Randomly I come across crazy ideas and some of them are probably right. About a year ago I heard of Branko Furst for the first time. He has pretty radical ideas about the heart and the vascular system. You would think by now we have a really good idea about how the vascular system works. I ask my anesthesia residents all the time what do they think is moving the blood in the body. All of them say the heart moves the blood. Branko Furst disagrees and he actually published a whole book about the evidence questioning the heart as the main thing that moves the blood in the body: “The Heart and Circulation: An Integrative Model”. He is a retired cardiac anesthesiologist and he thought about this problem for a long time. In his presentations he shows the echocardiography of a patient with left ventricular ejection fraction of almost 0%: youtube link. That patient was still alive. So the question is what was moving the blood in her body? The heart is definitely creating the pressure, but the blood movement is a different story. The scale of the vascular system is pretty incredible. Various sources estimate the total length of the blood vessels in the human body from around 6000 miles to around 60000 miles (Cleveland clinic). That is a massive system to manage for a heart that is around 250-350 grams in weight. Also our heart is very inefficient. The overall mechanical efficiency of a healthy heart muscle is roughly 10% to 20%, meaning that only 10-20% of the chemical energy is converted to mechanical energy (one source for the higher end, two sources for the lower end: here and here). On top of that the left ventricle ejection fraction in humans is around 50-70%, meaning that only 50-70% of the blood in the left ventricle will be ejected with every heart beat. Another issue is that the inside of the heart is not smooth and there is turbulent flow everywhere. Gerald Pollack gives a funny description of the problem in this youtube video. Gerald Pollack is a very legit researcher who is studying the structure of water, but that is a different crazy idea.
Alexander W. Branko Furst’s Radical Alternative. P T. 2017 Jan;42(1):33–39.