Effect of chronic beta-adrenergic receptor blockade in congestive cardiomyopathy

Catecholamine-responsive adenylate cyclase activity in human endomyocardial biopsies. Individual sensitivity to isoproterenol stimulation and propranolol inhibition

In the present study we have examined adenylate cyclase (AC) activity, the stimulation by isoproterenol and inhibition by propranolol, in endomyocardial biopsies from eleven patients with suspected cardiomyopathy. Biopsies were obtained by heart catheterization from the right endomyocardial surface of the interventricular septum. Three biopsies were taken from each patient (mean weight, 2.1 mg; range, 1.2-4.0 mg). One biopsy was studied by light microscopy. The two other biopsies were homogenized and AC activity in the homogenates was determined in the presence of different concentrations of isoproterenol and isoproterenol (5 micrograms/ml) combined with different concentrations of propranolol. Thus stimulation and inhibition curves were established for a pair of biopsies from each patient. Appropriate biopsy material was obtained in triplicate from only seven patients. In these patients the variance in maximal receptor stimulation (by isoproterenol) and inhibition (by propranolol) was significantly smaller in pairs of biopsies compared to the variance between all biopsies (p values from less than 0.05 to less than 0.025). Hence it is possible to determine AC activity, and adrenergic receptor function, in very small endomyocardial biopsies. New diagnostic possibilities could thereby be introduced.

A randomized trial of low-dose beta-blockade therapy for idiopathic dilated cardiomyopathy

Beta-blockade therapy to improve survival in idiopathic dilated cardiomyopathy (IDC) has been both advocated and criticized. However, randomized studies have not been performed. Thus, 50 patients with IDC were randomized in pairs to standard therapy (C) alone or with beta blockade (BB). Beta-blockade therapy with metoprolol was titrated from 12.5 to 50 mg twice daily as tolerated (final average dose, 61 mg/day). Groups were comparable in age (C, 50 +/- 15 years; BB, 51 +/- 13 years), gender (C, 76% male; BB, 56% male), entry functional class (C, 2.8 +/- 0.8; BB, 2.7 +/- 0.7), and left ventricular ejection fraction (C, 27 +/- 12%; BB, 29 +/- 10%). Follow-up averaged 19 months (range 1 to 38). One subject in each group was lost to follow-up. There were 3 early BB dropouts (within 2 days) due to low-output syndrome (2 patients) or fatigue (1 patient). Eleven patients died. By intention to treat, 5 BB and 6 C patients died (difference not significant). By actual treatment, 3 BB patients died, including 2 late dropouts (at 0.2, 10 and 17 months), and 8 C patients died (at 2, 9, 9, 15, 18, 24, 29 and 32 months, p = 0.12). In additional, functional evaluation on follow-up (functional class, San Diego questionnaire and exercise time) all tended to favor those receiving BB. Low-dose BB is tolerated in 80% of IDC patients on a long-term basis. Those continuing to take BB have a good prognosis. Mortality in C patients, however, is less than in some retrospective studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral beta-adrenergic blockade with metoprolol in chronic severe dilated cardiomyopathy

A double-blind crossover trial was performed to assess the effect of metoprolol in 10 patients (mean age 55 years) with severe dilated cardiomyopathy. All patients clinically had idiopathic dilated cardiomyopathy; however, at coronary angiography, four had occult coronary disease. All were in New York Heart Association functional class III with a left ventricular ejection fraction less than 35% as assessed by rest radionuclide ventriculography. Studies were performed before treatment, after 4 weeks of metoprolol therapy and after 4 weeks of placebo administration. Erect bicycle sprint exercise was used to determine maximal work load. Hemodynamic variables and radionuclide left ventricular ejection fraction were recorded at rest and during graded supine bicycle exercise. Cardiac medications were unchanged throughout the trial. The mean (+/- standard error of the mean) dose of metoprolol was 130 +/- 13 mg/day. Metoprolol did not change symptoms, chest X-ray findings or exercise tolerance (baseline 700 +/- 73, placebo 690 +/- 85, metoprolol 710 +/- 81 kilopond-meters [kpm]/min). Metoprolol produced a significant decrease in heart rate at rest and during exercise (p less than 0.001). Mean blood pressure and left ventricular filling pressure did not differ significantly in the baseline, placebo and metoprolol studies. There was a slight, but significant (p less than 0.05) decrease in cardiac index with metoprolol compared with placebo and baseline studies. The small, but significant increase in left ventricular ejection fraction from baseline to the metoprolol and placebo studies (p less than 0.001) was considered a result of spontaneous improvement rather than of therapy. No significant differences were found between the patients with and without coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Protection of turkeys against furazolidone-induced cardiomyopathy

When fed furazolidone, 700 ppm, with their mash, most turkey poults develop dilated cardiomyopathy characterized by gross left ventricular dilatation with thinning of both the left ventricular free wall and ventricular septum. Birds fed propranolol, but not digoxin, did not develop this cardiomyopathy. It is not known what pharmacologic property of propranolol conferred protection or if mammals would receive similar protection.

The frontiers of cardiomyopathy

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The contributions of sympathetic tone and the renin-angiotensin system to severe chronic congestive heart failure: response to specific inhibitors (prazosin and captopril)

The contribution of sympathetic tone and the renin-angiotensin system to the pathogenesis of chronic heart failure was evaluated. In 20 paired studies of the same 10 patients, the baseline hemodynamic and humoral correlates of congestive heart failure, and the response to alpha adrenergic blockade (prazosin) and angiotensin converting enzyme inhibition (captopril) were assessed. Despite the extent of failure, baseline plasma renin activity ranged from normal to very high. In contrast, baseline plasma catecholamine levels were always elevated. Baseline plasma norepinephrine reflected the severity of heart failure, correlating inversely with baseline cardiac index before administration of both drugs. Comparable improvement in left ventricular function was noted after acute therapy. Baseline renin and norepinephrine did not predict the response to prazosin, but baseline renin did predict the response to captopril: pulmonary wedge pressure (r=-0.776, p less than 0.01), stroke index (r=0.752, p less than 0.02), systemic vascular resistance (r=-0.673, p less than 0.05). In summary, elevated levels of plasma norepinephrine were inversely correlated with baseline cardiac function but norepinephrine levels did not change despite improved hemodynamics with specific prazosin therapy. The renin-angiotensin system exhibited a wide spectrum of activity and hemodynamic improvement with captopril was related to this activity. Absence of a correlation between plasma norepinephrine and plasma renin activity suggested that their contributions to vasoconstriction were not interdependent. Increased sympathetic tone was consistent in severe heart failure, whereas renin-angiotensin activity differed widely. The response to captopril can be used to identify a subset of patients with severe heart failure and adverse angiotensin-mediated vasoconstriction.

Neurohumoral control mechanisms in congestive heart failure

Neurohumoral vasoconstrictor systems may play an important role in the hemodynamic derangement and natural history of congestive heart failure (CHF) by raising impedance to left ventricular ejection and shifting blood centrally to augment cardiac filling. Activation of the sympathetic nervous system, and renin-angiotensin system, and the antidiuretic hormone-vasopressin system can be demonstrated in clinical CHF by increased plasma levels of norepinephrine, renin activity, and arginine vasopressin. Because the magnitude of increase in each of these hormones varies widely from patient to patient, profiling of the neurohumoral response might provide new insight into the mechanisms of regulation of the circulation in CHF and into specific management with drugs to inhibit or reverse the vasoconstrictor process. Preliminary encouraging experience with converting-enzyme inhibitors to block formation of angiotensin II and alpha-receptor blockers to inhibit norepinephrine-induced vasoconstriction raise the possibility that selective therapy may eventually have a place in long-term management of CHF. Controlled trials in a larger patient population are now required.

Beneficial effects of long-term beta-blockade in congestive cardiomyopathy

Twenty-eight patients with heart failure caused by congestive cardiomyopathy, which had been diagnosed according to the criteria of Goodwin and Oakley, were treated with beta-blocking agents for six to 62 months, except for four patients who died within two months. Repeated non-invasive investigations were performed before and during treatment as well as exercise tests and chest x-rays. The echocardiographic and pulse curve findings indicated an improvement in systolic and diastolic myocardial function. The ejection fraction increased from 0.32 +/- 0.02 to 0.42 +/- 0.04, and the third heart sound amplitude and rapid filling wave were significantly reduced. The functional classification improved in 15 patients while in 12 patients it remained unchanged and in one it deteriorated. During follow-up, 10 patients died, most of them suddenly. The mortality was lower than expected in this severely ill group of patients. The beneficial effect of chronic beta-blockade in patients with congestive cardiomyopathy suggests that catecholamines are involved in the pathogenesis of congestive cardiomyopathy, and that patients with congestive cardiomyopathy may have inappropriate sympathetic cardiac stimulation which can be reduced by chronic beta-blockade. It is suggested that beta-receptor blockade should be added to conventional treatment with digitalis and diuretics in all patients with severe myocardial failure caused by congestive cardiomyopathy.

Adverse effects of beta-blockade withdrawal in patients with congestive cardiomyopathy

Fifteen patients with congestive cardiomyopathy who had improved conspicuously on chronic administration of a beta-blocker were studied after withdrawal of the drug. In six patients there was a pronounced deterioration of their clinical condition, and in all of the remaining patients there was a significant decrease in ejection fraction, and signs of compromised diastolic function with pathological apex curves and an increase in third heart sound. All these changes were reversed within a few weeks to a few months after readministration of beta-blocking drugs. This study supports the idea that an aetiological factor in congestive cardiomyopathy may be a pathological response to sympathetic stimulation which could be partly controlled by administration of beta-blocking drugs.

Effects of work and acute beta-receptor blockade on myocardial noradrenaline release in congestive cardiomyopathy

Systemic hemodynamic changes and noradrenaline concentrations in coronary sinus blood were studied at rest and during work before and after acute beta-receptor blockade. Patients with congestive cardiomyopathy were compared to patients with primary valvular diseases and to healthy subjects. Noradrenaline concentrations were higher in coronary sinus blood than in arterial blood and increased after beta blockade and during work. Noradrenaline concentrations were more increased in patients with more pronounced myocardial failure and did not seem to separate patients with congestive cardiomyopathy from those with valvular disease. Patients with congestive cardiomyopathy showed a good hemodynamic tolerance toward acute beta blockade.

Haemodynamic effects of acute beta-adrenergic receptor blockade in congestive cardiomyopathy

Acebutolol ('Sectral'), a cardioselective beta-blocking drug, was administered intravenously in a dose of 25 mg to 10 patients with congestive cardiomyopathy. All of them were in a stable condition on antifailure regimens. The drug resulted in a statistically significant decline in left ventricular contractility as judged by peak left ventricular dP/dT and the contractility index. The mean aortic blood pressure also fell. There was a significant increase in end-diastolic and end-systolic left ventricular volumes. Mean values for heart rate, ejection fraction, left ventricular stroke work index, and cardiac output also fell, but the results were not statistically significant. Left ventricular distensibility as judged by the slope of the diastolic pressure-volume relation also improved significantly. A reduction in myocardial energy requirements, improved compliance, and lowering of arterial pressure would be haemodynamically advantageous. However, further cardiac dilatation and reduction contractility--the basic defects in congestive cardiomyopathy--could lead to further deterioration.

Prolongation of survival in congestive cardiomyopathy by beta-receptor blockade

24 patients with congestive cardiomyopathy (group I) were compared with a group of 13 controls with similar clinical findings and myocardial function who were selected retrospectively (group II) . All patients received digitalis and diuretics, but group I patients received beta-blockers as well. The survival-rate in group I patients (83%, 66%, and 52% after one, two, and three years respectively) differed significantly from that in group II subjects (46%, 19%, and 10%, respectively). This finding is supported by the demonstration that beta-blockade improved myocardial function in group I subjects. It is therefore suggested that beta-blockade prolongs survival in patients with congestive cardiomyopathy.

Effect of propranolol and phentolamine on myocardial necrosis after subarachnoid haemorrhage

A study was set up to assess the effect on the clinical course of subarachnoid haemorrhage (SAH) of giving propranolol 80 mg eight-hourly plus phentolamine 20 mg three-hourly by mouth for three weeks. Out of the 90 patients studied, 14 died. Two of the deaths occurred in an open pilot study of 10 patients, the remaining 12 deaths occurring in patients in a randomised double-blind placebo-controlled study. Postmortem examination was carried out on 12 of the patients, six of whom had been receiving placebo and six propranolol plus phentolamine. Necrotic myocardial lesions were present in the hearts of all six patients (age range 30-59 years) who died while taking placebo (all had had abnormal electrocardiograms (ECGs). In contrast, no necrotic lesions were found in the hearts of the six patients (age range 28-59) who died while receiving the drugs (all had previously had normal ECGs). We conclude that the necrotic myocardial lesions were induced by catecholamines and that propranolol had a cardioprotective effect. While death from a further haemorrhage in cases of SAH is not affected by propranolol and phentolamine, propranolol may have a beneficial effect in other potentially lethal stresses.

Cardiomyopathies in South Africa--a brief survey of the problem and current therapeutic approaches

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Treatment of congestive cardiomyopathy

Although the majority of patients with cardiomyopathy are in the category of primary or idiopathic cardiomyopathy, for which therapy is symptomatic and non-specific, there are a number of secondary forms of cardiomyopathy for which specific therapy is available, thus giving impetus to prompt and accurate diagnosis. Among inflammatory lesions, brucellosis, psittacosis and toxoplasmosis are examples. Treatable metabolic causes include thyrotoxicosis and thiamine deficiency, the latter as well as calorie-protein malnutrition are also preventable. There is presumptive evidence that the cardiomyopathy of haemochromatosis is benefited by repeated phlebotomies. Symptomatic relief of obstructive cardiomyopathy is achieved by beta-adrenergic blockade, although resection of obstructing myocardium still has a place. The therapeutic approach to the vast majority of cases of congestive cardiomyopathy is non-specific, comprising controlled activity, sodium restriction, digitalis and diuretics. Vasodilators and, occasionally, beta-adrenergic blockade may be beneficial. Pacemakers may be life-saving, whereas the place of anti-arrhythmics remains uncertain. Transplantation warrants further application. Valve replacement has little to offer. Primary prevention, comprising balanced nutrition, vaccines and genetic counselling, merits wider application. In individuals at risk or already afflicted, programmes of secondary prevention should include good nutrition, abstinence from alcohol and protection from drugs and toxins.