Theoretical study of the effects of vascular smooth muscle contraction on strain and stress distributions in arteries

To study the effects of smooth muscle contraction and relaxation on the str ain and stress distribution in the vascular wall, a mathematical model was proposed. The artery was assumed to be a thick-walled orthotropic tube made of nonlinear, incompressible elastic material. Considering that the contra ction of smooth muscle generates an active circumferential stress in the wa ll, a numerical study was performed using data available in the literature. The results obtained showed that smooth muscle contraction affects the res idual strains which exist in a ring segment cut out from the artery and exp osed to no external load. When the ring specimen is cut radially, it spring s open with an opening angle. The predicted monotonic increase of the openi ng angle with increasing muscular tone was in agreement with recent experim ental results reported in the literature. It was shown that basal muscular tone, which exists under physiological conditions, reduces the strain gradi ent in the arterial wall and yields a near uniform stress distribution. Dur ing temporary changes in blood pressure, the increase in muscular tone indu ced by elevated pressure tends to restore the distribution of circumferenti al strain in the arterial wall, and to maintain the dow-induced wall shear stress to normal level. (C) 1999 Biomedical Engineering Society. [S0090-696 4(99)00404-X].