The heart is not a pressure-pump, it is a vortexing/imploding machine and as it packages and turns groups of blood cells, that vortexing-spiraling-imploding action is what causes natural spin and the blood flows in the various directions. Pressure gradients are a byproduct of the heart moving the blood. The primary force is implosion and explosion - contraction and expansion. All other physical-science measurements come from that. Then, there is also the electro-magnetic aspects - which we'll discuss another time.
