The Effect of Digitalis on the Venous Pressure of Normal Individuals

Abstract

That the admiinistration of digitalis in heart failure causes an increase in cardiac output (per minute and per beat) and a fall in venous pressure is well known (1). It is also well establislhed that the exhibition of digitalis to normiial meni and dogs results in a decrease(l output (2, 3, 4, 5, 6, Ini )fl:.l Stewart and Cohn (7) found a marked fall in venous pressure in one normiial subject after oral administration of digitan, using the Mioritz-Tabora (20) technlique of venous pressure determination. Simllultaneously in the first subject, and in two other subjects, tlhey found no constanit change wlhen a less accurate miiethod was used (that of allowing b)loo10 to rise in a dry tube).As Eyster (14) pointed out, it is impossible to deternmine whether the changes produced by digitalis in output are cardiac or extra-cardiac in origin unless the changes in venous pressure are known. In decomlipensated lhearts it is agreed (5, 7) that the increased output is due largely to the chalnge in ventricular tone, any peripheral action of digitalis being relatively uniniiportant (although Wollheimi (15) and others (16,17) credit the reduction in effective (systemiiic) blood volume with miiore imiiportance in relieving congestive failure).Opinion differs widely, however, regarding the origin of the digitalis effects in the normiial organiismi. Cohn and his coworkers (7,18,19), unable to demiionstrate venous pressure changes, hold that the decreased car-(liac outtput is due to dimiinlished ventricular filling caused l) increased tone 847

THE EFFECT OF DIGOXIN ON THE RIGHT VENTRICULAR PRESSURE IN HYPERTENSIVE AND ISCHAeMIC HEART FAILURE

“…Both groups, however, observed a few cases in which the right atrial pressure fell without any significant change in cardiac output. This pressurereducing action was frequent enough to suggest that it might play a primary role; and this view was supported by (1) simultaneous observations that venesection might cause an increase in cardiac output of the same order as that produced by digoxin, and by (2) published work suggesting that digitalis reduced venous pressure in normal animals (Dock and Tainter, 1930) and in man (Rytand, 1933). This conception had the additional attraction of offering a possible explanation for some of the failures of digitalis therapy in certain instances of " high output heart failure " in which increased venous pressure was perhaps compensatory in nature.…”

A COMPARISON OF THE DIRECT PERIPHERAL ACTIONS UPON SYSTEMIC VENOUS PRESSURE OF k‐STROPHANTHOSID, DIGOXIN AND OUABAIN

“…On the other hand, Dock and Tainter [1930], Tainter and Dock [1930], and Katz, Rodbard, Friend and Rottersman [1938] found that therapeutic doses of digitalis in normal dogs caused a lowering of venous pressure. Rytand [1933] studied 8 normal human subjects and concluded that digitalis decreased venous pressure; the fall was so slight, however, that its significance was difficult to evaluate. McMichael and Sharpey-Schafer [1944] found that intravenous injection of therapeutic doses of digoxin lowered the mean right atrial pressure of 3 normal human subjects.…”