Beta-adrenergic blockade and cardiac arrhythmias

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.

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.

Significance of arrhythmias during the first 24 hours of acute myocardial infarction treated with alteplase and effect of early administration of a beta-blocker or a bradycardiac agent on their incidence

BACKGROUND

Although early intravenous beta-blocker therapy during acute myocardial infarction (AMI) reduces the incidence of fatal arrhythmias in patients not treated with thrombolytic agents, its antiarrhythmic effect in thrombolysed patients remains controversial. We investigated prospectively the arrhythmia incidence in 244 patients with AMI receiving alteplase and a double-blind randomized adjunctive therapy with intravenous atenolol, alinidine, or placebo. Moreover, the characteristics and prognostic significance of early arrhythmias and their relation with infarct size and coronary patency were evaluated.

METHODS AND RESULTS

All patients underwent 24-hour Holter monitoring on day 1 and were clinically followed in the hospital for 10 to 14 days. Coronary angiography was performed on day 10 to 14. Atenolol and alinidine significantly decreased the basic heart rate without causing more sinus arrest or higher-degree atrioventricular block. The prevalence of atrial fibrillation in alinidine patients was lower than in the atenolol patients (P = .007) but not lower than in placebo patients (P = .11). There was no effect of either agent on the incidence and frequency distribution of ventricular or supraventricular premature beats or on the incidence and characteristics of nonsustained ventricular tachycardia, accelerated idioventricular rhythm, sustained ventricular tachycardia (VT), or ventricular fibrillation (VF). On day 1, seven VF episodes were recorded in six patients (2.5%) and five VT episodes in five patients (2%). VF always started at < 2.5 hours after start of thrombolytic treatment and VT always at > 2.5 hours (average of 6 hours). Five of the seven VF and three of the five VT episodes started with an R-on-T. However, for all VT, the morphology of the first beat was the same as that of the following beats, suggesting that the sustained arrhythmia was not induced by an extrasystole. After day 1 and before hospital discharge, VF and VT developed in one and six patients, respectively. Three of the seven patients who developed VF during the first 2 weeks underwent coronary angiography; all three had an occluded infarct-related artery. In contrast, only one of nine patients with early or late VT had an occluded vessel. Patients with VT and VF on day 1 had a significantly larger enzymatic infarct size than those without the arrhythmia (P = .02), and a similar trend was noted for VT or VF after day 1 (P = .19). However, none of the patients with VT or VF on day 1 developed a life-threatening arrhythmia later during the hospital stay. Also, none of the seven patients with VT or VF after day 1 had experienced a major rhythm disturbance during the first 24 hours.

CONCLUSIONS

(1) Our data do not support the hypothesis that beta-blockers or bradycardiac agents might reduce the incidence of major arrhythmias when used in conjunction with thrombolytic therapy. (2) The pathogeneses of VT and VF early during AMI are clearly distinct. (3) VT or VF during the first 2 weeks is a marker for a larger infarct. (4) We could not detect a relation between malignant arrhythmias on day 1 and recurrences within the following 2 weeks.

Arrhythmias during the acute phase of reperfusion therapy for acute myocardial infarction: Effects of β-adrenergic blockade

In 107 patients with acute myocardial infarction, the incidence of ventricular arrhythmias during the acute phase of thrombolysis was examined by means of Holter monitoring. In patients with a patient infarct-related artery as assessed angiographically at 90 minutes, the occurrence of accelerated idioventricular rhythms was noted significantly more frequently than in patients with a permanent occluded vessel. This arrhythmia peaked in the first 180 minutes after the start of thrombolysis. In addition, single ventricular premature beats and runs of ventricular tachycardia were also more common in patients with successful reperfusion. The effects of acute intravenous administration of beta-blockers were examined in 66 patients without contraindications to this therapeutic approach. There were no differences in the occurrence of any type of rhythm disorders in patients with (n = 43) or without beta-blockade (n = 23). Thus ventricular arrhythmias particularly accelerated idioventricular rhythms, and single ventricular premature beats occur more frequently in patients with a patent infarct artery within the first 24 hours after thrombolysis. Acute intravenous beta-blockade does not appear to exert significant antiarrhythmic effects during this period.

Meta-analysis of clinical trials as a scientific discipline. I: Control of bias and comparison with large co-operative trials

Meta-analysis is an important method of bridging the gap between undersized randomized control trials and the treatment of patients. However, as in any retrospective study, the opportunities for bias to distort the results are widespread. Attempts must be made to introduce the controls found in prospective studies by blinding the selection of papers and extraction of data and making blinded duplicate determinations. Informal and personalized methods of obtaining data are probably more liable to error and bias than employing only published data. Publication bias is a serious problem requiring further research. There also need to be more comparisons of meta-analysed small studies with large co-operative trials.

Beta blockade during and after myocardial infarction: an overview of the randomized trials

Long-term beta blockade for perhaps a year or so following discharge after an MI is now of proven value, and for many such patients mortality reductions of about 25% can be achieved. No important differences are clearly apparent among the benefits of different beta blockers, although some are more convenient than others (or have slightly fewer side effects), and it appears that those with appreciable intrinsic sympathomimetic activity may confer less benefit. If monitored, the side effects of long-term therapy are not a major problem, as when they occur they are easily reversible by changing the beta blocker or by discontinuation of treatment. By contrast, although very early IV short-term beta blockade can definitely limit infarct size, more reliable information about the effects of such treatment on mortality will not be available until a large trial (ISIS) reports later this year, with data on some thousands of patients entered within less than 4 hours of the onset of pain. Our aim has been not only to review the 65-odd randomized beta blocker trials but also to demonstrate that when many randomized trials have all applied one general approach to treatment, it is often not appropriate to base inference on individual trial results. Although there will usually be important differences from one trial to another (in eligibility, treatment, end-point assessment, and so on), physicians who wish to decide whether to adopt a particular treatment policy should try to make their decision in the light of an overview of all these related randomized trials and not just a few particular trial results. Although most trials are too small to be individually reliable, this defect of size may be rectified by an overview of many trials, as long as appropriate statistical methods are used. Fortunately, robust statistical methods exist--based on direct, unweighted summation of one O-E value from each trial--that are simple for physicians to use and understand yet provide full statistical sensitivity. These methods allow combination of information from different trials while avoiding the unjustified direct comparison of patients in one trial with patients in another. (Moreover, they can be extended of such data that there is no real need for the introduction of any more complex statistical methods that might be more difficult for physicians to trust.) Their robustness, sensitivity, and avoidance of unnecessary complexity make these particular methods an important tool in trial overviews.

Combined effects of propranolol and ethanol on human psychomotor performance

Twelve male subjects were given placebo or 160 mg propranolol, in divided doses, during a 24-hr period before drinking a beverage containing 0 or 50 ml ethanol/70 kg body weight. Tests designed to measure mental and motor performance were administered 75 min after the last dose of propranolol. The tests performed included the wobble board (WB), pursuit meter (PM), delayed auditory feedback (DAF), pegboard (PB), tapping, time estimation (TE), and a modified Cornell medical index (CMI). A mean blood ethanol concentration of 48.0 +/- 9.1 mg/dl and a mean plasma propranolol level of 33.1 +/- 13.1 ng/ml were achieved. Ethanol alone significantly impaired performance in 12 out of 20 tests (p less than 0.05). Propranolol significantly (p less than 0.05) antagonized the decrement in psychomotor performance induced by ethanol on the PM. In all other tests, there was no significant interaction between ethanol and propranolol. Propranolol alone had no significant effect on the psychomotor tests. When the drugs were combined, the subjective symptoms, as measured by the CMI, showed a trend toward being additive. This study suggests that no adverse interaction occurs between therapeutic doses of propranolol and minimum impairment doses of ethanol.

Ventricular antiarrhythmic effects of beta-adrenergic blocking drugs: a review of mechanism and clinical studies

Beta-adrenergic blocking drugs are now commonly used in patients with ventricular arrhythmias. This review examines the possible mechanisms of their ventricular antiarrhythmic effect. Actions on the myocardial cell, as well as actions on the central and autonomic nervous system, are reviewed. Many clinical studies have attempted to show the efficacy of beta blockers in controlling ventricular arrhythmia and decreasing the incidence of sudden death after acute myocardial infarction. Although some of these clinical trials tended to show an impact on sudden death, the size of these trials or their design problems do not allow firm conclusions to be made. The Beta Blocker Heart Attack Trial (BHAT) is a placebo-controlled, double-blind, randomized trial of propranolol currently under way in the United States. Important additions to the previous trials include the addition of drug levels to ensure beta-blocking dosage, long-term electrocardiographic monitoring, and a study population of 4200 patients followed for an average of three years. These important design features will be of value in addressing some of the unanswered questions presented in this review.

Antiarrhythmic effects of acute betablockade with atenolol on supraventricular tachycardias at rest and during exercise

In a total of 18 patients, 7 females and 11 male patients with ages ranging from 23 to 70 years (mean: 45.5 +/- 14.5) diagnostic His bundle studies incorporating programmed atrial and ventricular pacing for the induction of tachycardias was performed before and after betablockade with the cardioselective betablocking agent atenolol, in a dose of 5 mg given iv. over 3 to 5 minutes. In 7 patients the pacing procedure could be repeated following ergometric exercise in order to evaluate the influence of a raised sympathetic tone on the conditions initiating paroxysmal tachycardias. At rest, atenolol prevented the pacing induced tachycardias (20 dysrhythmias in 18 patients) in 3/5 individuals with Wolff-Parkinson-White (WPW)-syndrome, in 4/6 cases with atrial tachycardias, in 4/6 patients presenting atrial flutter, in 2/2 cases developing AV-nodal tachycardias and in 1/1 individual with ventricular tachycardia. Thus, in 13 out of 19 (68%) supraventricular dysrhythmias patients benefitted from atenolol by preventing or controlling the tachycardia. Ergometric exercise changed the tachycardia or echo zone in 5/8 arrhythmias after betablockade when compared to the controls before administration of atenolol (3/5 improvement by narrowing of the tach- or echo zone, 1/5 prevention of tachycardia, 1/5 impairment due to widening of the tachycardia zone). Considering only the prevention of tachycardias, the antiarrhythmic potency of atenolol was improved in one patient with pacing induced flutter and impaired in one individual with a WPW syndrome, by ergometric exercise. These results suggest that atenolol seems to provide a good antiarrhythmic action, especially in supraventricular tachycardias, and that an increased sympathetic tone during exercise may modify the antidysrhythmic strength of betablockade.

Comparison of newer antiarrhythmic agents

In the past decade a number of new antiarrhythmic drugs ahve been introduced. They have been extensively used in the acute phase of myocardial infarction. Few, if any, long-term comparative trials of these newer agents have been reported. Most of these newer agents have been shown to be able to reduce the frequency of ventricular arrhythmias but not the mortality rate. Beta blockers and some antiplatelet adhesive drugs, however, have reduced the mortality rate following myocardial infarction. There is a need for long-term properly stratified trials of these effective agents.

Multicentre post-infarction trial of propranolol in 49 hospitals in the United Kingdom, Italy, and Yugoslavia

A multicentre study of survivors of an anterior myocardial infarction is reported. The trial consisted of 720 patients and was a double-blind, placebo-controlled study with propranolol 40 mg three times a day. Trial entry was at two to 14 days (mean 8.5 days) and follow-up at one, three, and in most centres, six and nine months. The trial was designed to detect a 50 per cent reduction in mortality and this was not shown. The non-fatal reinfarction rate was similar in both groups. Subgroup analysis identified several prognostic risk factors for death, none of which interacted with treatment.

The effect of a selective beta adrenergic blocking agent on ventricular arrhythmias in the first year following myocardial infarction

Fifty-five patients with recent acute myocardial infarction entered a single-blind cross-over trial to assess the effect of oral practolol 200 mg twice daily on the incidence and nature of ventricular arrhythmias in the first year following myocardial infarction. Patients had 24-hour Holter electrocardiogram tape monitoring at two weeks following infarction and at three-monthly intervals for one year. Twenty-six patients completed the full year of the trial with 12% of tape recordings technically unsatisfactory. A total of 46 periods of comparison of the action of practolol versus placebo therapy were available in thirty patients. Whilst receiving the selective beta adrenergic blocking agent, practolol, there was a significant reduction in the percentage of studied hours during which salvos of ventricular premature beats occurred (P < 0.025), however the percentage of patients in whom salvos were recorded was unchanged. The incidence of all other ventricular arrhythmias was not reduced in the practolol group. When the effect of practolol was related to the site of infarction, anterior or inferior, there was no significant reduction in the incidence of ventricular arrhythmias.

Propranolol in supraventricular tachycardias of childhood

9 children with supraventricular tachycardias refractory to conventional therapy were treated with propranolol. In 3 children normal sinus rhythm was restored. In 3 others frequency of paroxysmal arrhythmias was decreased. In 1 reduction of ventricular response to the ectopic rhythm was achieved, and in 2 remaining patients, propranolol had no effect. The dosage of propranolol ranged from 0·5 to 4·0 mg/kg per day, given orally, with few side effects. It appears that propranolol can play an important role in treatment of supraventricular arrhythmias of childhood unresponsive to conventional therapy.

Psychopharmacologic management of anxiety in the cardiac patient

Of 253 patients who had suffered acute myocardial infarction ( MI), 88 percent received daytime sedation while hospitalized. Sixty percent of all prescriptions were for phenobarbital, 30 percent for chlordiazepoxide, and 6 percent for meprobamate. In addition, 79 percent of patients received night time hypnotic medication. Sixty-six percent of such prescriptions were for short-acting barbiturates, 21 percent for chloral hydrate, and 7 percent for diphenhydramine. Multiple drug use was common.

The barbiturates, while inexpensive sedative agents, are of questionable efficacy in reducing anxiety and probably produce only general CNS depression. A narrow margin of safety, liability to produce habituation, and antagonism of warfarin-type anticoagulants are other disadvantages. The benzodiazepine tranquilizers, whose antianxiety efficacy is more clearly established, do not produce general CNS depression, have a wide margin of safety, and do not interact with oral anticoagulants.

Antidepressant agents, phenothiazine tranquilizers, and propranolol were used infrequently or not at all. The risks associated with the use of these agents in patients with acute myocardial infarction are considerable and should be weighed carefully before they are administered.

Clinical experience with dextro-alprenolol

Experience with dextro-alprenolol in nine patients has shown that it is relatively ineffective in treating arrhythmias associated with acute myocardial infarction. Marginal effectiveness in the control of ventricular ectopic beats after myocardial infarction is outweighed by an appreciable hypotensive effect with risk of infarction. The drug was ineffective in the management of supraventricular arrhythmias.

Effects of propranolol on the transmembrane potentials of ventricular muscle and Purkinje fibers of the dog

Papillary muscle-false tendon tissue preparations isolated from dog hearts were perfused with Tyrode's solution containing propranolol in concentrations ranging from 0.1 to 20.0 mg/liter. Transmembrane action potentials of both ventricular muscle fibers and Purkinje fibers were recorded. With sufficient concentration of drug, the velocity of the upstroke and the overshoot of both fiber types decreased. The curve relating upstroke velocity to level of membrane potential for Purkinje fibers was displaced to the right and down. The ability of both ventricular muscle fibers and Purkinje fibers to respond to rapid frequencies of stimulation was decreased. Repolarization of Purkinje fibers was accelerated by propranolol, but repolarization of ventricular muscle fibers was unaffected. Duration of the effective refractory period of Purkinje fibers decreased; that of ventricular muscle fibers was unchanged. Graded responses and decremental impulse conduction in Purkinje fibers were abolished in the presence of propranolol. Low doses of propranolol which caused no change in the transmembrane potential completely blocked the increase in Purkinje diastolic depolarization normally induced by epinephrine. The possible mechanisms by which propranolol might exert its antiarrhythmic actions on ventricular arrhythmias were discussed.