Aorta, pressure curves

FIGURE 8.5 Ventricular and root aortic pressures (solid curves, left ordinate) and ventricular outflow (dashed curve, right ordinate) computed using the model of Equation 8.8 for a normal canine left ventricle pumping into a normal arterial circulation. The topmost solid curve corresponds to a clamped aorta (isovolumic). This ventricle has initial volume of 45 ml and pumps out 30 ml, for an ejection fraction of 66%, about normal. 

Velocity varies across the vessel due to viscous and inertial effects as mentioned earher. The velocities in Figure 56.3 were measured at one point in the artery. Velocity profiles are complex because the flow is pulsatile and vessels are elastic, curved, and tapered. Profiles measured in the thoracic aorta of a dog at normal arterial pressure and cardiac output are shown in Figure 56.4. Backflow occurs during diastole, and profiles are flattened even during peak systohc flow. The shape of the profiles varies considerably with mean aortic pressure and cardiac output [Ling et al., 1973]. 

Fig. 1 Ensemble-averaged original signals (ECG, Plv, Pao, AZ) and the calculated (dPLv/dt, d PAc/dP, d Z/dP) signals. The pressure in the LV and aorta was recorded with the same catheter-tip manometer during different cardiac cycles with similar durations. For convenient presentation of the related blood volume changes, AZ curves and their derivatives, are inverted, i.e., the positive deflections of the curves correspond to the decrease in impedance.

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