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Radiation-induced cardiomyopathy in the dog
S L McChesney1, E L Gillette, B E Powers
1Department of Radiology and Radiation Biology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins 80523.
Radiation Research
|January 1, 1988
Summary
Thoracic irradiation causes progressive heart damage in dogs, including fibrosis and cell loss, detectable by 12 months. While no heart failure was seen at 1 year, histological changes indicate future risks.
Area of Science:
- Cardiology
- Radiation Oncology
- Veterinary Pathology
Background:
- Radiation therapy for thoracic malignancies can affect cardiac structures.
- Understanding radiation-induced heart disease (RIHD) is crucial for patient outcomes.
- Beagle dogs serve as a relevant model for studying cardiovascular responses to radiation.
Purpose of the Study:
- To investigate the long-term histological and morphometric effects of thoracic irradiation on the canine heart.
- To evaluate the temporal progression of radiation-induced cardiac damage.
- To assess potential functional and structural cardiac alterations post-irradiation.
Main Methods:
- Sequential necropsies and histological evaluations of beagle dogs subjected to thoracic irradiation.
- Dose fractionation: 36, 44, or 52 Gy in 4-Gy fractions over 4 weeks.
- Morphometric analyses of myocardium, pericardium, atria, and aorta at various time points (1, 3, and 12 months post-irradiation).
Main Results:
- Minimal histological damage observed at 1 month, with increased ventricular/septal weight due to edema.
- Endothelial and mesothelial cell damage evident by 3 months.
- By 12 months: myocardial thinning, muscle/Purkinje cell loss, extensive fibrosis (subendocardial, epicardial), intimal proliferation in coronary arteries, pericardial thickening, and decreased smooth muscle to elastin ratio in the aorta.
- Severe fibrosis localized to the right atrium.
- No clinical heart failure at 1 year, but histological/functional myocardial damage present.
Conclusions:
- Thoracic irradiation induces progressive, dose-dependent cardiac damage in dogs, manifesting as cellular loss, fibrosis, and vascular changes.
- Histological evidence of myocardial injury persists at 1 year, suggesting potential for future complications with aging or stress.
- Further research is needed to elucidate the interactions between irradiated lung and heart tissues.