Sex differences in Carotid bifurcation anatomy and the distribution of atherosclerotic plaque

Plaque formation at arterial bifurcations depends on vessel anatomy, particularly the relative sizes of the branches, and the ratio of the outflow to inflow area. The facts that carotid plaque is more common in men and that carotid bruits in the absence of stenosis are more frequent in women raise the possibility that there are sex differences in carotid bifurcation anatomy. We studied 5395 angiograms from the European Carotid Surgery Trial. To minimize secondary changes we excluded angiograms with >/=50% stenosis and also studied vessels with no disease. We measured arterial diameters at disease-free points and calculated the following ratios: internal/common (ICA/CCA); external/common (ECA/CCA); internal/external (ICA/ECA) carotid arteries; carotid bulb/CCA; and outflow/inflow area. We related these to sex and also studied the distribution of plaque in the whole trial population. Among 2930 angiograms with