STUDY OF SIMULTANEOUS RIGHT AND LEFT ATRIAL PRESSURE PULSES UNDER NORMAL AND EXPERIMENTALLY ALTERED CONDITIONS

Publisher Website
Google Scholar
Abstract
Right and left atrial pressure pulses were simultaneously recorded in 30 open-chest dogs. No consistent syn-chronicity or asynchronicity between comparable events in the 2 atria was observed. Left arterial pressure was usually greater than right during the entire atrial cycle, but the direction of the pressure gradient across the interatrial septum might reverse during a cycle. The pressure relation between the atria was also studied under various circulatory conditions. Rapid blood or saline infusion always increased left atrial pressure more than right, as did central vagus stimulation. Hemorrhage decreased left atrial pressure more than right. The existence of a pressure gradient and the variations thereof was due to a difference between the volume elasticity characteristics of the atria, the left atrio-venous system being less distensible than the right. Changes in atrial inflow were more correctly inferred from changes in atrial pressure just at the beginning or end of ventricular filling. The atrial volume elasticity coef. was greatest at these points since the A-V valves were closed and a relatively small change in inflow would produce a relatively large change of atrial pressure. The greater volume elasticity coef. of the left atriovenous system accounts for the greater left atrial pressures found in cases with interatrial septal defects, and indicates that the elevated left atrial pressure is not entirely pathological. Furthermore, the more restricted dis-tensibility of the left atrium accounts for the failure of infusions to reverse the direction of blood flow through the shunt.