[Coronary collaterals in patients with total obstruction of the proximal left anterior descending artery: their pathways and functional significance]

Abstract

The relationship of patterns of collateral pathways and the functions of collaterals in patients with proximal occlusion of the left anterior descending artery (LAD) was analyzed by coronary arteriography and left ventriculography. Forty-seven patients with dominant right coronary artery (RCA) as anatomic variations had nearly the same filling areas from three major collateral pathways from the RCA to the LAD via conus branches, marginal branches, and septal perforator. The grades of collateral flows were classified as good, fair and poor according to the sizes and numbers of collateral channels, and the filling density of contrast in each collateral and three (basal, mid and apical) segments of the main trunk of the LAD. On left ventriculography in the right anterior oblique projection, the anterior wall was divided into five segments, and the regional ejection fraction in each segment was measured from end-diastolic and end-systolic areas. Three main collateral pathways and connections to the LAD were observed from the RCA. Those were the conus branches to the basal-mid LAD, the marginal branches to the mid-apical LAD, and the posterior descending branches to the basal-mid LAD via the septal perforators. Only seven patients showed normal contraction in all of the segments (Group I). In seven patients with normal contraction in the basal-mid segments and reduced contraction in the apical segment of the anterior wall, the main collateral pathways from the RCA to the LAD were the posterior descending branches via the septal perforators (Group II). In 10 patients with reduced contraction in the basal-mid segments and normal contraction in the apical segment of the anterior wall, the main collateral pathways from the RCA were the conus branches and/or the marginal branches to the LAD (Group III). In the other 23 patients with reduced contraction in entire segments (Group IV), the patterns of segmental contraction were similar to those of either Group II or Group III. These findings indicate that in the majority of cases collateral circulation from the RCA did not preserve wall contraction in all segments perfused by the occluded LAD at rest, and suggest that various patterns of segmental contraction may be influenced by the dominant of collateral pathways.