Flow patterns in cavae, pulmonary artery, pulmonary vein, and aorta in intact dogs

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Abstract
Ultrasonic flow transducers were implanted in dogs and the animals were allowed to recover completely. In the vena cava, flow reversed with atrial systole, and the 2 forward-flow waves were coincident with descent of the atrioventricular valve with ventricular contraction and with the filling phase of ventricular diastole. Pulmonary vein flow was remarkably similar to caval flow, and in the absence of transmitted pulmonary artery pressure pulses, the venous flow patterns are attributed to vis a fronte. Right ventricular ejections begins slightly before and ends shortly after left ventricular ejection, and has a more rounded contour. Inspiration produces 2 major changes in flow patterns: an increased heart rate which shortens the filling time for the ventricles, tending to reduce the stroke volume unless compensated by the enhanced venous return produced by inspiration. The transmission time of this inspiratory surge to the left heart is usually very brief, less than that of 2 heartbeats; effect of respiration on stroke volume; venous flow patterns; venous return; determinants of stroke volume; ventricular suction.

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