[Interdependence of preload, afterload and contractility: their relation to cardiac function curve]

Abstract

Formerly, the major determinants of cardiac performance, i.e., preload, afterload contractility, and heart rate had been considered independent. This individual concept of these determinants was originally advocated by E.H. Sonnenblick in 1960's, providing an extremely useful tool in understanding basic cardiac mechanical physiology. We now know, however, that these determinants of cardiac performance are, in fact, interdependent with each other both at cellular and at ventricular levels. This concept of the interdependency of the determinants, in turn, is of practical importance during the conduct of clinical anesthesia. Since we cannot isolate one determinant from the other, we have to deal with them as they are. Furthermore, monitoring a parameter of one aspects of the patient's cardiac performance is not sufficient to understand or estimate patient's status. It is necessary to integrate these informations to make clinical decision under uncertain situations.