Fig. 10
From: Left ventricular function: time-varying elastance and left ventricular aortic coupling
Top: in a normal heart increased contractility does not change the normally steep ventricular function curve so this does not change cardiac output much. In contrast, changes in venous return cause large changes in cardiac output so, in health, cardiac output is primarily controlled by the peripheral circulation. Bottom: in a failing heart changes in venous return curves no longer result in substantial changes in cardiac output but raise venous pressure (solid circle to open circle on bottom ventricular function curve). Now an increase in contractility results in a substantial increase in cardiac output and decrease in end-diastolic pressure (filled circle on lower ventricular function curve to filled circle on upper ventricular function curve)