Ventricular response to a pressure load. Left ventricular function curves in intact animal.

• The normal left ventricular response to progressive proximal aortic obstruction has three phases: (1) a phase of complete compensation in which, following transitory elevations of end-diastolic ventricular pressure (EDVT) and end-diastolic ventricular volume (EDVV), the peak ventricular pressure (PVP) is increased and cardiac output is maintained though end-diastolic ventricular pressure and volume return almost to normal"; (2) an as yet poorly defined phase of partial compensation in which peak ventricular pressure is further augmented and cardiac output is usually slightly diminished while end-diastolic ventricular pressure and volume are increased2' ' •"'•"; and (3) a, phase of decompensation in which peak ventricular pressure reaches a maximum and then decreases as cardiac output sharply falls and end-diastolic ventricular pressure and volume progressively rise. During the phase of partial compensation, the relation of end-diastolic ventricular pressure to the peak ventricular pressure might be expressed in the form of a ventricular "pressure-function" curve, analogous to the more usual "flow-function" curve which relates end-diastolic ventricular pressure to ventricular stroke volume (or stroke work) under conditions of a changing inflow load.