Notes on the Muscular Architecture of the Left Ventricle

Abstract

The canine and human left ventricular myocardium is a syncitium at all levels and an individual fiber has branching connections of several directions with adjacent fibres. Therefore the question of discrete "muscle bundles" in the left ventricle depends upon a predominance of branchings in one direction over branchings in other possible directions. Statistical methods must be added to geometric methods, then, to develop a model of the fibre organization of the left ventricle. To do this, 2 levels of generalization were employed; first, an overall, average direction of fibers; second, the fiber-to-fiber relationship. For the first, there proves to be a 360[degree] helical clockwise system of outer fibres, and, as a generalization, another 360[degree] helical system of internal fibres opposite to it in direction, that is, counterclockwise from base to apex. For the second, there proves to be also a fiber-to-fiber helical relationship. Between the 2 generalizations, there are successive "generations" of helical relationships. Some conjectures are offered regarding the embryologic morphogenesis of this architecture, and of such specialized parts of the muscular system as the fiber vortex at the apex of the left ventricle.