Effects of beta blockers on ventricular dysfunction after myocardial infarction: tolerability and survival effects

Sudden cardiac death from the perspective of coronary artery disease

Sudden cardiac death accounts for approximately 50% of all deaths attributed to cardiovascular disease in the United States. It is most commonly associated with coronary artery disease and can be its initial manifestation or may occur in the period after an acute myocardial infarction. Decreasing the rate of sudden cardiac death requires the identification and treatment of at-risk patients through evidence-based pharmacotherapy and interventional strategies aimed at primary and secondary prevention. For this review, we searched PubMed for potentially relevant articles published from January 1, 1970, through March 1, 2014, using the following key search terms: sudden cardiac death, ischemic heart disease, coronary artery disease, myocardial infarction, and cardiac arrest. Searches were enhanced by scanning bibliographies of identified articles, and those deemed relevant were selected for full-text review. This review outlines various mechanisms for sudden cardiac death in the setting of coronary artery disease, describes risk factors for sudden cardiac death, explores the management of cardiac arrest, and outlines optimal practice for the monitoring and treatment of patients after an acute ST-segment elevation myocardial infarction to decrease the risk of sudden death.

Randomized active-controlled study comparing effects of treatment with carvedilol versus metoprolol in patients with left ventricular dysfunction after acute myocardial infarction

BACKGROUND

Carvedilol has previously been demonstrated to be beneficial in patients with acute myocardial infarction (AMI) and left ventricular (LV) dysfunction. However, metoprolol has not to date been randomly evaluated in the same patient population. The objective of this study was to compare the effects of treatment with carvedilol versus metoprolol in patients with LV dysfunction after AMI.

METHODS

The study enrolled 313 high-risk patients with anterior AMI and LV ejection fraction of <45%, randomly assigned to treatment with carvedilol or metoprolol. Patients were followed-up for a mean period of 13.4 months. The primary end point was time to composite adverse events (t-CAE). The secondary end points were time to composite hard events (t-CHE) and health-related quality of life.

RESULTS

No differences were found either in the primary end point of t-CAE or in the secondary end point of t-CHE. A significant benefit was observed in 4 of 8 health-related quality of life domains in the carvedilol group, with fewer carvedilol group patients being withdrawn from therapy in the hospital.

CONCLUSIONS

Treatment with carvedilol, in comparison to that with metoprolol in patients with AMI and LV dysfunction, did not differ significantly in regard to the primary end point of t-CAE or to the secondary end point of t-CHE but resulted in better long-term quality of life and favorable early safety profile.

Hospitalizations due to unstable angina pectoris in diastolic and systolic heart failure

Patients with diastolic heart failure (HF), i.e., clinical HF with normal or near normal left ventricular ejection fraction (LVEF), may develop unstable angina pectoris (UAP) due to epicardial atherosclerotic coronary artery disease and/or to subendocardial ischemia, even in the absence of coronary artery disease. However, the risk of UAP in ambulatory patients with diastolic HF has not been well studied. We examined incident hospitalizations due to UAP in 916 patients with diastolic HF (LVEF >45%) without significant valvular heart disease and 6,800 patients with systolic HF (LVEF <or=45%) in the Digitalis Investigation Group trial. During a 38-month median follow-up, 12% of patients (797 of 6,800) with systolic HF (incidence rate 435 per 10,000 person-years) and 15% of patients (138 of 916) with diastolic HF (incidence rate 536 per 10,000 person-years) were hospitalized for UAP (adjusted hazard ratio for diastolic HF 1.22, 95% confidence interval [CI] 1.02 to 1.47, p = 0.032). There was a graded increase in incident hospital admissions for UAP with increasing LVEF. Hospitalizations for UAP occurred in 11% (520 of 4,808, incidence rate 407 per 10,000 person-years), 14% (355 of 2,556, incidence rate 496 per 10,000 person-years), and 17% (60 of 352, incidence rate 613 per 10,000 person-years) of patients with HF, respectively, with LVEF values <35%, 35% to 55%, and >55%. Compared with patients with HF and an LVEF <35%, the adjusted hazard ratios for UAP hospitalization in those with LVEF values 35% to 55% and >55% were, respectively, 1.17 (95% CI 1.02 to 1.34, p = 0.028) and 1.57 (95% CI 1.20 to 2.07, p = 0.026). In conclusion, in ambulatory patients with chronic HF, a higher LVEF was associated with increased risk of hospitalizations due to UAP. As in patients with systolic HF, those with diastolic HF should be routinely evaluated for myocardial ischemia and managed accordingly.

Effects of long-term adrenergic beta-blockade on left ventricular diastolic filling in patients with acute myocardial infarction

BACKGROUND

Left ventricular (LV) systolic and diastolic function are known to be affected in the wake of a myocardial infarction (MI). beta-Adrenergic blocking agents have demonstrated improvement of LV systolic and diastolic function in patients with dilated cardiomyopathy and theoretically would have same beneficial effects in MI. beta-Adrenergic blocking agents are widely used in MI; however only few reports on changes of LV systolic and diastolic function during long-term treatment after acute MI are available.

METHODS

Two-dimensional and Doppler echocardiography were used to evaluate LV diastolic filling in 77 patients randomly assigned to placebo (n = 38) or metoprolol (n = 39). The patients were randomly assigned at day 5 to 7 (baseline) after acute MI and were treated for 12 months. LV diastolic filling was assessed by pulsed Doppler measurements of transmitral and pulmonary venous flow.

RESULTS

Mitral E-wave deceleration time was prolonged in the metoprolol group (baseline vs 12 months: 167 +/- 51 ms to 218 +/- 36 ms; P =. 01) versus the placebo group (baseline vs 12 months: placebo 174 +/- 46 ms to 189 +/- 41 ms), which implies a less restrictive filling of the LV in the metoprolol group. This was supported by a decrease of E/A ratio (baseline vs 12 months: placebo, 1.06 +/- 0.40 to 0.96 +/- 0.29; metoprolol, 1.09 +/- 0.33 to 0.80 +/- 0.21; P =.05) and prolongation of the isovolumetric relaxation time in the metoprolol treated group (baseline vs 12 months: placebo, 83 +/- 19 ms to 95 +/- 20 ms; metoprolol, 82 +/- 23 ms to 117 +/- 22 ms; P =.01). The difference between mitral A wave and pulmonary venous flow reversal duration was significantly changed during follow-up (baseline vs 12 months: placebo, 22 +/- 11 ms to 24 +/- 11; metoprolol, 11 +/- 21 to 32 +/- 17 ms; P =.02). Patients with normal LV filling pattern at baseline in the metoprolol group preserved a normal LV filling pattern during the study, and patients with restrictive LV filling pattern in the metoprolol group had a nonrestrictive LV filling pattern develop. Maximal or near maximal changes of the diastolic Doppler measurements occurred by 3 months of follow-up, whereas a significant increase in LV ejection fraction was noted after 12 months treatment with metoprolol.

CONCLUSIONS

Long-term treatment with the beta-blocking agent metoprolol seems to improve LV diastolic filling after acute MI. Less restrictive LV filling was noted during beta-blockade indicated by a significant prolongation of the mitral E deceleration time, which was predominantly noted in patients with restrictive LV filling. This observation might have prognostic implications because this LV filling pattern is known to be associated with poor outcome. The changes of LV diastolic filling occurred during the first 3 months, whereas systolic recovery was seen at up to 12 months of treatment.

Mechanisms and management of ventricular dysrhythmias in heart failure

Despite recent pharmacologic and surgical advances in the management of heart failure, the morbidity and mortality rates of this chronic illness remain high. Ventricular dysrhythmias are common in heart failure and may be independently associated with increased mortality rates. Although the risks of sudden cardiac death leading to the patient's death are increased by the presence of complex ventricular dysrhythmias, the management of dysrhythmias is subject to controversy. The purpose of this article is to review the normal electrophysiologic properties of the heart and to examine the likely mechanisms, diagnostic approaches, and proposed treatments for ventricular dysrhythmias in heart failure.

Comparative efficacy of a DA2/alpha2 agonist and a beta-blocker in reducing adrenergic drive and cardiac fibrosis in an experimental model of left ventricular dysfunction after coronary artery occlusion

Attenuation of neuroendocrine activation may be beneficial in congestive heart failure. Sympathetic nervous system overactivity can be reduced by receptors blockade or by reducing norepinephrine (NE) spillover. This study evaluated and compared the effects of a DA2-dopaminergic receptor/alpha2-adrenoceptor agonist (CHF-1024) and a beta1-adrenoreceptor antagonist in terms of hemodynamics, ventricular remodeling, beta-adrenergic drive, and cardiac fibrosis after myocardial infarction (MI) in rats. MI was induced by left coronary artery ligation in 213 rats, whereas 12 were left unoperated on. After 2 months, the operated-on animals were treated for 1 more month with CHF-1024 at either 0.33 mg/kg/day (low dose) or 1 mg/kg/day (high dose) or with metoprolol (10 mg/kg/day), delivered through implanted osmotic minipumps. Plasma concentration and urinary excretion of NE were measured before the rats were killed. Hemodynamic variables were measured and morphometric analysis was done on the diastole-arrested hearts to quantify left ventricular remodeling and interstitial collagen density. Metoprolol treatment tended to normalize LV end-diastolic pressure (LVEDP). CHF-1024 at either dose, and metoprolol, significantly reduced collagen deposition in LV of infarcted animals (from 8.8 +/- 0.5% LV area in vehicle-treated rats to 6.6 +/- 0.2% or 6.4 +/- 0.2% after the low or high dose of CHF-1024, respectively; p < 0.05). Similarly, CHF-1024 at either dose reduced the plasma concentration of NE (from 224 +/- 53 pg/ml to 60 +/- 7 pg/ml or 87 +/- 13 pg/ml; p < 0.05) and urinary excretion of NE in rats with MI, whereas beta-blockade did not affect these variables. In conclusion, CHF-1024 infused for 1 month to rats with LV dysfunction reduced heart rate, NE spillover, and collagen deposition, without unwanted effects, only appearing at the higher dose. Effective beta-blockade with metoprotol reduced LVEDP with no effects on heart function. Neither DA2/alpha2 stimulation nor beta-blockade altered LV remodeling after coronary artery ligation.

Primary prevention of sudden cardiac death in heart failure: will the solution be shocking?

Sudden cardiac death (SCD) may occur in as many as 40% of all patients who suffer from heart failure. This review describes the scope of the problem, risk factors for SCD, the effect of medications used in heart failure on SCD and the potential effect of the implantable cardioverter-defibrillator in primary prevention.

Rationale, design, and organization of the Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF). The International Steering Committee

Metoprolol is a cardioselective beta blocker that has been shown to improve left ventricular function and symptoms of congestive heart failure (CHF) and also to decrease the number of hospitalizations due to CHF. However, the effects of metoprolol on mortality in patients with CHF have yet to be determined. Accordingly, the Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF) has been designed to investigate the effect of once-daily dosing of metoprolol succinate controlled release/extended release (CR/XL) when added to standard therapy in patients with CHF. A total of 3,200 patients will be recruited for this international, double-blind, randomized, placebo-controlled survival study. The 2 primary objectives of MERIT-HF are to determine the effect of metoprolol CR/XL on (1) total mortality and (2) the combined endpoint of all-cause mortality and all-cause hospitalizations (time to first event). Eligible patients are 40-80 years old, with a reduced left ventricular ejection fraction (< or =0.40) and symptoms of CHF (New York Heart Association functional classes II-IV). After a 2-week placebo run-in period, an optimal allocation procedure will be used to randomize patients in a 1:1 ratio to metoprolol CR/XL or matching placebo. After an initial titration phase starting with 12.5 mg or 25 mg once daily (depending on functional class), the target dose will be 200 mg in all patients who tolerate this dose. The mean follow-up is estimated to be 2.4 years. The study data will be analyzed on an intention-to-treat basis. An Independent Safety Committee will monitor the safety aspects of the trial, and an Independent Endpoint Committee will classify all endpoints.

What can we expect from prophylactic implantable defibrillators?

Death due to ventricular tachyarrhythmia (VT) remains an important public health problem; patients with prior myocardial infarction (MI) constitute the largest identifiable population for prophylactic interventions. Targeting of progressively higher-risk subgroups of post-MI survivors carries inevitable tradeoffs with respect to the global impact of interventions on overall mortality. Therapy with aspirin, beta blockers, and angiotensin-converting enzyme (ACE) inhibitors comprise the benchmark against which all additional interventions, including implantable defibrillators, must be measured. Initial enthusiasm for empiric amiodarone therapy has been tempered by the limited benefit demonstrated in recent randomized trials. Trials of other class III antiarrhythmic drugs, including both d,l-sotalol and d-sotalol, have also failed to demonstrate survival benefit. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated significantly improved survival associated with defibrillators in a small subgroup of post-MI survivors with a high short-term risk of death. The ultimate number and optimal criteria for selection of patients who may benefit from prophylactic defibrillator therapy after MI will undergo continued evolution as new data from current and ongoing trials become available.

Cardiac and hemodynamic effects of TZC-5665, a novel pyridazinone derivative, and its metabolite in humans and dogs

1. TZC-5665 is a novel pyridazinone derivative with vasodilatory and beta-adrenergic blocking activities and type III phosphodiesterase inhibitory action. 2. In healthy volunteers, TZC-5665 was rapidly absorbed and immediately metabolized. Its main metabolite, M-2, remained at a higher concentration in plasma. Orally administered TZC-5665 reduced end-diastolic left ventricular volume (20.16 ml) and exhibited a tendency to increase ejection fraction (0.04). 3. In dogs, M-2 dose-dependently increased cardiac contractility and reduced both preload and afterload. These effects appeared more potent in the failed heart than in the normal heart. At the same dose (30 micrograms/kg), the effects of M-2 seem to be more potent than those of milrinone. 4. We concluded that TZC-5665 is a useful medication for treating patients with chronic congestive heart failure (CHF) because of the positive inotropic and vasodilating effects due to its active metabolite in addition to its own beta-adrenergic blocking actions.

Additive beneficial effects of beta-blockers to angiotensin-converting enzyme inhibitors in the Survival and Ventricular Enlargement (SAVE) Study. SAVE Investigators

OBJECTIVES

This study assessed whether treatment with a beta-adrenergic blocking agent in addition to the use of the angiotensin-converting enzyme (ACE) inhibitor captopril decreases cardiovascular mortality and morbidity in patients with asymptomatic left ventricular dysfunction after myocardial infarction (MI) and whether the presence of neurohumoral activation at the time of hospital discharge predicts the effects of beta-blocker treatment in these patients.

BACKGROUND

Both beta-blockers and ACE inhibitors have been shown to have beneficial effects in patients with left ventricular dysfunction but no overt heart failure after MI. These patients often have persistent neurohumoral activation at the time of hospital discharge, and one would expect that patients with activation of the sympathetic nervous system derive the most benefit from treatment with beta-blockers. However, beta-blockers are underutilized in this high risk group of patients, and it is unknown whether their beneficial effects are additive to those of ACE inhibitors.

METHODS

We performed a retrospective analysis of data from the Survival and Ventricular Enlargement (SAVE) study and its neurohumoral substudy. The relations between beta-blocker use at the time of randomization and neurohumoral activation and the subsequent development of cardiovascular events were analyzed by use of Cox proportional hazards models controlling for covariates.

RESULTS

After adjustment for baseline imbalances, beta-blocker use was associated with a significant reduction in risk of cardiovascular death (30%, 95% confidence interval [CI] 12% to 44%) and development of heart failure (21%, 95% CI 3% to 36%), but the reduction in recurrent MI (11%, 95% CI 13% to 31%) was not significant. These reductions were independent of the use of captopril. Beta-blockers were not found to have a greater effect in patients with neurohumoral activation at the time of hospital discharge.

CONCLUSIONS

The beneficial effects of beta-blocker use at the time of hospital discharge in patients with asymptomatic left ventricular dysfunction after MI appear to be additive to those of captopril and other interventions known to improve prognosis. Neurohumoral activation at the time of hospital discharge fails to identify those patients who will derive the greatest benefit from treatment with beta-blockers.

Beta-blocker use in systolic heart failure and dilated cardiomyopathy

Statistics regarding long-term survival for patients with heart failure are discouraging today. Converting enzyme inhibitors have produced a modest effect on mortality. beta-Blockers may be the next addition to standard therapy for heart failure because they generate consistent improvements in hemodynamic factors, symptom scores, and submaximal exercise tolerance in randomized, controlled clinical trials. They augment ejection fraction, reduce heart volume, and consistently lower neurohormonal activation as reflected by plasma norepinephrine levels. Trials with carvedilol and bisoprolol suggest an effect on mortality similar to that with converting enzyme inhibitor trials. Future studies, especially the beta-blocker Evaluation Survival Trial (BEST), with mortality as the main end point should elucidate the degree of effect on mortality further.

Beta adrenergic blockade in the treatment of sustained ventricular tachycardia or ventricular fibrillation

The value of beta-blockers as antiarrhythmic drugs in patients with sustained VT or VF has received only little attention. This article summarizes the current state of knowledge regarding the identification of patients with sustained VT or VF with the highest benefit of beta-blockade. The antiarrhythmic mechanisms of beta-blockade and its efficacy as single or adjuvant therapy in patients with sustained VT or VF are reviewed. Current insights into the effects of beta-blockade in patients suffering from VT, in particular in the setting of heart failure, are discussed and future directions are considered.

Benefit of converting enzyme inhibition on left ventricular volumes and ejection fraction in patients receiving beta-blockade after myocardial infarction. CONSENSUS II multiecho study group

Beta-blockers reduce infarct size and improve survival after acute myocardial infarction (MI). Post-MI angiotensin-converting enzyme inhibition also improves survival and may attenuate left ventricular (LV) dilatation. We evaluated the effect of early enalapril treatment on LV volumes and ejection fraction (EF) in patients on concomitant beta-blockade after MI. Intravenous enalaprilat or placebo was administered <24 hours after MI and was continued orally for 6 months. LV volumes were assessed by echocardiography 3 +/- 2 days, 1 and 6 months after MI. Change in LV diastolic volume during the first month was attenuated with enalapril (2.7 vs placebo 6.5 ml/m2 change; p < 0.05), and significantly lower LV diastolic and systolic volumes were observed with enalapril treatment compared with placebo at 1 month (enalapril 47.21 23.9 vs placebo 53.1/29.2 ml/m2; p < 0.05) and at 6 months (enalapril 47.9/24.8 vs placebo 53.8/29.6 ml/m2; p < 0.05). EF was also significantly higher 1 month after MI in these patients (enalapril 50.4% vs placebo 46.4%; p < 0.05). Our date demonstrate that early enalapril treatment attenuates LV volume expansion and maintains lower LV volumes and higher EF in patients receiving concurrent beta-blockade after MI. A possible additive effect of combined therapy should be evaluated prospectively.

Prediction of cardiac death in patients with a very low ejection fraction after myocardial infarction: a Cardiac Arrhythmia Suppression Trial (CAST) study

The Cardiac Arrhythmia Suppression Trial (CAST) database was analyzed with a Cox proportional hazards regression model to predict the mortality of patients with very poor left ventricular systolic function (ejection fraction < or = .20). Predictors of total death or cardiac arrest were (relative risk), QRS duration (1.10/10 msec increase), coronary artery bypass grafting (0.38), basal heart rate (1.26/10 min-1 increase), diastolic blood pressure (0.79/10 mm Hg increase), diabetes mellitus (1.59), EF (0.94/1 U increase), and ease of suppression (the ability to suppress ambient ventricular ectopy on the lowest dose of the first randomly chosen CAST drug) (0.64). Predictors of arrhythmic death or arrhythmic cardiac arrest included thrombolysis (0.44), coronary artery bypass grafting (0.38), diuretic use (1.71), heart rate (1.21/10 min-1 increase), calcium channel blocker use (1.69), and QRS duration (1.10/10 msec increase). Thus easily measurable clinical and laboratory variables help predict prognosis in this clinically important subgroup. The pathophysiologic basis for and the clinical implications of the ease of ventricular arrhythmia suppression correlating with prognosis requires further study.

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.

Controlled trials with beta blockers in heart failure: metoprolol as the prototype

Early studies of acute beta-blocking drug therapy, such as metoprolol and acebutolol, in patients with idiopathic dilated cardiomyopathy (IDC) and survivors of acute myocardial infarction were interpreted to have detrimental or, at best, neutral effects on cardiac and clinical hemodynamics. Subsequent trials of longer duration with metoprolol versus placebo in patients with IDC demonstrated an "exceptional response" to beta-blocker therapy in some individuals. Hemodynamics and patient demographic characteristics appear not to predict those patients who may or may not benefit. Controlled trials with newer beta-adrenoceptor modulating drugs--such as xamoterol, bucindolol, and carvedilol--have been equivocal in some situations. Xamoterol has been associated with progressive heart failure and increased sudden cardiac deaths, whereas bucindolol improved clinical heart failure symptoms and testing hemodynamic parameters, as did treatment with carvedilol, in patients with ischemic cardiomyopathy. The success of these agents in patients with congestive heart failure may be in their ability to modulate the excessive myocardial stimulation of the beta-adrenergic nervous system while benefitting the dynamics of the peripheral system.