Race-ethnic Variation in Carotid Bifurcation Geometry Sebastian Koch, MD,* Donoffa Nelson, MS,* Tatjana Rundek, MD, PhD,* Jay Mandrekar, PhD,† and Alejandro Rabinstein, MD‡ Background: Disturbances in local blood flow influenced by arterial geometry con- tribute to atherogenesis. Carotid bifurcation hemodynamics depend on the relative sizes of the common carotid artery (CCA), internal carotid artery (ICA), and external carotid artery (ECA), which vary considerably among individuals. The prevalence of carotid bifurcation atherosclerosis differs among race-ethnic groups and is gener- ally lower in African Americans despite a more adverse vascular risk factor profile. We here examine whether there are race-ethnic differences in carotid bifurcation anatomy. Methods: The diameters of the CCA, carotid bulb, ICA, and ECA were mea- sured from consecutive cerebral angiograms of African American, white, and Carib- bean Hispanic patients. The bulb/CCA, ICA/CCA, ECA/CCA, ECA/ICA, and total cross-sectional outflow/inflow ratio ([ICA 2 1 ECA 2 ]/CCA 2 ) were calculated. Results: The final analysis included 272 bifurcations of which 103 were among white, 87 Hispanic, and 82 African American patients. The mean age of the population was 59.8 6 15.8 years and 148 (54.4%) were men. African Americans had a lower ICA/ CCA ratio (P ,.001) and ICA/ECA ratio (P ,.0001) and a higher ECA/CCA ratio (P , .0001) in comparison with the other two groups. Conclusion: We found significant differences in the relative sizes of the ICA, ECA, and CCA among race-ethnic groups. African Americans had a proportionally smaller ICA and larger ECA in comparison with whites and Caribbean Hispanics. Key Words: Carotid geometry—atherosclerosis—race-ethnic differences. Ó 2009 by National Stroke Association Atherosclerosis occurs at discrete points within the vas- cular system. Consistent involvement of arterial bifurca- tions suggests an important role of local hemodynamic factors. 1,2 In fact, atherosclerosis often affects only one carotid bifurcation within an individual, sparing the con- tralateral side despite a shared environment of genetic predisposition and vascular risk factors. 3-5 Significant interindividual and intraindividual variation in carotid bifurcation geometry has been described. 3,4,6 It has been proposed that arterial bifurcations with a relatively larger artery entering and proportionally smaller arteries leaving (i.e., a high ratio of inflow cross-sectional area to out- flow cross-sectional area) are subject to greater hemody- namic stress and a local proatherogenic milieu. 4,7,8 Race-ethnic differences in the distribution of athero- sclerosis are well described. Whites tend to have a higher prevalence of extracranial carotid atherosclerosis than African Americans. 9-14 Intracranial atherosclerosis on the other hand has a higher prevalence in other race- ethnic groups. 15 Although some of these disparities may be attributable to differences in vascular risk factors it is unknown whether anatomic variations at arterial bifurca- tions may also be contributing. We undertook this study to examine structural differ- ences in the carotid bifurcation among whites, African Americans, and Hispanics. Methods We reviewed carotid bifurcation anatomy from all consecutive catheter cerebral angiograms requested by From the *Department of Neurology, University of Miami, Miller School of Medicine, †Department of Neurology; and ‡School of Med- icine, Mayo Clinic, Rochester Minnesota. Received November 25, 2008; revision received January 6, 2009; accepted January 20, 2009. Address correspondence to Sebastian Koch, MD, Department of Neurology, University of Miami, Miller School of Medicine, 1150 NW 14 St, Suite 609, Miami, FL 33136. E-mail: skoch@med.miami.edu. 1052-3057/$—see front matter Ó 2009 by National Stroke Association doi:10.1016/j.jstrokecerebrovasdis.2009.01.002 Journal of Stroke and Cerebrovascular Diseases, Vol. 18, No. 5 (September–October), 2009: pp 349-353 349