Computational analysis of the effects of exercise on hemodynamics in the carotid bifurcation.

The important influence of hemodynamic factors in the initiation and progression of arterial disease has led to numerous studies to computationally simulate blood flow at sites of disease and examine potential correlative factors. This study considers the differences in hemodynamics produced by varying heart rate in a fully coupled fluid-structure three-dimensional finite element model of a carotid bifurcation. Two cases with a 50% increase in heart rate are considered: one in which peripheral resistance is uniformly reduced to maintain constant mean arterial pressure, resulting in an increase in mean flow, and a second in which cerebral vascular resistance is held constant so that mean carotid artery flow is nearly unchanged. Results show that, with increased flow rate, the flow patterns are relatively unchanged, but the magnitudes of mean and instantaneous wall shear stress are increased roughly in proportion to the flow rate, except at the time of minimum flow (and maximum flow separation) when shear stress in the carotid bulb is increased in magnitude more than threefold. When cerebral peripheral resistance is held constant, the differences are much smaller, except again at end diastole. Maximum wall shear stress temporal gradient is elevated in both cases with elevated heart rate. Changes in oscillatory shear index are minimal. These findings suggest that changes in the local hemodynamics due to mild exercise may be relatively small in the carotid artery.