MSc Thesis Abstract - David Pinney
This three student project set out to investigate tools for the modelling of the closure event of Mechanical Heart Valves.
This part of the study aimed to investigate the possibility of determining the closing speeds of a Mechanical Heart Valve (MHV) in an in-vitro environment, using Continuous Wave (CW) Doppler Ultrasound. The closing speed of the MHV leaflets provides important information for the calculation of the dynamic stresses and potential structural damage to the valve.
The first main part of the project aims to use Continuous Wave Doppler ultrasound to measure the velocities involved over the course of the valve closure event. It is anticipated that the closure event has a duration of the order of a few milliseconds. This part of the project is to be further sub-divided into two distinct parts to be carried out by different members of the project team: one to construct and evaluate a suitable test-rig to hold an artificial heart valve rigidly such that a study of the heart-valve dynamics can be undertaken by coupling it with the ultrasound probe. The other sub-part is to devise a method of extracting the information from the analogue output of the ultrasound machine suitable for producing a velocity/time profile in a Personal Computer (PC).
A Shelhigh accelerated rate fatigue tester was used during the course of this study, along with a Huntliegh Healthcare Multi-Dopplex 2 hand-held Doppler ultrasound machine. These were used to investigate the motion of a simple spring-loaded valve and a Bjork-Shiley (BS) monostrut valve. It was found that under the conditions used, the BS valve had a peak closing velocity of between approximately 10cm/s and 17cm/s depending on the simulated heart rate.
The second main part of the project, carried out by the third member of the project team, aims to combine solid and fluid mechanics of the complex heart valve motion and solve them together in a single computational package, Field Operations And Manipulations (FOAM). This could lead eventually to modelling of the heart valve closure dynamics computationally. This can be sub-divided into solving the Poiseuille's equations, leading to modelling of pulsatile flow in an elastic tube and then applying this to artificial heart-valve closure.