Beta-adrenergic blockade in congestive heart failure: answering the old questions

Cardiac and hemodynamic effects of the sinus node inhibitor tedisamil dihydrochloride in patients with congestive heart failure due to dilated cardiomyopathy

Clinical and experimental investigations have demonstrated an inverse relation between heart rate and myocardial performance in patients with congestive heart failure. Accordingly, this study was designed to investigate the hemodynamic effect of the novel bradycardic compound tedisamil in patients with heart failure. We hypothesized that tedisamil would reduce heart rate and thereby improve hemodynamic parameters of failing hearts with an inverse force-frequency relation. Tedisamil was administered intravenously in nine patients with dilated cardiomyopathy (NYHA II-III). Hemodynamic measurements by right heart catheterization were carried out at time points -30, 10, 20 min, 1, 2, 4, and 6 h. Tedisamil decreased heart rate significantly from 84 +/- 6 beats/min to 73 +/- 4 beats/min (at 10 min; p < 0.05). Stroke volume index remained unchanged, and cardiac index tended to decrease transiently. Mean blood pressure increased from 98 +/- 5 to 104 +/- 6 mm Hg (p < 0.05) because of an increase in systemic vascular resistance from 1,619 +/- 145 to 2,079 +/- 198 dyn x s x cm(-5) (at 20 min; p < 0.05). Diastolic pulmonary pressure and pulmonary vascular resistance showed similar changes. Pulmonary capillary wedge pressure increased from 12 +/- 3 to 16 +/- 4 mm Hg (at 20 min; p < 0.05). Although tedisamil resulted in a significant heart-rate reduction, this was not associated with an improvement of hemodynamics. This may be due to increased afterload of the left and right ventricle. In these patients, tedisamil increased vascular resistance, which is unwanted in the treatment of congestive heart failure.

Use of beta-adrenoceptor blockers in patients with congestive heart failure

The beneficial effect of chronic beta-blockade in patients with congestive heart failure has been repeatedly shown since its introduction into treatment for this condition in 1975. Still this kind of therapy remains controversial, it is sometimes regarded as a therapeutic paradox, and its use is mainly limited to specialist centers. Various favorable effects of beta-blockers in patients with heart failure due to idiopathic dilated cardiomyopathy and ischemic heart disease have been demonstrated, the principal among them being reduction in energy requirements and ischemia, antiarrhythmogenic effect, improvement of diastolic function, protection of myocytes against catecholamine overload, centrally mediated increase in vagal tone, upregulation of beta-adrenergic receptors, and possible blockade of autoantibodies against beta 1-receptors. Although most of the studies used metoprolol, these effects may be relevant to certain other beta-blockers. Despite very solid pathophysiological and pharmacological rationales for the use of beta-blockade, a major obstacle for a general acceptance of this therapeutic concept is the striking contrast between hemodynamic changes during the acute effect and long-term treatment. When titrated carefully from very low doses and used with a true commitment to long-term treatment, beta-blockers have been shown to prevent further deterioration of heart failure and to improve hemodynamics, exercise tolerance, quality of life, and prognosis.

Beneficial effects of metoprolol in heart failure associated with coronary artery disease: a randomized trial

OBJECTIVES

This clinical trial was performed to determine the safety and clinical impact of titrated metoprolol therapy in patients with heart failure, documented coronary artery disease and a low ejection fraction.

BACKGROUND

Despite known cardiodepressant effects, long-term use of beta-adrenergic antagonists appears to be beneficial in patients with idiopathic dilated cardiomyopathy. However, this therapy has not been critically evaluated in patients with heart failure and coronary artery disease.

METHODS

In 50 patients with heart failure, known coronary artery disease and an ejection fraction < or = 0.40, we examined the impact of metoprolol therapy in a 6-month double-blind, placebo-controlled randomized trial, assessing the frequency of heart failure exacerbations and changes in symptoms (New York Heart Association functional class), ejection fraction and exercise duration. Placebo-treated patients who completed 6-month follow-up studies then underwent a trial with metoprolol therapy (crossover group).

RESULTS

Metoprolol was titrated to a mean maximal dose of 87 mg/day (range 25 to 100) without serious adverse reactions. During double-blind therapy, use of a beta-blocker was associated with a significant reduction in the number of hospital admissions (4% vs. 32%, p < 0.05), overall improved functional class (p = 0.02), increased ejection fraction (4 +/- 7% [mean +/- SD] compared with 0 +/- 6%, p < 0.05) and a greater increase in exercise duration (193 +/- 276 vs. 38 +/- 213 s with placebo, p < 0.01). Crossover outcome paralleled the favorable impact seen during randomized metoprolol therapy.

CONCLUSIONS

Cautious use of titrated metoprolol appears to be safe and beneficial when added to standard heart failure therapy in patients with dilated cardiomyopathy associated with coronary artery disease.

Differentiating systolic from diastolic heart failure: pathophysiologic and therapeutic considerations

PURPOSE

To compare and contrast the pathophysiology and therapy of heart failure with normal and abnormal systolic ventricular function.

METHODS

Review of basic pathophysiologic mechanisms, clinical data, and therapeutic trials.

CONCLUSIONS

The clinical features of heart failure may be similar regardless of whether ventricular function is normal or abnormal. However, the pathophysiologic mechanisms leading to heart failure with normal ventricular function differ considerably from those producing heart failure with abnormal systolic function. The key problems in heart failure with abnormal systolic function involve impaired contractility, neuroendocrine activation, increased intracardiac volume and pressure, and enhanced sensitivity to change in afterload. With normal systolic function, the key problem is an abnormal diastolic pressure/volume relationship, which may be due to a variety of active and passive processes affecting diastole. Assessing left ventricular systolic function is crucial before initiating therapy in a patient with heart failure, since treatment for systolic dysfunction may be ineffective or even counterproductive if symptoms are due to abnormal diastolic properties with preserved systolic function.