The cardiovascular effects of digitalis in normal man

Abstract

Studies are reported that were designed to elucidate the actions of digitalis on the force of contraction of the normal human heart and on the peripheral circulation in intact, unanesthetized man. The drug, administered in clinically important doses to normal sub;ects, resulted in a greater rate of rise of intraventricular pressure, in a shorter duration of time from the onset of contraction to peak myocardial tension, and in an improvement in the force‐velocity relationship of the contractile element of cardiac muscle. These findings indicate that the glycoside stimulates the contractile force of the normal heart. In normal subjects, digitalis resulted in direct arterial and venoconstriction of the systemic beds. In patients with heart failure, digitalis stimulated the contractile state of the heart, but, in contrast to the normal subjects, the glycoside elevated the reduced forearm blood flow and lowered the elevated forearm vascular resistance and venous tone. It was postulated that this vasodilatory action was indirect, that it overrode the direct stimulating effect on the peripheral vascular beds, and resulted from the augmentation of the lowered cardiac output in the heart failure state. Thus, the effects of the glycoside on the peripheral vasculature were dependent on the circulatory state of the patient at the time the drug was administered. These observations indicate that the digitalis glycosides have both cardiac and extracardiac actions and that these actions occur in normal subjects as well as in patients with congestive heart failure.

Assessment of Contractility Following Proscillaridin A in Dog Hearts both Normal and Pretreated with Propranolol

“…The present investigation shows in accordance with other authors [8,12] that there are no fundamen tal differences of the glycoside effect in normal and failing hearts.…”

Digitalis Induced Haemodynamic Changes in Patients with Vascular Disease during a Preoperative Exercise Test

“…The principal effects of digitalization on the resting patients were a significant decrease in PC W P together with increase of approximately 15% in LVSWI and VO, and a minor, but signifi-cant, increase in MAP. The latter was presumably due to the effect of digoxin on the systemic vascular resistance (Mason 1966;Garan et at. 1973) which increased but not significantly.…”

Local and systemic effects of Na+/K+ ATPase inhibition

“…This effect appears to be independent of the vascular bed studied [9]. Pretreatment with the antiadrenergic agent guanethidine did not affect the vasoconstriction, suggesting that the constriction was direct and not mediated through the sympathetic nervous system [10].…”

“…In normal subjects, acute administration of ouabain results in arterial and venous constriction, whereas, in patients with heart failure, the drug reduces the elevated forearm vascular resistance [10]. This inhibition of reflex vasoconstriction appears to override the direct vasoconstrictive action of the compound on the peripheral vascular bed that is present in normal subjects.…”