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 effect of blood flow alteration on caliber and morphology of in situ internal thoracic arteries.

METHODS

Six dogs underwent creation of a unilateral 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 the control; sides were alternated among cases. Blood flow was measured for shear stress calculation before and after surgical alteration. After 2 months, internal thoracic arteries were harvested with the entire anterior chest plate, which was dynamically inflated and fixed with 10% formalin at a controlled pressure of 120 mm Hg after angiography had been done at the same pressure. The luminal diameters were then measured at eight levels on the angiograms. Arterial tissue samples were taken at three levels and embedded, sectioned, and treated with hematoxylin-eosin and Verhoeff-van Gieson stains. Digital imaging analysis was used for quantitative morphometric studies.

RESULTS

All fistulas remained patent. In comparison with control arteries, high-flow internal thoracic arteries dilated and low-flow internal thoracic arteries narrowed, which was associated with significant change in shear stress for both groups. There were no substantial structural changes in the walls of either group.

CONCLUSION

In the dog, the luminal diameter of the internal thoracic artery responds to altered blood flow without intimal thickening or other undesirable wall changes.