Comparative Effects of Volume Loading on Pulmonary Venous Flow in Dogs with Normal Heart and with Myocardial Ischemia

Abstract

The influences of cardiac loading conditions and left ventricular performance on pulmonary venous flow are poorly understood. The authors studied the effects of volume loading on the pattern of pulmonary venous flow in normal and ischemic hearts. Thirteen anesthetized dogs were equipped with a transit-time ultrasonic flow probe around the left upper pulmonary vein. In 6 of the dogs, the left anterior descending artery was ligated to induce myocardial ischemia. The remaining 7 dogs had normal hearts. Heart rate was fixed at 110 beats/minute by right atrial pacing. Dextran was infused from the femoral vein until mean left atrial pressure increased 3 mm Hg above the baseline value in both groups. In normal heart, systolic pulmonary venous flow volume (SI) increased significantly, but early diastolic flow volume (DI) did not show a significant change during volume loading. The ratio of SI/DI increased significantly (1.12 +/- 0.34 vs 2.11 +/- 0.49, P < 0.05). After ligation of the left anterior descending artery, the SI and DI decreased significantly. The ratio of SI/DI did not show a significant change (0.88 +/- 0.32 vs 0.87 +/- 0.30, ns). In dogs with myocardial ischemia, volume loading caused increases in the SI and DI. However, no significant change was observed in the ratio of SI/DI (0.87 +/- 0.30 vs 0.97 +/- 0.36, ns). These findings demonstrate that left ventricular performance influences the alteration in pulmonary venous flow pattern that is caused by systemic volume loading.

Relationships between velocities of pulmonary venous flow and plasma concentrations of atrial natriuretic peptide in healthy dogs

“…Analysis of our data revealed that volume overload caused an increase in the systolic PVF velocity and a marked increase in the S:D ratio, which was closely correlated with PCWP and plasma ANP concentration. In other studies, 5,6,23 investigators reported that systolic PVF velocity increases following volume overloading but that diastolic PVF velocity remains unchanged. In addition, the S:D ratio is strongly correlated with increases in left atrial pressure.…”

“…3,4 The PVF velocity recordings, which consist of forward flows (S wave [reservoir function] and D wave [conduit function]) and retrograde flows (AR wave [booster function]), have been considered in clinical settings. [3][4][5][6][7][8] The PVF velocities are influenced by hemodynamic pressure gradients between the pulmonary vein and left atrium, which has been measured by use of transesophageal echocardiography in sedated dogs. 7 In another study, 1 investigators reported that the difference in the duration of pulmonary venous and mitral flow during atrial contraction is related to the…”

Assessing Diastolic Function with Doppler Echocardiography Using a Novel Index: Ratio of the Transmitral Early Diastolic Velocity to Pulmonary Diastolic Velocity

“…Previous studies have showed that PVF velocity is influenced by the pulmonary venous-left atrial hemodynamic pressure gradient [6]. Similarly, D wave is influenced by hemodynamic changes in the left atrial pressure, created by relaxation of the atrium and ventricle, and rapid transmitral filling of the left ventricle [2,3,5,22,26]. Therefore, the D wave velocity is dependent on the same factors that influence the E wave velocity, such as the left atrial pressure and LV relaxation [5,22,26].…”

“…After mitral valve opening, the E wave corresponds to the period during early LV diastole when the LV pressure decreases as a result of ventricular relaxation, which allows the left atrium to fill the left ventricle. At this time, the left atrial pressure drops, as the blood flows from the left atrium into the left ventricle until the pressures equalize; this allows the pulmonary veins to refill the left atrium as indicated by the D wave, i.e., conduit function [2,3,5,6,22,26].…”

“…During early ventricular diastole, E wave velocity is influenced by the left ventricle-left atrial hemodynamic pressure gradient [5,6,22,26]. Similarly, D wave velocity is influenced by the pulmonary venous-left atrial hemodynamic pressure gradient [2,3,5,22,26]. Since it is known that D wave velocity is influenced by rapid transmitral filling of the left ventricle, i.e., E wave, in healthy dogs [2,5,22], it is thought that conduit function of atrium support and regulate ventricular diastolic function.…”