Myocardial fiber architecture and left ventricular function.

This paper develops several working hypotheses regarding the coupling between myocardial fiber architecture and left ventricular function. First, the coupling between spiral myocardial fibers and left ventricular torsional deformation and ejection fraction is examined. A proposal is then made to account for the observed change in orientation of myocardial fibers from a right hand helix in the subendocardium, through circumferential fibers in the midwall, to a left hand helix in the subepicardium in terms of a requirement for generating physiological values of both ejection fraction and pressure as well as equilibration of transmural fiber work. Finally, a pumping hypothesis is developed linking the contraction of each transmural layer of fibers to one another via collagen struts and weaves, with the resulting force transmitted to the epicardium and thence, by means of hydraulic forces associated with the constant volume property of the LV wall, to the endocardium to reduce the volume of the left ventricular chamber.