Influence of three mechanical bileaflet prosthetic valve designs on the three-dimensional flow field inside a simulated aorta

Abstract

The current design of the bileaflet valve, the leaflets of which open outside first, differs significantly from the natural valve whose leaflets open center first. This difference generates a completely different flow field in the bileaflet valve compared to that in the natural heart valve. In a previous study, it was demonstrated that the valve design greatly affects the aortic flow field as well as the circulatory flow inside sinuses of Valsalva, using saline solution as a working fluid. A limited discussion on the turbulence flow field that could be generated by the valve was provided. In this continuation of that study, therefore, a dynamic PIV study was conducted to analyze the influence of the heart valve design on the aortic flow field, and particularly on the turbulent profile. This study also aimed to determine the influence of the viscosity of the testing fluid. Three bileaflet prostheses-the St. Jude Medical (SJM), the On-X, and the MIRA valves-were tested under pulsatile flow conditions. Flow through the central orifice of the SJM valve was slower than that through the newer designs. The newer designs tend to show strong flow through all orifices. The On-X valve generates simple jet-type flow while the MIRA valve with circumferentially curved leaflets generates a strong but three-dimensionally diffuse flow, resulting in a more complex flow field downstream of the aortic valve with higher turbulence. A 180° orientation that is more popular clinically seems to provide a less diffuse flow than a 90° orientation. The effect of increasing the viscosity was found to be an increase in the flow velocity through the central orifice and a more organized flow field for all of the valves tested.

Integrated strategy for in vitro characterization of a bileaflet mechanical aortic valve

“…However, the two lateral jets (A and B for the left and right jet, respectively) are more intense than the central jet C, suggesting that the flow through lateral orifices starts to develop earlier than in the central region. Moreover, the jet emerging from the right leaflet (B) develops slightly earlier than the left one (A), according to the asymmetric phenomenon observed in the valve leaflets dynamics [ 62 ]. Such asymmetry should be related to the presence of the sinuses of Valsalva, as confirmed by the flow evolution at successive time instants [ 29 ].…”

Reduction of aberrant aortic haemodynamics following aortic root replacement with a mechanical valved conduit†

“…Design features of the On-X valve, such as the flared inlet and larger length-to-diameter ratio, may form a more cohesive central flow jet by mimicking the natural left ventricular outflow tract [9,10]. It is also possible that the ability for valve leaflets to fully open reduces erratic flow observed with other bileaflet mechanical valves [3,8]. Single leaflet mechanical valves and bileaflet valves that do not open to a full 90°create more diffuse flow jets, leading to more aberrant 3D flow patterns [8].…”

“…It is also possible that the ability for valve leaflets to fully open reduces erratic flow observed with other bileaflet mechanical valves [3,8]. Single leaflet mechanical valves and bileaflet valves that do not open to a full 90°create more diffuse flow jets, leading to more aberrant 3D flow patterns [8]. However, this study was not designed to have the sensitivity to illustrate a cause-and-effect relationship between individual design features and ascending aortic haemodynamics.…”

“…However, three-dimensional (3D) visualization of pre-and postoperative flow patterns have been performed for various mechanical prostheses, stented/stentless bioprostheses and autografts, showing highly aberrant postoperative aortic haemodynamics in all cases [3,7]. On-X valves have been shown to create a strong central flow and low turbulence [8][9][10], but no analysis of pre-and postoperative 3D flow patterns for these valves has been performed. In light of this, we conducted a pilot investigation of how ARR with this mechanical valved conduit may affect transvalvular pressure gradients and ascending aortic haemodynamics in terms of flow helicity and vorticity.…”

Causes and treatment strategies of unilateral leaflet shedding of bileaflet mechanical prosthetic heart valves after surgery

“…This shows that the different forward pressures on the valve leaves lead to different types of losses of the valve leaves. Toshinosuke Akutsu et al found that the turbulence that is formed in the coronary sinus will counteract the opening and closing of the valve lea ets, which causes pressure on the valve lea ets and reduces their service life [9] . Therefore, the requirements for our industrial design are higher, and it is necessary to adjust the opening and closing angle of the valve leaves by combining the changes in the uid dynamics and the differences in human anatomy, especially when perfecting the use and design of the valve in animal experiments and in vitro experiments.…”