DEVELOPMENT OF CORONARY COLLATERAL CIRCULATION IN MINIATURE SWINE AND EFFECTS OF SEVERAL DRUGS*.

Abstract

To determine whether or not the development of collateral channels can be accelerated by administration of vasodilators and whether the opening up of functional collateral channels is associated with an improved survival rate, a gradual occlusion of the major branches of the left coronary artery was produced in miniature swine with an Ameroid constrictor. Oral administration of drugs (twice a day) was started seven days before operation and was continued throughout the experimental period of 2 months. While the survival rate of the untreated animals was 6/15 (40%), survival rates of animals treated with adenosine potentiators, dipyridamole and dilazep were 4/7 (57.1 %) and 5/7 (71.4%), respectively. However, a significant improvement of the survival rate was attained by KI 2119; survival rate was 6/7 (85.7 %). Coronary angiography of the survived control animals revealed numerous, fine, collateral communications between the left and right coronary arteries. Treatment with dipyridamole and dilazep resulted in formation of a dense network of thick collaterals. To quantitate the degree of formation of the collateral channels, the anatomic anastomotic indices (AAl's) were calculated using histological specimens of the anterior free wall of the left ventricle. According to Menick et al. (16), AAI is a good measure of the functional capacity of the collateral vessels. AAI's of the animals treated with di-pyridamole and dilazep were 2416.6+454.0 and 1864.7+248.3 as compared with 704.3+407.9 of the untreated animals. AAI's of the KI 2119-treated animals did not differ from those of the control animals. A linear correlation was observed between the survival rate and AAI's (r=0.74, p<0.05), indicating a close relationship between the survival rate and the development of functional collateral channels.