Dynamic geometry of the left ventricle

Abstract

Some instantaneous geometric changes of the left ventricle during the cardiac cycle have been discussed. The importance of involving size, shape and changes in wall thickness in mathematical manipulations designed to study ventricular mechanics has been stressed. It is suggested that changes of size, shape and wall thickness provide special mechanical advantages to the ventricle during the various phases of the cardiac cycle. It is proposed that the equivalent geometric model of the left ventricle is a thick-walled, nonprolate ellipsoid. Changes in size of the left ventricle alter the manner in which it contracts. Changes in shape of the ventricle during the cardiac cycle alter the relation from moment to moment between internal volume and surface area. Changes in wall thickness alter the stresses distributed across the ventricular wall and adjust the wall stress during the cardiac cycle within certain limits as yet undefined and for reasons which are as yet not understood. Thus it is clear that for any given heart rate, myocardial inotropic state and ventricular pressure, the stresses and tension within the ventricular wall are major functions of not only pressure but ventricular size, shape and wall thickness.