Effects of low dose enoximone for chronic congestive heart failure

Oral treatment with enoximone in patients referred for cardiac transplantation

A prospective, uncontrolled, open ended study was performed to assess the effect of treatment with oral enoximone therapy in patients with end stage cardiac failure unresponsive to conventional treatment. The primary objective of treatment, hospital discharge, was achieved in 27 of 35 patients studied. Baseline haemodynamics were obtained in 21 patients. The mean cardiac index of patients who improved by one or more grades (New York Heart Association) was 2.1 litres/min while, in those who had less improvement, the mean cardiac index was 1.5 l/min (P less than 0.01). The average duration of treatment was 13 weeks, treatment being discontinued in 25 patients within twelve weeks. The main reasons for discontinuation were side effects (n = 11), and progressive cardiac failure (n = 7). The prognosis of patients in whom therapy was discontinued was very poor, only 5 of 28 being discharged from hospital without cardiac transplantation. Sudden death was uncommon (1/13), and Holter monitoring in 17 showed no aggravation of ventricular arrhythmias. Oral treatment with enoximone is a useful adjunct in the treatment of end stage cardiac failure.

Medical management of chronic heart failure: inotropic, vasodilator, or inodilator drugs?

On the basis of pathophysiologic mechanisms, the medical therapy of today for chronic heart failure is reviewed. The advantages and disadvantages of the vasodilator drugs and the inotropic drugs are presented. Finally, the therapeutic value of the inodilator drugs, which combine the central myocardial effects of positive inotropic agents with those of peripheral vasodilators, is discussed. In particular, the orally available dopaminergic agents, such as ibopamine, which interact with beta-receptors in the heart (mediating a positive inotropic effect) as well as with dopaminergic receptors in the peripheral vessels (mediating a systemic vasodilator effect) and in the kidneys (potentiating the natriuretic effect of diuresis), seem to be an advancement in the modern medical therapy of chronic heart failure. Data are shown during long-term treatment with ibopamine, in which the sustained clinical benefit in heart failure was not diminished, despite a decrease of the adrenergic receptors in blood cells. Dopamine plasma concentration was permanently normalized during long-term treatment. The discrepancy between clinical improvement and the measured adrenergic downregulation may be due to the interference of the inodilator with neurohormonal systems at multiple sites and is probably independent of receptor activation. It is suggested that the biosynthesis of noradrenaline is improved by increasing intracellular dopamine transport.

Acute and long-term hemodynamic response to low-dose enoximone in refractory heart failure

Enoximone possesses both positive inotropic and vasodilatory properties. In heart failure, doses varying between 3 mg/kg and 6 mg/kg produce a beneficial acute hemodynamic response but have been associated with significant side effects. Little is known about the long-term hemodynamic efficacy of this agent. To assess whether a lower dose of enoximone could produce both acute and long-term hemodynamic benefits and be better tolerated, 15 patients with refractory heart failure were given enoximone 100 mg every 8 hours (mean dose, 1.7 mg/kg). The cardiac index, pulmonary capillary wedge pressure, pulmonary artery pressure, right atrial pressure, systemic vascular resistance, pulmonary vascular resistance, and stroke volume index all improved significantly during the first 24 hours. The systemic blood pressure and heart rate did not alter appreciably during this period. Five of six patients remaining on therapy at 6 months had a follow-up hemodynamic study. Sustained improvement was seen in the cardiac index, pulmonary capillary wedge pressure, and pulmonary artery pressure when compared to baseline (all p less than 0.05). A satisfactory trend, which did not reach statistical significance, was noted in the right atrial pressure (p = 0.09) and stroke volume index (p = 0.06). Diarrhea occurred in one patient. These findings indicate that enoximone has a beneficial acute and long-term hemodynamic effect at a low dose that is clinically well tolerated.

Controlled and uncontrolled studies of phosphodiesterase III inhibitors in contemporary cardiovascular medicine

The phosphodiesterase inhibitors are new inotrope vasodilators that have beneficial hemodynamic effects in patients with congestive heart failure (CHF). The most extensively studied agents are milrinone and enoximone. Both drugs have clearly been shown in numerous studies to improve hemodynamics in patients with CHF when given acutely by either the intravenous or oral route. In long-term studies, milrinone has been shown to have sustained beneficial hemodynamic effects during active treatment. Effects on exercise tolerance have been less clear-cut in several uncontrolled trials, but a recent large-scale randomized trial does show sustained improvement in exercise performance. When milrinone is withdrawn after long-term therapy, some studies show worsened cardiac performance; the exact cause remains ill-defined, but could be due to deterioration of baseline ventricular function or to "rebound." Both uncontrolled studies and a large recently reported randomized trial show that the hemodynamic response to readministration of milrinone after withdrawal is well-preserved, i.e., no tolerance is observed. Studies of enoximone show that its acute hemodynamic effects are similar to those of milrinone, but its long-term efficacy, using both hemodynamic and exercise end points, is less clear-cut, and no large-scale randomized trials of enoximone therapy have yet been reported. The studies of both these agents performed thus far indicate that the phosphodiesterase inhibitors have considerable promise for both acute and long-term treatment of patients with CHF.

Vasodilator and inotropic drugs for the treatment of chronic heart failure: distinguishing hype from hope

During the past 10 years, more than 80 orally active vasodilator and inotropic agents have been tested in the clinical setting to evaluate their potential utility in the treatment of chronic heart failure. Although the initial reports of all of these drugs suggested that each represented a major therapeutic advance, only three agents--digoxin, captopril and enalapril--have produced consistent long-term hemodynamic and clinical benefits in these severely ill patients. Most of the other drugs that have been tested have not (to date) distinguished themselves from placebo therapy in large-scale, controlled trials, even though these agents produce hemodynamic effects that closely resemble those seen with digitalis and the converting-enzyme inhibitors. These observations suggest that the hemodynamic derangements that characteristically accompany the development of left ventricular dysfunction cannot be considered to be the most important pathophysiologic abnormality in chronic heart failure. Although cardiac contractility is usually depressed in this disease, positive inotropic agents do not consistently improve the clinical status of these patients. Similarly, although the systemic vessels are usually markedly constricted, drugs that ameliorate this vasoconstriction do not consistently relieve symptoms, enhance exercise capacity or prolong life. Hence, correction of the central hemodynamic abnormalities seen in heart failure may not necessarily provide a rational basis for drug development, and future advances in therapy are likely to evolve only by attempting to understand and modify the basic physiologic derangements in this disorder.