Introduction
Ionising radiation during diagnostic and therapeutic cardiology and radiological procedures are very common in present day medical practice and are one of the largest medical sources of radiation to humans.1 Increasing prevalence of obesity in the general population, obesity has become more prevalent among patients undergoing cardiac catheterisation.2 Increasing body mass Index results in higher patient radiation doses during coronary angiography.2 The greatest source of physician radiation exposure during cardiac catheterisation comes from the patient, which itself is proportional to patient radiation dose.2 The raise in obesity has impacted radiation usage in the catheterisation laboratory because obese patients undergoing fluoroscopic procedures receive greater radiation doses than non obese patients.3, 4, 5 Increase in radiation is attributable to the increased energy required to overcome tissue attenuation and facilitate a sufficient number of photons reaching the image intensifier to generate adequate images.6 The greatest source of physician radiation exposure during cardiac catheterisation comes from scatter radiation. Chronic repeated exposure to low doses of ionizing radiation that is thought to account for increased incidence of premature cataract formation. 7, 8 The dose area product (DAP), related to the effective dose, is a measure of stochastic risk and a potential quality indicator.9 Very simple radiation reduction techniques enabled us to reduce median dose area product for below the values for coronary angiography and percutaneous coronary intervention.10, 9 Procedures that utilize ionizing radiation should be performed in accordance with the As Low As Achievable (ALARA) principle. Fluoroscopy time is a non- dosimetric quantity. It is readily available.
Nevertheless it does not incorporate information about dose rate and skin entrance ports.11, 12 Radial approach when compared to femoral approach, former one carried more radiation dose.13, 14 Novel noise fluoroscopy system, such as those utilize real time image noise reduction technology, have been demonstrated to reduce radiation doses by ≈ 50% or more. 15, 16, 17, 18 Evidence of a detectable acute DNA damage response in operators performing fluoroscopic procedures has been demonstrated. 19 Long term radiation exposure among interventional cardiologists has been linked to multiple adverse effects. 20, 21
Aim
The aim of the study is to find out the effect of body mass index on the radiation exposure of patient in radial coronary angiogram.
Objective
As quoted by previous studies, body mass index has very high influencing factor on the radiation exposure of patient. Our aim is to find out BMI effect on patient radiation exposure exclusively on patients who undergo radial coronary angiogram. Recently as we are getting more obese patients with coronary artery disease as the whole world is going through pandemic of obesity. As such obesity is responsible for procedure related complications from vascular access to final outcome of the procedure. Since radiation exposure has many short term to long term effects, like skin rash to cancer. This study intended to the effect of BMI on radiation exposure. We have chosen patients who undergone coronary angiogram exclusively through radial access as it is the preferred one when compared to femoral access. Illustrative (Figure 1 A and B) is shown as examples from our study.'At the same time radial access coronary angiogram cause more radiation when compared to femoral access.
Materials and Methods
Study was conducted in Thanjavur Medical College in the Dept. of Cardiology. From the coronary angiogram and case history of 77 coronary heart disease admitted in the cardiology department between month of July and August of 2021. Angiogram was done in Single plane catheterisation lab Phillips Allura XD 10. Body mass index was measured using patients height in metres and weight in Kilograms. BMI = Kg/ m2. z Patient radiation exposure was measured by the catheterisation lab system and the radiation metrics like fluoroscopy time, Air kerma and Dose area product are taken from radiation log of Individual procedure for that particular patient. Physician radiation dose as measured by Thermiluminescent dosimeter (TLD) Badge was not taken as it is beyond the scope of this study. Study group was divided into four groups with BMI. a < = 21 b.21.01 to 25.0. c. 25.01 to 29.00. d. > 29.01. Measurement of patients’ radiation exposure was assessed by Dose Area Product which was measured in Gy-cm2. Fluoroscopy time of procedure also measured. Baseline characteristics like age, gender, co-morbidities blood pressure, ejection fraction family history and personal habits like smoking and alcohol were also studied. Coronary angiogram was done with multiple angulated views in Phillips Allura XD Single plane catheterisation lab.
Results
Descriptive variables in baseline characteristics were measured as mean. Categorical valuables were measured as frequency. Our study population has 23 female patients and 54 male patients (Figure 2). That constitutes 29.9 % for female and 70.1 % for male patients. Personal habits of study population like alcoholics 19.5 %, smoking 26.0% smoking and alcoholic 19.5 and no bad habits 35.1 % (Figure 3). Co- morbid conditions Diabetes alone 22.1 %, Diabetes and systemic hypertension put together constitutes 22.1%, Systemic hypertension alone constitutes 27.3 %. Nil constitutes about 28.6%.(Figure 4) Altogether 77.9 % of patient has no family history of coronary artery disease. Rest of 22.1% patients has family history of coronary artery disease. Overall disease spectrum in our study Antero septal myocardial infarction 3.9 %
Table 1
Radiation exposure
Table 2
Cumulativedose area product and bod mass index crosstab
|
|
BMI |
Total |
||
|
<= 25.00 |
25.01+ |
|||
|
CUM DAP |
<= 30.000 |
17 |
21 |
38 |
|
30.001+ |
17 |
22 |
39 |
|
|
Total |
34 |
43 |
77 |
|
Table 3
Fluoroscopy time and body mass index. Crosstab Count
|
|
BMI |
Total |
||
|
<= 25.00 |
25.01+ |
|||
|
Flouro time |
<= 3.200 |
19 |
20 |
39 |
|
3.201+ |
15 |
23 |
38 |
|
|
Total |
34 |
43 |
77 |
|
Anterior wall myocardial infarction 48.1%, Inferior wall myocardial infarction 33.8%, Non ST elevation myocardial infarction 6.5% and Unstable angina 7.8 %. Patient with body mass Index was divided into four groups and their distribution BMI a. < 21.00 -9.1 %, b. 21.01- 25.00- 35.1% c. 25.01-29.00 – 48.10 % d. 29.0+ - 7.8 % (Figure 5) Only less number of patients were in our study population beyond BMI 29 and less than 21 . Minimum age 34 years and maximum 73yrs mean age 42.08 years with Standard deviation being 10.872.
Minimum height of patients 145 cm and maximum being 175 cm. Mean value 158.4 cm and the standard deviation is 63.81. Weight of the study population minimum value 46 kg, maximum value 80 Kg. Mean value is 63.81 Kg and the standard deviation is 7.907.
Cumulative air kerma and cumulative dose area product, and fluoroscopy time are divided into below median and above median and then associated with Body mass Index.(Table 1)
On assessing cumulative dose area product for convenience of analysis in view of less study subjects in group d and a. Study population BMI is divided into two major groups i:e Below 25 and above 25. Cumulative dose area product into less than 30 Gy-cm 2 more than 30 Gy-cm2 We got the value of chi square = 0.01. and P= 0.919 which is not significant. (Table 1) Based on this analysis radiation exposure of patient is not associated with Body mass index within the BMI range of our study population.
Compared with BMI < 25, a patient BMI≥ 40 was associated with 2.1 fold increase in patient radiation dose and 7 fold increase in physician radiation dose.6 Increase in radiation dose is attributable to the increase energy required to overcome tissue attenuation and facilitates sufficient number of photons reaching the image intensifier to generate adequate images.
As per study by Ran D Madder. MD, Stacie Van Oosterhout. Med, Abbey Mulder, BSN. RN. Jan 2019. Circulation. Cardiovascular Interventions, DAP Vs BMI Group with BMI < 25 has DAP 44.5 Gy-cm2, 25 -29.9 DAP is 56 Gy- cm2,30- 34.9 DAP is 69.1 Gy- cm2, 35-39.9 DAP is 77.8 Gy- cm2, ≥ 40 DAP is 91.8 Gy- cm2 P value derived was < 0.001. In our study centre population none of the individual had BMI more than 35. Based on this, the subset of patients coming to our centre from nearby semi urban and rural areas yet to have considerable number of morbid obesity or class II obese patients, since most of them are leading physically active life style, epidemic of pandemic yet have its impact in this geographical area.
Body mass index was divided above and below 25 for convenience of calculation. Chi square value is 0.667 and the P= Value is 0.414. (Table 3) After confounding factors like catheter engagement difficult cases, radial spasm, anxious patients BMI was not correlating with fluoroscopy time in our study group. Our study group has predominantly between BMI of 21 and 29. A group and d group in the extreme of sample has less number. In study conducted by Ran D Madder as per reference 1, Fluoroscopy time in minutes with BMI value < 25.0 is 5.9 min, 25-30 is 5.6 min , 30-35 is 5.9 min, 35- 39.9 is 6.1 min, ≥ 40 is 7.0 with P Value of 0.26 1 which is not significant and correlates with our study.
Discussion
Long term radiation exposure among interventional cardiologists has been linked to multiple adverse effects7, 8 and the prevalence of obesity in cardiac catheterisation laboratory has been increased over time.2 Obesity is associated with increased health problems in patients. 10 Patient radiation exposure increases with body mass index especially with more than BMI 35.Body mass index is increasing the risk of physician radiation exposure as mentioned above and low sustained radiation exposure has inherent radiation hazards not only for the patients but also to the treating interventional cardiologist like cataract, carcinoma etc. Apart from radiation exposure BMI also has procedure related issues right from vascular access to outcome of procedure. Fluoroscopy time also increases, though statistically not significant proportionate to body mass index.
Conclusion
From our study patient radiation exposure as measured by Dose Area Product is incremental but statistically not significant enough to conclude positive correlation. As study is carried out in Tier II city, single centre study involving sample population who carry out physically active life style incidentally found to be predominantly between BMI of 21 to 29. Epidemic of obesity still to conquer this geographical area significant enough to produce coronary artery disease. Fluoroscopy time and cumulative air kerma also not significantly related to body mass index in the given range of our study
