In-Vivo Measurement of Regional Strains in Myocardium

Abstract

The motion of the heart wall and its relationship to cardiac function have been the subject of intensive investigation for many years. While large rigid body motions (translations and rotations) have been observed in myocardium, it is the relative motion ( the deformation or strain) that may best be associated with the muscle’s contractile abilities. These strains accompany the large internal stresses and forces that react against the blood in order to raise its pressure and eject it from the chamber. During contraction, the normal left ventricular wall undergoes large and complex patterns of deformation that have been partly characterized by both global and local dimensional measurements. The motion of the left ventricle is often identified with the shape changes of an axisymmetric membrane or shell. Thus, early studies in cardiac mechanics focused on variations in global cardiac dimensions such as chamber volumes and areas, major and minor semi-axes, and circumferential shortening and shortening velocities as measured by changes in ventricular radius (Rushmer et al, 1956; Hawthorne, 1961; Mitchell et al, 1969; Rankin et al, 1976).