Newer oral inotropic agents: phosphodiesterase inhibitors.

Phosphodiesterase inhibitors are potent inotropic and vasodilator agents that have attracted intense investigative interest in recent years as a potential treatment for congestive heart failure resulting from left ventricular dysfunction. These agents increase intracellular Ca availability by increasing cyclic AMP levels and improve cardiac performance by (a) enhancing contractility, (b) reducing left ventricular afterload, and (c) improving diastolic compliance of the left ventricle. Increased cardiac work leads to an increase in myocardial oxygen consumption, but increased coronary flow prevents an imbalance of myocardial oxygen supply and demand. Available data indicate that renal perfusion may increase as a result of the increase in cardiac output, but much of the decrease in systemic vascular resistance apparently occurs in musculoskeletal tissue. The hemodynamic improvements associated with these agents are well documented, but whether they actually affect the prognosis remains uncertain.