Synopsis: Diagnosing Flow Problems in Mechanical Heart Valves
More than 100,000 people each year—according to recent estimates—receive a mechanical heart valve to help regulate impaired blood flow. However, valve recipients require life-long blood thinner medication to combat blood clotting, which is a direct result of turbulence generated by the valves’ rigid structure. To explore how modifications to valve design could help reduce turbulence, Hadi Zolfaghari and Dominik Obrist from the University of Bern, Switzerland, performed detailed simulations of blood flowing through mechanical heart valves. They identified vortices forming near the leading edges of the valve’s moving parts as a possible origin of blood turbulence and proposed that modifying the edge geometry could provide an engineering fix.
One of the most common types of artificial heart valves, called bileaflet valves, hit the market in 1979. These pyrolytic carbon devices have hinged flaps that open and close to control blood flow. Previous computational studies have shown that turbulence develops downstream of the flaps, but until now, researchers have not identified the root cause.
Rather than study the flow in the wake of the valve, Zolfaghari and Obrist focused on the flaps and observed whether fluid passing by their leading edges remained stable or not. This targeted analysis, which was inspired by aerodynamic modeling of airflow over airplane wings, revealed a correlation between vortices on the leading edges and turbulence in the downstream flow. By repeating the simulations with a valve having more tapered flaps, they demonstrated a possible design that could limit vortex formation and reduce turbulence. However, they say that eliminating vortex formation entirely would require very careful optimization procedures.
This research is published in Physical Review Fluids.
Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.