[Role of digitalis glycosides in the treatment of cardiac failure]. / Place des digitaliques dans le traitement de l'insuffisance cardiaque.

While no doubt has ever been cast on the usefulness of digitalis in cardiac failure with atrial fibrillation and a fast ventricular rate, they are periodically brought into question regarding chronic cardiac failure in sinus rhythm. While they have not been supplanted by new positive inotropic agents, they are in competition with converting enzyme inhibitors. Recent therapeutic trials have shown that digitalis preparations, alone or in association with converting enzyme inhibitors, have beneficial effects on symptoms and exercise duration in patients with symptomatic impaired left ventricular systolic function. While the effects of digitalis preparations on mortality remain unknown, a large North American study should soon provide an answer to this question.

Digitalis, a defibrillatory drug.

Digitalis glycosides have an antiarrhythmic effect in atrial fibrillation, as defibrillatory drugs. These drugs could be classified in a group of antiarrhythmic drugs close to the ventricular defibrillating drugs recently proposed. The reasons for this opinion are shown in this work.

An "autonomic" classification of antiarrhythmic drugs.

An alternative classification schema for antiarrhythmic drugs is proposed based primarily on the autonomic "side effects" of these drugs in addition to their electrophysiologic actions. In this new schema, Class I (local anesthetics) is subdivided into 1A (quinidine-like agents with cholinergic blocking actions) and 1B (agents such as lidocaine without autonomic activity). Class II comprises the digitalis glycosides which have vagotonic effects. Class III contains drugs with antiadrenergic activity, subdivided into IIIA (beta-blockers such as propranolol), IIIB (norepinephrine-release inhibitors such as bretylium) and IIIC (non-specific adrenergic blockers such as amiodarone). Class IV includes the calcium channel blockers. Thus, with the exception of Classes IB and IV, all antiarrhythmics possess important autonomic properties. A possible link between autonomic and electrophysiologic effects is suggested by this schema. Classical pharmacologic theory separates the anticholinergic and membrane-active effects of quinidine-like (1A) drugs. An alternative theory is that the anticholinergic effects of 1A agents are germane to the antiarrhythmic actions of drugs in this class. A unifying hypothesis is that the acetylcholine receptor or a site with similar structure may participate directly in the binding of 1A drugs to the ventricular conduction system. This hypothesis is supported by: 1) the anti-muscarinic effects of all Class 1A agents; 2) previous data showing binding of these agents to atrial cholinergic receptors; 3) prominent His-Purkinje cholinergic innervation; 4) striking structural similarity between cocaine, the prototypical membrane anesthetic, and atropine; and 5) quinidine-like effects of tricyclic antidepressants and phenothiazines which have cholinergic properties. Additional ramifications of this autonomic classification are discussed.