Effect of alprenolol on mortality among patients with definite or suspected acute myocardial infarction. Preliminary results

Beta-blockers in hypertension: overview and meta-analysis of randomized outcome trials

BACKGROUND

Meta-analyses from randomized outcome-based trials have challenged the role of beta-blockers for the treatment of hypertension. However, because they often include trials on diseases other than hypertension, the role of these drugs in the choice of the blood pressure (BP)-lowering treatment strategies remains unclear.

METHODS

Electronic databases were searched for randomized trials that compared beta-blockers vs. placebo/no-treatment/less-intense treatment (BP-lowering trials) or beta-blockers vs. other antihypertensive agents in patients with or without hypertension (comparison trials). Among BP-lowering trials and according to baseline comorbidity, we separately considered trials in hypertension, trials without chronic heart failure or acute myocardial infarction, and trials with either chronic heart failure or acute myocardial infarction. Seven fatal and nonfatal outcomes were calculated (random-effects model) for BP-lowering or comparison trials.

RESULTS

A total of 84 BP-lowering or comparison trials (165 850 patients) were eligible. In 67 BP-lowering trials (68 478 patients; mean follow-up 2.5 years; baseline SBP/DBP, 136/82 mmHg), beta blockers were associated with a lower incidence of major cardiovascular events [risk ratio 0.85 and 95% confidence interval (95% CI) 0.78-0.92] and all-cause death (risk ratio 0.81 and 95% CI 0.75-0.86). Restriction of the analysis to five trials recruiting exclusively hypertensive patients (18 724 patients; mean follow-up 5.1 years; baseline SBP/DBP 163/94 mmHg), a -10.5/-7.0 mmHg BP decrease was accompanied by reduction of major cardiovascular events by 22% (95% CI, 6-34). In 24 comparison trials (103 764 patients, 3.92 years of mean follow-up), beta-blockers compared with other agents were less protective for stroke and all-cause death in all trials and in trials conducted exclusively in hypertensive patients (averaged risk ratio increase 20 and 6%, respectively, for both cases).

CONCLUSION

Compared with other antihypertensive agents, beta-blockers appear to be substantially less protective against stroke and overall mortality. However, they exhibit a substantial risk-reducing ability for all events when prescribed to lower BP in patients with modest or more clear BP elevations, and therefore can be used as additional agents in hypertensive patients.

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.

Clinical outcomes with β-blockers for myocardial infarction: a meta-analysis of randomized trials

BACKGROUND

Debate exists about the efficacy of β-blockers in myocardial infarction and their required duration of usage in contemporary practice.

METHODS

We conducted a MEDLINE/EMBASE/CENTRAL search for randomized trials evaluating β-blockers in myocardial infarction enrolling at least 100 patients. The primary outcome was all-cause mortality. Analysis was performed stratifying trials into reperfusion-era (> 50% undergoing reperfusion or receiving aspirin/statin) or pre-reperfusion-era trials.

RESULTS

Sixty trials with 102,003 patients satisfied the inclusion criteria. In the acute myocardial infarction trials, a significant interaction (Pinteraction = .02) was noted such that β-blockers reduced mortality in the pre-reperfusion (incident rate ratio [IRR] 0.86; 95% confidence interval [CI], 0.79-0.94) but not in the reperfusion era (IRR 0.98; 95% CI, 0.92-1.05). In the pre-reperfusion era, β-blockers reduced cardiovascular mortality (IRR 0.87; 95% CI, 0.78-0.98), myocardial infarction (IRR 0.78; 95% CI, 0.62-0.97), and angina (IRR 0.88; 95% CI, 0.82-0.95), with no difference for other outcomes. In the reperfusion era, β-blockers reduced myocardial infarction (IRR 0.72; 95% CI, 0.62-0.83) (number needed to treat to benefit [NNTB] = 209) and angina (IRR 0.80; 95% CI, 0.65-0.98) (NNTB = 26) at the expense of increase in heart failure (IRR 1.10; 95% CI, 1.05-1.16) (number needed to treat to harm [NNTH] = 79), cardiogenic shock (IRR 1.29; 95% CI, 1.18-1.41) (NNTH = 90), and drug discontinuation (IRR 1.64; 95% CI, 1.55-1.73), with no benefit for other outcomes. Benefits for recurrent myocardial infarction and angina in the reperfusion era appeared to be short term (30 days).

CONCLUSIONS

In contemporary practice of treatment of myocardial infarction, β-blockers have no mortality benefit but reduce recurrent myocardial infarction and angina (short-term) at the expense of increase in heart failure, cardiogenic shock, and drug discontinuation. The guideline authors should reconsider the strength of recommendations for β-blockers post myocardial infarction.

Influence of beta-blockers on the myocardial mRNA expressions of circadian clock- and metabolism-related genes

Daily rhythms are regulated by a master clock-system in the suprachiasmatic nucleus and by a peripheral clock-system in each organ. Because norepinephrine is one of the timekeepers for the myocardial circadian clock that influences cardiac metabolism, it is speculated that a beta-blocker may affect the circadian clock and metabolism in heart tissue. In this study, thirty mg/kg/day of propranolol (a lipophilic beta-blocker) or atenolol (a hydrophilic beta-blocker) was given orally to Wistar rats for 4 weeks. The mRNA expressions of Bmal1 and E4BP4 in heart tissue were suppressed by the beta-blockers. However, the mRNA expressions of these clock genes in the suprachiasmatic nucleus were unchanged. Myocardial mRNA expressions of lactate dehydrogenase a and pyruvate dehydrogenase kinase 4 were also suppressed by the beta-blockers. In addition, ATP content in heart tissue was significantly elevated by the beta-blockers throughout 24 hours. The effects of propranolol and atenolol did not differ significantly. This study showed for the first time that a beta-blocker affects myocardial clock gene expression. Propranolol and atenolol increased ATP content in heart tissue throughout 24 hours. The influences of beta-blockers may be negligible on the SCN, and may be independent of lipid solubility on heart tissue. It is well known that these drugs exert a protective effect against myocardial ischemia, which may be mediated by an increase in the preservation of myocardial ATP.

The long-term effect of alprenolol on plasma apolipoproteins A-I and B

The concentration of lipids, lipoproteins and apolipoprotein A-I and B was measured in the plasma of 33 patients, enrolled in a double-blind, controlled trial of alprenolol in myocardial infarction, after one year on the study medication and again after 6 months off the medication. Sixteen patients received 200 mg alprenolol twice daily and 17 received placebo. There were no statistically significant differences between the parameters in the two groups after one year on medication. However, when medication was stopped, the ratio of apolipoprotein B to apolipoprotein A-I fell by 9% in the alprenolol group and increased by 2% in the placebo group. This difference was statistically significant. Our results suggest that alprenolol, a beta-blocker with weak intrinsic sympathomimetic effect, has slight effects on plasma lipoproteins. These effects were apparent only by measurements of apolipoproteins.

Changes in heart size during long-term timolol treatment after myocardial infarction

The effect of long-term timolol treatment on heart size after myocardial infarction was evaluated by X-ray in a double-blind study including 241 patients (placebo 126, timolol 115). The follow-up period was 12 months. The timolol-treated patients showed a small but significant increase in heart size from baseline in contrast to a decrease in the placebo group. These differences may be caused by timolol-induced bradycardia and a compensatory increase in end-diastolic volume. The timolol-related increase in heart size was observed only in patients with normal and borderline heart size. In patients with cardiomegaly, the increase in heart size was similar in both groups. After re-infarction, heart size increased in the placebo group and remained unchanged in the timolol group.

Beta blockers after myocardial infarction--aspects on study design based on current knowledge

The beta-blocker trials published so far may be subdivided into three different categories: 1) retrospective, 2) prospective non-conclusive, 3) prospective conclusive studies. The retrospective studies suffer the weaknesses of the retrospective method and may only be used as supportive evidence. There have so far been four prospective studies producing positive results, three with alprenolol and one with practolol. The studies presented support the concept that practolol and alprenolol reduce the long-term mortality due to sudden death from ischemic heart disease after myocardial infarction. All the studies have been criticized on various grounds and a list of unanswered remaining issues may be made. Acute and long-term effects of betablockade need not be the same. Our knowledge about the necessary doses and plasma levels is incomplete. All the studies published so far cover a maximum period of two years. If the study observation periods were prolonged it is likely that at some time the relative benefit becomes less. Ideal treatment should be reserved for those patients likely to derive significant benefit from it. At the present time identification of such patients is not sufficiently precise. Whether or not the beta-blockers have an antiarrhythmic effect, for instance demonstrated on chronic PVC's, this information is of little value in interpreting the proper mechanism of the beta-blockers in acute ischemia and lethal arrhythmias. In order to contribute new knowledge future studies should involve sufficiently large numbers of representative groups of patients, a stratified study design and a beta-blocker with ancillary properties different from alprenolol.

Beta-sympathetic blockade with chronotropic compensation in the management of heart disease

This presentation briefly describes the sympathetic and parasympathetic control of the heart, particularly in relation to coronary vascular effects. Autonomic disturbances following myocardial infarction and their significance are discussed. The influence of the autonomic system in chronic coronary heart disease is considered, particularly in relation to the beneficial effects which may be obtained by the combined use of beta-blocking drugs and cardiac pacing. Nine anginal patients with spontaneous or drug-induced bradycardia received temporary pacing and 27 others had pacemakers implanted. Pain was well controlled in the former group. Long term pacing produced worth-while benefit in 67% of the patients followed for periods up to 6 months, the figure falling to 50% among those followed for 24 months. Eight of the 27 relapsed. Thus, correction of bradycardia by pacing often produced a beneficial long term effect. A second group of 14 patients with ventricular arrhythmias was treated with beta-blocking agents combined with pacing. So far, 10 of these 14 have had their arrhythmias controlled either by the initial or by a modified drug regime. The results indicate that among patients with chronic coronary artery disease, beta-blockade to minimize cardiac sympathetic activity, coupled with pacing to prevent loss of chronotrophic control, often represents an effective combination for the management of refractory angina or arrhythmias.

Beta blockade and the secondary prevention of myocardial infarction

In 1965 Snow reported a clinical trial in which treatment with propranolol significantly reduced mortality following myocardial infarction. Unfortunately the design of this trial was inadequate by modern standards, and the results must be discounted. None of the studies published since then have provided convincing evidence that beta blockers are useful following myocardial infarction. Survival after a myocardial infarction depends principally upon the amount of heart muscle that has been destroyed, and it is probably unreasonable to expect any treatment to reduce mortality by more than 20 or 30%. In patients who survive an infarction for more than 48 hours, the expected fatality rate in the next year is approximately 15%. To detect a reduction of this mortality to 10%, 2300 patients would be needed in the trial. The analysis of several of the published trials has been made difficult by a lack of data, the failure on the part of authors and journal editors to agree on a common method of presenting results, and disagreement as to whether results should be analysed on an "all patients--intention to treat" basis or by considering only "clinical effectiveness" among patients who remained on treatment. Examples of these problems will be given, together with a suggested scheme for data presentation. The 95% confidence intervals of all the randomised and double blind studies of beta blockers after myocardial infarction show that by "intention to treat" analysis, none demonstrate a statistically significant reduction in mortality among treated patients. Only the practolol trial was of a reasonable size, but even here total mortality was not significantly reduced; the result is in any case of only theoretical interest. The trials showing a reduction of mortality in association with alprenolol treatment are not convincing, and the stratified trial design of one of these may have given misleading results because of the relatively small number of patients involved.

Treating individuals 2. Subgroup analysis in randomised controlled trials: importance, indications, and interpretation

Large pragmatic trials provide the most reliable data about the effects of treatments, but should be designed, analysed, and reported to enable the most effective use of treatments in routine practice. Subgroup analyses are important if there are potentially large differences between groups in the risk of a poor outcome with or without treatment, if there is potential heterogeneity of treatment effect in relation to pathophysiology, if there are practical questions about when to treat, or if there are doubts about benefit in specific groups, such as elderly people, which are leading to potentially inappropriate undertreatment. Analyses must be predefined, carefully justified, and limited to a few clinically important questions, and post-hoc observations should be treated with scepticism irrespective of their statistical significance. If important subgroup effects are anticipated, trials should either be powered to detect them reliably or pooled analyses of several trials should be undertaken. Formal rules for the planning, analysis, and reporting of subgroup analyses are proposed.

Secondary prevention of myocardial infarction: role of beta-adrenergic blockers and angiotensin-converting enzyme inhibitors

beta-Blockers reduce cardiovascular death and reinfarction in patients with a history of myocardial infarction (MI), and angiotensin-converting enzyme (ACE) inhibitors provide an overall survival benefit in patients with signs or symptoms of left ventricular (LV) dysfunction and a history of acute MI. Despite this, these agents remain underused in clinical practice. Appropriate patient selection in standard clinical practice should be encouraged in order to achieve a mortality rate reduction comparable to that seen in clinical trials. It appears from the findings of recent studies that the greatest benefit from beta-blocker therapy is achieved in patients who are more than 60 years of age and in patients at moderate or high risk for reinfarction and death (eg, patients with LV dysfunction or arrhythmias or both). Patients with class I-IV heart failure treated with ACE inhibitors have fewer recurrent infarctions, a lower incidence of severe congestive heart failure, and a reduced incidence of total cardiovascular death and sudden cardiac death. In addition to the studies completed in patients with MI, there are ongoing studies evaluating whether or not ACE inhibitors can reduce myocardial ischemic events in patients without a prior infarction who have coronary artery disease or hypertension and preserved LV function. There is also growing evidence that concomitant therapy with a beta-blocker and an ACE inhibitor may reduce mortality rates beyond that observed with ACE inhibitors alone in survivors of MI who have LV dysfunction.

Effect of beta blockade with and without sympathomimetic activity (ISA) on sympathovagal balance and baroreflex sensitivity

Beta blockers increase heart rate variability (HRV) and improve survival in coronary artery disease (CAD). The benefit of beta blockers with intrinsic sympathomimetic activity (ISA) in CAD still remains a matter of debate, and their effect on HRV has not yet been investigated. Therefore, we measured HRV, systolic blood pressure variability (BPV) and baroreflex sensitivity (BRS) under propranolol (PROP, without ISA, 160 mg q.d.), pindolol (PIN, with potent ISA, 15 mg q.d.) and placebo (PLA, q.d.) in 30 healthy subjects, aged 21-39 years, during controlled frequency breathing (0.30 Hz) in supine and tilt positions. PROP increased HRV in the high-frequency (0.15-0.40 Hz) band (PROP 7.4 +/- 1.0; PLA 6.9 +/- 1.4; PIN 6.8 +/- 1.0 ln MI2; P = 0.003), decreased BPV in the low-frequency band (at 0.1 Hz, Mayer waves) (PROP 0.6 +/- 0.7; PLA 1.3 +/- 1.1; PIN 1.2 +/- 1.2 ln mmHg2; P = 0.001) and enhanced BRS (PROP 14.6 +/- 9.5; PLA 8.0 +/- 6.8; PIN 8.7 +/- 6.8 ms mmHg-1; P = 0.001) in the supine position. After passive tilt, PROP decreased HRV in the low-frequency band (PROP 6.1 +/- 0.9; PLA 6.5 +/- 1.1; PIN 6.9 +/- 0.7 ln MI2; P < 0.001) and decreased Mayer waves (PROP 1.8 +/- 0.8; PLA 2.4 +/- 1.0; PIN 2.7 +/- 0.8 ln mm Hg2; P < 0.001). PIN increased the low-frequency HRV response, which is induced by passive tilt (PIN + 0.9 +/- 1.0; PLA + 0.3 +/- 1.3, PROP + 0.3 +/- 1.0 ln MI2; P = 0.026). Our results prove that beta-adrenergic blockade with potent ISA does not increase HRV, has no beneficial effect on autonomic balance and even exaggerates sympathetic responses to passive tilt.

Reappraisal of the importance of heart rate as a risk factor for cardiovascular morbidity and mortality

Heart rate is a key determinant of myocardial oxygen consumption. Several lines of evidence support a consistent association between heart rate and cardiovascular mortality. Increments in heart rate are positively related to cardiovascular and sudden death in patients with hypertension or previous myocardial infarction and in the elderly with heart disease. This relationship is important because a number of commonly used cardiovascular agents, such as beta-blockers and calcium antagonists (CAs), can affect heart rate. Beta-blockers decrease heart rate and reduce morbidity and mortality in post-myocardial infarction patients. The CAs are a structurally diverse group of agents with different physiologic effects. The dihydropyridine CAs are not associated with a reduction in heart rate. In fact, often they can cause reflex tachycardia as a result of potent systemic vasodilator action, which may provoke angina, especially in patients with ischemic heart disease. The nondihydropyridine CAs verapamil and diltiazem reduce heart rate but are associated with negative inotropy. Mibefradil, the first member of a new class of CAs, reduces heart rate and is not associated with negative inotropic effects. This unique pharmacologic profile may be of great value in treating hypertensive patients, particularly those with coexisting ischemic heart disease, and also patients with angina pectoris alone. However, the clinical benefit of pharmacologically reducing heart rate with mibefradil needs to be demonstrated in controlled trials.

Utility of beta-blockade treatment for older postinfarction patients

OBJECTIVE

The prevalence of myocardial infarction (MI) in older people is high. Whereas use of beta-blockers after MI is known to lower MI mortality in younger adults, its efficacy for adults more than 75 years of age remains less clear. We hypothesized that use of beta-blockers after MI in older adults would improve clinical outcomes.

DESIGN

Retrospective cohort study.

SETTING

A community-based, tertiary-care teaching hospital.

METHODS

A total of 1011 consecutive MI patients aged 60 to 89 were admitted to Boston's Beth Israel Hospital between January 1988 and September 1989 and were screened for this study. One hundred eighteen patients met eligibility criteria, of whom 76 received metoprolol, > or = 25 mg/day for at least 5 days after their MI. Forty-two age and clinically matched patients were similarly suitable for beta-blocker therapy, but it was omitted by their physicians during and after hospitalization. The latter group served as controls.

MEASUREMENTS

Mortality, reinfarction, and subsequent hospital admissions were measured.

RESULTS

MI patients aged 60 to 89 years who were treated with metoprolol had an age-adjusted mortality reduction of 76% (RR 0.24; P < .001; 95% CI 0.11-0.54). Multivariate logistic regression analysis showed a 12% mortality reduction (95% CI 0.75-1.00) among older MI patients, attributable to metoprolol therapy. Reinfarction rates were unchanged in patients receiving metoprolol therapy, and subsequent rehospitalizations were significantly increased among the metoprolol patients.

CONCLUSIONS

Use of metoprolol significantly reduced mortality in older MI patients. The fact that metoprolol-treated patients had neither reduced reinfarctions or rehospitalizations may relate to methologic limitations of this study. The mortality data support the hypothesis that older patients benefit from postinfarction beta-blockade.

Beta blocker use in the treatment of community hospital patients discharged after myocardial infarction

OBJECTIVE

To explore the reasons for underutilization of beta blocker treatment after acute myocardial infarction.

DESIGN

A retrospective chart review.

SETTING

Two large community hospitals in Milwaukee, Wisconsin.

PATIENTS/PARTICIPANTS

All subjects (n = 694) discharged alive from July 1, 1990, to June 30, 1991, who had a diagnosis of acute myocardial infarction were eligible. Of these, 250 had missing data, resulting in a final sample of 444.

RESULTS

Twenty-nine percent of the 444 patients were prescribed beta blocker therapy on discharge. Characteristics of the patients and their treatment associated with receipt of beta blocker therapy were identified with a logistic regression model. The adjusted odds ratios were 0.52 for female gender, 0.34 for no health insurance, 0.21 for chronic obstructive pulmonary disease, 0.46 for congestive heart failure, 0.28 for atrioventricular block, 1.86 for hypertension, 1.93 for chest pain during acute myocardial infarction, and 4.65 for prehospital beta blocker use. Prescription of beta blocker therapy was also influenced by receipt of other treatment modalities. The adjusted odds ratios were 0.23 for receipt of beta blocker therapy associated with myocardial revascularization, 0.18 for prescription on discharge of calcium channel blockers, and 0.22 for receipt of angiotensin-converting enzyme inhibitors.

CONCLUSION

A minority of patients discharged after acute myocardial infarction receive beta blocker therapy, and women are only half as likely as men to receive it, after controlling for other factors. Though there are no data relating to whether calcium channel blockers or angiotensin-converting enzyme inhibitors lessen the protective effect of beta blocker therapy post-acute myocardial infarction, it would appear that these agents are frequently being used in lieu of beta blocker therapy for post-acute myocardial infarction patients.

Beta-adrenergic blockers as cardioprotective agents

The evidence supporting and describing cardioprotective effects of beta-adrenergic blocker treatment is surveyed. Details of the many studies that individually and collectively document the ability of long-term and acute beta-blocker therapy to reduce overall mortality, sudden cardiovascular death, and nonfatal reinfarction in patients surviving or experiencing a myocardial infarction are described. A discussion of the mechanisms by which beta blockers probably and theoretically achieve these benefits includes the suggestion that they may reduce plaque rupture, thus indirectly inhibiting thrombosis. It is also suggested that, in the future, further cardioprotective benefits may accrue to the use of beta blockers in conjunction with thrombolysis and of beta blockers with a duration of action sustained throughout a full 24 hours.

Reduction of mortality, sudden death and non-fatal reinfarction with beta-adrenergic blockers in survivors of acute myocardial infarction: a new hypothesis regarding the cardioprotective action of beta-adrenergic blockade

Beta-adrenergic blockers have been shown definitely to reduce the incidence of total mortality, cardiovascular mortality, sudden death and nonfatal reinfarction in survivors of an acute myocardial infarction. The mechanisms to explain this protective action of beta blockers have never been elucidated conclusively, and include the antiarrhythmic and myocardial oxygen demand-reducing effects of the drugs. An antithrombotic mechanism has also been suggested. However, beta blockers have relatively weak antiplatelet activity, suggesting that their antithrombotic effects may be related to prevention of coronary artery plaque rupture and the subsequent propagation of an occlusive arterial thrombus rather than direct anticoagulant action. The therapeutic ability of beta blockers to attenuate the hemodynamic consequences of catecholamine surges, may protect a vulnerable atherosclerotic plaque from fracture, thereby reducing risk of coronary thrombosis, myocardial infarction and death.

Beta-adrenergic blockade and calcium channel blockade in myocardial infarction

Because of their hemodynamic and antiarrhythmic actions, beta-adrenergic blockers and calcium-entry blockers have been suggested for use in patients with myocardial infarction (MI) for reducing infarct size, preventing ventricular ectopy, and for prolonging life in survivors of acute MI. Experimental studies have suggested their usefulness in these areas. Clinical studies have demonstrated a role for beta-blockers in the hyperacute phase of MI, and in longterm treatment of infarct survivors. Calcium channel blockers appear to have somewhat less utility in patients with Q wave MIs, but may have an important role in therapy of the non-Q wave infarct.

Costs and effectiveness of routine therapy with long-term beta-adrenergic antagonists after acute myocardial infarction

We analyzed the costs and effectiveness of routine therapy with beta-adrenergic antagonists in patients who survived an acute myocardial infarction. On the basis of data pooled from the literature, this form of therapy resulted in a 25 percent relative reduction annually in the mortality rate for years 1 to 3 and a 7 percent relative reduction for years 4 to 6 after a myocardial infarction. The estimated cost of six years of routine beta-adrenergic-antagonist therapy to save an additional year of life was $23,400 in low-risk patients, $5,900 in medium-risk patients, and $3,600 in high-risk patients, assuming that the entire benefit of earlier treatment is lost immediately after six years. Under a more likely assumption--that the benefit of six years of treatment wears off gradually over the subsequent nine years--the estimated cost of therapy per year of life saved would be $13,000 in low-risk patients, $3,600 in medium-risk patients, and $2,400 in high-risk patients. As compared with coronary-artery bypass grafting and the medical treatment of hypertension, routine beta-adrenergic-antagonist therapy has a relatively favorable cost-effectiveness ratio.

Predictors of non-fatal ischemic events after myocardial infarction

We characterize predictors of reinfarction and angina in 403 consecutive men aged 60 years or less who underwent heart catheterization within one month (18 +/- 6 days) after a qualifying myocardial infarction. Angiography showed obstructive lesions (greater than or equal to 50% diameter reduction) in 380 patients. One-, two- and three-vessel disease was found in 143 (36%), 139 (35%) and 98 (29%) patients, respectively. After 57 months of follow-up there were 60 deaths (12%), 41 patients (10%) sustained a new infarction and 210 (52%) had angina. Cox regression analysis selected the number of diseased vessels as the only independent 'predictor of reinfarction; independent predictors of angina were the number of diseased vessels and a history of angina prior to the qualifying infarction. Risk stratification showed the probability of reinfarction at 6 years to be significantly lower (P less than 0.001) in patients with one-vessel disease (12%) than in those with two- (30%) and three-vessel disease (37%). Similarly the probability of angina was also lower (P less than 0.001) in patients with one-vessel disease (51%) as compared to those with two- (72%) and three-(74%) vessel involvement. Thus multi-vessel disease is the main predictor of new non-fatal ischemic events after myocardial infarction.

Serum magnesium, calcium, phosphate and PTH following long-term beta-blockade in ischaemic heart disease

In 40 patients with ischaemic heart disease the serum levels of magnesium, parathyroid hormone (PTH), phosphate, calcium, and ionized calcium remained unchanged and within normal limits following treatment for 12 months with alprenolol (n = 20) or placebo (n = 20). No changes occurred during a 2 week withdrawal period. The clinical implication is that the non-cardioselective betablocker alprenolol can be given to patients with ischaemic heart disease without the risk of inducing potentially cardiotoxic disturbances in serum magnesium and serum calcium levels. Whether this applies to cardioselective beta-blockers remains to be established.

Drug treatment of hypertension

There are several first choices for the treatment of mild and moderate hypertension. The selection of a drug may be influenced by concomitant pathology, with positive indications for particular drugs, e.g. coexistent angina, indicating use of a beta-receptor blocking drug or calcium antagonist; fluid retention indicating a diuretic; or contraindication e.g. asthma, and beta-adrenoceptor blocking drugs. beta-Adrenoceptor blocking drugs have the advantage of a long history and of possibly being cardioprotective following myocardial infarction, but they have not yet been established as primary preventive agents in hypertensive patients. The alpha-receptor blocking drugs have the advantage of favourably affecting lipid profile and blood pressure. Therefore, there may be advantages in the use of combined alpha- and beta-blockade. The diuretics, which have the advantage of being inexpensive, are widely used but long term metabolic effects, particularly hypokalaemia, cause concern. This is correctable by co-administration of a potassium sparing diuretic and often preventable by using low doses of the diuretic. Diet may be important as hypokalaemia appears to be less of a problem where potassium intake is high. Experience with calcium antagonists is widening but the use of converting enzyme inhibitors is more limited, and some physicians are less ready to use them as first choice in mild hypertension at present. Drugs like methyldopa, clonidine, the adrenergic neurone inhibitory drugs are now used more as reserve agents. More severe cases of hypertension may require drugs from 2 of the 3 major groups: beta-blocking drugs, vasodilators and diuretics. In some cases, drugs from each of these 3 groups will be required.

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.

[Predictor function of hemorheologic parameters with reference to the incidence of manifest circulatory disorders: Concept of the Aachen study]

The prevention of cardiovascular disease has up till now generally been limited to control of the classical risk factors. The primary problem of the risk factor model is, that although a statistically verified relationship exists between risk factors and vascular disease, an individual prognosis is presently impossible. Surveys that show a relation between risk factors and impaired blood fluidity support the conception that a change in blood fluidity could be considered an early detection screening of vascular diseases. Prospective studies have shown that the hematocrit is related to circulatory disturbances. The main aim of the present study was to determine the clinical relevance of rheological parameters (hematocrit, plasma viscosity, erythrocyte rigidity, thrombocyte aggregation, erythrocyte aggregation), and the importance of altered blood fluidity as a predictor of manifest cerebral, cardiac or peripheral vascular disturbance.

Effect of timolol on mortality and reinfarction after acute myocardial infarction: prognostic importance of heart rate at rest

Long-term timolol treatment after acute myocardial infarction is associated with a significant reduction in mortality and nonfatal reinfarction. To evaluate whether the reduction in mortality and morbidity is exclusively or partly dependent on a reduction in heart rate (HR), cardiac events in the Norwegian Timolol Multicenter Study were analyzed according to resting HR at baseline and at 1 month of follow-up Resting HR at baseline was a significant predictor of total death and all events (total death plus nonfatal reinfarction) both in placebo- and in timolol-treated patients. In the placebo group the median resting HR was unchanged from baseline to 1 month control (72 beats/min), but was reduced from 72 beats/min to 56 beats/min in the timolol group. Resting HR during follow-up remained a significant predictor of total death. Further, mortality at a given HR during treatment was not markedly different whether the HR was spontaneous or caused by timolol. Timolol treatment was related to a significant reduction in mortality, and this study suggests that the major effect of timolol treatment on mortality after acute myocardial infarction may be attributed to the reduction in HR. Timolol treatment was also associated with an overall reduction in nonfatal reinfarction. However, nonfatal reinfarction was inversely related to resting HR during follow-up, indicating that although coronary artery occlusion in low-risk patients may cause nonfatal reinfarction, the outcome in high-risk patients is more likely to be death. When analyzing mortality and nonfatal reinfarction combined, timolol treatment was related to a reduction in cardiac events at any given HR, suggesting that factors in addition to HR reduction are important in the protective effects of timolol.

Early use of beta-adrenergic-blocking agents in acute myocardial infarction

Of recent interest is the acute use of beta-adrenergic-blocking agents in patients who have suffered an acute myocardial infarction (AMI). Acute use of beta-blockers refers to initiation of therapy within hours following the onset of symptoms suggestive of AMI. The proposed goal of therapy is to alter the infarction process to improve mortality. Because of the hyperadrenergic activity present in patients during an infarction, beta-blockers are theoretically an attractive therapeutic intervention because of their sympatholytic properties. Acute use of beta-blockers has been shown to limit infarct size, as determined by cardiac enzyme activity, and reduce the incidence of major ventricular arrhythmias. Beta-blockers may also prevent infarction in patients with symptoms suggestive of infarction. However, the acute use of beta-adrenergic-blocking agents has not been shown to reduce short-term (less than or equal to 30 d) mortality. In view of this fact, the acute use of beta-adrenergic-blocking agents cannot be recommended.

Use of beta-adrenergic blocking agents after myocardial infarction

Long-term clinical trials have been carried out to evaluate the effectiveness of beta-adrenergic blocking agents in modifying the natural history of myocardial infarction (MI). In most of these studies, a lower mortality rate was documented in patients receiving a beta-blocker than in those receiving placebo. The drugs may have both antiarrhythmic and antiischemic effects. In patients without contraindications to beta-blocker treatment, a relative reduction in mortality of 25% can be expected for at least one to two years, with the reduction higher in older patients or patients having complications at infarction. Study results indicate benefit from starting beta-blocker therapy early after infarction, and some benefit from starting late seems a reasonable assumption. Evidence also points to a benefit from prolonged therapy. Beta-blockers are well tolerated in most patients; those major side effects that do occur are often cardiovascular.

The effects of metoprolol and dazmegrel, alone and in combination, on arrhythmias induced by coronary artery occlusion in conscious rats

The effects of metoprolol and the thromboxane synthetase inhibitor dazmegrel, alone and in combination, were examined in a model of coronary artery occlusion in conscious rats. In a dose (2 mg kg-1), intravenously, that resulted in a marked bradycardia (of 50-80 beats min -1) metoprolol did not influence the incidence or severity of the ventricular arrhythmias that occur in the first 20 min following occlusion, nor did it improve survival (assessed at both 20 min and 16 h). In a dose (5 mg kg-1), intravenously, that in another conscious rat model involving tissue hypoperfusion inhibited thromboxane production, dazmegrel also did not modify ischaemic arrhythmias or survival. In contrast, metoprolol and dazmegrel (2 mg kg-1 and 5 mg kg-1 i.v.) when given together prior to coronary artery occlusion, produced a significant reduction in mortality both at 20 min and 16 h (e.g. from 60-75% in the control, metoprolol alone and dazmegrel alone groups and only 25% in the combined-treatment group). This was due to a decrease in the incidence of terminal ventricular fibrillation. The results suggest that a combination of beta-adrenoceptor blocking drug with a drug that inhibits thromboxane synthesis may offer more protection against ischaemia-induced ventricular fibrillation than either drug used alone. They suggest a role for both catecholamines and thromboxane in the genesis of ischaemia-induced ventricular fibrillation.

Long-term treatment with metoprolol after myocardial infarction: effect on 3 year mortality and morbidity

The effects of metoprolol treatment in patients surviving acute myocardial infarction have been investigated in a double-blind randomized study. The patients were stratified according to age, infarct size and type of ventricular arrhythmias before administration of metoprolol, 100 mg twice daily (n = 154), or placebo (n = 147). All patients were followed up for 36 months. There were 31 (29 cardiac) and 25 (20 cardiac) deaths in the placebo and metoprolol groups, respectively. Subgroup analyses showed a significant reduction of cardiac death in patients with a large infarct (32.1% with placebo versus 12.5% with metoprolol, p less than 0.05) as a result of active treatment. Sudden death rates were 14.7% in the placebo versus 5.8% in the metoprolol group (p less than 0.05). The incidence of nonfatal reinfarction was 21.1% in the placebo versus 11.7% in the metoprolol group (p less than 0.05). The reduction in nonfatal reinfarction was similar in all pretreatment risk strata. The difference between the two groups in cumulative number of cardiac deaths and patients experiencing nonfatal reinfarction increased throughout the study. Furthermore, cerebrovascular events (p less than 0.05) and coronary bypass surgery (p = 0.058) were more frequent in the placebo group. In conclusion, after 36 months of metoprolol treatment after myocardial infarction, there was a significant reduction of nonfatal reinfarction and sudden death in all patients and a reduction of cardiac death in those with a large infarct.

Enhancement of visit adherence in the national beta-blocker heart attack trial

Efforts were made in the Beta Blocker Heart Trial (BHAT), a double-blind study of 3837 post-MI patients, to enhance visit adherence, a measure of compliance that is not subjective and can be easily monitored. Of the required visits, 93.9% were completed in the window, 3.9% of the patients were classified as dropouts and 12 persons were lost to follow-up. Methods used to enhance compliance varied with circumstances but included appointment reminders, assistance with transportation, minimal waiting times, newsletters, continuity of care, involvement of family members, and close contact with private physicians. Comparisons of the BHAT visit adherence rates to those from other clinical trials are difficult to make because there are few reports in the literature regarding follow-up in large multicenter clinical trials. However, data obtained through personal communications, as well as published reports, indicate that adherence in primary prevention trials was generally less than that of secondary prevention trials. Adherence rates in the BHAT tended to be slightly higher than those of comparable trials.

Secondary prevention after myocardial infarction: subgroup analysis of patients at risk in the Norwegian Timolol Multicenter Study

Timolol treatment after myocardial infarction is generally related to a significant reduction in both mortality and reinfarction compared with placebo. Retrospective analyses of the timolol study are performed on subgroups of patients with a high placebo mortality. The present study shows that these patients are target groups for secondary prevention, as they benefit most from timolol treatment after myocardial infarction. In patients 65-75 years of age, the number of cardiac deaths and reinfarctions prevented by timolol treatment is twice as high as that of patients below 65 years of age. Timolol treatment is well tolerated in the older age group and the contraindications for timolol treatment are independent of age up to 75 years. The reduction in mortality and reinfarction is independent of heart size at baseline. However, in patients with cardiomegaly and compensated heart failure on treatment with digitalis and diuretics, timolol treatment may be of special importance because of the very high incidence of cardiac death in this group of patients. In patients with compensated heart failure on treatment with digitalis and diuretics, timolol treatment does not precipitate heart failure. Patients with stable diabetes mellitus basically behave like nondiabetic patients regarding inclusion rate, side effects, and timolol-related reduction in mortality and reinfarction. Decisions concerning secondary prevention with timolol should be independent of preinfarction and postinfarction angina. In conclusion, 70-80% of all the patients below 75 years of age surviving myocardial infarction, without contraindication to beta-blocker treatment, can be treated with timolol 10 mg twice daily to reduce mortality and reinfarction. In contrast to previous routines, secondary prevention with beta blockers should be especially directed to high-risk patients.

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.

Early intervention with a beta-blocking drug after acute myocardial infarction

Several controlled studies with long-term administration of beta blockers in postinfarction patients have demonstrated a reduction in cardiac events and mortality. During acute myocardial infarction (AMI), conventional treatment is directed mainly at such complications as pump failure and arrhythmias. Another approach attempts to influence the natural evolution of impending myocardial necrosis by interrupting the process in its reversible phase. In a double-blind trial with metoprolol in suspected or definite AMI, 1,395 patients were studied, 698 of whom received metoprolol and 697 placebo. The 3-month mortality was 36% lower in the metoprolol group (p = 0.024). A reduction in severe ventricular arrhythmias (ventricular fibrillation and tachycardia) was also seen. Chest pain was reduced and there was less need of analgesic drugs in the metoprolol group. Intervention within 12 hours resulted in a limitation of infarct size, a decreased need for furosemide and a shortened hospital stay. A significant reduction in mortality was maintained after 2 years of follow-up despite the same treatment in both groups between 3 and 24 months. Early institution of metoprolol in AMI has resulted in reduced mortality and morbidity.