Optimal branching of human arterial bifurcations

The area ratio, defined as the combined cross-sectional areas of the daughter branches divided by that of the parent artery, is an important indicator of "expansion" or "narrowing" in an arterial tree. In 120 morphologically normal human arterial bifurcations, angiographically studied, we measured branch artery diameters at and away from the bifurcation point to obtain "beta" and "D" ratios, respectively. These results were compared with optimal curves. Area ratio D values showed better agreement than area ratio beta with theoretical curves; for area ratio D, the positive regression line showed the same trend as expected from theory (y = 1.26 + 0.153x); for area ratio beta, the regression line was negative, showing a trend opposite to theory (y = 0.962 - 0.191x). Area ratio beta showed a significant correlation coefficient (r = 0.194; P less than 0.05) associated with aging, while for area ratio D it was not the same (r = 0.023; P less than 0.05). A significant correlation coefficient was also found between both of the area ratios and total branching angle. The new area ratio D, reflecting the branching geometry nearer to the bifurcation, is more promising than area ratio beta in the evaluation of optimal arterial bifurcation.