Lower blood clot risk in artificial heart valves
Millions of people have to take anticoagulant drugs. Patients with mechanical heart valves also rely on medicines that are popularly known as blood thinners. However, those affected could possibly be able to live without such preparations.
Mechanical heart valves made of plastic and metal have a very long service life. However, the foreign material of the artificial heart valve affects blood clotting, which is why affected patients have increased blood clotting. As a result, they suffer from a higher risk of a blood clot (thrombosis) and therefore have to take anticoagulant medications for a lifetime, explains the Federal Center for Health Education (BZgA) on the “organspende-info.de” portal. But this could possibly be changed.
Daily anticoagulant medication
As the University of Bern wrote in a recent report, people with mechanical heart valves have to take blood thinners every day because they have an increased risk of blood clots and stroke.
Now researchers at the ARTORG Center at the University of Bern have discovered how turbulent blood flow develops in the valves, which can ultimately lead to clots.
According to the experts, design optimization could greatly reduce this risk and enable those affected to live without medication.
Increased risk of clot formation
Most people know turbulence from aviation: certain wind conditions ensure a bumpy passenger flight. But blood flow can also be turbulent within human vessels.
Turbulence can occur, for example, when the blood flows along the bends or edges of the vessels and the flow speed changes abruptly. Turbulent blood flow creates additional forces that can increase the likelihood of blood clots.
These clots grow slowly until they are carried away by the bloodstream and can cause a stroke by occluding an artery in the brain.
Patients with an artificial heart valve have an increased risk of such a clot formation. This is known from the observation of those affected after the implantation of an artificial valve.
This is especially true for people with mechanical heart valves who are given blood thinners every day to prevent stroke. So far, however, it was unclear why mechanical heart valves promote clot formation far more than other types of valves, for example biological heart valves made from animal tissue.
Strong turbulence in the blood stream
Two engineers from the Cardiovascular Engineering Group at the ARTORG Center for Biomedical Engineering Research at the University of Bern have now successfully identified a mechanism that can contribute significantly to clot formation.
To do this, the scientists used complex mathematical methods from hydrodynamic stability theory, a sub-area of fluid mechanics that has been used successfully for many decades to develop fuel-efficient aircraft.
It is said to be the first translation of these methods, which combine physics and applied mathematics, into medicine.
Using extensive simulations on supercomputers at the Centro Svizzero di Calcolo Scientifico in Lugano (Switzerland), the research team was able to show that the current shape of the valve flaps of the heart valve leads to strong turbulence in the blood stream.
"Using the simulation data, we were able to observe how the blood impinged on the front edge of the valve wings and how the blood flow quickly became unstable and caused turbulent eddies," explains Hadi Zolfaghari, first author of the study.
“Due to the high forces that arise, blood clotting is activated and clots can form in the backflow area directly behind the valve. With the help of supercomputers, we were able to find a cause of the turbulence in these heart valves and found a technical solution for this using hydrodynamic stability theory. ”
Their results were published in the "Physical Review Fluids" magazine.
Even a slightly modified design would bring about an improvement
According to the notification, the mechanical heart valves examined in the study consist of a metal ring and two hinged wings that open and close with each heartbeat, allowing the blood to flow out of the heart but not flow back in.
The team also examined how the heart valve could be improved. It was shown that a slightly modified design of the valve wings allows the blood to flow without creating instabilities that lead to turbulence - similar to a healthy heart.
Such turbulence-free blood flow would significantly reduce the tendency to clot and stroke.
Normal life without taking medication permanently
According to the University of Bern, more than 100,000 people receive a mechanical heart valve every year. Because of the high risk of clot formation, these people must take blood thinning medication daily and for life.
If the design of the heart valves were improved from a fluid mechanical point of view, it would be conceivable in the future that these patients with implants no longer need any blood thinners. You could live a normal life - without an increased risk of stroke and without taking medication permanently.
"The design of mechanical heart valves has hardly been adapted since their development in the 1970s," explains Dominik Obrist, head of the research group at the ARTORG Center.
“In contrast, there was a lot of research and further development in other engineering areas, such as aircraft construction. If you consider how many people wear an artificial heart valve, it is time to talk about design optimizations to enable them to live a better life, ”said the expert. (ad)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- University of Bern: Less risk of blood clots in artificial heart valves, (accessed: January 14, 2020), University of Bern
- Federal Center for Health Education (BZgA): The heart valve transplant, (accessed: January 14, 2020), organspende-info.de
- Hadi Zolfaghari and Dominik Obrist: Absolute instability of impinging leading edge vortices in a submodel of a bileaflet mechanical heart valve; in: Physical Review Fluids, (published: 06.12.2019), Physical Review Fluids