Association between arterial bifurcation anatomy and angiographic plaque ulceration among 4,627 carotid stenoses

Stability of atheromatous plaques is influenced by local mechanical and haemodynamic factors, such as plaque motion and shear stress. However, although blood vessel anatomy is an important determinant of haemodynamics, particularly at bifurcations, there have been no previous clinical studies of the association between arterial anatomy and plaque ulceration. We therefore studied arterial anatomy and plaque ulceration using angiograms of 4,627 carotid bifurcations with atheromatous disease from the European Carotid Surgery Trial (ECST). We studied the vessel diameter and area ratios that have been shown in flow models to affect local haemodynamics and shear stress, and which are known to vary widely between and within individuals (internal to common, external to common, external to internal carotid artery and outflow/inflow area). Angiographic plaque surface morphology was defined as ulcerated or not ulcerated. To avoid any potential bias due to selective inclusion of patients in the ECST, we studied the contralateral, and usually asymptomatic, as well as the symptomatic carotid artery. To correct for the effects of systemic factors that might influence plaque stability, we also studied the relationship between the degree of asymmetry of bifurcation anatomy within individuals and the presence of plaque ulceration. Despite considerable inter-individual variation in carotid anatomy, we found no association between the prevalence of angiographic plaque ulceration and any of the anatomical parameters studied in either symptomatic or contralateral carotid arteries. There were also no associations between ipsilateral bifurcation anatomy and plaque ulceration in individuals with unilateral plaque ulceration. Carotid arterial anatomy does not appear to be an important determinant of plaque stability. Other factors that influence local haemodynamics, such as the anatomy and composition of the plaque itself may be more important.