Digitalis use for its inotropic effect in cardiac failure lacks measurable therapeutic objectives, making dosages uncertain and benefits difficult to detect compared to its dromotropic use.
The clinical application of digitalis for heart failure is complicated by the inability to set measurable therapeutic objectives and uncertain dosing, unlike its use for rate control in atrial fibrillation.
Digitalis has two clinically relevant actions: the dromotropic action, which slows transmission of impulses through the conducting system, and the inotropic action, which strengthens cardiac contractility. The former serves as the basis for the use of digitalis in controlling ventricular rate in atrial fibrillation and for its use as an antiarrhythmic agent. The latter constitutes the basis for its use in cardiac failure. When digitalis is used for its dromotropic action, a measurable therapeutic objective is established in each case and the drug is administered in adequate (broadly variable) dosages until the objective is attained. In a small fraction of patients, toxic reactions develop before the objective can be accomplished, in which case alternative treatment must be used. In contrast, when digitalis is used for its inotropic effect, measurable therapeutic objectives cannot be set, dosages are uncertain, and benefits are difficult to detect. It is therefore not surprising that
Arthur Selzer (Thu,) conducted a review in Cardiac Failure. Digitalis was evaluated. Digitalis use for its inotropic effect in cardiac failure lacks measurable therapeutic objectives, making dosages uncertain and benefits difficult to detect compared to its dromotropic use.