Acute effects of beta 1-selective and nonselective beta-adrenergic receptor blockade on cardiac sympathetic activity in congestive heart failure

Left ventricular systolic function after inhalation of beta-2 agonists in healthy athletes

Inhaled beta-2 adrenoceptor agonists (iβ2A) are routinely used as bronchodilators in the treatment of asthma. However, their cardiac effects in athletes are scarcely examined. Thus, the aim of this study was to evaluate the effects of iβ2A on left ventricular (LV) systolic function (SF) by echocardiography in healthy, non-asthmatic female and male endurance athletes. A randomized, double-blinded, placebo-controlled, balanced, 4-way complete block cross-over study was conducted. Twenty-four healthy athletes (12f/12m: 22.9 ± 2.7/24.4 ± 4.6 years) randomly completed 4 study arms (placebo; salbutamol; formoterol; formoterol + salbutamol). After inhalation of the study medication, the participants performed a 10-min time trial (TT) on a bicycle ergometer. After each TT an echocardiography was performed to determine LVSF. Blood samples were collected pre, post, 3 h and 24 h post TT. In females, total serum concentrations for salbutamol and formoterol were higher. LV ejection fraction (LVEF) and LV global longitudinal strain (LVendoGLS) showed a treatment effect for the whole study group (p < 0.0001) and a sex effect on LVEF (p = 0.0085). In women, there was a significant treatment effect for all medication arms (at least p ≤ 0.01) both on LVEF and LVendoGLS. In men only formoterol and formoterol + salbutamol displayed a treatment effect on LVEF (p = 0.0427, p = 0.0330; respectively), whereas on LVendoGLS only formoterol + salbutamol was significant (p = 0.0473). The iβ2A significantly influenced LVSF after an acute bout of exercise in healthy endurance athletes. These effects were even more pronounced when combining both iβ2A that supports a dose-dependent effect on cardiac function. Moreover, female athletes had higher serum concentrations of β2 agonists and stronger effects on LVSF compared to male athletes. This is mainly explained by differences in body weight and related plasma volume and may indicate a potential risk when increasing dose above the tested concentrations. Trial registration: At the European Union Drug Regulating Authorities Clinical Trials (Eudra CT) with the number 201,500,559,819 (registered prospectively on 09/12/2015) and at the German register for clinical studies (DRKS number 00010574 registered retrospectively on 16/11/2021).

Stroke Related Brain-Heart Crosstalk: Pathophysiology, Clinical Implications, and Underlying Mechanisms

The emergence of acute ischemic stroke (AIS) induced cardiovascular dysfunctions as a bidirectional interaction has gained paramount importance in understanding the intricate relationship between the brain and heart. Post AIS, the ensuing cardiovascular dysfunctions encompass a spectrum of complications, including heart attack, congestive heart failure, systolic or diastolic dysfunction, arrhythmias, electrocardiographic anomalies, hemodynamic instability, cardiac arrest, among others, all of which are correlated with adverse outcomes and mortality. Mounting evidence underscores the intimate crosstalk between the heart and the brain, facilitated by intricate physiological and neurohumoral complex networks. The primary pathophysiological mechanisms contributing to these severe cardiac complications involve the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic and parasympathetic hyperactivity, immune and inflammatory responses, and gut dysbiosis, collectively shaping the stroke-related brain-heart axis. Ongoing research endeavors are concentrated on devising strategies to prevent AIS-induced cardiovascular dysfunctions. Notably, labetalol, nicardipine, and nitroprusside are recommended for hypertension control, while β-blockers are employed to avert chronic remodeling and address arrhythmias. However, despite these therapeutic interventions, therapeutic targets remain elusive, necessitating further investigations into this complex challenge. This review aims to delineate the state-of-the-art pathophysiological mechanisms in AIS through preclinical and clinical research, unraveling their intricate interplay within the brain-heart axis, and offering pragmatic suggestions for managing AIS-induced cardiovascular dysfunctions.

Comparison between the ECG Outcomes of Metoprolol and Bisoprolol

BACKGROUND

Beta-blockers are essential agents in the management of cardiovascular diseases, such as heart failure, acute myocardial infarction (MI), and cardiac arrhythmias. However, there are diurnal variations in the cardioprotective effects of the subgroups as a result of their different pharmacokinetic, pharmacodynamic, and pharmacogenetic profiles.

OBJECTIVES

We aimed to compare metoprolol and bisoprolol in terms of electrocardiogram (ECG) outcomes.

METHODS

A retrospective cross-sectional study was conducted at Prince Sultan Cardiac Center. The trial included 404 patients who met the inclusion criteria (204 in the metoprolol arm and 200 in the bisoprolol arm). Using case record forms that had already been created, information, such as patient demographics, medical histories, and treatment histories, was taken from their medical files. The most recent ECG records were also gathered. The ethical approval for this study was obtained from Qassim ethical committee (approval number: 45-44-902).

RESULTS

There was no significant difference found between the patients in both arms in terms of baseline characteristics, age, or sex.

CONCLUSION

In this retrospective cross-sectional study, we have compared the effects of metoprolol and bisoprolol beta blockers on ECG changes. The findings have indicated no difference between metoprolol and bisoprolol groups in terms of all ECG readings, particularly PR/ms, QTC-ms, and ventricular rate. Further studies are required to confirm these findings.

Inhaled Short-Acting Beta Agonist Treatment-Associated Supraventricular Tachycardia in Children: Still a Matter of Concern in Pediatric Emergency Departments?

Inhaled selective short-acting β-2 agonists (SABA), such as salbutamol, are the rescue treatment of choice for the relief of symptoms of acute asthma exacerbations: one of the leading causes of pediatric emergency department admission and hospitalization. Cardiovascular events, including supraventricular arrhythmias, are the most frequent side effects reported with inhaled SABA in children with asthma and are the main reason for a continuing debate about their safety, despite their widespread use. Although supraventricular tachycardia (SVT) is the most common potentially serious dysrhythmia in children, the incidence and risk factor of SVT after SABA administration is currently unknown. We here reported three cases and conducted a review of the literature in an attempt to gain insight into this issue.

Clinical management of electrical storm: a current overview

The number of patients affected by electrical storm has been continuously increasing in emergency departments. Patients are often affected by multiple comorbidities requiring multidisciplinary interventions to achieve a clinical stability. Careful reprogramming of cardiac devices, correction of electrolyte imbalance, knowledge of underlying heart disease and antiarrhythmic drugs in the acute phase play a crucial role. The aim of this review is to provide a comprehensive overview of pharmacological treatment, latest transcatheter ablation techniques and advanced management of patients with electrical storm.

The 2021 Carl Ludwig Lecture. Unsympathetic autonomic regulation in heart failure: patient-inspired insights

Defined as a structural or functional cardiac abnormality accompanied by symptoms, signs, or biomarkers of altered ventricular pressures or volumes, heart failure also is a state of autonomic disequilibrium. A large body of evidence affirms that autonomic disturbances are intrinsic to heart failure; basal or stimulated sympathetic nerve firing or neural norepinephrine (NE) release more often than not exceed homeostatic need, such that an initially adaptive adrenergic or vagal reflex response becomes maladaptive. The magnitude of such maladaptation predicts prognosis. This Ludwig lecture develops two theses: the elucidation and judiciously targeted amelioration of maladaptive autonomic disturbances offers opportunities to complement contemporary guideline-based heart failure therapy, and serendipitous single-participant insights, acquired in the course of experimental protocols with entirely different intent, can generate novel insight, inform mechanisms, and launch entirely new research directions. I précis six elements of our current synthesis of the causes and consequences of maladaptive sympathetic disequilibrium in heart failure, shaped by patient-inspired epiphanies: arterial baroreceptor reflex modulation, excitation stimulated by increased cardiac filling pressure, paradoxical muscle sympathetic activation as a peripheral neurogenic constraint on exercise capacity, renal sympathetic restraint of natriuresis, coexisting sleep apnea, and augmented chemoreceptor reflex sensitivity and then conclude by envisaging translational therapeutic opportunities.

Comparison of short-acting versus extended-release nifedipine: Effects on hemodynamics and sympathetic activity in patients with stable coronary artery disease

We investigated the impact of short-acting and extended release nifedipine on sympathetic activity using radiotracer methodology in patients with stable coronary artery disease in order to more accurately document the response of the sympathetic nervous system to different formulations of this dihydropyridine calcium channel antagonist. Participants were randomized to placebo, short-acting or extended release nifedipine for 7–10 days. On the final day, systemic blood pressure, cardiac filling pressures, cardiac output, plasma norepinephrine (NE) and total body NE spillover were measured at baseline (time 0) and repeated at intervals for 6 hours. There were no differences in baseline measures between groups. Following the morning dose of study medication there were no changes in hemodynamics or sympathetic activity in the placebo group. However, there was a significant fall in blood pressure and a significant increase in total body NE spillover in both nifedipine groups. Importantly, the increase in sympathetic activity in response to short-acting nifedipine began earlier (30 minutes) and was much greater than that observed in the extended release group, which occurred later (270 minutes). These findings confirm that sustained therapy with nifedipine is associated with activation of the sympathetic nervous system which is dependent on the pharmacokinetics of the formulation.

A Recalcitrant Electrical Storm and Implantable Defibrillator Exhaustion: Treatment Implications According to and Beyond Guidelines

A 60-year-old patient presented with recalcitrant electrical storm (ES). Mild sedation and initial antiarrhythmic combination of esmolol and amiodarone did not affect the intensity of ES, which resulted in battery exhaustion. Oral propranolol in addition to intravenous amiodarone might be preferred in hemodynamically stable patients before interventional therapies. (Level of Difficulty: Intermediate.)

Propranolol Versus Metoprolol for Treatment of Electrical Storm in Patients With Implantable Cardioverter-Defibrillator

BACKGROUND

Electrical storm (ES), characterized by unrelenting recurrences of ventricular arrhythmias, is observed in approximately 30% of patients with implantable cardioverter-defibrillators (ICDs) and is associated with high mortality rates.

OBJECTIVES

Sympathetic blockade with β-blockers, usually in combination with intravenous (IV) amiodarone, have proved highly effective in the suppression of ES. In this study, we compared the efficacy of a nonselective β-blocker (propranolol) versus a β₁-selective blocker (metoprolol) in the management of ES.

METHODS

Between 2011 and 2016, 60 ICD patients (45 men, mean age 65.0 ± 8.5 years) with ES developed within 24 h from admission were randomly assigned to therapy with either propranolol (160 mg/24 h, Group A) or metoprolol (200 mg/24 h, Group B), combined with IV amiodarone for 48 h.

RESULTS

Patients under propranolol therapy in comparison with metoprolol-treated individuals presented a 2.67 times decreased incidence rate (incidence rate ratio: 0.375; 95% confidence interval: 0.207 to 0.678; p = 0.001) of ventricular arrhythmic events (tachycardia or fibrillation) and a 2.34 times decreased rate of ICD discharges (incidence rate ratio: 0.428; 95% CI: 0.227 to 0.892; p = 0.004) during the intensive care unit (ICU) stay, after adjusting for age, sex, ejection fraction, New York Heart Association functional class, heart failure type, arrhythmia type, and arrhythmic events before ICU admission. At the end of the first 24-h treatment period, 27 of 30 (90.0%) patients in group A, while only 16 of 30 (53.3%) patients in group B were free of arrhythmic events (p = 0.03). The termination of arrhythmic events was 77.5% less likely in Group B compared with Group A (hazard ratio: 0.225; 95% CI: 0.112 to 0.453; p < 0.001). Time to arrhythmia termination and length of hospital stay were significantly shorter in the propranolol group (p < 0.05 for both).

CONCLUSIONS

The combination of IV amiodarone and oral propranolol is safe, effective, and superior to the combination of IV amiodarone and oral metoprolol in the management of ES in ICD patients.

β-1 adrenoceptors and AT1 receptors may not be involved in catecholamine-induced lethal arrhythmias

An excessive amount of catecholamines produce arrhythmias, but the exact mechanisms of this action are not fully understood. For this purpose, Sprague–Dawley rats were treated with or without atenolol, a β1-adrenoceptor blocker (20 mg/kg per day), for 15 days followed by injections of epinephrine for cumulative doses of 4 to 128 μg/kg. Another group of animals were pretreated with losartan, an angiotensin receptor (AT1) blocker (20 mg/kg per day), for comparison. Control animals received saline. Varying degrees of ventricular arrhythmias were seen upon increasing the dose of epinephrine, but the incidence and duration of the rhythm abnormalities as well as the number of episodes and severity of arrhythmias were not affected by treating the animals with atenolol or losartan. The levels of both epinephrine and norepinephrine were increased in the atenolol-treated rats but were unchanged in the losartan-treated animals after the last injection of epinephrine; the severity of arrhythmias did not correlate with the circulating catecholamine levels. These results indicate that both β1-adrenoceptors and AT1 receptors may not be involved in the pathogenesis of catecholamine-induced arrhythmias and support the view that other mechanisms, such as the oxidation products of catecholamines, may play a crucial role in the occurrence of lethal arrhythmias.

Risk of adverse cardiovascular events with use of inhaled long-acting bronchodilators in management of chronic obstructive pulmonary disease

Inhaled long-acting bronchodilators, including long-acting β₂ agonists (LABAs) and long-acting muscarinic antagonists (LAMAs) are the mainstay therapy in the treatment of chronic obstructive pulmonary disease (COPD), a disease that poses a heavy burden on morbidity and mortality worldwide. Use of LABAs and LAMAs in patients with COPD, however, has been concerned about an increased risk of adverse cardiovascular events, despite inconsistent findings reported from randomized controlled trials (RCTs) and observational studies. In this review, we detailed the relevant evidence generated from RCTs and observational studies with respect to the risk of cardiovascular disease with use of LABAs and LAMAs in management of COPD, and analyzed the contradictory findings in the literature, as well as recommended future research directions to clear the air regarding the cardiovascular safety of inhaled long-acting bronchodilators.

Effects of Carvedilol Versus Metoprolol on Platelet Aggregation in Patients With Acute Coronary Syndrome: The PLATE-BLOCK Study

Platelet aggregation plays a pivotal role in acute coronary syndrome (ACS). In this setting, β-blockers (BBs) are used to counteract the effects of catecholamines on heart. Circulating catecholamines can also potentiate platelet reactivity, mainly through α₂- and β₂-adrenoceptors on human platelets' surface, thus BB may affect platelet aggregation; however, the effects of different BBs on platelet aggregation in contemporary-treated patients with ACS have been poorly investigated. One hundred patients with ACS on dual antiplatelet therapy with aspirin and ticagrelor were randomized to receive treatment with carvedilol, a nonselective BB (n = 50), or metoprolol, a selective β₁-blocker (n = 50), at maximum tolerated dose. Light transmission aggregometry was performed at randomization (T0) and at 30-day follow-up (T30), and the results were expressed as a percentage of maximum platelet aggregation (MPA). The primary end point was epinephrine-induced MPA at 30 days. Patients were predominantly men (80%), and mean age was 57.3 ± 9.7 years. The 2 randomized groups were well balanced for baseline characteristics. At T0, mean MPA was similar between the groups (18.96 ± 9.05 vs 18.32 ± 9.21 with 10 µM epinephrine, 14.42 ± 9.43 vs 15.98 ± 10.08 with 20 µM adenosine diphophate (ADP), and 13.26 ± 9.83 vs 14.30 ± 9.40 with 10 µM ADP for carvedilol and metoprolol, respectively, all p = NS). At 30 days, platelet aggregation induced by epinephrine was significantly lower in the carvedilol group than in the metoprolol group (23.52 ± 10.25 vs 28.72 ± 14.37, p = 0.04), with a trend toward the lower values of ADP-induced MPA (20 µM ADP 19.42 ± 13.84 vs 24.16 ± 13.62, p = 0.09; 10 µM ADP 19.12 ± 12.40 vs 22.57 ± 13.59, p = 0.19). In conclusion, carvedilol, a nonselective BB, reduces residual platelet reactivity in patients with ACS compared with the selective BB, metoprolol.

Melatonin protects against the pathological cardiac hypertrophy induced by transverse aortic constriction through activating PGC-1β: In vivo and in vitro studies

Melatonin, a circadian molecule secreted by the pineal gland, confers a protective role against cardiac hypertrophy induced by hyperthyroidism, chronic hypoxia, and isoproterenol. However, its role against pressure overload-induced cardiac hypertrophy and the underlying mechanisms remains elusive. In this study, we investigated the pharmacological effects of melatonin on pathological cardiac hypertrophy induced by transverse aortic constriction (TAC). Male C57BL/6 mice underwent TAC or sham surgery at day 0 and were then treated with melatonin (20 mg/kg/day, via drinking water) for 4 or 8 weeks. The 8-week survival rate following TAC surgery was significantly increased by melatonin. Melatonin treatment for 8 weeks markedly ameliorated cardiac hypertrophy. Compared with the TAC group, melatonin treatment for both 4 and 8 weeks reduced pulmonary congestion, upregulated the expression level of α-myosin heavy chain, downregulated the expression level of β-myosin heavy chain and atrial natriuretic peptide, and attenuated the degree of cardiac fibrosis. In addition, melatonin treatment slowed the deterioration of cardiac contractile function caused by pressure overload. These effects of melatonin were accompanied by a significant upregulation in the expression of peroxisome proliferator-activated receptor-gamma co-activator-1 beta (PGC-1β) and the inhibition of oxidative stress. In vitro studies showed that melatonin also protects against angiotensin II-induced cardiomyocyte hypertrophy and oxidative stress, which were largely abolished by knocking down the expression of PGC-1β using small interfering RNA. In summary, our results demonstrate that melatonin protects against pathological cardiac hypertrophy induced by pressure overload through activating PGC-1β.

Acute effects of angiotensin-converting enzyme inhibition versus angiotensin II receptor blockade on cardiac sympathetic activity in patients with heart failure

The beneficial effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (ANG II) receptor antagonists in patients with heart failure secondary to reduced ejection fraction (HFrEF) are felt to result from prevention of the adverse effects of ANG II on systemic afterload and renal homeostasis. However, ANG II can activate the sympathetic nervous system, and part of the beneficial effects of ACE inhibitors and ANG II antagonists may result from their ability to inhibit such activation. We examined the acute effects of the ACE inhibitor captopril (25 mg, n = 9) and the ANG II receptor antagonist losartan (50 mg, n = 10) on hemodynamics as well as total body and cardiac norepinephrine spillover in patients with chronic HFrEF. Hemodynamic and neurochemical measurements were made at baseline and at 1, 2, and 4 h after oral dosing. Administration of both drugs caused significant reductions in systemic arterial, cardiac filling, and pulmonary artery pressures (P < 0.05 vs. baseline). There was no significant difference in the magnitude of those hemodynamic effects. Plasma concentrations of ANG II were significantly decreased by captopril and increased by losartan (P < 0.05 vs. baseline for both). Total body sympathetic activity increased in response to both captopril and losartan (P < 0.05 vs. baseline for both); however, there was no change in cardiac sympathetic activity in response to either drug. The results of the present study do not support the hypothesis that the acute inhibition of the renin-angiotensin system has sympathoinhibitory effects in patients with chronic HFrEF.

Pharmacodynamics ofβ-Blockers in Heart Failure: Lessons from the Carvedilol Or Metoprolol European Trial

Heart failure is a growing public health problem in the United States, and the approach to the treatment of heart failure has undergone a radical transformation in the past decade. The use of β-blocker therapy in heart failure patients is now widely recommended, based on evidence from large-scale clinical trials demonstrating that bisoprolol, carvedilol, and extended-release metoprolol succinate significantly reduce morbidity and mortality in patients with heart failure. Although these agents appear to provide similar benefits, the question remains whether pharmacologic differences among them could translate to differences in clinical outcomes. The Carvedilol Or Metoprolol European Trial (COMET) compared nonselective blockade of the β1-/β2-/α1-adrenergic receptors with carvedilol versus selective β1-blockade with immediate-release metoprolol tartrate in patients with chronic heart failure. The trial found that carvedilol significantly reduced all-cause mortality compared with immediate-release metoprolol tartrate, although there were no differences in hospitalizations. Herein we review the pharmacokinetics and pharmacodynamics of metoprolol and carvedilol. In doing so, several issues regarding the design of COMET are identified that could alter the interpretation of the results of this trial. These include the choice of dose and dosage regimen of immediate-release metoprolol tartrate, a dosage form that has never been shown to reduce mortality in patients with heart failure. Additional studies are needed to fully understand whether there are any advantages of selective versus nonselective adrenergic blockade and whether there are any clinically meaningful differences in effectiveness between β-blockers with proven benefit in the management of chronic heart failure. The results of COMET demonstrate that all β-blockers and dosage forms are not interchangeable when prescribed for heart failure. Clinicians should choose only those agents (and dosage forms) that have been proven to reduce mortality in this patient population.

[Electrical storm in the emergency room: clinical pathways]

In patients with structural heart disease, occurrence of an electrical storm (ES) is associated with increased mortality acutely and during medium term follow-up. Depending on the underlying heart disease and baseline type of arrhythmia, different clinical pathways have to be followed to reach sustained freedom from ventricular arrhythmia recurrences. Trigger elimination, sympathetic blockade (initially using betablockers and sedation), antiarrhythmic therapy with amiodarone and catheter ablation, treatment of heart failure and invasive hemodynamic support are cornerstones of the treatment. We present an algorithm which may help to organize an optimized treatment for each ES patient, implementing invasive treatment options like coronary angioplasty, catheter ablation and invasive circulatory support. Further studies are necessary to evaluate medium term outcome of such a structured therapy.

Cardiovascular function in large to small hibernators: bears to ground squirrels

Mammalian hibernation has intrigued scientists due to extreme variations in normal seasonal physiological homeostasis. Numerous species manifest a hibernation phenotype although the characteristics of the hypometabolic state can be quite different. Ground squirrels (e.g., Sciuridae) are often considered the prototypical hibernator as individuals in this genus transition from an active, euthermic state (37 °C) to a nonresponsive hibernating state where torpid body temperature commonly falls to 3-5 °C. However, the hibernating state is not continuous as periodic warming and arousals occur. In contrast, the larger hibernators of genus Ursus are less hypothermic (body temperatures decline from approximately 37°-33 °C), are more reactive, and cyclical arousals do not occur. Both species dramatically reduce cardiac output during hibernation from the active state (bears ~75 % reduction in bears and ~97 % reduction in ground squirrels), and both species demonstrate hypokinetic atrial chamber activity. However, there are several important differences in cardiac function between the two groups during hibernation. Left ventricular diastolic filling volumes and stroke volumes do not differ in bears between seasons, but increased diastolic and stroke volumes during hibernation are important contributors to cardiac output in ground squirrels. Decreased cardiac muscle mass and increased ventricular stiffness have been found in bears, whereas ground squirrels have increased cardiac muscle mass and decreased ventricular stiffness during hibernation. Molecular pathways of cardiac muscle plasticity reveal differences between the species in the modification of sarcomeric proteins such as titin and α myosin heavy chain during hibernation. The differences in hibernation character are likely to account for the alternative cardiac phenotypes and functional strategies manifested by the two species. Molecular investigation coupled with better knowledge of seasonal physiological alterations is dramatically advancing our understanding of small and large hibernators and their evolutionary differences.

Differential effects of nonselective versus selective β-blockers on cardiac sympathetic activity and hemostasis in patients with heart failure

Carvedilol, a nonselective β-blocker, may be more effective than the selective β-blocker metoprolol in reducing the risk of thromboembolic events in heart failure. The aim of this study was, first, to assess whether there is a differential response in cardiac sympathetic activity by (123)I-meta-iodobenzylguanidine ((123)I-MIBG) imaging when either β-blocker is used. Second, we assessed whether that response correlates with levels of various serum factors that serve as markers for coagulability.

METHODS

In this prospective, randomized, open-label crossover study with masked outcome assessments, stable heart failure patients (left ventricular ejection fraction < 40%) homozygous for the Arg16/Gln27 (n = 13) or Gly16/Glu27 haplotype (n = 8) of the β2-receptor were randomized to equipotent dosages of carvedilol or metoprolol for two 6-wk periods. Primary outcome was sympathetic activity as measured by (123)I-MIBG myocardial washout. Secondary outcomes included markers of hemostasis.

RESULTS

(123)I-MIBG cardiac washout was lower during carvedilol than metoprolol treatment (12.9% ± 3.9% vs. 22.1% ± 2.8%, respectively, P = 0.003), irrespective of β2-adrenergic receptor haplotype. In addition, treatment with carvedilol resulted in a lower von Willebrand factor than did metoprolol (149% ± 13% vs. 157% ± 13%, respectively, P = 0.01), irrespective of β2-adrenergic receptor haplotype.

CONCLUSION

Compared with metoprolol, carvedilol resulted in greater reduction of sympathetic activity after 6 wk of treatment and lower von Willebrand factor concentrations in both Arg16/Gln27 and Gly16/Glu27 individuals. Therefore, carvedilol may reduce the risk of thromboembolic events in patients with heart failure, irrespective of β2-receptor haplotype status.

Statin therapy lowers muscle sympathetic nerve activity and oxidative stress in patients with heart failure

Despite standard drug therapy, sympathetic nerve activity (SNA) remains high in heart failure (HF) patients making the sympathetic nervous system a primary drug target in the treatment of HF. Studies in rabbits with pacing-induced HF have demonstrated that statins reduce resting SNA, in part, due to reductions in reactive oxygen species (ROS). Whether these findings can be extended to the clinical setting of human HF remains unclear. We first performed a study in seven statin-naïve HF patients (56 ± 2 yr; ejection fraction: 31 ± 4%) to determine if 1 mo of simvastatin (40 mg/day) reduces muscle SNA (MSNA). Next, to control for possible placebo effects and determine the effect of simvastatin on ROS, a double-blinded, placebo-controlled crossover design study was performed in six additional HF patients (51 ± 3 yr; ejection fraction: 22 ± 4%), and MSNA, ROS, and superoxide were measured. We tested the hypothesis that statin therapy decreases resting MSNA in HF patients and this would be associated with reductions in ROS. In study 1, simvastatin reduced resting MSNA (75 ± 5 baseline vs. 65 ± 5 statin bursts/100 heartbeats; P < 0.05). Likewise, in study 2, simvastatin also decreased resting MSNA (59 ± 5 placebo vs. 45 ± 6 statin bursts/100 heartbeats; P < 0.05). In addition, statin therapy significantly reduced total ROS and superoxide. As expected, cholesterol was reduced after simvastatin. Collectively, these findings indicate that short-term statin therapy concomitantly reduces resting MSNA and total ROS and superoxide in HF patients. Thus, in addition to lowering cholesterol, statins may also be beneficial in reducing sympathetic overactivity and oxidative stress in HF patients.

Cardiac sympathetic activation in patients with pulmonary arterial hypertension

Patients with congestive heart failure (CHF) due to left ventricular (LV) dysfunction have sympathetic activation specifically directed to the myocardium. Although pulmonary arterial hypertension (PAH) is associated with increased systemic sympathetic activity, its impact on sympathetic drive to ventricular myocardium is unknown. Fifteen patients with PAH (9 women; 54 ± 12 years) were studied: 10 with idiopathic PAH and 5 with a connective tissue disorder. We measured hemodynamics, as well as radiolabeled and endogenous concentrations of arterial and coronary sinus norepinephrine (NE). These measures were repeated after inhaled nitric oxide (NO). Measurement of transcardiac NE concentrations and the cardiac extraction of radiolabeled NE allowed calculation of the corrected transcardiac gradient of NE (CTCG of NE). Comparative data were collected from 15 patients (9 women: 55 ± 12 yr) with normal LV function and 15 patients with CHF (10 women; 53 ± 12 yr). PAH patients had elevated arterial NE concentrations compared with those with normal LV function but were similar to those with CHF. The CTCG of NE was higher in those with PAH than in the normal LV group (3.6 ± 2.2 vs. 1.5 ± 0.9 pmol/ml; P < 0.01) but similar to that seen in those with CHF (3.3 ± 1.4; P = NS). Inhaled NO, which reduced pulmonary artery pressure and increased cardiac output, had no effect on cardiac sympathetic activity. Therefore, cardiac sympathetic activation occurs in PAH. The mechanism of this activation remains uncertain but does not involve elevations in left heart filling pressure.

β-adrenergic blockade attenuates cardiac dysfunction and myofibrillar remodelling in congestive heart failure

Although β-adrenoceptor (β-AR) blockade is an important mode of therapy for congestive heart failure (CHF), subcellular mechanisms associated with its beneficial effects are not clear. Three weeks after inducing myocardial infarction (MI), rats were treated daily with or without 20 and 75 mg/kg atenolol, a selective β₁-AR antagonist, or propranolol, a non-selective β-AR antagonist, for 5 weeks. Sham operated rats served as controls. All animals were assessed haemodynamically and echocardiographically and the left ventricle (LV) was processed for the determination of myofibrillar ATPase activity, α- and β-myosin heavy chain (MHC) isoforms and gene expression as well as cardiac troponin I (cTnI) phosphorylation. Both atenolol and propranolol at 20 and 75 mg/kg doses attenuated cardiac hypertrophy and lung congestion in addition to increasing LV ejection fraction and LV systolic pressure as well as decreasing heart rate, LV end-diastolic pressure and LV diameters in the infarcted animals. Treatment of infarcted animals with these agents also attenuated the MI-induced depression in myofibrillar Ca²⁺-stimulated ATPase activity and phosphorylated cTnI protein content. The MI-induced decrease in α-MHC and increase in β-MHC protein content were attenuated by both atenolol and propranolol at low and high doses; however, only high dose of propranolol was effective in mitigating changes in the gene expression for α-MHC and β-MHC. Our results suggest that improvement of cardiac function by β-AR blockade in CHF may be associated with attenuation of myofibrillar remodelling.

Beta-receptor selectivity of carvedilol and metoprolol succinate in patients with heart failure (SELECT trial): a randomized dose-ranging trial

STUDY OBJECTIVE

To determine whether metoprolol succinate (a beta(1)-selective beta-blocker) remains beta(1)-selective compared with carvedilol (a nonselective beta-blocker) during upward titration of doses in patients with American College of Cardiology (ACC) stage C heart failure.

DESIGN

Prospective, randomized, parallel-arm study. Setting. General clinical research center.

PATIENTS

Twenty-five beta-blocker-naïve adults with New York Heart Association functional classes II or III heart failure (i.e., ACC stage C). Intervention. Patients received either immediate-release carvedilol 3.125 mg twice/day or controlled-release metoprolol succinate 25 mg once/day; doses were titrated upward by doubling the dose every 2 weeks until reaching a maximum tolerated dose or a goal dose of carvedilol 25 mg twice/day and metoprolol 200 mg/day. Before each dose titration, terbutaline (a beta-receptor agonist) was infused at 6 mg/kg over 1 hour for determination of beta(2)-blockade.

MEASUREMENTS AND MAIN RESULTS

Patients were studied at baseline and after each dose titration of metoprolol succinate (at 25, 50, 100, and 200 mg once/day) and immediate-release carvedilol (at 3.125, 6.25, 12.5, and 25 mg twice/day). Glucose and potassium concentrations were measured twice serially at baseline, every 10 minutes during infusion, every 15 minutes for the first hour after infusion, and every 30 minutes for the second hour after infusion. The median area under the concentration-time curve (AUC) was calculated for changes in glucose and potassium concentrations. As assessed by glucose AUC, there was no significant difference in the degree of beta(2)-blockade between metoprolol 200 mg and carvedilol 25 mg. In contrast to these data, the degree of beta(2)-blockade as assessed by potassium AUC was greater for carvedilol compared with metoprolol across all doses.

CONCLUSION

In this ACC stage C heart failure population, carvedilol was nonselective at all clinically relevant doses, whereas metoprolol succinate was beta(1)-selective at low doses and became progressively nonselective at higher doses.

Prevalence and prognostic significance of adrenergic escape during chronic beta-blocker therapy in chronic heart failure

AIMS

Like aldosterone escape to ACE-inhibitors, adrenergic escape (AE) to beta-blockers appears conceivable in chronic heart failure (CHF), as generalized systemic neurohumoral activation has been described as the pathophysiological basis of this syndrome. The aim of this study was to examine the prevalence and prognostic value of AE with respect to different beta-blocker agents and doses.

METHODS AND RESULTS

This was a prospective, observational study of 415 patients with systolic CHF receiving chronic stable beta-blocker therapy. AE was defined by norepinephrine levels above the upper limit of normal. Irrespective of the individual beta-blocker agents used and the dose equivalent taken, the prevalence of AE was 31-39%. Norepinephrine levels neither correlated with heart rate (r=0.02; 95% CI: -0.08-0.11; P=0.74) nor were they related to underlying rhythm (P=0.09) or the individual beta-blocker agent used (P=0.87). The presence of AE was a strong and independent indicator of mortality (adjusted HR: 1.915; 95% CI: 1.387-2.645; chi2: 15.60).

CONCLUSION

We verified the presence of AE in CHF patients on chronic stable beta-blocker therapy, irrespective of the individual beta-blocker agent and the dose equivalent. As AE might indicate therapeutic failure, the determination of AE could help to identify those patients with CHF that might benefit from more aggressive treatment modalities. Heart rate, however, is not a surrogate for adrenergic escape.

Differential effects of carvedilol and metoprolol succinate on plasma norepinephrine release and peak exercise heart rate in subjects with chronic heart failure

Dosing equivalency of carvedilol and metoprolol remains a debate. Degree of beta 1-blockade is best assessed by blunting of the exercise-induced heart rate. Accordingly, the authors have investigated dosing equivalency by examining baseline and peak exercise heart rates and norepinephrine levels in subjects with chronic heart failure treated with carvedilol or metoprolol. Thirty-seven subjects treated with carvedilol (32.9 +/- 3.5 mg; n = 23) or metoprolol succinate (XL) (96.4 +/- 15.9 mg; n = 14) referred for cardiopulmonary exercise testing were studied prospectively. Carvedilol versus metoprolol XL subjects did not differ with respect to baseline heart rate (73 +/- 2 vs 70 +/- 3 bpm), or baseline plasma norepinephrine levels (597.5 +/- 78.3 vs 602.1 +/- 69.6 pg/mL), P = NS. However, despite similar peak exercise norepinephrine levels (2735.8 +/- 320.1 vs 2403.1 +/- 371.6 pg/mL), heart rate at peak exercise was higher in subjects receiving carvedilol (135 +/- 4 bpm) than those receiving metoprolol XL (117 +/- 6 bpm), P = 0.02. Similar norepinephrine release and more complete beta 1-blockade is observed in well-matched subjects with chronic heart failure treated with a mean daily dose of metoprolol XL 96.4 mg compared with carvedilol 32.9 mg.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.

Neuroprotection during cardiac surgery

Cerebral injury following cardiac surgery continues to be a significant source of morbidity and mortality after cardiac surgery. A spectrum of injuries ranging from subtle neurocognitive dysfunction to fatal strokes are caused by a complex series of multifactorial mechanisms. Protecting the brain from these injuries has focused on intervening on each of the various etiologic factors. Although numerous studies have focused on a pharmacologic solution, more success has been found with nonpharmacologic strategies, including optimal temperature management and reducing emboli generation.

Beta-Blocker Treatment of Chronic Heart Failure: Comparison of Carvedilol and Metoprolol

Beta blockers have been shown to prolong survival in chronic heart failure. It is currently a matter of debate whether any beta blocker is superior to the other in terms of improving symptoms, left ventricular function, or prognosis. A number of comparative studies have been performed with metoprolol, a beta1-selective second-generation beta blocker, and carvedilol, a nonselective and vasodilatative third-generation beta blocker. This review will focus on the different pharmacological profiles of carvedilol and metoprolol as well as on the clinical consequences derived from these differences. The results indicate that in some studies carvedilol is superior to metoprolol in improving left ventricular ejection fraction. However, because there is no conclusive evidence that carvedilol is superior to metoprolol in terms of prognosis, it is not justified to substitute metoprolol with carvedilol. Comparative data on mortality reduction are not available before termination of the Carvedilol or Metoprolol European Trial. Nevertheless, the different effects of both beta blockers on the beta-adrenergic system have an impact on tolerability and beta-adrenergic responsiveness and thus exercise tolerance in heart-failure patients.

Cardiopulmonary bypass management and neurologic outcomes: an evidence-based appraisal of current practices

Neurologic complications after cardiac surgery are of growing importance for an aging surgical population. In this review, we provide a critical appraisal of the impact of current cardiopulmonary bypass (CPB) management strategies on neurologic complications. Other than the use of 20-40 microm arterial line filters and membrane oxygenators, newer modifications of the basic CPB apparatus or the use of specialized equipment or procedures (including hypothermia and "tight" glucose control) have unproven benefit on neurologic outcomes. Epiaortic ultrasound can be considered for ascending aorta manipulations to avoid atheroma, although available clinical trials assessing this maneuver are limited. Current approaches for managing flow, arterial blood pressure, and pH during CPB are supported by data from clinical investigations, but these studies included few elderly or high-risk patients and predated many other contemporary practices. Although there are promising data on the benefits of some drugs blocking excitatory amino acid signaling pathways and inflammation, there are currently no drugs that can be recommended for neuroprotection during CPB. Together, the reviewed data highlight the deficiencies of the current knowledge base that physicians are dependent on to guide patient care during CPB. Multicenter clinical trials assessing measures to reduce the frequency of neurologic complications are needed to develop evidence-based strategies to avoid increasing patient morbidity and mortality.

Beta-blockers in heart failure: are pharmacological differences clinically important?

Beta-blockers are not an homogeneous group of agents. Only three beta-blockers, carvedilol, bisoprolol and metoprolol succinate, have had favorable effects on prognosis in controlled clinical trials in the patients with chronic heart failure. However, pharmacological differences exist between them. Metoprolol and bisoprolol are selective for beta(1)-adrenergic receptors while carvedilol blocks also beta(2)-, and alpha(1)- adrenergic receptors, and has associated antioxidant, anti-endothelin and antiproliferative properties. In COMET carvedilol was associated with a significant reduction in mortality compared to metoprolol tartrate further showing that different beta-blockers may have different effects on the outcome. These differences may be related to the ancillary properties of carvedilol or to its broader antiadrenergic profile. However, also more effective and prolonged blockade of beta1 adrenergic receptors may occur with carvedilol compared to metoprolol.

Inhaled beta2-adrenoceptor agonists: cardiovascular safety in patients with obstructive lung disease

Although large surveys have documented the favourable safety profile of beta(2)-adrenoceptor agonists (beta(2)-agonists) and, above all, that of the long-acting agents, the presence in the literature of reports of adverse cardiovascular events in patients with obstructive airway disease must induce physicians to consider this eventuality. The coexistence of beta(1)- and beta(2)-adrenoceptors in the heart clearly indicates that beta(2)-agonists do have some effect on the heart, even when they are highly selective. It should also be taken into account that the beta(2)-agonists utilised in clinical practice have differing selectivities and potencies. beta(2)-agonist use has, in effect, been associated with an increased risk of myocardial infarction, congestive heart failure, cardiac arrest and sudden cardiac death. Moreover, patients who have either asthma or chronic obstructive pulmonary disease may be at increased risk of cardiovascular complications because these diseases amplify the impact of these agents on the heart and, unfortunately, are a confounding factor when the impact of beta(2)-agonists on the heart is evaluated. Whatever the case may be, this effect is of particular concern for those patients with underlying cardiac conditions. Therefore, beta(2)-agonists must always be used with caution in patients with cardiopathies because these agents may precipitate the concomitant cardiac disease.

The haemodynamic effects of propranolol and atenolol medication on dobutamine infusion in patients with coronary artery obstructive disease

We compared the haemodynamic effects of beta-blockers on dobutamine infusion in 60 patients undergoing coronary artery bypass graft surgery. All patients had been taking propranolol (n = 30) or atenolol (n = 30) pre-operatively for at least 1 month. After sternotomy, dobutamine was infused at 2 microg/kg per min, and the dose increased to 4 microg/kg per min and then 8 microg/kg per min, at 15-min intervals. In both groups, dobutamine infusion did not increase the cardiac index or the heart rate, but was associated with an increase in mean arterial pressure, systemic vascular resistance index and mean pulmonary arterial pressure in a dose-dependent manner. The haemodynamic responses to dobutamine infusion were similar in the two groups. We conclude that pre-operative medication with beta-blockers reduced the inotropic and chronotropic effects of dobutamine infusion. There was no difference between the modification produced by propranolol, a non-selective beta-blocker, and that produced by atenolol, a selective beta1-blocker, however.

Selective versus nonselective β-adrenergic receptor blockade in chronic heart failure: differential effects on myocardial energy substrate utilization

BACKGROUND

Non-selective and selective beta-blockers have been shown to improve outcomes in chronic heart failure (CHF). Recent data suggests the non-selective beta-blockers have a more favourable effect on outcomes than beta(1)-selective agents. We sought to examine the differential effects of non-selective versus selective beta-blockade on myocardial substrate utilization in patients with CHF.

METHODS AND RESULTS

Twenty-two patients with CHF were randomised to the non-selective beta-blocker carvedilol or the selective beta-blocker metoprolol (double-blind). Measurement of hemodynamics, arterial and coronary sinus free fatty acid (FFA) and lactate levels, and cardiac norepinephrine spillover (CANESP) were made before and after 4 months of therapy. In the carvedilol group (n=11), there was a significant reduction in myocardial FFA uptake (0.12+/-0.02 to 0.1+/-0.02 mmol/l, P<0.03). By contrast, in the metoprolol group (n=11) there was no change in myocardial FFA extraction. Carvedilol therapy tended to increase myocardial lactate extraction (0.24+/-0.05 to 0.35+/-0.08 mmol/l, P=0.08) while metoprolol therapy resulted in a trend in the opposite direction (0.18+/-0.03 to 0.11+/-0.04 mmol/l, P=0.09). The change in lactate extraction in the carvedilol group was significantly different from that in the metoprolol group (+0.11+/-0.06 vs. -0.09+/-0.04 mmol/l, P<0.01). Carvedilol treatment caused a significant reduction in CANESP while metoprolol had a neutral effect (-95+/-27 vs. 25+/-42 pmol/min, carvedilol vs. metoprolol P<0.03).

CONCLUSION

Carvedilol treatment caused a 20% reduction in myocardial free fatty acid extraction while metoprolol had a neutral effect. These differences are most probably related to the differential effects of these two agents on efferent cardiac sympathetic activity and may be relevant to the reported differential effects of these drugs on clinical outcomes.

Hemodynamic effects of carvedilol infusion and the contribution of the sympathetic nervous system in rats with heart failure

We investigated the contribution of the sympathetic nervous system (SNS) in maintaining the blood pressure and in regulating the cardiac function during and after carvedilol administration in rats with heart failure (group F). Left ventricular end-diastolic pressure, percent functional shortening, and rates of intraventricular pressure rise were significantly changed by carvedilol infusion as compared with the basal values in group N (normal rats), but not in group F. The left ventricular end-diastolic pressure was elevated, corresponding to the enhancement of the plasma norepinephrine (NE) concentration caused by carvedilol infusion, in group N. The enhancement of the plasma NE concentration induced by carvedilol administration in group F was higher than that in group N. The value for the maximal hypertensive effect of NE intravenous infusion (Emax) was decreased, and the plasma NE concentration at half-maximal effect (EC50) was increased in group F as compared with the values in group N. These results indicate that the SNS (presynaptic) activity is increased and that the SNS receptor sensitivity in the cardiovascular regulation system is decreased in heart failure.

The effect of diabetes on the interrelationship between jugular venous oxygen saturation responsiveness to phenylephrine infusion and cerebrovascular carbon dioxide reactivity

In this study, we examined whether cerebrovascular carbon dioxide (CO(2)) reactivity was related to the response of jugular venous oxygen saturation (SjvO(2)) to phenylephrine infusion in diabetic patients during cardiopulmonary bypass. Forty diabetic patients scheduled for coronary artery bypass graft surgery were studied, and 40 age-matched nondiabetic cardiopulmonary bypass patients served as controls. Cerebrovascular CO(2) reactivity was measured continuously using transcranial Doppler. Mean arterial blood pressure (MAP) was increased by repeated phenylephrine infusion until reaching 100% of baseline values. There was a significant difference in absolute CO(2) reactivity between the diabetic and control groups (controls, 2.8 +/- 0.7 cm. s(-1). mm Hg(-1); diabetics, 2.2 +/- 1.1 cm. s(-1). mm Hg(-1); P = 0.02). Among the diabetics, absolute CO(2) reactivity in insulin-dependent patients was less than that in noninsulin-dependent patients (diet therapy group, 3.2 +/- 0.7; glibenclamide group, 2.6 +/- 0.7; insulin-dependent group, 1.0 +/- 0.7; P < 0.01). There was a correlation between absolute CO(2) reactivity and the mean slope of SjvO(2) versus MAP for increasing MAP (r = 0.54; P < 0.0001). In conclusion, we found that the interrelationship between SjvO(2) responsiveness to phenylephrine infusion and cerebrovascular CO(2) reactivity, as well as impaired cerebrovascular autoregulation, were associated with previous hyperglycemia.

Do β-blockers prolong survival in heart failure only by inhibiting the β1-receptor? A perspective on the results of the COMET trial

Experimental and clinical studies indicate that carvedilol exerts multiple antiadrenergic effects in addition to beta(1)-receptor blockade, but the prognostic importance of these actions has long been debated. This controversy has now been substantially advanced by the results of the recently completed Carvedilol Or Metoprolol European Trial (COMET), which showed that carvedilol (25 mg twice daily) reduced mortality by 17% when compared with metoprolol (50 mg twice daily), P=.0017--a result that was consistent with the differences seen across earlier controlled trials with beta-blockers in survivors of an acute myocardial infarction and in patients with chronic heart failure. Questions have been raised about the interpretation of these findings in view of the fact that the trial did not use the dose or formulation of metoprolol that was shown to prolong life in a placebo-controlled trial (ie, Metoprolol CR/XL [Controlled Release] Randomized Intervention Trial in Heart Failure). Pharmacokinetic and pharmacodynamic analyses, however, indicate that the dosing regimen of metoprolol selected for use in the COMET trial produces a magnitude and time course of beta(1)-blockade during a 24-hour period that is similar to the dose of carvedilol targeted for use in the trial. These analyses suggest that the observed difference in the mortality effects of metoprolol and carvedilol is not related to a difference in the magnitude or time course of their beta(1)-blocking effects but instead reflect antiadrenergic effects of carvedilol in addition to beta(1)-blockade.

The Effects of Isoflurane-Induced Electroencephalographic Burst Suppression on Cerebral Blood Flow Velocity and Cerebral Oxygen Extraction During Cardiopulmonary Bypass

We investigated the effects of isoflurane-induced burst suppression, monitored with electroencephalography (EEG), on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and autoregulation in 16 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopulmonary bypass (CPB) with mild hypothermia (32 degrees C) in fentanyl-anesthestized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular vein bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Autoregulation was tested during changes in mean arterial blood pressure (MAP) within a range of 40-80 mm Hg, induced by sodium nitroprusside and phenylephrine before (control) and during additional isoflurane administration to an EEG burst-suppression level of 6-9/min. Isoflurane induced a 27% decrease in CBFV (P < 0.05) and a 13% decrease in COE (P < 0.05) compared with control. The slope of the positive relationship between CBFV and cerebral perfusion pressure (CPP = MAP - JVP) was steeper with isoflurane (P < 0.05) compared with control, as was the slope of the negative relationship between CPP and COE (P < 0.05). We conclude that burst-suppression doses of isoflurane decrease CBFV and impair autoregulation of cerebral blood flow during mildly hypothermic CPB. Furthermore, during isoflurane administration, blood flow was in excess relative to oxygen demand, indicating a loss of metabolic autoregulation of flow.

IMPLICATIONS

The effects of isoflurane on cerebral blood flow velocity (CBFV) and oxygen extraction (COE) as a function of perfusion pressure were studied. When added to fentanyl anesthesia, isoflurane induced a 27% and 13% decrease in CBFV and COE, respectively. CBFV became more pressure-dependent with isoflurane indicating an impaired autoregulation.

The cardiovascular system

The ageing process is associated with important changes in the responses of the cardiovascular system to pharmacological stimuli. They are not limited to the arterial system, involved in the modulation of cardiac afterload and vascular resistance, but they also involve the low-resistance capacitance venous system and the heart. The main changes include loss of large artery compliance, dysfunction of some of the systems modulating resistance vessel tone, increased activity of the sympathetic nervous system, and reduced haemodynamic responses to inotropic agents. This review focuses on the effects of ageing on arterial and venous reactivity to drugs and hormones, the autonomic nervous system, and the cardiovascular responses to inotropic agents. Some of the age-related changes might be at least partially reversible. This may have important therapeutic implications.

Risk of mortality and heart failure exacerbations associated with inhaled beta-adrenoceptor agonists among patients with known left ventricular systolic dysfunction

OBJECTIVES

Recent studies suggest that myocardial beta(2)-adrenoceptors may be important in chronic heart failure. We sought to determine if use of selective beta(2)-agonists was associated with hospitalization for heart failure and all-cause mortality.

METHODS

We studied a cohort of patients with left ventricular systolic dysfunction (LVSD). The outcome was the first hospitalization with a primary diagnosis of chronic heart failure or death from any cause. The exposure was the average number of beta-agonist canisters filled per month in the 90 days prior to and 15 days after enrollment.

RESULTS

Among 1,529 subjects, the relative risk (RR) of chronic heart failure hospital admission associated with inhaled beta-agonists followed a dose-response relationship: RR for one canister per month, 1.4 (95% confidence interval [CI], 0.9 to 2.0), RR for two canisters per month, 1.7 (95% CI, 1.2 to 2.5), and RR for three canisters per month, 2.1 (95% CI, 1.4 to 3.1). The RR of death demonstrated a similar finding: RR for one canister per month, 0.9 (95% CI, 0.5 to 1.5), RR for two canisters per month, 1.3 (95% CI, 0.9 to 2.1), and RR for three canisters per month, 2.0 (95% CI, 1.3 to 3.1). Adjusting for potential confounding factors did not affect the estimates.

CONCLUSION

Among subjects with LVSD, inhaled beta-agonists were associated with an increased risk of heart failure hospitalization, and all-cause mortality. Clinicians should carefully consider the etiology of dyspnea when prescribing beta-agonists to patients with LVSD.

Should beta-blockers be used for the treatment of pediatric patients with chronic heart failure?

In multiple clinical trials, beta-blockers have been shown to significantly improve morbidity and mortality in adults with chronic congestive heart failure, but there is little reported experience with their use in children. Heart failure involves activation of the adrenergic nervous system and other neurohumoral systems in order to maintain cardiovascular homeostasis. These compensatory mechanisms have been shown to cause myocardial damage with chronic activation, which has been hypothesized to be a major contributing factor to the clinical deterioration of adults with heart failure. Studies have demonstrated inhibition of this neurohumoral response and concomitant clinical benefits with beta-blockers. Consequently, beta-blockers have evolved to become an important part of comprehensive medical therapy for congestive heart failure in adults. Pediatric heart failure represents an entirely different spectrum of disease, caused more commonly by congenital heart disease than cardiomyopathy. Surgical palliation and correction are important components of pediatric heart failure therapy, and residual, postsurgical cardiac lesions can lead to chronic heart failure. Although neurohumoral activation in children is similar to that in adults with heart failure, there are important differences from adults in physiology and developmental changes that are especially observed in infants. Current published clinical experience with beta-blocker use in children with heart failure is limited to case series with relatively small numbers of patients. Nevertheless, these series show consistent symptomatic improvement, and improvement in ventricular systolic function in patients with cardiomyopathies and congenital heart disease, similar to findings in adults. Adverse effects were common and many patients in these studies had adverse outcomes (death and/or need for transplantation). One study has noted differences in pharmacokinetics in children compared with adults. However, a multicenter, randomized controlled trial to evaluate carvedilol in pediatric heart failure from systolic ventricular dysfunction is currently ongoing and should help to clarify the efficacy and tolerability of carvedilol in children.

Sympathetic activation in human heart failure: diverse mechanisms, therapeutic opportunities

Plasma noradrenaline (NA) concentrations relate both to the severity of heart failure, and to its impact on survival, but have shortcomings that limit their usefulness as measures of sympathetic discharge. Neural recordings and the isotopic dilution method for determining organ-specific rates of NA spillover into plasma have enhanced our understanding of mechanisms responsible for sympathetic activation. Because the arterial baroreceptor reflex control of heart rate is impaired in heart failure, a parallel reduction in the reflex inhibition of sympathetic outflow has been assumed. However, human heart failure is characterized by rapidly responsive arterial baroreflex regulation of muscle sympathetic nerve activity (MSNA), attenuated cardiopulmonary reflex modulation of MSNA, and activation of a cardiac-specific sympatho-excitatory reflex related to increased cardiopulmonary filling pressures. Together, these baroreceptor mediated mechanisms account only, in part, for the time course and magnitude of adrenergic activation in heart failure. Non-baroreflex sympatho-excitatory mechanisms include: a metaboreflex arising from exercising skeletal muscle, mediated, in part, by adenosine, co-existing sleep apnoea, and pre-junctional facilitation of NA release. Thus, sympathetic activation in the setting of impaired systolic function reflects the net balance and interaction between augmented excitatory and diminished inhibitory influences. Variation, between patients, in the dynamics, magnitude and progression of sympathetic activation mandates an individualized approach to investigation and therapy. Excessive sympathetic outflow to the heart and periphery can be addressed by several complimentary strategies: attenuating these sympatho-excitatory stimuli, modulating the neural regulation of NA release, and blocking the actions of catecholamines at post-junctional receptors.

Increasing mean arterial blood pressure has no effect on jugular venous oxygen saturation in insulin-dependent patients during tepid cardiopulmonary bypass

Preexisting diabetes mellitus is one of the major factors related to adverse postoperative neurological disorders after cardiac surgery. In previous reports, we found that diabetic patients more often experienced cerebral desaturation than nondiabetic patients during normothermic cardiopulmonary bypass (CPB). The purpose of this study was to examine the effects of increasing mean arterial blood pressure (MAP) by the administration of phenylephrine on internal jugular venous oxygen hemoglobin saturation (SjvO2) during tepid CPB in diabetic patients. We studied 20 diabetic patients scheduled for elective coronary artery bypass graft surgery and, as a control, 20 age-matched nondiabetic patients. After the induction of anesthesia, a fiberoptic oximetry catheter was inserted into the right jugular bulb to monitor SjvO2. After measuring the baseline partial pressure of the arterial and jugular venous blood gases and cardiovascular hemodynamic values, MAP was increased by the repeated administration of a 10-microg bolus of phenylephrine until it reached 100% of baseline values. There was a significant difference in SjvO2 value between the Diabetic and CONTROL GROUPs after the administration of phenylephrine (Diabetic group, 56% +/- 6%;

CONTROL GROUP

60% +/- 4%) (P < 0.05). There was a significant difference in the arterial-jugular oxygen content difference value between the Diabetic and CONTROL GROUPs after the administration of phenylephrine (diabetic group, 4.9% +/- 0.6%; CONTROL GROUP, 4.5% +/- 0.4%) (P < 0.05). We subdivided the Diabetic group into three groups (Diet Therapy group [n = 4], Glibenclamide group [n = 10], and Insulin-Dependent group [n = 6]). There was a significant difference in the mean slopes of SjvO2 versus cerebral perfusion pressure for increasing cerebral perfusion pressure between the Insulin-Dependent group and the other groups (Dunnett test: P = 0.04). Increasing MAP had no effects on the SjvO2 value in insulin-dependent patients during tepid CPB.

IMPLICATIONS

We examined the effects of increasing mean arterial blood pressure (MAP) by the administration of phenylephrine on internal jugular venous oxygen saturation (SjvO2) during tepid cardiopulmonary bypass in diabetic patients and found that increasing MAP had no effect on the SjvO2 value in insulin-dependent patients.

Effect of carvedilol on microcirculatory and glucose metabolic regulation in patients with congestive heart failure secondary to ischemic cardiomyopathy

In a randomized (2:1), double-blinded design study, we studied 25 patients with congestive heart failure (66 +/- 9 years, ejection fraction 30 +/- 7%) before and after 23-week treatment with the beta blocker carvedilol 25 mg twice daily (n = 17) or placebo (n = 8) in addition to standard therapy. Using dynamic positron emission tomography, myocardial perfusion at rest and perfusion reserve after dipyridamole (0.56 mg/kg/min) were measured. Myocardial glucose uptake and plasma levels of catecholamines were also estimated. Carvedilol treatment reduced the rate-pressure product (8,781 +/- 2,672 vs 6,342 +/- 1,346, p <0.01) and improved ejection fraction (29 +/- 7% vs 37 +/- 11%, p <0.001), whereas no changes were observed in the control group. Perfusion at rest was unchanged in the placebo group (0.81 +/- 0.17 vs 0.86 +/- 0.23 ml/g/min, p = NS), whereas the carvedilol-treated group showed a significant reduction (0.88 +/- 0.26 vs 0.75 +/- 0.16 ml/g/min, p <0.05). Dipyridamole-induced hyperemia was significantly reduced after carvedilol treatment (1.51 +/- 0.45 vs 1.31 +/- 0.51 ml/g/min, p <0.001), whereas myocardial perfusion reserve was unaltered. Carvedilol did not alter myocardial glucose uptake (0.33 +/- 0.14 vs 0.32 +/- 0.12 micromol/g/min, p = NS) or the plasma catecholamines levels. We therefore conclude that in patients with congestive heart failure, carvedilol reduced resting and hyperemic perfusion. No effect on glucose uptake or catecholamine levels was observed. The reduced perfusion at rest must reflect reduced perfusion demand and thereby a higher threshold for myocardial ischemia and protection against myocardial damage or malignant arrhythmia. These effects may serve as a pathophysiologic explanation for the reduced mortality in patients with congestive heart failure who receive carvedilol.