Background: Established vascular risk factors do not fully explain the incidence of both early (Intimal Medial Thickness, IMT) and advanced (plaque formation) atherosclerosis of the carotid system. The present study evaluated the relationship between variants of the Internal Carotid Artery (ICA) origin and the prevalence of IMT elevation and plaque formation quantified ultrasonically in a communitybased sample.

Methods and results: 3271 members of 3 german health insurance companies (mean age š SD, 51 š 12 years; 49.2% men) were examined using a 7.5 10 MHz linear transducer for B-mode imaging of the extracranial carotid system on both sides. Intimal Medial Thickness (IMT) was automatically determined within the ICA bulb, the carotid bifurcation and the common carotid artery (interobserver reliability, r D 0.86). ICA plaque formation was expressed as the percentage of luminal narrowing (interobserver reliability, r D 0.9). ICA origin relative to the external carotid artery was determined in transverse sections and expressed in angle degrees (lateral/dorsolateral, 0–120 dorsal/dorsomedial, 120–270). Mean bulb IMT was 0.68 š 0.37 mm in dorsolateral and 0.80 š 0.45 mm in dorsomedial ICAs (p< 0.0001), bif. IMT was 0.79 š 0.45 mm and 83 š 0.45 mm (p D 0.706), and com. IMT was 0.63 š 0.17 mm and 0.64 š 0.18 mm (p D 0.907), respectively. Plaque formation was significantly more frequent in dorsomedial than dorsolateral ICAs (7.9% vs. 2.2%, p< 0.0001). These differences persisted after adjustment for established vascular risk factors. Conclusion: Dorsomedial ICA origin is significantly and independently associated with a higher degree of both early and advanced atherosclerosis. These findings support the role of local anatomic and hemodynamic factors in the pathogenesis of atherosclerosis at the carotid bifurcation.