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Figure 3 Hemodynamic data in a model of aortic stenosis were obtained using a dual micromanometer catheter and a transit time flow probe. (A) The simultaneous instantaneous electrocardiogram, aortic and left ventricular (LV) pressures, transaortic volume flow (Q), and aortic pressure gradient (P) are shown. During late ejection P is negative. (B) The phase diagram of P-Q for this cardiac cycle demonstrates the nonlinearity and time dependence of the P-Q relationship. EKG = electrocardiogram. From Bermejo et al. (15), with permission.