Computer modeling of fluid dynamics related to a myocardial bridge in a coronary artery.

Fluid mechanics associated with blood flows induced by the so-called myocardial bridge (MB) has been studied systematically using a computational fluid dynamic modeling of the Newtonian, incompressible, two-dimensional, unsteady flow in a channel with a time-dependently flushing in/out indentation. During each cycle, a train of vortex wave flow was observed downstream of the phasic stenosis and both upper and lower walls suffer severely from consistently high, oscillating wall shear stresses (WSS). Extensive studies were conducted on the influence of the Reynolds number, the geometry and the Strouhal number of the MB movement on the nature of the vortex flow and the time-dependent wall shear stress distribution. Special attention was drawn to the relationship between the vortex wave and the pressure distribution. It was found that the pressure gradient changed markedly during one cycle, which was apparently dominated by the dynamics of the indentation. A steep, adverse pressure gradient was observed when the indentation was flushing out, which corresponded to the existence of the most developing vortices. It implies the possibility that the MB in a coronary artery can produce an extremely low pressure region immediately downstream of the phasic stenosis, where elastic choking or collapse of the coronary artery might occur.