Cardiac output (CO), also known as heart output denoted by the symbols Q {\displaystyle Q} , or Q ˙ c {\displaystyle {\dot {Q}}_{c}} , is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, by the left and right ventricle, per unit time. Cardiac output (CO) is the product of the heart rate (HR), i.e. [Source: Wikipedia ]