EXPERT ANALYSIS FROM EUROPCR 2016
PARIS (FRONTLINE MEDICAL NEWS) – What most interventional cardiologists and electrophysiologists do not know about their health risks due to occupational radiation exposure and how best to protect themselves could fill a book – or better still, make for an illuminating 2-hour expert panel discussion at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.
“There’s a problem of lack of awareness on the part of interventional cardiologists, and also of institutional insensitivity to the problem,” declared Emanuela Piccaluga, MD, an investigator in the eye-opening Healthy Cath Lab study. This Italian national study showed that cardiac catheterization laboratory staff had radiation exposure duration–dependent increased risks of cataracts, cancers, and skin lesions, as well as other radiogenic noncancer effects: anxiety and depression, hypertension, and hyperlipidemia.
Cardiologists at some European hospitals have to pay for their own lead aprons and other protective gear. And even if the hospital does pick up the bill, administrators often balk at authorizing replacement of a lead apron that has developed microfractures and cracks. They view these imperfections as cosmetic defects, unaware that the damage renders the apron less protective, according to Dr. Piccaluga of Niguarda Ca’ Granda Hospital in Milan.
Ariel Roguin, MD , head of interventional cardiology at Rambam Medical Center in Haifa, Israel, said every cardiologist working with radiation should understand the three principles of radiation reduction, which he refers to in shorthand as “TDS,” for Time, Distance, and Shielding. Radiation is here to stay in cardiology, he said, but interventionalists can maximize their safety by keeping the fluoroscopy time and number of acquired images down, standing as far away as possible from both the radiation source and patient while still getting the job done well, and using appropriate shielding routinely.
Dr. Roguin gained notoriety with his report that 26 of 30 interventional cardiologists with glioblastoma multiforme or other brain malignancies had left-hemisphere cancers and 1 had a midline malignancy; only 3 were right-sided ( Eur Heart J. 2014 Mar;35:599-600 ). That distribution is highly unlikely to be due to play of chance, given that an interventional cardiologist’s left side is the side that’s usually exposed to more radiation.
“We should form a wall against radiation. Apart from the leaded aprons, for every procedure we all should also use lead skirts going from the table to the floor to block backscatter, ceiling-mounted overhead radiation shields, special glasses to protect against cataracts, and thyroid collars. And it’s very important to wear a dosimeter with sound; it helps increase awareness of our exposure,” he said.
Dr. Roguin has been a pioneer in the use of a thin, 0.5-mm lead shield draped across the patient’s abdomen from the umbilicus down during radial-access angiography. In a 322-patient randomized trial, he and his coinvestigators showed that this practice results in a threefold reduction in radiation to the operator, albeit at the cost of doubling the patient’s radiation exposure ( Catheter Cardiovasc Interv. 2015 Jun;85:1164-70 ).
“We now routinely do our radials with the lead apron across the patient’s abdomen. We’ve reached the conclusion that we work with radiation in the cath lab every day for many years and the patient is there only once or twice in a lifetime, hopefully,” the cardiologist explained.
With the growing popularity of radial-access interventions, audience members wanted to know if there is an advantage in terms of radiation exposure to left versus right radial artery access. The answer is no, according to Dr. Roguin.
“There are several studies showing no difference in radiation exposure. Left radial artery access is faster, but you’re leaning on the patient and getting more radiation as a result, while with right radial access you have to do more catheter manipulation, which takes longer. Both approaches involve more radiation to the operator than the transfemoral approach,” he said.
Dr. Piccaluga presented highlights from the Healthy Cath Lab study, sponsored by the Italian Society of Invasive Cardiology and the Italian National Research Council’s Institute of Clinical Physiology. The study involved detailed self-administered questionnaires completed by 218 interventional cardiologists and electrophysiologists, 191 nurses, and 57 technicians regularly exposed to ionizing radiation in the cardiac cath lab for a median of 10 years, along with 280 unexposed controls.
A variety of health problems were more frequent in the cath lab personnel regularly exposed to radiation. Rates were consistently highest in the cardiologists, followed next by the cath lab nurses, and then the radiation technicians.
Rates of health problems were highest in the 227 individuals with at least 13 years of cath lab radiation exposure. For example, their adjusted risks of cataracts, hypertension, hypercholesterolemia, and cancers were respectively 9-, 1.7-, 2.9-, and 4.5-fold fold greater than in unexposed controls, as detailed in a recent report ( Circ Cardiovasc Interv. 2016 April. doi: 10.1161/CIRCINTERVENTIONS.115.003273 ).
Dr. Piccaluga also shared data from several other pertinent recent studies in which she was a coinvestigator. In one, 83 cardiologists and nurses working in cardiac catheterization laboratories and 83 matched radiation-nonexposed controls completed a neuropsychological test battery. The radiation-exposed group scored significantly lower on measures of delayed recall, visual short-term memory, and verbal fluency, all of which are skills located in left hemisphere structures of the brain – the side with more exposure to ionizing radiation during interventional procedures ( J Int Neuropsychol Soc. 2015 Oct;21:670-6 ).
In another study, Dr. Piccaluga and her coinvestigators had participants perform an odor-sniffing test. Olfactory discrimination in the cardiac cath lab staffers was significantly diminished in a pattern that has been identified in other studies as an early signal of impending clinical onset of Alzheimer’s and Parkinson’s diseases ( Int J Cardiol. 2014 Feb 15;171:461-3 ).
And in yet another study, Dr. Piccaluga and her coworkers found that left and right carotid intima-media thickness as measured by ultrasound in cardiac cath lab personnel having high lifetime radiation exposure was significantly greater than in those with low exposure and in nonexposed controls. In the left carotid artery, but not the right, intimal-medial thickness was significantly correlated with a total occupational radiologic risk score.
Moreover, the Italian investigators found a significant reduction in leukocyte telomere length – a biomarker for accelerated vascular aging – in cardiac cath lab staff regularly exposed to ionizing radiation, compared with controls ( JACC Cardiovasc Interv. 2015 Apr 20;8:616-27 ).
All of these findings, she stressed, make a persuasive case for interventional cardiologists doing everything they can to protect themselves from unnecessary radiation exposure at all times.
How to best go about accomplishing this was the territory covered by Alaide Chieffo, MD, of San Raffaele Scientific Institute in Milan.
The patient-related factors germane to radiation dose – procedure complexity and body thickness – are outside physician control. But there are plenty of operator-dependent factors, including, for starters, procedural experience. In one classic study, Dr. Chieffo noted, Greek investigators showed that interventional cardiologists’ radiation exposure dose was 60% greater in their first year of practice than in their second year.
Distance from the patient is crucial, she observed, since the patient is the greatest source of radiation to the operator. If the operator is 35 cm from the patient, the radiation exposure is fourfold greater than at a distance of 70 cm. At a distance of 17.5 cm, the exposure intensity is 16-fold greater than at a 70-cm distance. And at 8.8 cm of distance, it’s 64 times greater.
Image acquisition is another key variable within the interventionalist’s control. Cine images entail 12- to 20-times greater radiation doses than those of fluoroscopy, so don’t resort to cine when fluoroscopy will do. Also, reducing the fluoroscopy frame rate from 15 to 7.5 frames per second significantly decreases the amount of radiation released while providing images of adequate quality for many procedures. Tight collimation, the use of manually inserted wedge filters, and thoughtful selection of tube angulations result in less radiation for both patient and physician. It has been shown that tube angulations that expose a patient to intense radiation levels increase the operator’s radiation exposure exponentially. The least-irradiating tube angulations are caudal posteroanterior 0°/30°– angulation for the left coronary main stem, cranial posteroanterior 0°/30°+ for the left anterior descending coronary artery bifurcation, and right anterior oblique views of 40° or more. Left anterior oblique projections are the most radiation intensive, according to a comprehensive study ( J Am Coll Cardiol. 2004 Oct 6;44:1420-8 ), Dr. Chieffo continued.
Panelist Ghada Mikhail, MD , of Imperial College London, said there is some relatively new operator protective gear available. She cited lightweight protective caps, for example, but an audience show of hands indicated almost no one uses them.
“Protectors for the breasts and gonads are available. You can wear them underneath the lead. The extra time to put them on is worthwhile,” she said.
“I think the risk of radiation is completely underestimated,” Dr. Mikhail added. “We have a responsibility to young trainees to teach them about radiation protection, which a lot of institutions and supervisors don’t do. That’s partly because a lot of them don’t know the details.”
All of the speakers indicated they had no financial conflicts regarding their presentations.