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Figure 2 (A) Invasive pressure-volume loops and analysis used to derive (E_es). Multiple beats are recorded before and during transient obstruction of the inferior vena cava. (B) Noninvasive assessment of (E_es(sb)) displayed in pressure-volume plane from the same example. Two sets of (volume, pressure) data points are measured and used to predict E_es(sb). The dotted area represents a schematic pressure-volume loop based on these points. From these data, E_es(sb) is estimated using equation 4. (C) Example of pressure-volume data at rest and after dobutamine stimulation. (D) Corresponding noninvasive E_es(sb) for the same example displayed in C. Darkened areas are schematic loops from the two points. Pd = diastolic arterial pressure at the onset of ejection; Pes = left ventricular end-systolic pressure; SV = stroke volume; Ved = left ventricular end-diastolic pressure; Ves = left ventricular end-systolic volume.