X-Ray Dose Delivered During Coronary Angioplasty

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Author(s): 

Jean-Louis Georges, MD and Bernard Livarek, MD

To the Editor,

We have read with attention the article by Azpiri-Lopez et al,1 showing a significant 38% reduction in radiation dose to patients undergoing PCI after training of operators in radiation protection, and we congratulate the authors for this result. However, despite their efforts, the doses to patient reported in this article remain strikingly high, ranging from 3- to 5-fold the doses commonly reported during percutaneous coronary intervention (PCI) in Europe and the United States.2-4 In a national survey of about 30,000 PCIs performed at 44 centers in 2010 (RAY’ACT survey5; submitted for publication), the mean kerma air product (KAP) was 75 Gy.cm-2 (median, 57 Gy.cm-2; interquartile range, 33-95 Gy.cm-2), compared to the 260 Gy.cm-2 reported after training by Azpiri-Lopez, and the mean cumulated dose or air kerma at reference point (Ka,r) was 1.4 Gy (median, 1.1 Gy; interquartile range, 0.6-1.8 Gy). In RAY’ACT, 75% of PCIs delivered a Ka,r lower than 1.8 Gy, and only 0.9% of PCIs delivered a Ka,r >5 Gy, which was the mean value in the Azpiri-Lopez study before training. The reasons for these large discrepancies are unclear. The use of the median instead of the mean value would have been more appropriate, since Ka,r and KAP are not normally distributed, and mean values are pulled in the direction of the extreme values. PCIs were performed with 2 different pieces of equipment, but problems affecting one of the x-ray sources or the measure of the dose appear unlikely, since a good correlation between doses from both pieces of equipment has been demonstrated in healthy volunteers. Unfortunately, no data were provided on the body mass index of patients, which is a major component of patient dose. The homogeneity between operators is not given. Also, it would have been interesting to detail the fluoroscopy time and the number of frames registered in cinegraphy, in order to understand why such high doses have been delivered, even after radioprotection training of operators. Lastly, a clinical follow-up is recommended in patients having received high skin dose, with an accepted threshold of Ka,r >5 Gy,4 due to the risk of deterministic skin lesions in such patients. We would have appreciated to inclusion of the rate of skin injuries related to PCIs in this series of patients. 

References

  1. Azpiri-Lopez JR, Assad-Morell JL, Gonzalez-Gonzalez JG, et al. Effect of physician training on the x-ray dose delivered during coronary angioplasty. J Invasive Cardiol. 2013;25(3):109-113.
  2. Padovani R, Vano E, Trianni A, et al. Reference levels at European level for cardiac interventional procedures. Radiat Prot Dosimetry.2008;129(1-3):104-107.
  3. Georges JL, Livarek B, Gibault-Genty G, et al. Reduction of radiation delivered to patients undergoing invasive coronary procedures. Effect of a programme for dose reduction based on radiation-protection training. Arch Cardiovasc Dis. 2009;102(12):821-827.
  4. Fetterly KA, Mathew V, Lennon R, Bell MR, Holmes DR Jr, Rihal CS. Radiation dose reduction in the invasive cardiovascular laboratory: implementing a culture and philosophy of radiation safety. JACC Cardiovasc Interv. 2012;5(8):866-873.
  5. Georges JL, Belle L, Dechanet A, et al. Multicentre national survey of patient exposure to x-rays during coronary angiography and percutaneous transluminal coronary intervention. The RAY ACT study (Abstr). Eur Heart J.2012;32(Suppl):1001.

Author Reply

We fully agree with the comments by Georges and Livarek. To further clarify, our study stemmed from the observation that patients undergoing angioplasty in our catheterization laboratory were receiving excessive radiation. Quality assurance, requested by Joint Commission International and recently adopted by our institution, brought some light into this important issue.1 A 38% dose reduction was achieved after voluntary physician training and modifications to the x-ray delivery were put in practice. 

As pointed out, our final Ka,r of 3.39 Gy and PKA of 233 Gy·cm-2 were still high when compared to international reports. This is, in part, likely due to the fact that we perform angiography and angioplasty with stent placement both at once. According to the International Atomic Energy Agency (IAEA), the 75th percentile for these is Ka,r of 2.7 Gy and PKA of 138.3 Gy·cm-2.2 

It is true that data are not normally distributed, and that the use of mean values could skew the results. It is also true, though, that their use is practical when making statistical comparisons. Further analysis of our data showed that, after training, the median for Ka,r  became 3.00 Gy (interquartile range, 1.64-4.61 Gy) and that for PKA became 203 Gy·cm-2 (interquartile range, 121-322 Gy·cm-2). Although lower than the mean, they are still high: 2.3 times higher than observed in the IAEA study.2

Unfortunately, we do not have data on body mass index, but we do know that 70% of Mexicans are overweight or obese.3 This translates into an increase in the dose of administered radiation, particularly of PKA. 

We decided against including our data on fluoroscopy time, since it is well known that this metric can be misleading and should not be used to measure possible x-ray induced damage.4 

Currently, our quest is to spread this information among our country’s interventional cardiologists: we will urge them to measure and report the amount of radiation administered in all cases; to follow patients who received 5 Gy; and to report any resulting injuries. This will help us better understand and establish the incidence of deterministic effect. Additional investigation of these metrics is warranted. In the meantime, we are sponsoring radiological-protection workshops in the major national cardiovascular meetings. 

José Ramón Azpiri-López, MD

José Luis Assad-Morell, MD

José Gerardo González-González, MD

References

  1. The Joint Commission Sentinel Events Policy and Procedures. http://www.jointcommission.org/SentinelEvents/PolicyandProcedures, 2007.
  2. IAEA. Establishing guidelines levels in x-ray guided medical interventional procedures: a pilot study. Safety Report Series No. 59. 1 ed. Vienna, Austria: International Atomic Energy Agency, 2009.
  3. Gutiérrez JP R-DJ, Shamah-Levy T, Villalpando-Hernández S, et al. Encuesta Nacional de Salud y Nutrición 2012. Resultados Nacionales. Cuernavaca, México: Instituto Nacional de Salud Pública (MX), 2012.
  4. Chambers CE, Fetterly KA, Holzer R, et al. Catheter Cardiovasc Interv.2011;77(4):546-556. 

______________________________

From the Centre Hospitalier de Versailles, Le Chesnay, France.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted April 9, 2013, final version accepted April 10, 2013.

Address for correspondence: Jean-Louis Georges, MD, MSc, Centre Hospitalier de Versailles, Service de Cardiologie, Hopital André Mignot, 177 rue de Versailles, Le Chesnay, 78150, France. Email: [email protected] 

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