Kinematics of the Beating Heart

We introduce a new approach to the quantification of myocardial strain. It utilizes the theoretical frame work of kinematics and can thus account for the large time-varying displacements present in the intact beating heart. For arbitrary small segments of myocardium, we show how these displacements can be described completely by a rotation tensor and a stretch tensor. We demonstrate the physiologic meaning of this analysis in an anesthetized dog. An epicardial region was seen to exhibit a local twist quantified by the rotation tensor and a segmental shortening quantified by the stretch tensor.