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The pulmonary venous systolic flow pulse—its origin and relationship to left atrial pressure

^a St. Paul’s Hospital, Vancouver, British Columbia, Canada
^* Rikshospitalet, Oslo, Norway

View larger version (27K): [in a new window]   Figure 1 Schematic presentation of principles of wave intensity analysis: (A) Fluid inside a tube is set into motion by pushing an upstream piston by a constant force. The graph to the right displays velocity (U), pressure (P) and the product of increments in pressure (dP) and velocity (dU); i.e., dP x dU. Because there is a transient rise both in fluid pressure (+dP) and in velocity (+dU), dP x dU is positive. The +dP x dU indicates a forward-going wave and the +dP indicates a compression wave, thus a forward-going compression wave. (B) Fluid is set into motion by pulling a downstream piston. This causes a decrease in pressure (–dP), but an increase in velocity (+dU), resulting in a negative dP x dU. The –dP x dU indicates a backward-going wave, the –dP indicates an expansion wave, thus a backward-going expansion wave. The components of each of the four possible waves are outlined in Table 1.

View larger version (23K): [in a new window]   Figure 2 Representative traces showing pulmonary venous pressure and flow velocities by ultrasound transit time and by intravascular electromagnetic velocity sensor. Qualitatively similar velocity traces were obtained by either method. The figure shows the four pulmonary venous flow pulses, the A-wave during atrial contraction, the S1 and S2 waves during ventricular systole, and the D-wave early diastole. A = flow purse during atrial systole; D (diastole) = early diastolic flow pulse; S1 = early systolic flow pulse; S2 = late systolic flow pulse.

View larger version (17K): [in a new window]   Figure 3 The figure shows the four pulmonary venous flow pulses, the A-wave during atrial contraction, the S1 and S2 waves during ventricular systole and the D-wave during early diastole. The numbers indicate four major waves in the dPdU trace. During atrial contraction the rise in pressure and decrease in velocity cause a negative dPdU (1), indicating a net backward-going compression wave. During atrial relaxation and during early ventricular systole corresponding to S1, PV pressure is falling and velocity is rising. Therefore dPdU is negative (2), indicating a backward-going expansion wave. Later in systole, corresponding to S2, PV pressure is rising and velocity is rising, and therefore dPdU is positive (3). This indicates a net forward-going compression wave. During early diastole, PV pressure is falling and velocity is rising and dPdU is negative (4), indicating a net backward-going expansion wave. dPdU = product of increments in pressure (dP) and velocity (dU) over 5 ms intervals; PV = pulmonary vein. Other abbreviations as in Figure 2.

View larger version (30K): [in a new window]   Figure 4 The effect of volume loading on pulmonary vein flow pattern and dPdU. Abbreviations as in Figures 2 and 3.