HOW DOES TORQUE ACT ON MECHANICAL HEART VALVES?

In life, there are many applications of torque. An interesting one is that of mechanical heart valves. In this blog, we will explore how torque acts on mechanical heart valves as it is very interesting and important for those who have mechanical heart valves. Why is torque so important for mechanical heart valves? It is very important because it affects many different aspects of heart valves. Some of these include the durability of the valve, the valve’s function, and that of patient outcomes. When torque is applied correctly, the risk of blood clotting and cell damage is significantly lowered.

What is a mechanical heart valve? A mechanical heart valve is a prosthetic valve for the heart that is made of carbon, metal, or some other kind of durable material. One that is built with good durability will last a lifetime. With a mechanical heart valve, patients usually are required to take blood-thinning medication which often lasts a lifetime. This is to help reduce the risk of blood clotting. Some with mechanical heart valves also hear a very slight clicking sound as the valves open and close. What generates torque in mechanical heart valves? One thing that generates the torque is that of blood flow and pressure differentials, which is what tilting-disc and bileaflet designs primarily use to function. Additionally, in some medical scenarios, external magnetic fields during MRI scans can also generate torque in mechanical heart valves.

Fluid dynamic torque is the main source of where the torque comes from during normal heart function. This happens between the blood flow and the rigid leaflets of the valve. For the opening and closing dynamics, the pressure gradient across the valve is driven by the pumping action in the heart, which in turn opens and closes the leaflets. From that, blood flows and exerts torque on the surfaces of the leaflets. The torque is applied to a hinge point or pivot point and creates rotation in the leaflet.

Another part of fluid dynamics in mechanical heart valves relating to the use of torque is that of turbulence and flow patterns. One disadvantage of mechanical heart valves is that they are not as flexible which in return creates more flow disruption. Because of this stiffness, eddies (which are localized and often irregular swirls within a larger fluid flow) and turbulent flow patterns enter the blood streams. The effect of turbulence on blood cells is one that is not great. It can possibly cause blood clots and platelet activation. A well designed valve will reduce the amount of turbulence from the torque.

The last part that is influenced by fluid dynamic torque is leakage flow. When closed, mechanical heart valves are designed with a small amount of "leakage". This is intentional as it prevents stagnation and clot formation by scouring critical areas like that of the hinges.

There is a part of torque in mechanical heart valves that can actually happen on the outside. Externally induced torque happens when a patient with a mechanical heart valve goes through an MRI. For minor strength magnetic fields in more common strength MRI’s, this is a minor issue. However, for higher field strengths, it can cause problems. It can increase back pressure and cause the mechanical valve to malfunction. The heart's workload is then increased, which can be bad for patients (especially those that are older in age).

Overall, the application of torque on mechanical heart valves is very interesting and important. It is an ongoing goal to create better, safer mechanical heart valves to improve the lives of those who need it. If we can understand the effects of torque better for mechanical heart valves, we can mitigate torque related issues and create safer prosthetic heart valves.

Thank you for reading!