Morphology of the great arteries in chronic experimental coarctation in dogs.

Vascular changes of the great arteries could be one explanation for the serious complications and persistent hypertension after coarcectomy among patients with coarctation. This possibility was studied by evaluating the morphology of the coronary artery, aorta and middle cerebral artery in 7 experimental 9-month-old dogs in which a coarctation of the thoracic aorta had been made at the age of 2 months. A classical coarctation syndrome with high blood pressure and intense collateral circulation developed during growth. Five sham-operated dogs living in the same laboratory environment served as a control group. Morphometric measurements showed medial thickening of the coronary artery wall in the coarctated dogs (135 vs 103 microns, P less than 0.05). The relative amount of glycosaminoglycans of the media was also greater in the study group (14.8% vs 8.1%, P less than 0.02). The relative number of medial nuclei was significantly greater in the coarctated dogs (P less than 0.025), reflecting medial hyperplasia. Vacuolated smooth muscle cells and fragmented elastic membranes were found in the media of the aortas of coarctated animals. No significant differences between the groups were found in the cerebral arteries. It is suggested that re-evaluation of the optimal age of patients with coarctation for surgical repair is obviously necessary.