New positive inotropic drugs for the treatment of congestive heart failure

Positive inotropic agents can stimulate the severely depressed myocardium in late stages of heart failure. However, symptomatic benefits are only gained by improvement in the deranged peripheral circulation, which produces symptoms and limitations. In augmenting cardiac output and reducing filling pressures, the effects of positive inotropic agents and vasodilators are similar and additive, and the "contractile reserve of the heart" in response to inotropic stimulation may limit efficacy of these agents. Although symptomatic benefits occur in patients with severe heart failure after improvement in peripheral blood flow distribution, survival may not be altered, because this appears to be determined more by the amount of myocardial damage and its progression, and neither of these is affected by either inotropic agents or vasodilators. Indeed, in early stages of heart failure, therapy must be redirected toward preventing further myocardial cell loss rather than stimulating pump function.