Impact of design parameters on bileaflet mechanical heart valve flow dynamics.

Background And Aim Of The Study: One significant problem encountered during surgery to implant mechanical heart valve prostheses is the propensity for thrombus formation near the valve leaflet and housing. This may be caused by the high shear stresses present in the leakage jet flows through small gaps between leaflets and the valve housing during the valve closure phase.

Methods: A two-dimensional (2D) study was undertaken to demonstrate that design changes in bileaflet mechanical valves result in notable changes in the flow-induced stresses and prediction of platelet activation.

Flow fields generated by peristaltic reflex in isolated guinea pig ileum: impact of contraction depth and shoulders.

The guinea pig ileum responds to distension with characteristic wall movements, luminal pressure gradients, and outflow (the peristaltic reflex). To date, little is known about whether the peristaltic reflex generates flow events other than laminar flow. Here we used a numerical method to solve for the flow generated by moving walls to assess occlusive contractions (case 1), nonocclusive contractions (case 2), and contractions with steep shoulders (case 3) for which visual parameters of wall movements are published.