EFFECT OF ALTERED BLOOD-FLOW ON THE CALIBER AND MORPHOLOGY OF THE INTERNAL THORACIC ARTERY IN THE DOG

Objective: The purpose of this study was to evaluate in dogs the effec t of blood flow alteration on caliber and morphology of in situ intern al thoracic arteries. Methods: Six dogs underwent creation of a unilat eral distal arteriovenous fistula between the internal thoracic artery and vein at the sixth rib to create high flow, and in six others the internal thoracic artery was unilaterally skeletonized and dissected, For both groups the contralateral internal thoracic artery served as t he control; sides were alternated among cases, Blood flow was measured for shear stress calculation before and after surgical alteration, Af ter 2 months, internal thoracic arteries were harvested with the entir e anterior chest plate, which was dynamically inflated and fixed with 10% formalin at a controlled pressure of 120 mm Hg after angiography h ad been done at the same pressure, The luminal diameters were then mea sured at eight levels on the angiograms. Arterial tissue samples were taken at three levels and embedded, sectioned, and treated with hemato xylin-eosin and Verhoeff-van Gieson stains. Digital imaging analysis w as used for quantitative morphometric studies, Results: All fistulas r emained patent. In comparison with control arteries, high-flow interna l thoracic arteries dilated and low-flow internal thoracic arteries na rrowed, which was associated with significant change in shear stress f or both groups, There were no substantial structural changes in the wa lls of either group, Conclusion: In the dog, the luminal diameter of t he internal thoracic artery responds to altered blood flow without int imal thickening or other undesirable wall changes.