Left ventricular volume in thrombolysed patients with acute anterior myocardial infarction: the effect of captopril and xamoterol

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.

Cardiac magnetic resonance imaging parameters as surrogate endpoints in clinical trials of acute myocardial infarction

Cardiac magnetic resonance (CMR) offers a variety of parameters potentially suited as surrogate endpoints in clinical trials of acute myocardial infarction such as infarct size, myocardial salvage, microvascular obstruction or left ventricular volumes and ejection fraction. The present article reviews each of these parameters with regard to the pathophysiological basis, practical aspects, validity, reliability and its relative value (strengths and limitations) as compared to competitive modalities. Randomized controlled trials of acute myocardial infarction which have used CMR parameters as a primary endpoint are presented.

Cardiac magnetic resonance imaging parameters as surrogate endpoints in clinical trials of acute myocardial infarction

Cardiac magnetic resonance (CMR) offers a variety of parameters potentially suited as surrogate endpoints in clinical trials of acute myocardial infarction such as infarct size, myocardial salvage, microvascular obstruction or left ventricular volumes and ejection fraction. The present article reviews each of these parameters with regard to the pathophysiological basis, practical aspects, validity, reliability and its relative value (strengths and limitations) as compared to competitive modalities. Randomized controlled trials of acute myocardial infarction which have used CMR parameters as a primary endpoint are presented.

Feasibility of arresting the process of remodeling

Heart failure (HF) is a massive public health issue. Ventricular remodeling is pivotal to the pathophysiology/progression of HF and an attractive target for intervention. It currently is believed that interdicting the natural history of ventricular remodeling will be crucial to controlling the HF epidemic. This article reviews the current data on the feasibility of arresting this process. This review is not meant to be exhaustive but provides a brief overview of the approaches being contemplated in this field.

Surrogate end points in heart failure

Because of the increasing number of pharmacologic strategies available for treatment of heart failure (HF), the time has come to reassess the adequacy of end points used to evaluate therapeutic efficacy. Interest in the use of surrogate end points in clinical studies is increasing. A surrogate end point is defined as a measurement that can substitute for a true end point for the purpose of comparing specific interventions or treatments in a clinical trial. A true end point is one that is of clinical importance to the patient (e.g., mortality or quality of life), whereas a surrogate end point is one biologically closer to the disease process (e.g., ejection fraction or left ventricular volume in HF). The prime motivation for the use of a surrogate end point concerns the possible reduction in sample size or trial duration. Such reductions have important cost implications and in some cases may influence trial feasibility. Another, perhaps more important, aspect of measuring surrogate end points is that they increase our understanding of the mechanism of action of drugs and thus may help physicians to take a more enlightened approach in managing their patients. In this article we have analyzed the possible potentials of the surrogate end points in clinical studies of patients with chronic HF. Other uses of possible surrogates are discussed, and the limitations in finding true surrogates are mentioned. At this time we conclude there is no well established surrogate in HF.

Measurement of left ventricular volume after anterior myocardial infarction: comparison of magnetic resonance imaging, echocardiography, and radionuclide ventriculography

We have compared echocardiography (echo) and radionuclide ventriculography (RNV) with magnetic resonance imaging (MRI) for the measurement of left ventricular (LV) volume and ejection fraction. Seventy asymptomatic patients were studied up to 12 days after first Q wave anterior myocardial infarction and again after 6 months. Each patient had LV volume measured by all three techniques within 24 hours of each other on each occasion. LV end-systolic and end-diastolic volume index (LVESVI and LVEDVI) and LV ejection fraction (LVEF) were measured using the modified Simpson formula (echo), a counts-based method (RNV), and a multislice area summation method (MRI). Radionuclide volumes were measured both with and without correction for attenuation of isotope. Echocardiography overestimated LV volume compared with MRI. Mean (SD) differences (echo-MRI) were: LVEDVI + 10.6 ml/m2 (16.8), LVESVI + 13.7 ml/m2 (12.9), LVEF -8.5% (11.2). RNV underestimated both volume and ejection fraction compared with MRI. Mean differences (RNV-MRI) were: LVEDVI -25.4 ml/m2 (23.8), LVESVI -5.0 ml/m2 (18.6), LVEF -13.8% (10.4). Variability in the difference between echo and MRI and between RNV and MRI was very similar for LVEF (coefficient of variation 23.9% echo, 22.2% RNV) but there was greater variability in the radionuclide than the echo measurements of absolute volume. Variability of the radionuclide measurements was reduced by not correcting for attenuation, and this finding may improve the radionuclide technique for serial measurements of percentage change in volume. Long-term inter-study reproducibility of MRI for LVEF (coefficient of reproducibility) was 10.9%, for echo it was 10.6%, and for RNV it was 14.6%. We conclude that measurements of LV volume depend on the method used and are not interchangeable. Echocardiography agrees more closely with MRI than RNV for the measurement of absolute volume, but the two techniques are similar for the measurement of LVEF.

Effect of very early angiotensin-converting enzyme inhibition on left ventricular dilation after myocardial infarction in patients receiving thrombolysis: results of a meta-analysis of 845 patients. FAMIS, CAPTIN and CATS Investigators

OBJECTIVES

We sought to investigate the effect of angiotensin-converting enzyme (ACE) inhibition <9 h after myocardial infarction (MI) on left ventricular (LV) dilation in patients receiving thrombolysis.

BACKGROUND

The ACE inhibitors reduce mortality after MI. Attenuation of LV dilation has been suggested as an important mechanism.

METHODS

The data of 845 patients with three-month echocardiographic follow-up after MI were combined from three randomized, double-blind, placebo-controlled studies. The criteria for these studies included: 1) thrombolytic therapy; 2) ACE inhibition within 6 to 9 h; and 3) evaluation of LV dilation as the primary objective.

RESULTS

The ACE inhibitor was started 3.2+/-1.7 h after the patients' first (mainly, 85%) anterior MI. After three months, LV dilation was not significantly attenuated by very early treatment with an ACE inhibitor. The diastolic volume index was attenuated by 0.5 ml/m2 (95% confidence interval [CI] -1.5 to 2.5, p = 0.61), and the systolic volume index by 0.5 ml/m2 (95% CI -1.0 to 1.9, p = 0.50). Subgroup analysis demonstrated that LV dilation was significantly attenuated by ACE inhibitor treatment for patients in whom reperfusion failed. In contrast, LV dilation was almost unaffected by ACE inhibitor treatment in successfully reperfused patients.

CONCLUSIONS

We could not demonstrate attenuation of LV dilation in patients receiving thrombolysis by ACE inhibitor treatment within 6 to 9 h after MI. We speculate that very early treatment with an ACE inhibitor has a beneficial effect on LV remodeling only in patients in whom reperfusion failed. Other mechanisms may be responsible for the beneficial effects of ACE inhibitors in successfully reperfused patients after MI.

Short- and long-term effects of early fosinopril administration in patients with acute anterior myocardial infarction undergoing intravenous thrombolysis: results from the Fosinopril in Acute Myocardial Infarction Study. FAMIS Working Party

BACKGROUND

Angiotensin-converting enzyme inhibitors are used in patients who have myocardial infarction with left ventricular (LV) dysfunction. Few data are available in patients whose LV function is within the normal range.

METHODS AND RESULTS

The Fosinopril in Acute Myocardial Infarction Study was a 2-year, randomized, double-blind, placebo-controlled, multicenter study of 285 patients with anterior acute myocardial infarction and was designed to investigate the effects of the early (<9 hours) administration of fosinopril and thrombolysis on (1) changes in echocardiographically evaluated LV volumes at 3 months and (2) long-term occurrence of death and congestive heart failure. LV volumes were normal at baseline in more than 70% of patients and were comparable between groups both at baseline and after 3 months of treatment. Fosinopril-treated patients showed a 30% reduction in the 2-year combined prevalence of death or moderate-to-severe congestive heart failure (New York Heart Association class III-IV) despite having a worse clinical profile at baseline. The benefit of fosinopril was confirmed both in patients without congestive heart failure at admission and in those with ejection fraction >40% at baseline. Moreover, the incidence of significant ventricular arrhythmias was lower in the fosinopril group (0.8% vs 6.0%, p < 0.02).

CONCLUSIONS

The results of the Fosinopril in Acute Myocardial Infarction Study suggest that early treatment with fosinopril can benefit patients with acute myocardial infarction in addition to a prevention of LV remodeling.