The time course of aortic pressure (AP), cardiac output (CO), ventricular volume (VV), and atrial pressure (AtP) if afterload is constant (4 U) and preload increased from 6 mm Hg to 8 mm Hg. (a) In initial conditions (20–60 s; preload is 6 mm Hg) all variables are in steady state. Atrial pulse pressure (AtP max/AtP min) is 5.2/3.5 mm Hg. Preload increased first to 7 mm Hg (60–120 s) and then to 8 mm Hg (120–180 s). Note that at each step CO is transiently decreased, but within about 10 s it is increased to a new steady-state level. Similarly, SV and AP are increased. AtP pulse is increased. After preload is returned to 6 mm Hg, AP, AtP, and VV return to initial conditions level. CO is transiently increased but within about 15 s it also returns to the initial condition level. (b) The P-V loop diagram in conditions above. Note that, if preload is increased from 6 mm Hg to 8 mm Hg, ESVV is about 40 mL, while EDVV is increased from 117 mL to about 158 mL. The EF increases from 66% to about 72%. Ventricular work is given in mm Hg·mL and in J.
