In vitro comparison of steady and pulsatile flow characteristics of jellyfish heart valve

Abstract

In examining the hydrodynamic performance of artificial heart valves in vitro, experiments are carried out under either steady or pulsatile flow conditions. Steady flow experiments are simple to set up and analysis of the data is also simple; however, their validity and accuracy have been questioned. In this study, the flow characteristics of jellyfish valves are evaluated and analyzed for steady and pulsatile flow conditions. The analysis is given in terms of velocity and shear stress distributions for a cardiac flow rate of 4.51/ min, and the corresponding steady flow rate is measured at two locations, 0.5D and 1D downstream of the valve face (D being the diameter of the pipe). At the 0.5D location, the velocity profile results obtained for both flow conditions indicated that jetting flow occurred close to the wall, and flow reversal as well as stagnation zones occurred in the core of the valve chamber. These phenomena were also evident in the shear stress profiles for both pulsatile and steady flow conditions. At this location, the maximum difference between the steady and pulsatile values of peak velocity is about 18%. However, the maximum difference between the peak shear stresses was in the range of 5%-7%. At the 1D location, the flow characteristics observed under both the pulsatile and steady, flow conditions were almost identical, with a maximum difference between the peak values of less than 4%. From the data presented here, it can be stated that, at least in the initial optimization of the valve hemodynamic performance, the steady hydrodynamic

Bioengineering Strategies for Polymeric Scaffold for Tissue Engineering an Aortic Heart Valve: An Update

“…In an attempt to understand valve dynamics, researchers have traditionally relied on experimental techniques to analyze the complex motion of the valve mechanics. Various experimental tools have been used, including echocardiography (69, 70), particle image velocimetry (PIV) (71–74), and laser Doppler velocimetry (LDV) (11–14, 75, 76). However, these studies used a very simplified configuration of the valves and neglected (or at least oversimplified) the effect of the sinus of Valsalva and effect of circulations within these cavities on the valve dynamics (12).…”

“…Alternatively, bioprosthetic valves are hemodynamically superior to the mechanical ones, and they do not need anticoagulation therapy. They suffer, however, from calcification that contributes to the deterioration of leaflet tissue, leading to regurgitation through tears in calcified leaflets in a short period of time (between 10 and 15 years) and to the subsequent need for follow-up emergency surgical therapy or even to death (11–14). It is recognized that with bioprosthetic valves, fixation of natural tissues via glutaraldehyde initiates soluble proteins which subsequently amalgamate into the organizational proteins, resulting in inflexible leaflets and structural instability (7, 15, 16).…”