Figure 1. Schematic illustration of the method used to obtain end-systolic pressure-length relationship area (ESPLR^area). The linear relationship between end-systolic pressure (P) and left ventricular end-systolic diameter (D) is characterized by its slope (E sub max) and its length axis intercept (D⁰). The minimum (D^min) and maximum (D^max) end-systolic left ventricular diameters measured during the baseline period served as the limits of integration to calculate the area beneath the curve (ESPLR^area, dark shaded area). After positive inotropic intervention, the curve is shifted up or to the left of baseline. ESPLR^areaof this curve (total shaded area) is obtained using D^minand D^maxof the control period.