Individual patient data meta-analysis of beta-blockers in heart failure: rationale and design

Role of β-blockers in Preventing Heart Failure and Major Adverse Cardiac Events Post Myocardial Infarction

β-blockers have been widely utilized as a part of acute myocardial infarction (AMI) treatment for the past 40 years. Patients receiving β-adrenergic blockers for an extended period following myocardial infarction have a higher chance of surviving. Although many patients benefited from β-blockers, many do not, including those with myocardial infarction, left ventricle dysfunction, chronic pulmonary disease, and elderly people. In individuals with the post-acute coronary syndrome and normal left ventricular ejection fraction (LVEF), the appropriate duration of betablocker therapy is still unknown. There is also no time limit for those without angina and those who do not need β-blockers for arrhythmia or hypertension. Interestingly, β-blockers have been prescribed for more than four decades. The novel mechanism of action on cellular compartments has been found continually, which opens a new way for their potential application in cardiac failure and other cardiac events like post-myocardial infarction. Here, in this review, we studied β-blocker usage in these circumstances and the current recommendations for β-blocker use from clinical practice guidelines.

Redefining β-blocker response in heart failure patients with sinus rhythm and atrial fibrillation: a machine learning cluster analysis

BACKGROUND

Mortality remains unacceptably high in patients with heart failure and reduced left ventricular ejection fraction (LVEF) despite advances in therapeutics. We hypothesised that a novel artificial intelligence approach could better assess multiple and higher-dimension interactions of comorbidities, and define clusters of β-blocker efficacy in patients with sinus rhythm and atrial fibrillation.

METHODS

Neural network-based variational autoencoders and hierarchical clustering were applied to pooled individual patient data from nine double-blind, randomised, placebo-controlled trials of β blockers. All-cause mortality during median 1·3 years of follow-up was assessed by intention to treat, stratified by electrocardiographic heart rhythm. The number of clusters and dimensions was determined objectively, with results validated using a leave-one-trial-out approach. This study was prospectively registered with ClinicalTrials.gov (NCT00832442) and the PROSPERO database of systematic reviews (CRD42014010012).

FINDINGS

15 659 patients with heart failure and LVEF of less than 50% were included, with median age 65 years (IQR 56-72) and LVEF 27% (IQR 21-33). 3708 (24%) patients were women. In sinus rhythm (n=12 822), most clusters demonstrated a consistent overall mortality benefit from β blockers, with odds ratios (ORs) ranging from 0·54 to 0·74. One cluster in sinus rhythm of older patients with less severe symptoms showed no significant efficacy (OR 0·86, 95% CI 0·67-1·10; p=0·22). In atrial fibrillation (n=2837), four of five clusters were consistent with the overall neutral effect of β blockers versus placebo (OR 0·92, 0·77-1·10; p=0·37). One cluster of younger atrial fibrillation patients at lower mortality risk but similar LVEF to average had a statistically significant reduction in mortality with β blockers (OR 0·57, 0·35-0·93; p=0·023). The robustness and consistency of clustering was confirmed for all models (p<0·0001 vs random), and cluster membership was externally validated across the nine independent trials.

INTERPRETATION

An artificial intelligence-based clustering approach was able to distinguish prognostic response from β blockers in patients with heart failure and reduced LVEF. This included patients in sinus rhythm with suboptimal efficacy, as well as a cluster of patients with atrial fibrillation where β blockers did reduce mortality.

FUNDING

Medical Research Council, UK, and EU/EFPIA Innovative Medicines Initiative BigData@Heart.

Beta-blocker efficacy across different cardiovascular indications: an umbrella review and meta-analytic assessment

BACKGROUND

Beta-blockers are widely used for many cardiovascular conditions; however, their efficacy in contemporary clinical practice remains uncertain.

METHODS

We performed a prospectively designed, umbrella review of meta-analyses of randomised controlled trials (RCTs) investigating the evidence of beta-blockers in the contemporary management of coronary artery disease (CAD), heart failure (HF), patients undergoing surgery or hypertension (registration: PROSPERO CRD42016038375). We searched MEDLINE, EMBASE and the Cochrane Library from inception until December 2018. Outcomes were analysed as beta-blockers versus control for all-cause mortality, myocardial infarction (MI), incident HF or stroke. Two independent investigators abstracted the data, assessed the quality of the evidence and rated the certainty of evidence.

RESULTS

We identified 98 meta-analyses, including 284 unique RCTs and 1,617,523 patient-years of follow-up. In CAD, 12 meta-analyses (93 RCTs, 103,481 patients) showed that beta-blockers reduced mortality in analyses before routine reperfusion, but there was a lack of benefit in contemporary studies where ≥ 50% of patients received thrombolytics or intervention. Beta-blockers reduced incident MI at the expense of increased HF. In HF with reduced ejection fraction, 34 meta-analyses (66 RCTs, 35,383 patients) demonstrated a reduction in mortality and HF hospitalisation with beta-blockers in sinus rhythm, but not in atrial fibrillation. In patients undergoing surgery, 23 meta-analyses (89 RCTs, 19,211 patients) showed no effect of beta-blockers on mortality for cardiac surgery, but increased mortality in non-cardiac surgery. In non-cardiac surgery, beta-blockers reduced MI after surgery but increased the risk of stroke. In hypertension, 27 meta-analyses (36 RCTs, 260,549 patients) identified no benefit versus placebo, but beta-blockers were inferior to other agents for preventing mortality and stroke.

CONCLUSIONS

Beta-blockers substantially reduce mortality in HF patients in sinus rhythm, but for other conditions, clinicians need to weigh up both benefit and potential risk.

Impact of Renal Impairment on Beta-Blocker Efficacy in Patients With Heart Failure

BACKGROUND

Moderate and moderately severe renal impairment are common in patients with heart failure and reduced ejection fraction, but whether beta-blockers are effective is unclear, leading to underuse of life-saving therapy.

OBJECTIVES

This study sought to investigate patient prognosis and the efficacy of beta-blockers according to renal function using estimated glomerular filtration rate (eGFR).

METHODS

Analysis of 16,740 individual patients with left ventricular ejection fraction <50% from 10 double-blind, placebo-controlled trials was performed. The authors report all-cause mortality on an intention-to-treat basis, adjusted for baseline covariates and stratified by heart rhythm.

RESULTS

Median eGFR at baseline was 63 (interquartile range: 50 to 77) ml/min/1.73 m2; 4,584 patients (27.4%) had eGFR 45 to 59 ml/min/1.73 m2, and 2,286 (13.7%) 30 to 44 ml/min/1.73 m2. Over a median follow-up of 1.3 years, eGFR was independently associated with mortality, with a 12% higher risk of death for every 10 ml/min/1.73 m2 lower eGFR (95% confidence interval [CI]: 10% to 15%; p < 0.001). In 13,861 patients in sinus rhythm, beta-blockers reduced mortality versus placebo; adjusted hazard ratio (HR): 0.73 for eGFR 45 to 59 ml/min/1.73 m2 (95% CI: 0.62 to 0.86; p < 0.001) and 0.71 for eGFR 30 to 44 ml/min/1.73 m2 (95% CI: 0.58 to 0.87; p = 0.001). The authors observed no deterioration in renal function over time in patients with moderate or moderately severe renal impairment, no difference in adverse events comparing beta-blockers with placebo, and higher mortality in patients with worsening renal function on follow-up. Due to exclusion criteria, there were insufficient patients with severe renal dysfunction (eGFR <30 ml/min/1.73 m2) to draw conclusions. In 2,879 patients with atrial fibrillation, there was no reduction in mortality with beta-blockers at any level of eGFR.

CONCLUSIONS

Patients with heart failure, left ventricular ejection fraction <50% and sinus rhythm should receive beta-blocker therapy even with moderate or moderately severe renal dysfunction.

Beta-blockers for heart failure with reduced, mid-range, and preserved ejection fraction: an individual patient-level analysis of double-blind randomized trials

Aims

Recent guidelines recommend that patients with heart failure and left ventricular ejection fraction (LVEF) 40-49% should be managed similar to LVEF ≥ 50%. We investigated the effect of beta-blockers according to LVEF in double-blind, randomized, placebo-controlled trials.

Methods and results

Individual patient data meta-analysis of 11 trials, stratified by baseline LVEF and heart rhythm (Clinicaltrials.gov: NCT0083244; PROSPERO: CRD42014010012). Primary outcomes were all-cause mortality and cardiovascular death over 1.3 years median follow-up, with an intention-to-treat analysis. For 14 262 patients in sinus rhythm, median LVEF was 27% (interquartile range 21-33%), including 575 patients with LVEF 40-49% and 244 ≥ 50%. Beta-blockers reduced all-cause and cardiovascular mortality compared to placebo in sinus rhythm, an effect that was consistent across LVEF strata, except for those in the small subgroup with LVEF ≥ 50%. For LVEF 40-49%, death occurred in 21/292 [7.2%] randomized to beta-blockers compared to 35/283 [12.4%] with placebo; adjusted hazard ratio (HR) 0.59 [95% confidence interval (CI) 0.34-1.03]. Cardiovascular death occurred in 13/292 [4.5%] with beta-blockers and 26/283 [9.2%] with placebo; adjusted HR 0.48 (95% CI 0.24-0.97). Over a median of 1.0 years following randomization (n = 4601), LVEF increased with beta-blockers in all groups in sinus rhythm except LVEF ≥50%. For patients in atrial fibrillation at baseline (n = 3050), beta-blockers increased LVEF when < 50% at baseline, but did not improve prognosis.

Conclusion

Beta-blockers improve LVEF and prognosis for patients with heart failure in sinus rhythm with a reduced LVEF. The data are most robust for LVEF < 40%, but similar benefit was observed in the subgroup of patients with LVEF 40-49%.

Heart Rate and Rhythm and the Benefit of Beta-Blockers in Patients With Heart Failure

BACKGROUND

The relationship between mortality and heart rate remains unclear for patients with heart failure with reduced ejection fraction in either sinus rhythm or atrial fibrillation (AF).

OBJECTIVES

This analysis explored the prognostic importance of heart rate in patients with heart failure with reduced ejection fraction in randomized controlled trials comparing beta-blockers and placebo.

METHODS

The Beta-Blockers in Heart Failure Collaborative Group performed a meta-analysis of harmonized individual patient data from 11 double-blind randomized controlled trials. The primary outcome was all-cause mortality, analyzed with Cox proportional hazard ratios (HR) modeling heart rate measured at baseline and approximately 6 months post-randomization.

RESULTS

A higher heart rate at baseline was associated with greater all-cause mortality for patients in sinus rhythm (n = 14,166; adjusted HR: 1.11 per 10 beats/min; 95% confidence interval [CI]: 1.07 to 1.15; p < 0.0001) but not in AF (n = 3,034; HR: 1.03 per 10 beats/min; 95% CI: 0.97 to 1.08; p = 0.38). Beta-blockers reduced ventricular rate by 12 beats/min in both sinus rhythm and AF. Mortality was lower for patients in sinus rhythm randomized to beta-blockers (HR: 0.73 vs. placebo; 95% CI: 0.67 to 0.79; p < 0.001), regardless of baseline heart rate (interaction p = 0.35). Beta-blockers had no effect on mortality in patients with AF (HR: 0.96, 95% CI: 0.81 to 1.12; p = 0.58) at any heart rate (interaction p = 0.48). A lower achieved resting heart rate, irrespective of treatment, was associated with better prognosis only for patients in sinus rhythm (HR: 1.16 per 10 beats/min increase, 95% CI: 1.11 to 1.22; p < 0.0001).

CONCLUSIONS

Regardless of pre-treatment heart rate, beta-blockers reduce mortality in patients with heart failure with reduced ejection fraction in sinus rhythm. Achieving a lower heart rate is associated with better prognosis, but only for those in sinus rhythm.

A Review of the External Validity of Clinical Trials with Beta-Blockers in Heart Failure

BACKGROUND

Beta-blockers (BBs) are the mainstay prognostic medication for all stages of chronic heart failure (CHF). There are many classes of BBs, each of which has varying levels of evidence to support its efficacy in CHF. However, most CHF patients have one or more comorbid conditions such as diabetes, renal impairment, and/or atrial fibrillation. Patient enrollment to randomized controlled trials (RCTs) often excludes those with certain comorbidities, particularly if the symptoms are severe. Consequently, the extent to which evidence drawn from RCTs is generalizable to CHF patients has not been well described. Clinical guidelines also underrepresent this point by providing generic advice for all patients. The aim of this review is to examine the evidence to support the use of BBs in CHF patients with common comorbid conditions.

METHODS

We searched MEDLINE, PubMed, and the reference lists of reviews for RCTs, post hoc analyses, systematic reviews, and meta-analyses that report on use of BBs in CHF along with patient demographics and comorbidities.

RESULTS

In total, 38 studies from 28 RCTs were identified, which provided data on six BBs against placebo or head to head with another BB agent in ischemic and nonischemic cardiomyopathies. Several studies explored BBs in older patients. Female patients and non-Caucasian race were underrepresented in trials. End points were cardiovascular hospitalization and mortality. Comorbid diabetes, renal impairment, or atrial fibrillation was detailed; however, no reference to disease spectrum or management goals as a focus could be seen in any of the studies. In this sense, enrollment may have limited more severe grades of these comorbidities.

CONCLUSIONS

RCTs provide authoritative information for a spectrum of CHF presentations that support guidelines. RCTs may provide inadequate information for more heterogeneous CHF patient cohorts. Greater Phase IV research may be needed to fill this gap and inform guidelines for a more global patient population.

Effect of age and sex on efficacy and tolerability of β blockers in patients with heart failure with reduced ejection fraction: individual patient data meta-analysis

OBJECTIVES

To determine the efficacy and tolerability of β blockers in a broad age range of women and men with heart failure with reduced ejection fraction (HFrEF) by pooling individual patient data from placebo controlled randomised trials.

DESIGN

Prospectively designed meta-analysis of individual patient data from patients aged 40-85 in sinus rhythm at baseline, with left ventricular ejection fraction <0.45.

PARTICIPANTS

13,833 patients from 11 trials; median age 64; 24% women.

MAIN OUTCOME MEASURES

The primary outcome was all cause mortality; the major secondary outcome was admission to hospital for heart failure. Analysis was by intention to treat with an adjusted one stage Cox proportional hazards model.

RESULTS

Compared with placebo, β blockers were effective in reducing mortality across all ages: hazard ratios were 0.66 (95% confidence interval 0.53 to 0.83) for the first quarter of age distribution (median age 50); 0.71 (0.58 to 0.87) for the second quarter (median age 60); 0.65 (0.53 to 0.78) for the third quarter (median age 68); and 0.77 (0.64 to 0.92) for the fourth quarter (median age 75). There was no significant interaction when age was modelled continuously (P=0.1), and the absolute reduction in mortality was 4.3% over a median follow-up of 1.3 years (number needed to treat 23). Admission to hospital for heart failure was significantly reduced by β blockers, although this effect was attenuated at older ages (interaction P=0.05). There was no evidence of an interaction between treatment effect and sex in any age group. Drug discontinuation was similar regardless of treatment allocation, age, or sex (14.4% in those give β blockers, 15.6% in those receiving placebo).

CONCLUSION

Irrespective of age or sex, patients with HFrEF in sinus rhythm should receive β blockers to reduce the risk of death and admission to hospital.Registration PROSPERO CRD42014010012; Clinicaltrials.gov NCT00832442.

β blockers for heart failure

End under-prescribing for women and older adults

Atrial fibrillation in heart failure: what should we do?

Heart failure (HF) and atrial fibrillation (AF) are two conditions that are likely to dominate the next 50 years of cardiovascular (CV) care. Both are increasingly prevalent and associated with high morbidity, mortality, and healthcare cost. They are closely inter-related with similar risk factors and shared pathophysiology. Patients with concomitant HF and AF suffer from even worse symptoms and poorer prognosis, yet evidence-based evaluation and management of this group of patients is lacking. In this review, we evaluate the common mechanisms for the development of AF in HF patients and vice versa, focusing on the evidence for potential treatment strategies. Recent data have suggested that these patients may respond differently than those with HF or AF alone. These results highlight the clear clinical need to identify and treat according to best evidence, in order to prevent adverse outcomes and reduce the huge burden that HF and AF are expected to have on global healthcare systems in the future. We propose an easy-to-use clinical mnemonic to aid the initial management of newly discovered concomitant HF and AF, the CAN-TREAT HFrEF + AF algorithm (Cardioversion if compromised; Anticoagulation unless contraindication; Normalize fluid balance; Target initial heart rate <110 b.p.m.; Renin-angiotensin-aldosterone modification; Early consideration of rhythm control; Advanced HF therapies; Treatment of other CV disease).

Safety and efficacy of digoxin: systematic review and meta-analysis of observational and controlled trial data

OBJECTIVE

To clarify the impact of digoxin on death and clinical outcomes across all observational and randomised controlled trials, accounting for study designs and methods.

DATA SOURCES AND STUDY SELECTION

Comprehensive literature search of Medline, Embase, the Cochrane Library, reference lists, and ongoing studies according to a prospectively registered design (

PROSPERO

CRD42014010783), including all studies published from 1960 to July 2014 that examined treatment with digoxin compared with control (placebo or no treatment).

DATA EXTRACTION AND SYNTHESIS

Unadjusted and adjusted data pooled according to study design, analysis method, and risk of bias.

MAIN OUTCOME MEASURES

Primary outcome (all cause mortality) and secondary outcomes (including admission to hospital) were meta-analysed with random effects modelling.

RESULTS

52 studies were systematically reviewed, comprising 621,845 patients. Digoxin users were 2.4 years older than control (weighted difference 95% confidence interval 1.3 to 3.6), with lower ejection fraction (33% v 42%), more diabetes, and greater use of diuretics and anti-arrhythmic drugs. Meta-analysis included 75 study analyses, with a combined total of 4,006,210 patient years of follow-up. Compared with control, the pooled risk ratio for death with digoxin was 1.76 in unadjusted analyses (1.57 to 1.97), 1.61 in adjusted analyses (1.31 to 1.97), 1.18 in propensity matched studies (1.09 to 1.26), and 0.99 in randomised controlled trials (0.93 to 1.05). Meta-regression confirmed that baseline differences between treatment groups had a significant impact on mortality associated with digoxin, including markers of heart failure severity such as use of diuretics (P=0.004). Studies with better methods and lower risk of bias were more likely to report a neutral association of digoxin with mortality (P<0.001). Across all study types, digoxin led to a small but significant reduction in all cause hospital admission (risk ratio 0.92, 0.89 to 0.95; P<0.001; n=29,525).

CONCLUSIONS

Digoxin is associated with a neutral effect on mortality in randomised trials and a lower rate of admissions to hospital across all study types. Regardless of statistical analysis, prescription biases limit the value of observational data.

The Genetic Challenges and Opportunities in Advanced Heart Failure

The causes of heart failure are diverse. Inherited causes represent an important clinical entity and can be divided into 2 major categories: familial and metabolic cardiomyopathies. The distinct features that might be present in early disease states can become broadly overlapping with other diseases, such as in the case of inherited cardiomyopathies (ie, familial hypertrophic cardiomyopathy or mitochondrial diseases). In this review article, we focus on genetic issues related to advanced heart failure. Because of the emerging importance of this topic and its breadth, we sought to focus our discussion on the known genetic forms of heart failure syndromes, genetic testing, and newer data on pharmacogenetics and therapeutics in the treatment of heart failure, to primarily encourage clinicians to place a priority on the diagnosis and treatment of these potentially treatable conditions.

Carvedilol Compared With Metoprolol Succinate in the Treatment and Prognosis of Patients With Stable Chronic Heart Failure: Carvedilol or Metoprolol Evaluation Study

BACKGROUND

β-Blockers exert a prognostic benefit in the treatment of chronic heart failure. Their pharmacological properties vary. The only substantial comparative trial to date-the Carvedilol or Metoprolol European Trial-has compared carvedilol with short-acting metoprolol tartrate at different dose equivalents. We therefore addressed the relative efficacy of equal doses of carvedilol and metoprolol succinate on survival in multicenter hospital outpatients with chronic heart failure.

METHODS AND RESULTS

Four thousand sixteen patients with stable systolic chronic heart failure who were using either carvedilol or metoprolol succinate were identified in the Norwegian Heart Failure Registry and The Heart Failure Registry of the University of Heidelberg, Germany. Patients were individually matched on both the dose equivalents and the respective propensity scores for β-blocker treatment. During a follow-up for 17 672 patient-years, it was found that 304 (27.2%) patients died in the carvedilol group and 1066 (36.8%) in the metoprolol group. In a univariable analysis of the general sample, metoprolol therapy was associated with higher mortality compared with carvedilol therapy (hazard ratio, 1.49; 95% confidence interval, 1.31-1.69; P<0.001). This difference was not seen after multivariable adjustment (hazard ratio, 0.93; 95% confidence interval, 0.57-1.50; P=0.75) and adjustment for propensity score and dose equivalents (hazard ratio, 1.06; 95% confidence interval, 0.94-1.20; P=0.36) or in the propensity and dose equivalent-matched sample (hazard ratio, 1.00; 95% confidence interval, 0.82-1.23; P=0.99). These results were essentially unchanged for all prespecified subgroups.

CONCLUSIONS

In outpatients with chronic heart failure, no conclusive association between all-cause mortality and treatment with carvedilol or metoprolol succinate was observed after either multivariable adjustment or multilevel propensity score matching.

Efficacy of β blockers in patients with heart failure plus atrial fibrillation: an individual-patient data meta-analysis

BACKGROUND

Atrial fibrillation and heart failure often coexist, causing substantial cardiovascular morbidity and mortality. β blockers are indicated in patients with symptomatic heart failure with reduced ejection fraction; however, the efficacy of these drugs in patients with concomitant atrial fibrillation is uncertain. We therefore meta-analysed individual-patient data to assess the efficacy of β blockers in patients with heart failure and sinus rhythm compared with atrial fibrillation.

METHODS

We extracted individual-patient data from ten randomised controlled trials of the comparison of β blockers versus placebo in heart failure. The presence of sinus rhythm or atrial fibrillation was ascertained from the baseline electrocardiograph. The primary outcome was all-cause mortality. Analysis was by intention to treat. Outcome data were meta-analysed with an adjusted Cox proportional hazards regression. The study is registered with Clinicaltrials.gov, number NCT0083244, and PROSPERO, number CRD42014010012.

FINDINGS

18,254 patients were assessed, and of these 13,946 (76%) had sinus rhythm and 3066 (17%) had atrial fibrillation at baseline. Crude death rates over a mean follow-up of 1·5 years (SD 1·1) were 16% (2237 of 13,945) in patients with sinus rhythm and 21% (633 of 3064) in patients with atrial fibrillation. β-blocker therapy led to a significant reduction in all-cause mortality in patients with sinus rhythm (hazard ratio 0·73, 0·67-0·80; p<0·001), but not in patients with atrial fibrillation (0·97, 0·83-1·14; p=0·73), with a significant p value for interaction of baseline rhythm (p=0·002). The lack of efficacy for the primary outcome was noted in all subgroups of atrial fibrillation, including age, sex, left ventricular ejection fraction, New York Heart Association class, heart rate, and baseline medical therapy.

INTERPRETATION

Based on our findings, β blockers should not be used preferentially over other rate-control medications and not regarded as standard therapy to improve prognosis in patients with concomitant heart failure and atrial fibrillation.

FUNDING

Menarini Farmaceutica Internazionale (administrative support grant).

Has beta-blocker use increased in patients with heart failure in internal medicine settings? Prognostic implications: RICA registry

INTRODUCTION AND OBJECTIVES

Underuse of beta-blockers has been reported in elderly patients with heart failure. The aim of this study was to evaluate the current prescription of beta-blockers in the internal medicine setting, and its association with morbidity and mortality in heart failure patients.

METHODS

The information analyzed was obtained from a prospective cohort of patients hospitalized for heart failure (RICA registry] database, patients included from March 2008 to September 2011) with at least one year of follow-up. We investigated the percentage of patients prescribed beta-blockers at hospital discharge, and at 3 and 12 months, and the relationship of beta-blocker use with mortality and readmissions for heart failure. Patients with significant valve disease were excluded.

RESULTS

A total of 515 patients were analyzed (53.5% women), with a mean age of 77.1 (8.7) years. Beta-blockers were prescribed in 62.1% of patients at discharge. A similar percentage was found at 3 months (65.6%) and 12 months (67.9%) after discharge. All-cause mortality and the composite of all-cause mortality and readmission for heart failure were significantly lower in patients treated with beta-blockers (hazard ratio=0.59, 95% confidence interval, 0.41-0.84 vs hazard ratio=0.64, 95% confidence interval, 0.49-0.83). This decrease in mortality was maintained after adjusting by age, sex, ejection fraction, functional class, comorbidities, and concomitant treatment.

CONCLUSIONS

The findings of this study indicate that beta-blocker use is increasing in heart failure patients (mainly elderly) treated in the internal medicine setting, and suggest that the use of these drugs is associated with a reduction in clinical events.