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Figure 1 (A) Pressure volume loops used to derive ventricular end systolic chamber stiffness (E_es) and end diastolic chamber stiffness (E_d). Multiple cardiac cycles measured at different levels of filling are recorded. The slope of the relation linking the upper left-hand corner of these beats (end systole) is E_es. The slope of the relation linking late diastolic points from these beats is E_d. (B) Relation between aortic arterial pulse pressure and the pulse pressure estimated from the ventricular pressure volume loop. For the loop, the pulse pressure is given by the difference between the pressure at the onset of ejection and the peak pressure (PP_LV), and it somewhat underestimates the measured arterial pulse pressure (PP_ao). However, PP_LV is highly correlated with PP_ao among individuals. (C) shows data from a separate group of 25 patients in which both ventricular pressure volume and aortic pressure data were recorded. This regression was r = 0.91, p < 0.0001 (SEE = 8 mm Hg), and this relation was then used to predict PP_ao from PP_LV.