Metoprolol in acute myocardial infarction reduces ventricular arrhythmias both in the early stage and after the acute event

Beta-blockers for suspected or diagnosed acute myocardial infarction

BACKGROUND

Cardiovascular disease is the number one cause of death globally. According to the World Health Organization, 7.4 million people died from ischaemic heart diseases in 2012, constituting 15% of all deaths. Acute myocardial infarction is caused by blockage of the blood supplied to the heart muscle. Beta-blockers are often used in patients with acute myocardial infarction. Previous meta-analyses on the topic have shown conflicting results ranging from harms, neutral effects, to benefits. No previous systematic review using Cochrane methodology has assessed the effects of beta-blockers for acute myocardial infarction.

OBJECTIVES

To assess the benefits and harms of beta-blockers compared with placebo or no intervention in people with suspected or diagnosed acute myocardial infarction.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, Science Citation Index Expanded and BIOSIS Citation Index in June 2019. We also searched the WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, Turning Research into Practice, Google Scholar, SciSearch, and the reference lists of included trials and previous reviews in August 2019.

SELECTION CRITERIA

We included all randomised clinical trials assessing the effects of beta-blockers versus placebo or no intervention in people with suspected or diagnosed acute myocardial infarction. Trials were included irrespective of trial design, setting, blinding, publication status, publication year, language, and reporting of our outcomes.

DATA COLLECTION AND ANALYSIS

We followed the Cochrane methodological recommendations. Four review authors independently extracted data. Our primary outcomes were all-cause mortality, serious adverse events according to the International Conference on Harmonization - Good Clinical Practice (ICH-GCP), and major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up). Our secondary outcomes were quality of life, angina, cardiovascular mortality, and myocardial infarction during follow-up. Our primary time point of interest was less than three months after randomisation. We also assessed the outcomes at maximum follow-up beyond three months. Due to risk of multiplicity, we calculated a 97.5% confidence interval (CI) for the primary outcomes and a 98% CI for the secondary outcomes. We assessed the risks of systematic errors through seven bias domains in accordance to the instructions given in the Cochrane Handbook. The quality of the body of evidence was assessed by GRADE.

MAIN RESULTS

We included 63 trials randomising a total of 85,550 participants (mean age 57.4 years). Only one trial was at low risk of bias. The remaining trials were at high risk of bias. The quality of the evidence according to GRADE ranged from very low to high. Fifty-six trials commenced beta-blockers during the acute phase of acute myocardial infarction and seven trials during the subacute phase. At our primary time point 'less than three months follow-up', meta-analysis showed that beta-blockers versus placebo or no intervention probably reduce the risk of a reinfarction during follow-up (risk ratio (RR) 0.82, 98% confidence interval (CI) 0.73 to 0.91; 67,562 participants; 18 trials; moderate-quality evidence) with an absolute risk reduction of 0.5% and a number needed to treat for an additional beneficial outcome (NNTB) of 196 participants. However, we found little or no effect of beta-blockers when assessing all-cause mortality (RR 0.94, 97.5% CI 0.90 to 1.00; 80,452 participants; 46 trials/47 comparisons; high-quality evidence) with an absolute risk reduction of 0.4% and cardiovascular mortality (RR 0.99, 95% CI 0.91 to 1.08; 45,852 participants; 1 trial; moderate-quality evidence) with an absolute risk reduction of 0.4%. Regarding angina, it is uncertain whether beta-blockers have a beneficial or harmful effect (RR 0.70, 98% CI 0.25 to 1.84; 98 participants; 3 trials; very low-quality evidence) with an absolute risk reduction of 7.1%. None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. Only two trials specifically assessed major adverse cardiovascular events, however, no major adverse cardiovascular events occurred in either trial. At maximum follow-up beyond three months, meta-analyses showed that beta-blockers versus placebo or no intervention probably reduce the risk of all-cause mortality (RR 0.93, 97.5% CI 0.86 to 0.99; 25,210 participants; 21 trials/22 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.1% and a NNTB of 91 participants, and cardiovascular mortality (RR 0.90, 98% CI 0.83 to 0.98; 22,457 participants; 14 trials/15 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.2% and a NNTB of 83 participants. However, it is uncertain whether beta-blockers have a beneficial or harmful effect when assessing major adverse cardiovascular events (RR 0.81, 97.5% CI 0.40 to 1.66; 475 participants; 4 trials; very low-quality evidence) with an absolute risk reduction of 1.7%; reinfarction (RR 0.89, 98% CI 0.75 to 1.08; 6825 participants; 14 trials; low-quality evidence) with an absolute risk reduction of 0.9%; and angina (RR 0.64, 98% CI 0.18 to 2.0; 844 participants; 2 trials; very low-quality evidence). None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. None of the trials assessed quality of life. We identified two ongoing randomised clinical trials investigating the effect of early administration of beta-blockers after percutaneous coronary intervention or thrombolysis to patients with an acute myocardial infarction and one ongoing trial investigating the effect of long-term beta-blocker therapy.

AUTHORS' CONCLUSIONS

Our present review indicates that beta-blockers for suspected or diagnosed acute myocardial infarction probably reduce the short-term risk of a reinfarction and the long-term risk of all-cause mortality and cardiovascular mortality. Nevertheless, it is most likely that beta-blockers have little or no effect on the short-term risk of all-cause mortality and cardiovascular mortality. Regarding all remaining outcomes (serious adverse events according to ICH-GCP, major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up), the long-term risk of a reinfarction during follow-up, quality of life, and angina), further information is needed to confirm or reject the clinical effects of beta-blockers on these outcomes for people with or suspected of acute myocardial infarction.

Epidemiology of ventricular tachyarrhythmia : Any changes in the past decades?

Ventricular tachyarrhythmias include potentially lethal episodes of sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) as well as hemodynamically tolerated ventricular ectopic activity. Sustained VT or VF may develop in the setting of acute myocardial infarction or as clinical sequelae of advanced cardiomyopathy. The incidence of these serious arrhythmias is estimated from retrospective and observational studies and registries of sudden cardiac arrest and sudden cardiac death. Over the past few decades, there has been a gradual decline in the incidence of life-threatening ventricular tachyarrhythmias which has been largely driven by upstream treatments for and prevention of coronary artery disease and its sequelae. In addition primary prevention implantable cardioverter-defibrillators (ICDs) have improved survival in patients at risk for malignant ventricular arrhythmias and sudden cardiac death. Improved understanding, and improved diagnostic and imaging methods have elucidated many of the previously classified "idiopathic" ventricular arrhythmias as inherited arrhythmic syndromes and occult cardiomyopathies. In addition, improved sensitivity and duration of ECG monitoring has allowed increased detection of ventricular ectopic activity.

A review and meta-analysis of studies on the effect and timing of β-blocker administration in patients with ST-segment elevation myocardial infarction

The utility of β-blockers during an evolving ST-segment elevation myocardial infarction (STEMI) has substantial theoretic physiological backing. This coupled with early successes using β-blockers in STEMI promulgated multiple guidelines expanding the use of this class of medication to all patients with acute coronary syndromes. However, recent studies have questioned the utility of β-blockers in the emergency department in these patients. The purpose of this article is to review the evidence behind the use of β-blockers in the emergency department for STEMI patients.

Effect of early treatment with anti-hypertensive drugs on short and long-term mortality in patients with an acute cardiovascular event

BACKGROUND

Acute cardiovascular events represent a therapeutic challenge. Blood pressure lowering drugs are commonly used and recommended in the early phase of these settings. This review analyses randomized controlled trial (RCT) evidence for this approach.

OBJECTIVES

To determine the effect of immediate and short-term administration of anti-hypertensive drugs on all-cause mortality, total non-fatal serious adverse events (SAE) and blood pressure, in patients with an acute cardiovascular event, regardless of blood pressure at the time of enrollment.

SEARCH STRATEGY

MEDLINE, EMBASE, and Cochrane clinical trial register from Jan 1966 to February 2009 were searched. Reference lists of articles were also browsed. In case of missing information from retrieved articles, authors were contacted.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing anti-hypertensive drug with placebo or no treatment administered to patients within 24 hours of the onset of an acute cardiovascular event.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed risk of bias. Fixed effects model with 95% confidence intervals (CI) were used. Sensitivity analyses were also conducted.

MAIN RESULTS

Sixty-five RCTs (N=166,206) were included, evaluating four classes of anti-hypertensive drugs: ACE inhibitors (12 trials), beta-blockers (20), calcium channel blockers (18) and nitrates (18). Acute stroke was studied in 6 trials (all involving CCBs). Acute myocardial infarction was studied in 59 trials. In the latter setting immediate nitrate treatment (within 24 hours) reduced all-cause mortality during the first 2 days (RR 0.81, 95%CI [0.74,0.89], p<0.0001). No further benefit was observed with nitrate therapy beyond this point. ACE inhibitors did not reduce mortality at 2 days (RR 0.91,95%CI [0.82, 1.00]), but did after 10 days (RR 0.93, 95%CI [0.87,0.98] p=0.01). No other blood pressure lowering drug administered as an immediate treatment or short-term treatment produced a statistical significant mortality reduction at 2, 10 or >/=30 days. There was not enough data studying acute stroke, and there were no RCTs evaluating other acute cardiovascular events.

AUTHORS' CONCLUSIONS

Nitrates reduce mortality (4-8 deaths prevented per 1000) at 2 days when administered within 24 hours of symptom onset of an acute myocardial infarction. No mortality benefit was seen when treatment continued beyond 48 hours. Mortality benefit of immediate treatment with ACE inhibitors post MI at 2 days did not reach statistical significance but the effect was significant at 10 days (2-4 deaths prevented per 1000). There is good evidence for lack of a mortality benefit with immediate or short-term treatment with beta-blockers and calcium channel blockers for acute myocardial infarction.

Responsiveness to diving reflex after acute myocardial infarction. Influence of early beta-adrenoceptor blocker therapy

We studied the influence of beta-adrenoceptor blockade on heart rate responses to facial immersion in ice-cooled water after acute myocardial infarction. Forty patients with acute myocardial infarction were randomized to the double-blind therapy with metoprolol 200 mg daily or matching placebo. Therapy was started as soon as possible after admission to hospital and continued for 15 days. After this initial period all patients were treated with beta-blockade during the subsequent 6 months. Repeated investigations of heart rate responses to facial immersion in ice-cooled water and 24-hour ECG-recordings were performed on day 15 (while patients were on study therapy), after 6 weeks, 3 and 6 months. Throughout the 6-month period, facial immersion elicited significant heart rate reductions in both treatment groups. No differences were found between the two groups or between different examinations during follow-up. There was no correlation between heart rate response to facial immersion and frequency of ventricular arrhythmia on a 24-hour monitoring. In conclusion, acute administration of metoprolol in myocardial infarction does not influence the bradycardial response to facial immersion either in the early postinfarction phase or during 6 months' follow-up. There is no relation between bradycardial response to face immersion and frequency of ventricular arrhythmias.

A multiple logistic regression analysis of in-hospital factors related to survival at six months in patients resuscitated from out-of-hospital ventricular fibrillation

INTRODUCTION

The impact of the immediate in-hospital post-resuscitation care after out-hospital cardiac arrest is not well known. Based on treatment variables and laboratory findings a multiple logistic regression model was created for the prediction of survival at 6 months from the event.

MATERIALS AND METHODS

A retrospective study of the hospital charts of patients successfully resuscitated and treated in one of three community hospitals from 1998 to 2000. In addition to several pre-hospital variables, the mean 72 h values of clinical features such as blood pressure, blood glucose concentration and initiated treatment used, were included in a forward multiple logistic regression model predicting survival at 6 months from the event.

RESULTS

The charts of 98 out of a total of 102 patients were sufficiently complete and included in the analysis. Variables independently associated with survival were age, delay before a return of spontaneous circulation, mean blood glucose and serum potassium, and the use of beta-blocking agents during post-resuscitation care. When those patients who were assigned a 'do not attempt to resuscitate' (DNAR) order during the first 72 h of treatment were excluded from the analysis blood glucose, blood potassium and the use beta-blocking agents remained independently associated with survival.

CONCLUSION

This study suggests that in-hospital factors are associated with survival from out-of-hospital cardiac arrest. The mean blood glucose and serum potassium during the first 72 h of treatment and the use of beta-blocking agents were significantly and independently associated with survival.

Acute ischemic syndromes. Adjunctive therapy

The acute coronary syndromes (ACS) represent a heterogeneous group of patients along a continuum of risk from unstable angina to non-ST-segment elevation myocardial infarction. ACS is a term that has been used to describe the constellation of clinical symptoms that represent acute myocardial ischemia. This article reviews the adjunctive medications that are used during emergency cardiovasculare care for the early management of patients experiencing the ACS. The adjunctive therapies are divided into early immediate treatment and then subsequent management in the acute care setting.

Amiodarone in the new AHA guidelines for ventricular tachyarrhythmias

OBJECTIVE

To delineate amiodarone's role in the new American Heart Association guidelines for ventricular tachyarrhythmias, review the literature that supports the use of amiodarone in ventricular tachyarrhythmias, describe the pharmaceutical properties of amiodarone and elucidate their clinical implications, and discuss the dosing, preparation, and administration of amiodarone.

DATA SOURCES

A search of MEDLINE (1966-October 2000) database and EMBASE Drugs and Pharmacology database (1980-October 2000) was performed. References from published articles and tertiary references were used to gather additional data.

DATA EXTRACTION

All articles were screened, and pertinent studies were identified and evaluated.

DATA SYNTHESIS

Recent trials have demonstrated amiodarone's usefulness in the setting of ventricular tachyarrhythmias. Based on these investigations and contrary to past guidelines, amiodarone is included in the 2000 advanced cardiovascular life support guidelines as a possible agent for hemodynamically stable monomorphic ventricular tachycardia (VT), non-QT prolonged polymorphic VT, and ventricular fibrillation (VF)/pulseless VT. Although not specifically evaluated in the setting of hemodynamically stable monomorphic VT and non-QT prolonged polymorphic VT, investigations by the intravenous Amiodarone Multicenter Trial Group and other clinical trials make amiodarone an acceptable choice for these arrythmia categories. The results of the ARREST (Resuscitation of Refractory Sustained Ventricular Tachyarrhythmias) trial prove amiodarone to be the antiarrhythmic of choice for VF/pulseless VT.

CONCLUSIONS

Amiodarone is classified as a IIb therapeutic intervention for all three arrhythmia categories, which makes it an acceptable, safe, and useful agent with fair to good evidence to support its use. In addition, amiodarone requires careful preparation and delivery to achieve safe and effective outcomes.

Analysis of arrhythmias in the Circadian Antiischemia Program in Europe (CAPE) study

The aim of this study was to analyze whether, in patients with long-standing (>4 years) coronary artery disease (CAD), the addition of the long-acting calcium channel blocker (CCB) amlodipine to conventional treatment [beta-blockers (BBLs) and nitrates] during anginal attacks would have a proarrhythmic effect. This was tested by analyzing data from patients who had taken part in the Circadian Anti-ischemia Program in Europe (CAPE) trial. After a 2-week, single-blind, run-in period (Phase 1), patients were randomized to amlodipine, 5 mg/day (first 4 weeks) and 10 mg/day (second 4 weeks), or placebo for 8 weeks (Phase 2). The 48-h Holter data were analyzed for 167 amlodipine-treated patients and 83 placebo patients based on a 2:1 randomization scheme. Sixty-three per cent of amlodipine patients and 67% of placebo patients were receiving concomitant BBLs, and >90% had taken sublingual nitrates during anginal attacks, as basic antiischemic therapy. After 7 weeks of therapy, when 48-h Holter monitoring was repeated, there were no significant changes in the frequency of ventricular arrhythmias in the placebo or amlodipine groups for all patients or subgroups of patients with or without BBLs. Also, between-group comparisons showed no significant differences in arrhythmias between amlodipine and placebo patients. In summary, amlodipine (5-10 mg/day) given to patients with severe, chronic CAD receiving conventional antiischemic therapy, did not produce any proarrhythmic effects.

Importance of beta blockade in the therapy of serious ventricular arrhythmias

Beta blockers have traditionally been considered relatively poor antiarrhythmic agents for patients with ventricular arrhythmias. This view is based on the observations that beta blockers are less effective in suppressing spontaneous ventricular ectopy or inducible ventricular arrhythmias than are the class I and class III agents. However, there are convincing data that beta blockers can have a clinically important antiarrhythmic effect and prevent arrhythmic and sudden death. Beta blockers have multiple potential effects that can contribute to a therapeutic antiarrhythmic action, including an antiadrenergic/vagomimetic effect, a decrease in ventricular fibrillation threshold, and prevention of a catecholamine reversal of concomitant class I/III antiarrhythmic drug effects. Postinfarction trials, recent congestive heart failure studies, and observations in patients who are at risk for sustained ventricular arrhythmias all suggest a potent antiarrhythmic effect of beta blockade.

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.

Empiric therapy with beta-blockers

The only class of drugs with significant effects on ventricular fibrillation and sudden death in humans is that of beta-blockers. The exact mechanisms for these prophylactic effects are not known but may be related to both antiischemic or antiarrhythmic influences. It seems reasonable to suggest that one should use a beta-blocker with proven effect on total mortality and sudden cardiac death after myocardial infarction as prophylaxis. Therefore, propranolol, timolol, or metoprolol, should be instituted in order to improve prognosis when there are no contraindications. In addition to possible effects on survival one would also expect to reduce the risk for new ischemic events with angina or reinfarction. In contrast, class I antiarrhythmic agents are useful for symptomatic ventricular arrhythmias but there is no proof for any effect on ventricular fibrillation and sudden cardiac death.

Effects of beta-blockade on the incidence of ventricular tachyarrhythmias during acute myocardial ischemia: experimental findings and clinical implications

Myocardial ischemia and infarction are the most common substrates for life-threatening ventricular tachyarrhythmias. Experimental and clinical evidence suggests that enhanced activity of the sympathetic nervous system plays an important role in the genesis of ischemia-related arrhythmias. In animal experiments, beta-blockers display significant antifibrillatory effects during the acute phase of myocardial ischemia. Preconditions for their antifibrillatory effects are high serum- and tissue-concentrations, and absence of a significant partial agonist activity. During the delayed phase of ischemic arrhythmias which starts 6-8 h after coronary occlusion, beta-blockers gain significance as antiarrhythmic and potentially antifibrillatory drugs, if sympathetic activity is enhanced. The presently available evidence suggests that the potentially antifibrillatory effects of beta-blockers are at least one of the major mechanisms by which these drugs may decrease mortality when given prophylactically in patients after myocardial infarction. However, it remains to be explained why beta-blockers, in a great number of prospective randomized trials, have reduced the incidence of sudden death only by an average of about 30%. This may be the result of their "specific" mechanisms acting in the setting of acute myocardial ischemia with enhanced adrenergic tone, whereas in the remaining patients other mechanisms such as a chronic arrhythmogenic substrate may be operative. A clearer separation of these various mechanisms seems mandatory in order to allow a more specific "targeted" administration of beta-blockers. This is the more important since none of the available prospective studies that used antiarrhythmic agents has shown an improvement of prognosis, but, instead showed a worsening of the mortality rate.

Effect of diltiazem on cardiac rate and rhythm after myocardial infarction. Multicenter Diltiazem Postinfarction Trial Investigators

The a priori hypothesis that diltiazem would reduce the frequency and repetitiveness of ventricular arrhythmias was tested 3 months after myocardial infarction in patients participating in the Multicenter Diltiazem Postinfarction Trial. After 3 months of follow-up, 1,546 of the 2,466 patients enrolled had a 24-hour continuous electrocardiographic recording that contained greater than or equal to 12 hours of analyzable data. They were similar to the patients who survived 3 months but chose not to have a 24-hour electrocardiographic recording (i.e., they were representative of the entire group that survived 3 months). After 3 months of follow-up, there were no significant differences between the diltiazem and placebo groups in the prevalence of atrioventricular block, the frequency of atrial arrhythmias or the frequency or repetitiveness of ventricular arrhythmias. Heart rate was significantly lower (67 +/- 12 vs 71 +/- 12 beats/min) and there was a significantly greater proportion of patients with sinus pauses greater than or equal to 2 seconds in duration in the diltiazem group (6%) than in the placebo group (3%). Comparison with placebo revealed no evidence either for an anti- or proarrhythmic effect of diltiazem. There was no reduction in sudden or arrhythmic death attributable to diltiazem treatment; the fraction of total deaths that were arrhythmic by the Hinkle classification was 41% in the placebo group and 42% in the diltiazem group. It may be that the lack of effect of diltiazem on ventricular arrhythmias is partially responsible for its lack of effect on mortality after myocardial infarction.

Treatment of ventricular arrhythmias in the coronary patient: what sort of patient? For which rhythm disorder? With which procedure?

In the patient with coronary artery disease, complex ventricular arrhythmias and frequent ventricular arrhythmias appear to be independent risk factors for subsequent death, particularly in patients who have had myocardial infarction. In patients with symptomatic arrhythmias, treatment must be instituted and tested during rigorous supervision of the patient. Using both the noninvasive Holter monitoring/exercise test procedure and invasive electrophysiologic testing, a beneficial antiarrhythmic response after institution of antiarrhythmic agents indicates improved prognosis. However, a negative treatment response during programmed stimulation does not necessarily indicate bad prognosis. This is particularly true for testing during amiodarone treatment. For unselected patients, routine antiarrhythmic treatment cannot currently be recommended. Continuing studies will show whether screening for electrical instability of the myocardium, and institution of antiarrhythmic therapy thereafter, will improve overall survival. If patients tolerate beta-blocking treatment, this should probably be instituted because reductions in mortality have been found, particularly in high-risk patients.