Acute hemodynamic effects of pindolol and propranolol in patients with dilated cardiomyopathy: relevance of intrinsic sympathomimetic activity

Effect of beta-blocker treatment in dilated cardiomyopathy with bradyarrhythmias

This study was performed to evaluate whether beta-blocker therapy was effective in patients with nonischemic dilated cardiomyopathy (DCM) and bradyarrhythmias supported by pacemaker implantation. Beta-blocker therapy is useful for some patients with DCM, especially those with rapid heart rate or residual nonfibrotic myocardium in the left ventricle, but no data exist on whether beta-blocker therapy is useful in patients with DCM and bradyarrhythmias. The effectiveness of beta-blocker therapy was prospectively evaluated in patients with DCM and bradyarrhythmias supported by pacemaker implantation and compared with those without these arrhythmias. Beta-blocker therapy was started in 63 patients (45 men, 18 women, aged 11-83 years) with DCM, in whom 7 had bradyarrhythmias and 56 did not. These bradyarrhythmias were atrioventricular block, sick sinus syndrome and atrial fibrillation with slow heart rate. Of the 56 patients without bradyarrhythmias, 42 (75%) (group 1) responded to beta-blocker therapy, but 5 of the 7 with bradyarrhythmias (71%) (group 2) also responded. Left ventricular end-diastolic dimension was reduced (6.5 +/- 0.6 cm to 5.6 +/- 0.5 cm; p < 0.0001 in group 1; 6.6 +/- 0.8 cm to 5.5 +/- 0.2 cm; p < 0.02 in group 2) and left ventricular fractional shortening was improved (13 +/- 4% to 27 +/- 7%; p < 0.0001 in group 1; 12 +/- 4% to 29 +/- 10%; p < 0.05, in group 2) to the same degree in both groups. These results indicate that beta-blocker therapy for DCM is effective not only in patients without bradyarrhythmias but also in those with bradyarrhythmias supported with pacemaker implantation.

Effect of beta-blockade on mortality in patients with heart failure: a meta-analysis of randomized clinical trials

OBJECTIVES

We sought to evaluate the current evidence for an effect of beta-blockade treatment on mortality in patients with congestive heart failure (CHF).

BACKGROUND

Although numerous small studies have suggested a benefit with beta-blocker therapy in patients with heart failure, a clear survival benefit has not been demonstrated. A recent combined analysis of several studies with the alpha- and beta-adrenergic blocking agent carvedilol demonstrated a significant survival advantage; however, the total number of events was small. Furthermore, it is unclear if previous studies with other beta-blockers are consistent with this finding.

METHODS

Randomized clinical trials of beta-blockade treatment in patients with CHF from January 1975 through February 1997 were identified using a MEDLINE search and a review of reports from scientific meetings. Studies were included if mortality was reported during 3 or more months of follow-up.

RESULTS

We identified 35 reports, 17 of which met the inclusion criteria. These studies included 3,039 patients with follow-up ranging from 3 months to 2 years. Beta-blockade was associated with a trend toward mortality reduction in 13 studies. When all 17 reports were combined, beta-blockade significantly reduced all-cause mortality (random effect odds ratio [OR] 0.69, 95% confidence interval [CI] 0.54 to 0.88). A trend toward greater treatment effect was noted for nonsudden cardiac death (OR 0.58, 95% CI 0.40 to 0.83) compared with sudden cardiac death (OR 0.84, 95% CI 0.59 to 1.2). Similar reductions in mortality were observed for patients with ischemic (OR 0.69, 95% CI 0.49 to 0.98) and nonischemic cardiomyopathy (OR 0.69, 95% CI 0.47 to 0.99). The survival benefit was greater for trials of the drug carvedilol (OR 0.54, 95% CI 0.36 to 0.81) than for noncarvedilol drugs (OR 0.82, 95% CI 0.60 to 1.12); however, the difference did not reach statistical significance (p = 0.10).

CONCLUSIONS

Pooled evidence suggests that beta-blockade reduces all-cause mortality in patients with CHF. Additional trials are required to determine whether carvedilol differs in its effect from other agents.

Beta receptor antagonists in the treatment of heart failure

The use of beta-receptor antagonists in the treatment of heart failure is controversial. Available data do not allow general recommendations regarding their use. In dilated cardiomyopathy, several studies suggest that long-term treatment in individual patients reduces symptoms and increases exercise capacity. Short-term treatment is usually not beneficial, except in patients with ischemically induced left ventricular dysfunction. In heart failure, post myocardial infarction and in chronic ischemic heart disease, no proper long-term study has been performed to evaluate its effects. However, patients with acute myocardial infarction tolerate beta blockers, despite the presence of left ventricular dysfunction and long-term prognosis is improved. Newer agents, some with ancillary properties, such as intrinsic activity and vasodilatation, may have advantages. In the future we need a better description of the cardiac status in our patients in order to be able to select those that will respond favorably to beta-receptor antagonists. The mechanisms by which some patients improve are still obscure. Protection against receptor downregulation, restoration of receptor density, protection against cardiotoxicity of catecholamines, and improvement in ischemic systolic and diastolic left ventricular function are all possible. The fear that beta-receptor antagonists are dangerous in heart failure is in most instances not warranted, but an initial deterioration may have to be accepted in order to gain long-term beneficial effects. Ongoing studies in both idiopathic cardiomyopathy and in postinfarction failure will hopefully help us to define the use of beta-adrenoceptor antagonists in the future.

Effects of xamoterol in acute myocardial infarction: blood pressure, heart rate, arrhythmias and early clinical course

Xamoterol is a novel partial agonist of beta 1 adrenoceptors that reduces myocardial ischaemia and improves ventricular function in patients with mild to moderate heart failure. In a double blind, randomised, placebo controlled study, the effects of xamoterol given in a dose of 200 mg twice daily were studied in 51 consecutive patients with acute myocardial infarction, including 17 receiving diuretics for left ventricular failure. Treatment was started on the third day of admission and continued for 7 days. Blood pressure was recorded at 0900 daily, and 24 hour ambulatory electrocardiogram monitoring was commenced at this time on days 1 (pre-treatment), 4, 6 and 9 of admission. Additional drug therapy was recorded daily throughout the study. One patient died prior to randomisation and three were withdrawn (1 placebo, 2 xamoterol) with ventricular arrhythmias and/or disturbances of conduction. Compared to placebo, xamoterol had no effect on the rate of ventricular premature beats or ventricular tachycardia. Xamoterol increased nocturnal heart rate (0000-0600 hrs 79 +/- 2; placebo 72 +/- beats/min; P less than 0.03) but did not change blood pressure. Three patients receiving xamoterol, and 7 on placebo, required new (after randomisation) antianginal therapy. One patient treated with placebo developed new heart failure. These results show that xamoterol can be administered safely to selected patients following myocardial infarction, including those treated for mild heart failure.

Usefulness of bucindolol in congestive heart failure

The sympathetic hyperactivity of congestive heart failure (CHF) may worsen cardiovascular function by down-regulation of myocardial beta-receptors. For this reason, beta blockade is proposed to be useful in CHF. Bucindolol is a new beta blocker that has intrinsic nonadrenergically-mediated vasodilation and may be valuable in treatment of CHF. To test this, 19 patients with CHF were randomized in a double-blind protocol to 3 months of treatment with bucindolol (n = 12) or placebo (n = 7). Significant improvement was seen in the bucindolol group using invasive and noninvasive tests; treadmill time increased from 445 to 530 seconds (p = 0.04), Minnesota Living With Heart Failure Questionnaire score improved from 61 to 40 (p = 0.0001), cardiac output increased from 4.0 to 4.7 (p = 0.02), and systemic vascular resistance decreased from 1,888 to 1,481 (p = 0.04). Also, peak exercise heart rate and pulmonary capillary wedge pressure decreased significantly with treatment. There were no changes in the placebo group. We conclude that bucindolol may be an effective treatment for CHF when administered chronically and that its nonadrenergic vasodilation may be an important feature.