Fiber orientation and ejection fraction in the human left ventricle.

Fiber orientation and ventricular geometry are incorporated in a mathematical model for ejection fraction of the human left ventricle. The inadequacy of circularly oriented or "constrictor" fibers to explain high ejection fractions of cylindrical, spherical, or ellipsoidal reference ventricles is demonstrated. A class of "helical" fibers is then introduced from which ejection fractions predicted by physiologic amounts of fiber shortening on cylindrical and ellipsoidal reference ventricles are shown to be consistent with those calculated from biplane angio-cardiographic films.