The outflow tract of the left ventricle.

Intensive study of the infundibulum in congenital and acquired lesions has led to a much better appreciation of the anatomy and function of the right ventricular outflow tract in health and disease. The rapidly spreading practice of replacing severely damaged aortic and mitral valves, together with current interest in subaortic stenosis (Braunwald et al., 1964) have focused attention on the outflow tract of the left ventricle, which is more complex and less well understood than its opposite number on the right side of the heart. The object of this paper is to describe the anatomy of the left ventricular outflow tract, to illustrate its relation to other cardiac structures, and to emphasize the basic importance of the fibrous skeleton of the human heart. The cavity of each ventricle has a region that is concerned mainly with the inflow of blood from the corresponding atrium and one that is associated with the outflow of blood into either the pulmonary trunk or the ascending aorta. These two parts are now customarily designated the " inflow" and " outflow" tracts of the right and left ventricles. The outflow tracts lie above and in front of the inflow tracts and the walls of their terminal parts tend to be smoother than those of the inflow tracts, which are characterized by the raised muscular ridges of the trabeculte carnem.