Cardiac electrophysiology of adenosine. Basic and clinical concepts.

A denosine is an endogenous nucleoside that has potent electrophysiologic effects.1-4 As an antiarrhythmic agent, adenosine has several unique properties: 1) it is an intermediate metabolite (Figure 1), 2) it has a very short half-life (less than 1.5 seconds), 3) its effects are mediated by specific membrane receptors coupled to guanine nucleotide binding proteins (G proteins), and 4) it has sitespecific actions in the myocardium with important differential effects in supraventricular and ventricular tissue.' Adenosine also has an important role in regulating the myocardial oxygen supply-demand balance. Adenosine achieves this by increasing oxygen supply through coronary vasodilation and by reducing oxygen demand by decreasing myocardial contractility, antagonizing the effects of catecholamines, and depressing automaticity and conduction within the sinus and atrioventricular (AV) nodes.' Recently, the United States Food and Drug Administration approved the use of adenosine for therapy of paroxysmal supraventricular tachycardia (PSVT), the first clinical application of adenosine. The purpose of this review is to present a rational approach for the therapeutic applications of adenosine for cardiac arrhythmias based on an understanding of its cellular and integrative mechanisms of action.