Left ventricular end-systolic elastance is incorrectly estimated by the use of stepwise afterload variations in conscious, unsedated, autonomically intact dogs.

BACKGROUNDEnd-systolic elastance (Ees), the slope parameter of the end-systolic pressure (ESP)-volume (ESV) relation (ESPVR), is usually estimated in patients by producing stepwise, steady-state pharmacological afterload variations and collecting one ESP-ESV point from each step. The ESPVR is then constructed by fitting a linear equation to these points. In sedated, autonomically blocked dogs, it has been shown that when one point from control, one point from a state of increased afterload, and one point from a state of decreased afterload are used, the resulting Ees incorrectly estimates true Ees, defined as the slope of the ESPVR obtained by transient vena caval occlusion. We investigated if this was also the case in unsedated, autonomically intact dogs when the points used belonged to steady states of progressively decreasing or progressively increasing afterload pressure.METHODS AND RESULTSIn 10 conscious dogs instrumented with left ventricular (LV) endocardial sonomicrometers to measure LV volume, a ...