Pressure Gradients in the Atria and Pulmonary Veins in Man

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Abstract
During cardiac catheterization, a pressure gradient was found between a distal point in a pulmonary vein and either or both atrial chambers during the major portion of the cardiac cycle in 2 cases of atrial septal defect, in a 3d case wherein an anomalous pulmonary vein drained into the right atrium, and in a 4th in which an anomalous pulmonary vein emptied into the superior vena cava. The magnitude of the gradient between pulmonary vein and right atrium varied from 3 to 5.8 mm. of Hg with an avg. value of 4.2 mm. in the 4 cases studied. Evidence that this gradient could not be entirely due to an end pressure or Pitot effect was obtained from study of a model in which the end pressure effect was shown to be 0.5-0.8 mm. of Hg at the same calculated flow velocities. It is suggested that this pressure gradient is a result of the pressure transmitted by the right ventricle through the pulmonary circulation, and is an important factor in the left-to-right shunt observed at rest during quiet breathing in uncomplicated cases of atrial septal defect.