The Cardiohemodynamic Effects of Venous Congestion of the Legs or of Phlebotomy in Patients With and Without Congestive Heart Failure 1

The purpose of this study was to clarify the cardiohemodynamic responses to acute reduction in the effective circulating blood volume in man. McMichael and Sharpey-Schafer found that the cardiac output in normal subjects fell during venous congestion of the extremities (1). They attributed this reduction in cardiac output to a decrease in the right atrial pressure. Their observation that right atrial pressure usually falls during such acute reductions in the effective circulating blood volume was confirmed by Warren, Brannon, Stead, and Merrill (2), but these latter workers did not usually find an associated decrease in cardiac output. They therefore suggested that the cardiac output response is independent of changes in right atrial pressure, at least within physiological limits. However, observations by Howarth, McMichael, and SharpeySchafer (3) on the effects of phlebotomy and of venous congestion of the extremities in patients with congestive heart failure supported the concept that the level of right atrial pressure is an important factor in determining cardiac output. The studies reported herewith differ in certain aspects from all those just mentioned.