INFLUENCE OF THE GEOMETRY OF THE LEFT MAIN CORONARY-ARTERY BIFURCATION ON THE DISTRIBUTION OF SUDANOPHILIA IN THE DAUGHTER VESSELS

The proximal portions of the left anterior descending (LAD) and left c ircumflex (LCx) coronary arteries are among the sites most predisposed to atherosclerotic disease. This predisposition might be a consequenc e of their location immediately distal to the left main (LM) coronary artery bifurcation, which may increase the susceptibility of these seg ments by promoting an adverse fluid dynamic environment within them. T he detailed geometry of the bifurcation influences this environment an d would therefore affect the susceptibility of the proximal daughter v essels to disease. This hypothesis was tested by examination of the re lationship between the geometry of the LM bifurcation and the distribu tion of sudanophilia in the proximal portions of the LAD and LCx. The geometric parameters at the LM bifurcation, including all three angles and LM length, were obtained from multiangle photographs of 17 vascul ar casts by use of objective computer-based algorithms, A robust index , the relative proximal involvement (RPI), was developed to measure th e localization of disease to the proximal portions of the daughter ves sels. The RPI of the LAD segment correlated best with an interaction t erm that included the planarity of the LM bifurcation and the LCx-LAD branch angle (P=.013). In addition to supporting the concept of geomet ric risk factors, these observations also suggest that interactions be tween the hemodynamic influences of multiple geometric variables may p lay a role in the mediation of tissue susceptibility by geometric fact ors.