Blood flow in the heart is highly structured and stable with a complex vortical flow and very little turbulence. It is co-functional with the geometry and purpose of the heart itself.
Vortices created by the valves themselves are responsible for the correct functioning of those same valves.
This material on this page is taken largely from the PhD thesis of Charles Peskin: Flow patterns around heart valves : A digital computer method for solving the equations of motion.
Taylor and Wade (1969) (p 16 or 44 on the PDF) filmed blood flow in the heart using x-ray cinematography and dye and discovered the following:
- Flow is not turbulent
- Vortices are formed and are stable
- Boundary layers are thin
- There is no backflow through the valves before closure
- The flow pattern is species independent (dogs/sheep)
- The character of flow is completely different from that of steady flow in a pipe
- The flow profile across the valve opening is completely flat
The heart valve leaflets were seen not to flutter when either a steady or pulsatile flow passed through the valve. There was no backflow through the valves prior to closure and the valves were observed to be closed before flow reversal which implies that the valves were not closed by the flow reversal itself. Instead, the valves are pushed shut by the formation of small vortices behind the leaflets.
The flow profiles for laminar and turbulent flow in a pipe are slightly different but both show marked slowing at the boundary owing to friction between pipe and fluid.
The flow across the mitral valve showed a completely flat profile indicating little to no friction with the arterial walls, consistent with the idea that the arteries are lined with negatively charged EZ water (Pollack)
“The character of the flow is completely different from that of steady flow in a pipe. In particular the velocity profile is flat so that to a first approximation the bulk of the fluid is simply being transported as a rigid body” p. 17 (45)
The heart promotes blood flow to assist the operation of the heart itself:
“The basic flow patterns were characterised by stability of flow with no gross turbulence and only a slow tendency to lateral dispersion of streams. Fluid entering the atria during ventricular systole collected as an expanding bolus. The only site where swirling and dispersion was observed was in the right atrium adjacent to the entrance of the coronary sinus.
In ventricular diastole when the atrio-ventricular valves opened, stable streams were drawn into the ventricle through the valve canal. On reaching the valve outlet at the cusp margins, these streams diverged to flow around the lateral and septal walls of the ventricle and then down the ventricular aspect of the atrio-ventricular valve cusps.
At this stage they flowed adjacent and parallel to the entering stream and formed stable, expanding vortex systems behind the cusps, which were fed and maintained by the flow from the atrium.
There was no sign of flow reversal at the time of valve closure.” – Taylor and Wade
Fluid was pumped through six types of types of artificial valves by Weiting and the resulting flow examined. p.22 (50) It was found that slight variations in the geometry of the valves led to striking differences in the flow pattern.
The geometry and functioning of the heart together the characteristics of the blood flow and the intrinsic properties of blood as a fluid are all inextricably co-dependent with any alteration to a single element likely to disrupt the balance and lead to dysfunction of the entire system.
The vortices within the blood flow are a way of reducing friction, maximising blood flow, minimising the need for pressure and at the same time synchronising valve operation with blood flow to eliminate back-flow.
Flow patterns around heart valves – Charles Peskin – PhD thesis 1972
Flow through the mitral valve during diastolic filling of the left ventricle – Taylor, Wade 1969
Dynamic flow characteristics of heart valves – Weiting 1969
Experience in Using Titanium for Simulation of Immersed
Boundary Biological Systems –
The Fourth Phase of Water: Beyond Solid, Liquid, and Vapor – Gerald Pollack