The role of nitrates, beta blockers, and calcium antagonists in stable angina pectoris

Effects of beta-blocker withdrawal in patients with heart failure with preserved ejection fraction: A protocol for systematic review and meta-analysis

BACKGROUND

The primary chronic symptom of patients with heart failure with preserved ejection fraction (HFpEF) is severe exercise intolerance. The inability to adequately increase heart rate during exercise (chronotropic incompetence) is commonly present in HFpEF patients and contributes importantly to exercise intolerance in these patients. Since HFpEF patients often have cardiac comorbidities such as hypertension, coronary artery disease, and atrial fibrillation, beta-blockers are frequently prescribed for the treatment of these comorbidities. However, there is a concern that beta-blockers may worsen chronotropic incompetence by slowing heart rate in HFpEF patients and may further exacerbate their symptoms. There are several studies on the effects of beta-blocker withdrawal in HFpEF patients. We aim to perform the systematic review and meta-analysis of studies on the effects of beta-blocker withdrawal in HFpEF patients.

METHODS

This meta-analysis will include randomized controlled trials and prospective cohort studies on the effect of beta-blocker withdrawal in HFpEF patients. Information of studies will be collected from PubMed, Web of Science, and Scopus. The primary outcome will be peak oxygen uptake (peak VO2). The secondary outcome will be 6-minute walk distance. Other outcomes of interest will be health-related quality of life, plasma BNP levels, and cardiac structure and function.

DISCUSSION

This systematic review and meta-analysis will evaluate whether beta-blocker withdrawal is beneficial for HFpEF patients, providing evidence regarding beta-blocker withdrawal in these patients.

TRIAL REGISTRATION

Systematic review registration: INPLASY202370066.

Effect of beta-blockers on heart failure severity in patients with heart failure with preserved ejection fraction: a meta-analysis of randomized controlled trials

Patients with heart failure with preserved ejection fraction (HFpEF) are often elderly and likely to have cardiac comorbidities such as coronary artery disease (CAD) and atrial fibrillation (AF). The primary chronic symptom of HFpEF patients is severe exercise intolerance. The inability to adequately increase heart rate during exercise is commonly present in HFpEF patients and contributes to their exercise intolerance. Although beta-blockers are frequently used for the treatment of myocardial ischemia and tachycardia in HFpEF patients, there is a concern that slowing heart rate by beta-blockers may worsen chronotropic incompetence and further exacerbate their symptoms. Although the effect of beta-blockers on heart failure severity in HFpEF patients has been examined in randomized controlled trials (RCTs), results are inconsistent due partly to limited power. We aimed to conduct a meta-analysis of RCTs on the effect of beta-blockers on heart failure severity in HFpEF patients. The search of electronic databases identified 5 RCTs including 538 patients. In pooled analyses, beta-blockers did not significantly change the New York Heart Association (NYHA) class, exercise capacity expressed as metabolic equivalents, or plasma B-type natriuretic peptide (BNP) levels compared with control but with substantial heterogeneity across trials. In meta-regression analyses, the higher proportion of CAD or AF in the included trials was associated with a decrease in NYHA class and BNP levels and with an increase in exercise capacity. Thus, we found no clear beneficial effect of beta-blockers on heart failure severity in HFpEF patients. However, beta-blockers may be beneficial in HFpEF patients with CAD or AF.

Combination therapy with metoprolol and nifedipine versus monotherapy in patients with stable angina pectoris. Results of the International Multicenter Angina Exercise (IMAGE) Study

OBJECTIVES

This study was designed to investigate whether combination therapy with metoprolol and nifedipine provides a greater anti-ischemic effect than does monotherapy in individual patients with stable angina pectoris.

BACKGROUND

Combination therapy with a beta-adrenergic blocking agent (which reduces myocardial oxygen consumption) and a dihydropyridine calcium antagonist (which increases coronary blood flow) is a logical approach to the treatment of stable angina pectoris. However, it is not clear whether, in individual patients, this combined therapy is more effective than monotherapy.

METHODS

Two hundred eighty patients with stable angina pectoris were enrolled in a double-blind trial in 25 European centers. Patients were randomized (week 0) to metoprolol (controlled release, 200 mg once daily) or nifedipine (Retard, 20 mg twice daily) for 6 weeks; placebo or the alternative drug was then added for a further 4 weeks. Exercise tests were performed at weeks 0, 6 and 10.

RESULTS

At week 6, both metoprolol and nifedipine increased the mean exercise time to 1-mm ST segment depression in comparison with week 0 (both p < 0.01); metoprolol was more effective than nifedipine (p < 0.05). At week 10, the groups randomized to combination therapy had a further increase in time to 1-mm ST segment depression (p < 0.05 vs. placebo). Analysis of the results in individual patients revealed that 7 (11%) of 63 patients adding nifedipine to metoprolol and 17 (29%) of 59 patients (p < 0.0001) adding metoprolol to nifedipine showed an increase in exercise tolerance that was greater than the 90th percentile of the distribution of the changes observed in the corresponding monotherapy + placebo groups. However, among these patients, an additive effect was observed only in 1 (14%) of the 7 patients treated with metoprolol + nifedipine and in 4 (24%) of the 17 treated with nifedipine + metoprolol.

CONCLUSIONS

The mean additive anti-ischemic effect shown by combination therapy with metoprolol and nifedipine in patients with stable angina pectoris is not the result of an additive effect in individual patients. Rather, it may be attributed to the recruitment by the second drug of patients not responding to monotherapy.

Concomitant use of nitrates, calcium channel blockers, and beta blockers for optimal antianginal therapy

Despite the introduction of new mechanical techniques for revascularization, pharmacologic therapy continues to be the mainstay of antianginal therapy. The conventional antianginal medications, which include nitrates, beta blockers, and calcium channel blockers, act to correct the imbalance between myocardial supply and demand by increasing coronary blood flow, reducing myocardial oxygen requirements, or both. All three are appropriate for the management of angina caused by a fixed coronary obstruction, but nitrates and calcium channel blockers, which not only reduce demand but also increase supply, are preferred in cases of angina believed to involve a significant increase in vasomotor tone. Because of the different yet complementary mechanisms of action of the three classes of anti-ischemic drugs, use of these agents in combination is a rational approach to the treatment of angina unresponsive to monotherapy. Such combinations have been shown to enhance the therapeutic response achieved with single-agent therapy. In addition, the pharmacologic action of one of the components of the combination regimen may serve to offset side effects typically associated with the other.

Combination Therapy with Nicardipine and Beta-Adrenergic Blockade for Angina Pectoris

Nicardipine a second-generation dihidropyridine calcium antagonist, has been approved in oral formulation for use in the United States, and is under review for parenteral use. Nicardipine is the most vascular-selective agent of this class currently approved and should, on theoretical grounds, be ideal for combination therapy with beta-adrenergic blocking agents. Studies have shown that the combination of nicardipine and beta-blocking agents offers additional efficacy over monotherapy with either agent alone. The hemodynamic profile of combination therapy appears to be especially favorable in patients with diminished left ventricular function needing therapy with agents of both classes. Adverse effects are few and may be improved compared with other agents of the dihidropyridine class.

Chronic stable angina pectoris. Risk stratification and treatment

Workup of stable angina patients begins with careful history taking and evaluation of various risk factors, physical examination, and a resting electrocardiogram (ECG). A noninvasive exercise stress test is valuable for risk stratification. Abnormalities on a resting ECG or equivocal results on a stress test warrant an exercise test combined with thallium scintigraphy, which is more sensitive and specific. Cardiac catheterization is advisable for patients with chest discomfort and multiple risk factors, even if results of thallium testing are negative. Patients with severe or progressive angina or congestive heart failure should also have cardiac catheterization. Nitrates, beta-adrenergic blockers, and calcium channel blockers are cornerstones of medical therapy. Revascularization with coronary artery bypass graft is recommended for patients with left main coronary artery disease, left ventricular dysfunction, or severe proximal three-vessel coronary artery disease. Percutaneous transluminal coronary angioplasty (PTCA) is a good alternative for one- or two-vessel disease. Three-vessel PTCA can be accomplished, but its real role still remains to be established.

[Changes in myocardial metabolism induced by drugs used during intensive care]

More and more patients with coronary heart disease (CAD) are admitted to intensive care units. The drugs used to treat these patients have various effects on the myocardium which must be known in order to avoid worsening the CAD. This review examines the metabolic effects on the myocardium of the most commonly used drugs in intensive care. The physiology of myocardial oxygen supply is first recalled with regard to the coronary circulation, myocardial oxygen extraction and consumption. Digitalis glycosides do not affect the coronary circulation, but the decrease myocardial oxygen consumption in patients with heart failure, mainly by lowering heart rate. Dihydropyridine calcium blockers (nifedipine, nicardipine) increase coronary blood flow, despite a decrease in arterial blood pressure. Their effects on myocardial oxygen consumption are mediated by a sympathetic reflex. Verapamil decreases the heart rate and myocardial inotropism, and is responsible for coronary vasodilation. The result is a decrease in myocardial oxygen consumption. Diltiazem and bepridil have almost similar effects: they decrease myocardial oxygen consumption and increase blood supply to the heart. It has been recently shown that verapamil was the most depressant calcium channel blocking agent, and that it resulted in the most important decrease in myocardial metabolism. Beta-blocking agents decrease myocardial metabolism, except those with an important intrinsic sympathomimetic activity, such as pindolol. Amiodarone can be considered as an alpha and beta blocking drug: its main effect is to counteract the effects of endogenous catecholamines on myocardial metabolism. The sympathomimetic amines (noradrenaline, adrenaline, isoprenaline, dopamine, dobutamine) increase, to different extents, myocardial oxygen consumption. Vasodilators, such as the nitrates or sodium nitroprusside, decrease cardiac filling pressures, and increase myocardial blood flow, thus lowering myocardial oxygen consumption. Phosphodiesterase inhibitors (amrinone, enoximone) have both an inotropic and a vasodilating effect. They decrease cardiac afterload, and increase blood supply to the myocardium; this compensates for the increase in myocardial oxygen consumption due to the increase in myocardial contractility. Because all the drugs used in intensive care have different effects on myocardial metabolism, their reasoned use should avoid an inappropriate increase in oxygen demand.

Propranolol as xanthine oxidase inhibitor: implications for antioxidant activity

Propranolol is the beta-blocker most widely used in the management of cardiovascular disorders. It has been proposed that propranolol may act as a "chain-breaking" antioxidant. We have directly examined the ability of propranolol to inhibit superoxide-dependent, iron-promoted cardiac membrane phospholipid peroxidation, with xanthine oxidase (XOD) as a physiologically-recognized, enzymatic superoxide generator. Our results demonstrate that propranolol not only protects cardiac-membrane lipid from peroxidative damage, but also acts as a simple, reversible XOD inhibitor, noncompetitive with xanthine substrate. Propranolol, at effective antiperoxidant and XOD-inhibitory concentrations, cannot scavenge superoxide radical. The antiperoxidative profile of propranolol resembles that of the known XOD inhibitor allopurinol, although allopurinol, a tight-binding substrate-analog competitive with xanthine, inhibits XOD in a manner mechanistically very different from that of propranolol. Furthermore, the antiperoxidative profiles of both propranolol and allopurinol do not resemble those of chain-breaking antioxidants such as alpha-tocopherol. These data, along with the tendency of propranolol to concentrate in myocardial membranes and cytosol, suggest that the observed antioxidant action of propranolol, as a consequence of XOD inhibition, could play a pharmacologic role in propranolol's cardioprotective effects.