- The sheer volume of work which the heart would have to do if it were solely responsible for pumping inert blood through the vessels of the circulatory system. Blood is five times as viscous as water. According to the propulsion premise the heart would have to pump 8000 liters of blood a day in a body at rest and considerably more during activity, through millions of capillaries the diameters of which are sometimes smaller than the red blood cells themselves – a huge task for a relatively small, muscular organ weighing only 300 grams.
- Once the questions start being asked, the anomalies in currently accepted dogma become apparent. For instance, if blood were pumped under pressure out of the left ventricle into the aorta during systole, the pressure pulse would cause the aortic arch to try and straighten out, as happens in any Bourdon tube pressure gauge. In practice the exact opposite happens; the curve increases, indicating that the aorta is undergoing a negative, rather than a positive, pressure.
- Another paradoxical finding concerns the mechanics of fluid flow under pulsatile pressure. When a pressure pulse is applied to a viscous fluid in a closed vessel, the liquid initially resists movement through its own inertia. The pressure, therefore, peaks before the fluid velocity peaks. In the aorta, exactly the opposite happens where a peak flow markedly precedes peak pressure, a fact which was observed in 1860 by Chaveau and Lortet. So just what is going on inside the circulation?
Four Faulty Premises of the Heart as a “Pump”
As Marinelli et al point out, the pressure-propulsion model of blood circulation rests on four major premises:
- blood is naturally inert and must, therefore, be forced to circulate;
- there is a random mix of formed particles in the blood;
- blood cells are under pressure at all times;
- blood is amorphous and is forced to fill its vessels and take on their form.
All of these premises can be shown to be faulty. For example, far from having a random mix of the blood components in vessels, the cellular elements arrange themselves in a highly organized flow pattern in which the heavier red blood cells flow nearest to the axis of the vessels while the lighter platelets are nearer to the periphery. All of the formed elements are surrounded by a sleeve of plasma which is in contact with the vessel wall. However, a major misconception about how blood circulates is the assumption that it flows in a laminar fashion, whereas in reality the main pattern appears to be a vortex. This leads to a whole new concept of circulatory dynamics–one which goes a long way towards explaining the close interaction between the heart and the blood– both of which are derived from the same embryonic material.
Clues to circulatory physiology are found in embryology. Two of the main embryological observations have been that the blood starts circulating before the heart has been fully formed and that it circulates in a spiraling fashion, as in the single-stage tube heart of the chick before the valves have developed.
Why are we concerned about the way in which the blood circulates and the `heart as a pump’ paradox? Do we not already know enough about circulation in conventional terms for all practical purposes? No. Is all this really relevant? Yes. Not only should truth be sought for its own sake, but therapy based upon faulty premises can only be bad therapy.