R²=0.295). The magnitude of the relationship between patient AK and first operator radiation exposure was significantly larger among the CTO group when compared with the non-CTO group. Similar results were observed for the relationship between patient DAP radiation dose and first operator exposure in the CTO vs non-CTO PCI group (P=.05; Nagelkerke R²=0.246). 

Discussion

The major finding of our study is that routine use of a disposable, sterile radiation protection shield in CTO-PCI was associated with lower than anticipated operator radiation exposure. 

CTO-PCI can be challenging and is often associated with longer procedure time and patient and operator radiation exposure.³ CTO-PCI often requires use of multiple techniques and equipment until a final successful outcome is achieved.^9,10 Judicious use of radiation is critical for success in CTO-PCI; if patient radiation exceeds a threshold (usually 7-10 Gray air kerma dose) without lesion crossing, the procedure is terminated to minimize the risk of radiation skin injury. Experienced operators can achieve faster and more efficient revascularization, resulting in lower radiation exposure.¹¹

Limiting patient and operator exposure is of critical importance, since there is no safe dose of radiation and the principle of “as low as reasonably achievable” (ALARA) applies. Several measures can be taken to minimize radiation exposure, such as minimizing the “beam on” time for both fluoroscopy and cine angiography, using collimation, minimizing magnification, optimizing positioning of the patient, beam source, and image intensifier, and varying the radiation entry site.¹²

Use of new x-ray imaging equipment and software (such as the ECO system, Philips Allura Xper, Royal Philips Electronics) and use of 7.5 frames/second or lower fluoroscopy frame rate can further reduce patient radiation exposure.¹³ Reducing patient radiation exposure automatically reduces operator radiation exposure, yet additional measures such as shielding can further reduce operator exposure. The Radpad is a disposable, sterile, lead-free shield that is placed between the operator and patient to significantly reduce scatter radiation (Figure 1). Murphy et al recently performed a small randomized trial (n = 60) of use vs no use of the Radpad in elective complex PCI. They found that the Radpad group had significantly lower primary operator radiation exposure.⁴

Our study provided similar findings, demonstrating significant attenuation of operator radiation exposure with use of the Radpad in complex procedures. Although patient radiation exposure was more than three-fold higher in patients undergoing CTO vs non-CTO PCI, operator radiation exposure was similar in the two groups (Table 2). Use of a sterile radiation protection shield is easy to implement and carries low cost (approximately $20 per shield), making it an attractive choice for reducing occupational exposure to radiation in the cardiac catheterization laboratory. 

Study limitations. Our study is limited by the retrospective and observational design and the relatively small number of patients involved, which could potentially introduce bias in the interpretation of the results. The Radpad was used only in CTO-PCI; therefore, the generalizability of the results to other settings (specifically non-CTO interventions) is limited. However, the similar operator radiation exposure observed in the two groups suggest significant benefit with use of radio-absorbent drapes. A prospective, randomized, controlled trial would be important to confirm these findings and accurately estimate the magnitude of radiation dose reduction with Radpad. Use of real-time radiation monitoring can reduce operator radiation exposure,¹⁴ but it was used in all procedures included in the present study, both CTO and non-CTO PCI. Finally, as is common in veteran populations, most of the included patients were men, limiting generalizability in women; however, men constitute the majority of patients in most CTO-PCI series. 

Conclusion

Our study confirms results of previous research showing that use of a sterile radiation drape during CTO-PCI can significantly reduce operator radiation exposure and potentially reduce the risk for radiation-related complications. 

References

1. Roguin A, Goldstein J, Bar O, Goldstein JA. Brain and neck tumors among physicians performing interventional procedures. Am J Cardiol. 2013;111:1368-1372.
2. Klein LW, Miller DL, Balter S, et al. Occupational health hazards in the interventional laboratory: time for a safer environment. Catheter Cardiovasc Interv. 2009;73:432-438.
3. Brilakis ES, ed. Manual of Coronary Chronic Total Occlusion Interventions. A Step-By-Step Approach. Waltham, MA: Elsevier; 2013.
4. Murphy JC, Darragh K, Walsh SJ, Hanratty CG. Efficacy of the RADPAD protective drape during real world complex percutaneous coronary intervention procedures. Am J Cardiol. 2011;108:1408-1410.
5. Brambilla M, Occhetta E, Ronconi M, Plebani L, Carriero A, Marino P. Reducing operator radiation exposure during cardiac resynchronization therapy. Europace. 2010;12:1769-1773. 
6. Germano JJ, Day G, Gregorious D, Natarajan V, Cohen T. A novel radiation protection drape reduces radiation exposure during fluoroscopy guided electrophysiology procedures. J Invasive Cardiol. 2005;17:469-472.
7. Chambers CE. Radiation dose in percutaneous coronary intervention: OUCH... did that hurt? JACC Cardiovasc Interv. 2011;4:344-346.
8. Levine GN, Bates ER, Blankenship JC, et al. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary intervention. A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Society for Cardiovascular Angiography and Interventions. J Am Coll Cardiol. 2011;58:e44-e122.
9. Brilakis ES, Grantham JA, Rinfret S, et al. A percutaneous treatment algorithm for crossing coronary chronic total occlusions. JACC Cardiovasc Interv. 2012;5:367-379.
10. Michael TT, Mogabgab O, Fuh E, et al. Application of the “hybrid approach” to chronic total occlusion interventions: a detailed procedural analysis. J Interv Cardiol. 2014;27:36-43.
11. Michael TT, Karmpaliotis D, Brilakis ES, et al. Temporal trends of fluoroscopy time and contrast utilization in coronary chronic total occlusion revascularization: insights from a multicenter United States registry. Catheter Cardiovasc Interv. 2015;85:393-399. 
12.  Hirshfeld JW Jr, Balter S, Brinker JA, et al. ACCF/AHA/HRS/SCAI clinical competence statement on physician knowledge to optimize patient safety and image quality in fluoroscopically guided invasive cardiovascular procedures. A report of the American College of Cardiology Foundation/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training. J Am Coll Cardiol. 2004;44:2259-2282.
13. Wassef AW, Hiebert B, Ravandi A, et al. Radiation dose reduction in the cardiac catheterization laboratory utilizing a novel protocol. JACC Cardiovasc Interv. 2014;7:550-557.
14. Christopoulos G, Papayannis AC, Alomar M, et al. Effect of a real-time radiation monitoring device on operator radiation exposure during cardiac catheterization: the radiation reduction during cardiac catheterization using real-time monitoring study. Circ Cardiovasc Interv. 2014;7:744-750.

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From the ¹Veterans Affairs North Texas Health Care System and University of Texas Southwestern Medical Center, Dallas, Texas; and ²UTA College of Health Innovation, Arlington, Texas.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Banerjee reports research grants from Gilead and the Medicines Company; consultant/speaker honoraria from Covidien and Medtronic; ownership in MDCare Global (spouse); intellectual property in HygeiaTel. Dr Brilakis reports consulting/speaker honoraria from St. Jude Medical, Terumo, Asahi Intecc, Abbott Vascular, Elsevier, Somahlution, and Boston Scientific; research grants from Guerbet and InfraRedx; spouse is an employee of Medtronic.

Manuscript submitted September 25, 2014, provisional acceptance given October 27, 2014, final version accepted November 7, 2014.

Address for correspondence: Emmanouil Brilakis, MD, PhD, VA North Texas Health Care System, Cardiology, 4500 South Lancaster Road, Dallas, TX 75216. Email: esbrilakis@gmail.com