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Figure 8 Top panel: Relationship between single-beat M_w (SBM_w) estimates and multibeat M_w measurements in Group II. Multibeat data were obtained during vena caval occlusions performed before and during aortic constriction and calcium infusion. The relationships were not significantly different from the line of identity, whether based on individual measured k values (SBM_w,measured) or calculated assuming k to be constant at 0.7 (SBM_w,calculated). Bottom panel: Corresponding relationships between single-beat elastance (SBE_es) or PWR_max/EDV² and multibeat elastance (E_es). Both single-beat indexes correlated very poorly with multibeat E_es. M_w = slope of the PRSW relationship; PWR_max/EDV² = maximum left ventricular power divided by the square of end-diastolic volume.