The heart pressurizes the blood to increase the "surface phase" of water in the vessels that provides the electromotive force that moves the blood
In the past days, I have noticed a thing. Against the surface of blood vessels (or any surface of object filled with water), the water is forced into a solid phase that is denser than ice. This phase is "compressed ice", and has ejected the hydrogen ions that normally separate each molecular sheet in ice. They instead form a layer on top of it. In a narrow blood vessel like an arteriole, the inside is positively charged from this inner layer. Some of the hydrogen ions there, also distribute into the fluid itself, the blood. This makes the mass of the blood positively charged, causing the vessel itself to repel, or propel, the blood outwards.
Now, if you increase the pressure, somehow, you increase the amount of "surface phase", and the propulsion effect that is caused by it.
When I first heard of Tom Cowan's idea, I rejected it. But, there is a perfect way it fits. I know the "surface phase" is propelling blood. But if the heart is able to increase pressure specifically, rather than itself circulate the blood, it will increase the "surface phase" that will increase the propulsion effect of the vessels themselves. That it produces the propulsion of the vessels by creating pressure. It is exactly how the kidney works so I am pretty open to that it might be so.