Stereo photogrammetric studies on the dynamic geometry of the canine left ventricular epicardium

Length-time relationships of segments of the left ventricular epicardium were determined in eight anesthetized thoracotomized canine subjects. The instantaneous three-dimensional positions of four epicardial sites on both the anterior wall and lateral free wall were measured using a system (Analytic Stop Motion Stereo Photogrammetry) developed in these laboratories. Segmental shortening was found to be maximum at approximately right angles to the Left Anterior Descending Coronary Artery (LAD) in all regions studied, with the greatest extent of shortening in the mid base-apex region. Shortening of segments approximately parallel to the LAD was negligible near the septum and greatest on the lateral free wall. These findings support an asymmetric anisotropic model of normal ventricular systole in which all points on the lateral free wall move towards one another while simultaneously pivoting about a point near the apex, moving toward a relatively fixed septum.