Cardiac Work, Energy and Power
External work per beat, stroke work, can be determined from the area contained in the pressure-volume loop (Joule). Multiplication of stroke work by Heart Rate gives cardiac power (J/s or Watt; work per unit time). External power also can be calculated from the instantaneous product of ventricular (or aortic) pressure and flow. The calculation of energy and power does not require a linear system, as, for example, in the calculation of resistance and impedance. This makes the use of energy and power very broadly applicable in hemodynamics. Power and work are a characterization of heart and load together, while the End-Systolic Pressure-Volume Relation and Pump Function Graph characterize the heart.
KeywordsStroke work Energy External power Pump function Pressure-volume relation
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