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FJ
EXPRESS SUMMARY ARTICLE The Full-length version of this article is also available, published online March 31, 2005 as doi:10.1096/fj.04-3287fje. |
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* Institute of Clinical Physiology CNR, Pisa, Italy;
Cardiology Clinic Montevergine, Mercogliano, Italy; and
Institute of Nuclear Sciences, Belgrade, Serbia and Montenegro
1 Correspondence: Institute of Clinical Physiology, CNR, Via Aurelia Sud, Massa 54100, Italy. E-mail: andreas{at}ifc.cnr.it
SPECIFIC AIMS
Invasive cardiologists working in a busy catheterization laboratories represent, perhaps, the extreme far end (with the highest exposure) of the spectrum of medical radiation workers. The average exposure is 2–3 times higher than that of radiologists and has increased steadily in the past 20 years. With few exceptions, in hospitals with invasive cardiology facilities, badges that exceed the level 1 ALARA (as low as reasonably achievable) limits (<6 mSv/year) are worn by invasive cardiologists. This implies that cardiologists are exposed to significant levels of radiation, which could pose a health hazard if they do not abide by standard safety precautions. Damage to DNA is considered to be the main initiating event by which radiation damage to cells results in the development of cancer and hereditary disease. The yield of chromosomal aberrations is a strong predictor of cancer risk in humans. Chromosomal abnormalities can reliably be assessed by evaluating the frequency of micronuclei (MNs) in dividing cells because MNs mainly originate from chromosome breaks or whole chromosomes that fail to engage with the mitotic spindle when the cell divides. The aim of the present study was to assess the effects of chronic low dose X-ray radiation exposure on MN frequency of invasive cardiologists working in three high volume cardiac catheterization laboratories.
PRINCIPAL FINDINGS
1. Interventional cardiologists working in a large volume catheterization laboratory have higher levels of somatic DNA damage when compared with clinical cardiologists working outside the catheterization lab
We obtained peripheral blood from 62 physicians (age=40.6±1.5 years): 31 interventional cardiologists (Group I, exposed) and 31 clinical cardiologists (Group II, nonexposed). Exposed and control groups were comparable for baseline characteristics, including age, gender, smoking status, and years of hospital work. No subjects had a personal medical history of disease, cancer, or recent infectious state. In the exposed physicians, the mean cumulative equivalent doses over the last year was 4.06 ± 0.4 mSv.
Interventional cardiologists showed higher values of MNs (Group I=20.5±1.6 vs. Group II=12.8±1.3, P=0.001), although some overlap was obvious at individual subject analysis; Fig. 1
).
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2. The correlation between years of professional activity and MN frequency was detectable in interventional but not in clinical cardiologists
No significant correlation was observed between occupational radiation doses over the last year and MN frequency (r=0.16, P=0.51). In the exposed group, however, there was a significant correlation between MNs and years of work in the catheterization lab (r=0.428, P=0.02). In clinical cardiologists there was no correlation between years of hospital work and in frequency (r=0.253, P=0.17), as shown in Fig. 2
.
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3. Radiological exposure was an independent factor of MN frequency
On the overall study group, MNs showed a weak and positive correlation with age (r=0.259, P=0.04). In clinical cardiologists (but not in exposed physicians), current smokers had a significantly higher frequency of MNs in comparison to those who had never smoked (16.7
±1.8 vs. 11.2 ±1.4, P=0.04). Other confounding factors, such as gender, alcohol or caffeine intake, did not significantly affect MN frequency. Multiple regression analysis revealed that radiological exposure was the only independent factor of MN frequency [coefficient=6.7 (95% CI, 2.8–10.6), P=0.001].
CONCLUSIONS AND SIGNIFICANCE
This study highlights, for the first time, that invasive cardiologists working in a large volume catheterization laboratory have higher levels of MN (a cellular biomarker of somatic DNA damage) when compared with clinical cardiologists working in the same institutions outside the catheterization laboratory. Several in vivo studies have previously indicated that chronic low doses of ionizing radiations can lead to significant somatic DNA damage in exposed physicians. This effect seems to be cumulative over time, although the majority of these studies failed to establish a dose-effect relationship for low doses. Absence of an increase of somatic DNA damage in relation to the dose suggests a dominant modulation of underlying genetic substrate by environmental factors such as smoking in determining individual physician detriment. On the other hand, the biological variability is also intrinsic to the very definition of stochastic effect of low dose radiation, where only some patients will receive a meaningful damage—and we cannot predict in advance the patient who will suffer from radiation. Risk estimates at the population level can be highly inaccurate at the individual level. A biological dosimeter that measures true cellular injury resulting from that radiation could be a more accurate indicator of cancer risk than a physical dosimetry. Biomarkers could act like a Newton’s prism translating a generic population risk into a specific individual risk (Fig. 3
).
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These findings and the available evidence in literature are particularly relevant to an increased awareness of radiological risk among physicians and to the improvement in radiation protection procedures.
At present, the dominant factor is the lack of radiological awareness by the both the physician and the patient. This lack of awareness may lead to lack of implementation of the many simple, effective ways to reduce radiation exposure for both the patient and the operator in the catheterization lab, without compromising clinical efficacy.
FOOTNOTES
To read the full text of this article, go to http://www.fasebj.org/cgi/doi/10.1096/fj.04-3287fje; doi: 10.1096/fj.04-3287fje
This article has been cited by other articles:
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  M. G. Andreassi, A. Cioppa, S. Manfredi, C. Palmieri, N. Botto, and E. Picano Acute chromosomal DNA damage in human lymphocytes after radiation exposure in invasive cardiovascular procedures Eur. Heart J., September 2, 2007; 28(18): 2195 - 2199. [Abstract] [Full Text] [PDF]
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