Modest Influence of Velocity of Shortening on Systolic Force in the Left Ventricular Free Wall

Abstract

During normal, auxotonic contractions of the left ventricle (LV), wall force builds up to a high value during the isovolumic, pre- ejection phase and falls to lower levels during ejection. The drop in systolic force may be attributed to two main factors: 1) the reduction of the ventricular volume and consequent reduction of ventricular wall dimensions may cause force drop according to a direct force — length relationship; and/or 2) the shortening velocity may induce a drop in wall force through a force-velocity relationship which may reflect an influence of wall viscosity on the developed force or an inactivation effect like that seen during rapid length changes in isolated myocardial fiber preparations.