Approximately the size of a clenched fist and weighing about 9 ounces, the organ that we call the heart is a formidable device. — Every day, it pumps the equivalent of seven IBC containers of oxygenated blood around our bodies, that’s 7000 litres or 1850 US gallons. The human heart is effectively a twin pump system in one organ. Superficially, how it functions is straightforward and easy to understand. One of the left chambers…