The heart as a pump can be described by the pump function graph, the relation between mean ventricular pressure, and Cardiac Output. A pump function graph completely describes the heart as a pump and is similar to the characterization of industrial pumps and ventricular assist devices. When the load on the heart is increased, it will generate a higher pressure but a smaller Cardiac Output, and vice versa, resulting in a curved inverse relation. Increased contractility ‘rotates’ the pump function graph around the intercept with the flow axis. When diastolic filling and/or Heart Rate is increased, the pump function graph shifts in an ‘outward’ manner. The working point, i.e., the pressure and flow during normal function at rest, is found at maximal cardiac efficiency. The cardiac pump function graph is related with the force-velocity relation of muscle (see Chap. 13), and also with the end-systolic pressure-volume relationship (Chap. 14).
KeywordsCardiac pump function Hypertrophy Frank Starling Exercise Cardiac efficiency
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