STRESS-STRAIN RELATION OF CARDIAC-MUSCLE DETERMINED FROM VENTRICULAR PRESSURE-TIME RELATIONSHIPS DURING ISOVOLUMIC CONTRACTIONS

The stress-strain relation of systolic muscle fibers which constitute the left ventricular wall of a canine heart was derived only from pressure-time relationships at different ventricular volumes of isovolumic beat by using a largely deformable thick spherical shell model as a first approximation. The strain energy function being independent of the magnitude of forces generated by contraction was found to be uniquely determined by assuming those forces as forces caused by an eigen stress. The result based on this assumption was verified by several pressure-volume relationships obtained experimentally.