Figure 3.

The relationship between the steady state RAP as the dependent variable (DV) and the steady state LVP representing steady state SV as the independent variable (IV). The greater the LVP (as well as the RVP) due to positive inotropism, the greater the SV, and the lower the RAP. Similar to that in Figure 2, the changes in LAP (lines a, b, and c) are exaggerated. A secondary effect may result due to the greater SV or VR (not shown), which increases the preload to both right and left heart, thus leads to the shift of the right and left ventricular pressure curves upward and right-ward. It should be noted that in both Guyton’s and Levy’s experiments, the left heart was not stimulated as shown in Figure 3; the right heart was replaced by an artificial pump. Hence, manipulating the pumping rate to increase SV is equivalent to a positive inotropic effect on the right heart (not left heart) only.