Fig. 1. Schematic drawing of a pressure–volume loop, end-systolic pressure–volume relationship (with a slope of end-systolic elastance [Ees]), arterial pressure–volume relationship (with a negative slope of effective arterial elastance [Ea]), end-systolic pressure (Pes), ventricular pressure at which the ventricle begins to eject (Pad), and putative isovolumic pressure (Pmax) (left ). Also shown are bilinearly approximated time-varying elastance curve, E(t), slope ratio (k = tanθ2/tanθ1), pre-ejection period (PEP), and ejection time (ET) (right ). The horizontal dashed lines indicate the proportionality of elastance and pressure for a constant volume. See text for details.