Total Internal Mechanical Work of Ventricle Assessed from Quick Release Pressure-Volume Curve

A method is proposed for direct assessment of the total internal mechanical work of the cardiac ventricle from a pressure-volume diagram. First, a quick release pressure-volume curve of the lumped series elasticity of the ventricle is recorded. Next, this curve is transcribed on a pressure-volume loop diagram of a contraction of interest in such a way that the quick release curve passes through the end-systolic pressure-volume data point of the loop. Finally, planimetry of the triangular area bounded by the quick release curve, the isovolumic relaxation segment of the loop and the diastolic pressure-volume curve gives total ventricular mechanical internal work performed on the lumped series elasticity of the ventricle during systole. This method is much simpler and more direct than the conventional analytical method which requires a relatively simple geometric model of the ventricle, a formula for series elasticity with appropriate stiffness constants and a series of mathematical calculations based on many unverified assumptions on the shape, structure and mechanical properties of the ventricle.