Global Young's modulus of urethane plastic cast of left ventricular myocardium calculated from Roentgen angiographic silhouettes

A method based on the principle of conservation of energy is proposed for the evaluation of the global Young's modulus of the left ventricular myocardium in the passive state. Left ventricular transmural pressure and chamber volume data suffice for calculation of the external work performed during diastole, while the shape and dimensions of the left ventricle (recorded as videoroentgen angiograms) provide the necessary geometric information for the approximate evaluation of the strain energies by an axisymmetric, finite-element technique. To quantitate the accuracy of the proposed method, the global Young's moduli for six urethane casts of a canine left ventricle were determined and compared with the moduli of strips of the same urethane material measured directly. Roentgen silhouettes of the casts filled with known volumes of roentgen contrast medium were recorded on videotape at various stages of inflation. The calculated global Young's modulus corresponded to within ± 15% of the 0.5 to 6.0 × 10⁶ dyn/cm² range of values calculated directly from the stress-strain relationship of strips of the same urethane material.