Background: There is recent interest in the role of carotid bifurcation anatomy, geometry and hemodynamic factors in the pathogenesis of carotid artery atherosclerosis. Investigators have drawn parallel between certain anatomical and geometric configuration at the carotid bifurcation and its exposure to disturbed flow. An intriguing idea is that the vascular dimensions of the intracranial carotid artery may be optimally designed such that there is minimum work to maintain blood and pump it through a vascular system. It has been proposed that this occurs when the exponent power relationship between the radii of the parent artery and the daughter arteries is 3. In this study, we evaluate if the dimensions of bifurcation of the extracranial carotid artery follows this principle of minimum work.
Methods: This study involved subjects who had CT angiography at Monash Medical Centre between 2006-2007. Subjects with luminal stenosis > 30% were excluded. Following segmentation of the carotid artery, the radii and areas of the common carotid/parent artery and the two daughter arteries (internal and external carotid arteries) were determined. A non-linear equation solver was used to determine the optimum value of power n.
Results: When the equation was solved for radius, the value of n ranged from 1.4 to 1.8.
Conclusion: Our findings indicate that the principle of minimum work (as defined by power n of 3) may not apply at the carotid bifurcation and may suggest that additional factors play a role in the relationship between the parent and daughter vessels radii.