A prospective observational study of radiation trends in the cardiac catheterization laboratory

Suraj Khanal; Pavan Kumar Rasalkar; Rajesh Vijayvergiya

doi:10.4103/JCPC.JCPC_7_18

ORIGINAL ARTICLE

Year : 2018 | Volume : 7 | Issue : 3 | Page : 111-114

A prospective observational study of radiation trends in the cardiac catheterization laboratory

Suraj Khanal MBBS, MD, DM , Pavan Kumar Rasalkar MBBS, MD, DM , Rajesh Vijayvergiya MBBS, MD, DM
Department of Cardiology, Advanced Cardiac Centre, PGIMER, Chandigarh, India

Date of Web Publication

10-Jul-2018

Correspondence Address:
Dr. Suraj Khanal
Department of Cardiology, Advanced Cardiac Centre, 3^rd Floor, Block-C, PGIMER, Chandigarh - 160 012
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/JCPC.JCPC_7_18

Abstract

Background: Radiation exposure in cardiac catheterization laboratory (cath lab) is a health hazard not only to the interventional cardiologist, but also to the support staff as well as the patients. Data about radiation exposure in cath lab are lacking in India. We undertook this study to observe the radiation trends in a high-volume cath lab at a tertiary care center in India. Materials and Methods: A prospective study of radiation trends in the cardiac catheterization laboratory was carried out with regard to mean fluoroscopic time (FT, minutes), mean total cumulative dose (Gy), and mean dose area product (DAP) (Gycm²). Radiation exposures in various diagnostic and interventional procedures with respect to the above three parameters were studied. Radiation exposure in transradial and transfemoral routes was compared in the subgroup analysis. Results: A total of 2016 cases in which cath lab procedures were done during the period of 1 year were included in the study. Mean DAP for coronary angiography was 23.72 Gycm² and for percutaneous transluminal coronary angioplasty (PTCA) was 196.61 Gycm². If the complex PTCA procedures were excluded, the mean DAP was 33.19 Gycm². Radiation trends observed in our study were comparable to the international standards. Conclusions: Radiation exposure in cath lab is a health hazard and must be given due importance. By maintaining radiation hygiene and associated precautions, the radiation exposure in cath lab can be kept within acceptable limits as shown in our study.

Keywords: Cath lab, coronary angiography, dose area product, percutaneous transluminal coronary angioplasty, radiation

How to cite this article:
Khanal S, Rasalkar PK, Vijayvergiya R. A prospective observational study of radiation trends in the cardiac catheterization laboratory. J Clin Prev Cardiol 2018;7:111-4

How to cite this URL:
Khanal S, Rasalkar PK, Vijayvergiya R. A prospective observational study of radiation trends in the cardiac catheterization laboratory. J Clin Prev Cardiol [serial online] 2018 [cited 2023 Mar 29];7:111-4. Available from: https://www.jcpconline.org/text.asp?2018/7/3/111/236334

Introduction

The operator, support staff as well as patients in a cardiac catheterization laboratory (cath lab) are exposed to significant amount of radiations during the routine clinical practice. As compared to the other diagnostic and interventional radiological procedures that use fluoroscopy, exposure in cath lab is higher due to the configuration of X-ray machine, number of cases per day, duration, as well as complexity of the procedures.^[1] Exposure exceeding 5 sieverts/h has been reported in cath lab, especially in procedures such as electrophysiology studies (EPS) and complex percutaneous coronary interventions (PCIs).^[2] Therefore, the interventional cardiologist faces a special occupational hazard of radiation exposure that cannot be overlooked as there are many operators who are performing 400–800 PCIs per year for over 1–2 decades. The first guidelines for radiation safety in cardiac cath lab were published in 1992 by the Society of Cardiovascular Angiography and Interventions.^[3] Ever since the guidelines were published, the interventional cardiology field has witnessed an exponential growth. Although we have better machines these days with sophisticated software to limit the radiation exposure without hampering the image quality, the complexity of procedures such as chronic total occlusion (CTO) interventions and EPS have increased, thereby leading to an increase in the duration of the procedure as well as radiation exposure.

Radiation in the cath lab is generated using two different modes: fluoroscopy and cine. Although fluoroscopy involves 95% of the total X-ray time, it causes only 40% of the total radiation exposure due to the pulsed screening. Cine is used to acquire images and accounts for 60% of the total radiation exposure although it represents only 5% of the total X-ray time. This is due to the use of relatively high-dose rapid sequence screening during cine.^[1]

Radiation-induced side effects are well recognized, and prolonged procedures are associated with potentially serious adverse effects.^{[4],[5],[6],[7],[8]} Radiation produces two types of adverse effects, namely the deterministic effects which are dose related and stochastic effects which are independent of the dose. Deterministic effects have a dose-dependent threshold level below which these effects do not occur. However, once above the threshold level, both chances and severity of the effect increase linearly with the dose. These include cataract, sterility, hair loss, skin erythema, and fetal abnormality. Stochastic effects, on the other hand, occur by chance, and there is no threshold dose level for the same to occur. While the probability of the occurrence of stochastic effects is proportional to the radiation dose, the severity is independent of the dose, for example, cancer.

Given the potentially harmful adverse effects that radiation can cause, appropriate monitoring of radiation dose in cath lab is of prime importance. There are various methods of assessing the radiation dose in cath lab which include fluoroscopic time (FT), total cumulative dose, dose area product (DAP), and peak skin dose (PSD). FT is the total time duration of the fluoroscopic use without the cine time and is a poor indicator of the total radiation dose.^{[9],[10],[11]} However, the modern fluoroscopy software gives both fluoroscopy and cine time that can be used to assess the radiation risk. Total cumulative dose refers to the total radiation dose during a procedure in Gy. DAP is an output measurement of the total amount of radiation delivered to the patient. It is defined as the dose of radiation delivered to a patient or area of tissue multiplied by the area of skin exposed, expressed as Gycm ². DAP reflects not only the dose within the radiation field, but also includes the area of tissue irradiated. Due to the divergence of a beam emitted from a point source, the area irradiated increases with the square of the distance from the source, while radiation intensity decreases according to the inverse square of distance. DAP is independent of distance from the source. DAP value is readily available in all modern machines. It has been widely used in previous studies for comparison of radiation doses. Our study also uses mean DAP as the primary parameter to compare radiation doses. PSD is defined as the maximum dose received by any local area of patient skin in Gy. Both the probability and severity of deterministic skin effects increase as PSD increases. PSD >15 Gy is identified as a Sentinel event by the Joint Commission.^[12]

Despite the high exposure of radiation in cath lab and its proven adverse effects, data regarding radiation exposure in cath lab are lacking in India. We undertook this study to observe the radiation trends in a high-volume cath lab at a tertiary care center in India.

Materials and Methods

A prospective study of radiation trends in the cardiac catheterization laboratory between November 2013 and November 2014 was carried out in the Department of Cardiology at PGIMER, Chandigarh, with regard to mean FT (minutes), mean total cumulative dose (Gy), and mean DAP (Gycm ²).

Patients aged >18 years were required to have one of the procedures done at the designated cath lab. The procedure included coronary angiography, coronary angiography + left ventricular (LV) angiography, PCI of single-vessel disease (SVD), PCI of double-vessel disease (DVD), and PCI of triple-vessel disease (TVD). Procedures such as CTO interventions, failed percutaneous transluminal coronary angioplasty (PTCA), bifurcation PTCA, pediatric interventions, and EPS were excluded from the study. Radiation exposures in various diagnostic and interventional procedures were studied. Radiation exposure in transradial and transfemoral routes was compared in the subgroup analysis. The study was conducted according to the ethical principles stated in the latest version of Helsinki declaration and the applicable guidelines for Good Clinical Practice.

Results

A total of 2016 cases in which cath lab procedures were done during the period of 1 year were included in the analysis. Of the 2016 cases, coronary angiography was done in 834 (41.4%) patients, whereas coronary angiography + LV angiography and PCIs of SVD, DVD, and TVD were done in 546 (27.1%), 483 (24%), 132 (6.5%), and 21 (1%) patients, respectively. [Table 1] enumerates the data on radiation exposure in various diagnostic and interventional procedures measured in terms of mean FT, mean total radiation dose, and mean DAP.

Table 1: Radiation exposure in various diagnostic and interventional procedures measured in terms of mean fluoroscopic time, mean total radiation dose, and mean dose area product

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The mean FT was 20.38 min, the mean total radiation dose was 1.82 Gy, and mean DAP was 128.5 Gycm ², of which 30% was due to fluororadiation and 70% was due to cine radiation.

[Table 2] enumerates the amount of radiation exposure (mean DAP taken as parameter for radiation exposure) in radial versus femoral route. The mean FT, mean total radiation dose, and mean DAP in coronary angiographic procedures were 3.42 min (4.43 min for radial and 2.41 min for femoral), 0.31 Gy (0.42 Gy for radial and 0.2 Gy for femoral), and 23.72 Gycm ² (33.14 Gycm ² for radial and 14.30 Gycm ² for femoral), respectively. The mean FT, mean total radiation dose, and mean DAP in coronary angiographic + LV angiography procedures were 3.97 min (3.62 min for radial and 4.32 min for femoral), 0.28 Gy (0.28 Gy for radial and 0.28 Gy for femoral), and 28.94 Gycm ² (23.83 Gycm ² for radial and 34.05 Gycm ² for femoral), respectively.

Table 2: Amount of radiation exposure (mean dose area product taken as parameter for radiation exposure) in radial versus femoral route

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For PTCA of SVD, the mean FT, mean total radiation dose, and mean DAP were 9.84 min (5.50 min for radial and 14.18 min for femoral), 0.66 Gy (0.63 Gy for radial and 0.70 Gy for femoral), and 59.49 Gycm ² (41.95 Gycm ² for radial and 77.04 Gycm ² for femoral), respectively. For PTCA of DVD, the mean FT, mean total radiation dose, and mean DAP were 27.37 min (4.45 min for radial and 50.3 min for femoral), 2.61 Gy (0.54 Gy for radial and 4.68 Gy for femoral), and 176.56 Gycm ² (36.93 Gycm ² for radial and 316.2 Gycm ² for femoral), respectively, whereas for PTCA of TVD, the mean FT, mean total radiation dose, and mean DAP were 57.30 min (3.71 min for radial and 110.9 min for femoral), 5.25 Gy (0.46 Gy for radial and 10.05 Gy for femoral), and 353.80 Gycm ² (20.7 Gycm ² for radial and 686.9 Gycm ² for femoral), respectively.

The mean FT, mean total radiation dose, and mean DAP for combined PTCA procedures (SVD + DVD + TVD) were 31.60 min (4.55 min for radial and 58.66 min for femoral), 2.84 Gy (0.54 Gy for radial and 5.14 Gy for femoral), and 196.61 Gycm ² (33.19 Gycm ² for radial and 360.04 Gycm ² for femoral), respectively.

A total of 1083 cases were done by the radial route, whereas 933 cases were done by the femoral route. The mean FT was 4.34 min, mean total radiation dose was 0.46 Gy, and mean DAP was 31.31 Gycm ² for procedures done by the radial route as compared to 36.42 min, 3.18 Gy, and 225.69 Gycm ² for the procedures done by the femoral route.

Discussion

Although proven to have adverse effects, radiation exposure in cath lab is frequently overlooked. There are very few studies in India about radiation exposure in cath lab. In one such study, the mean DAP for coronary angiography was 55.86 Gycm ² before optimization and 27.71 Gycm ² after optimization of radiation exposure.^[13] Another study evaluating radiation exposure during PTCA revealed mean DAP values of 66.16 Gycm ² and 122.68 Gycm ² for single and multiple stents, respectively. After optimization of radiation, the mean DAP values were 48.7 Gycm ² and 65.44 Gycm ² for single and multiple stents, respectively.^[14] The diagnostic reference levels of mean DAP in the Western countries were 45 Gycm ² for coronary angiography and 75 Gycm ² for PTCA.^[14]

The mean DAP for coronary angiography in our study was 23.72 Gycm ², which was comparable to international standards. The mean DAP for PTCA in our study was 196.61 Gycm ², which was higher as compared to the international standards. However, it also included triple-vessel PTCA and complex procedures which were done through femoral route. Mean DAP for simple PTCA procedures that were done through radial route was 33.19 Gycm ², which was well within the limits of international standards. In the subgroup analyses, transradial and transfemoral routes were compared. As expected, in the plain coronary angiography, femoral route produced less radiation as compared to the radial route. However, the radial route produced much lesser radiation as compared to the femoral route in PTCA irrespective of the SVD, DVD, or TVD. It might be due to the fact that transradial route was used as the default strategy and transfemoral route was preferred only for the long and complex procedures. This is the most plausible explanation for more radiation exposure in femoral route as compared to the radial route in PTCA.

Despite being a high-volume cath lab, the radiation exposure was within acceptable limits at our center, primarily because of the strict adherence to the “Radiation Discipline” recommended by various guidelines. This included adoption of ALARA (As Low As Reasonably Achievable) principle,^[15],[16] regular standardization of the equipment, avoiding steep angulations, use of proper collimation, avoiding image amplification when not needed, setting lower frame rate (7.5–12.5 frames/s) in complex interventions rather than the usual 15 frames/s in order to keep the duration of Cine run minimum,^{[17],[18],[19],[20]} use of protective gears (lead aprons, eye goggles, ceiling mounted lead shield, thyroid shield, etc.),^[21],[22] use of femoral route for lengthy and complex procedures,^[23],[24] use of International Commission on Radiological Protection (ICRP)^[25] and American College of Cardiology ^[26] personal dosimeters, and radiation protection training as proposed by both the ICRP and the International Atomic Energy Agency.^{[18],[27],[28],[29],[30]}

Conclusions

Our study offers an insight into the trends of ionizing radiation exposure in the cath lab. The results re-iterate the fact that radiation exposure can be kept within acceptable limits even in a high-volume cath lab by following “Radiation Discipline” proactively. Further, a need to establish the reference for national-level standard seems warranted with the participation of other centers.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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