Each year about a quarter of a million heart valve operations are performed worldwide. Generally, replacement mechanical valves have an excellent in-service record. Theoretical calculations based on wear recorded in service indicate that they could function in the body for 200 years – if the patient lived that long!
With durability issues having been addressed, current design focus has shifted towards improving the performance of the valve.
Crude engineering simulations of the action of heart valves have been possible for some time, but recently more advanced modelling software has enabled us to map the flow of blood through the valve throughout the opening and closing cycle. This allows us to evaluate and map shear stress on the blood in the valve, and to either side of it. It also allows us to study the efficiency with which the valve opens, and how stable it is through the cycle.
In parallel with these developments there has been significant progress in the use of transient particle tracking to monitor shear history data for particles in the flow. These parameters are beginning to shed light on the links between the physical characteristics of the heart valve operation and physiological processes, such as haemolysis and thrombosis.