Reducing the Risk of Sudden Death in Heart Failure With β-Blockers

Heart failure treatment in patients with cardiac implantable electronic devices: Opportunity for improvement

BACKGROUND

Heart failure and reduced ejection fraction (HFrEF) is the predominant indication for cardiac resynchronization therapy (CRT) and implantable cardioverter-defibrillator (ICD) implantation. The care gap and opportunity to optimize guideline-directed medical therapy (GDMT) is unclear.

OBJECTIVE

We sought to define uptake, eligibility, dose, and adherence to GDMT in patients with CRT/ICD and HFrEF.

METHODS

MEDLINE was searched from 2000 to July 2021 for major randomized trials, registries, and cohort studies evaluating GDMT in this population. Thirty-eight studies focused on medical therapy in patients with CRT/ICD devices (CRT = 23, ICD = 11, and both = 4).

RESULTS

In the pivotal device trials, ACEI/ARB and beta-blocker use was high (mean 94%, range 41%-99%; and 83%, range 27%-97%, respectively), but mineralocorticoid receptor antagonists were modest (mean 45%, range 32%-61%), in keeping with guidelines of that era. Similar results were found in observational registries. CRT was associated with beta-blocker uptitration, while the effects on ACEI/ARB were less consistent. For beta blockers, 57%-68% of patients were uptitrated, increasing the mean percent of target dose achieved by 24% from baseline to follow-up. In one study, adherence increased, for ACEI/ARB from 37% to 55% and beta blockers 34% to 58%. Only 1 study assessed potential eligibility at implant for sacubitril-valsartan (72%) or ivabradine (28%), and no study examined sodium-glucose cotransporter-2 inhibitors. Increased uptake, titration, and dose was associated with reduced mortality, hospitalization, and device therapies.

CONCLUSION

Patients with HFrEF and ICD/CRT are undertreated with respect to GDMT, and there is opportunity to optimize therapy to improve morbidity and mortality.

Modulation of Sympathetic Activity and Innervation With Chronic Ivabradine and β-Blocker Therapies: Analysis of Hypertensive Rats With Heart Failure

BACKGROUND

Whether the reduction of heart rate with ivabradine (IVA) could affect sympathetic activation and cardiac innervation in heart failure (HF) remains unknown.

PURPOSE

The present study assessed the chronic effects of IVA and β-blocker on the systemic and local sympathetic nervous systems of hypertensive animals with HF.

METHODS AND RESULTS

The Dahl salt-sensitive rats received chronic IVA, bisoprolol (BIS), or placebo (CTL) therapy. The survival of the animal models with IVA and BIS significantly improved (median; 19.7 in IVA and 19.7 in BIS vs 17.0 weeks in CTL, P < .001). A similar decrease in 24-hour heart rate (mean; 305 in IVA and 329 in BIS vs 388 beats/min in CTL, P < .001) without effect on blood pressure, and an improvement in the left ventricular dysfunction (mean fractional shortening; 56.7% in IVA and 47.8% in BIS vs 39.0% in CTL, P < .001) were observed in the animals with IVA and BIS. However, a negative inotropic effect was only observed in the animals with BIS. Excessive urinary noradrenaline excretion in animals with CTL was only suppressed with the use of IVA (mean; 1.35 μg/d in IVA and 1.95 μg/d in BIS vs 2.27 μg/d in CTL, P = .002). In contrast, atrial noradrenaline and acetylcholine depletion in the animals with CTL improved and the tyrosine hydroxylase expression in the both atria were restored with the use of both IVA and BIS.

CONCLUSIONS

IVA therapy improved the survival of hypertensive animals with HF. Furthermore, it was associated with the amelioration of systemic sympathetic activation and cardiac sympathetic and parasympathetic nerve innervations. Chronic β-blocker therapy with negative inotropic effects had beneficial effects only on cardiac innervations.

Recent advancements in understanding endogenous heart regeneration-insights from adult zebrafish and neonatal mice

Enhancing the endogenous regenerative capacity of the mammalian heart is a promising strategy that can lead to potential treatment of injured cardiac tissues. Studies on heart regeneration in zebrafish and neonatal mice have shown that cardiomyocyte proliferation is essential for replenishing myocardium. We will review recent advancements that have demonstrated the importance of Neuregulin 1/ErbB2 and innervation in regulating cardiomyocyte proliferation using both adult zebrafish and neonatal mouse heart regeneration models. Emerging findings suggest that different populations of macrophages and inflammation might contribute to regenerative versus fibrotic responses. Finally, we will discuss variation in the severity of the cardiac injury and size of the wound, which may explain the range of outcomes observed in different injury models.

Increased mortality attributed to Chagas disease: a systematic review and meta-analysis

BACKGROUND

The clinical outcomes associated with Chagas disease remain poorly understood. In addition to the burden of morbidity, the burden of mortality due to Trypanosoma cruzi infection can be substantial, yet its quantification has eluded rigorous scrutiny. This is partly due to considerable heterogeneity between studies, which can influence the resulting estimates. There is a pressing need for accurate estimates of mortality due to Chagas disease that can be used to improve mathematical modelling, burden of disease evaluations, and cost-effectiveness studies.

METHODS

A systematic literature review was conducted to select observational studies comparing mortality in populations with and without a diagnosis of Chagas disease using the PubMed, MEDLINE, EMBASE, Web of Science and LILACS databases, without restrictions on language or date of publication. The primary outcome of interest was mortality (as all-cause mortality, sudden cardiac death, heart transplant or cardiovascular deaths). Data were analysed using a random-effects model to obtain the relative risk (RR) of mortality, the attributable risk percent (ARP), and the annual mortality rates (AMR). The statistic I(2) (proportion of variance in the meta-analysis due to study heterogeneity) was calculated. Sensitivity analyses and publication bias test were also conducted.

RESULTS

Twenty five studies were selected for quantitative analysis, providing data on 10,638 patients, 53,346 patient-years of follow-up, and 2739 events. Pooled estimates revealed that Chagas disease patients have significantly higher AMR compared with non-Chagas disease patients (0.18 versus 0.10; RR = 1.74, 95% CI 1.49-2.03). Substantial heterogeneity was found among studies (I(2) = 67.3%). The ARP above background mortality was 42.5%. Through a sub-analysis patients were classified by clinical group (severe, moderate, asymptomatic). While RR did not differ significantly between clinical groups, important differences in AMR were found: AMR = 0.43 in Chagas vs. 0.29 in non-Chagas patients (RR = 1.40, 95% CI 1.21-1.62) in the severe group; AMR = 0.16 (Chagas) vs. 0.08 (non-Chagas) (RR = 2.10, 95% CI 1.52-2.91) in the moderate group, and AMR = 0.02 vs. 0.01 (RR = 1.42, 95% CI 1.14-1.77) in the asymptomatic group. Meta-regression showed no evidence of study-level covariates on the effect size. Publication bias was not statistically significant (Egger's test p=0.08).

CONCLUSIONS

The results indicate a statistically significant excess of mortality due to Chagas disease that is shared among both symptomatic and asymptomatic populations.

Non-β-blocking R-carvedilol enantiomer suppresses Ca2+ waves and stress-induced ventricular tachyarrhythmia without lowering heart rate or blood pressure

Carvedilol is the current β-blocker of choice for suppressing ventricular tachyarrhythmia (VT). However, carvedilol's benefits are dose-limited, attributable to its potent β-blocking activity that can lead to bradycardia and hypotension. The clinically used carvedilol is a racemic mixture of β-blocking S-carvedilol and non-β-blocking R-carvedilol. We recently reported that novel non-β-blocking carvedilol analogues are effective in suppressing arrhythmogenic Ca(2+) waves and stress-induced VT without causing bradycardia. Thus, the non-β-blocking R-carvedilol enantiomer may also possess this favourable anti-arrhythmic property. To test this possibility, we synthesized R-carvedilol and assessed its effect on Ca(2+) release and VT. Like racemic carvedilol, R-carvedilol directly reduces the open duration of the cardiac ryanodine receptor (RyR2), suppresses spontaneous Ca(2+) oscillations in human embryonic kidney (HEK) 293 cells, Ca(2+) waves in cardiomyocytes in intact hearts and stress-induced VT in mice harbouring a catecholaminergic polymorphic ventricular tachycardia (CPVT)-causing RyR2 mutation. Importantly, R-carvedilol did not significantly alter heart rate or blood pressure. Therefore, the non-β-blocking R-carvedilol enantiomer represents a very promising prophylactic treatment for Ca(2+)- triggered arrhythmia without the bradycardia and hypotension often associated with racemic carvedilol. Systematic clinical assessments of R-carvedilol as a new anti-arrhythmic agent may be warranted.

Adrenergic nervous system in heart failure: pathophysiology and therapy

Heart failure (HF), the leading cause of death in the western world, develops when a cardiac injury or insult impairs the ability of the heart to pump blood and maintain tissue perfusion. It is characterized by a complex interplay of several neurohormonal mechanisms that become activated in the syndrome to try and sustain cardiac output in the face of decompensating function. Perhaps the most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are enormously elevated in HF. Acutely, and if the heart works properly, this activation of the ANS will promptly restore cardiac function. However, if the cardiac insult persists over time, chances are the ANS will not be able to maintain cardiac function, the heart will progress into a state of chronic decompensated HF, and the hyperactive ANS will continue to push the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, methods of measuring ANS activity in HF, the molecular alterations in heart physiology that occur in HF, along with their pharmacological and therapeutic implications, and, finally, drugs and other therapeutic modalities used in HF treatment that target or affect the ANS and its effects on the failing heart.

Current and future G protein-coupled receptor signaling targets for heart failure therapy

Although there have been significant advances in the therapy of heart failure in recent decades, such as the introduction of β-blockers and antagonists of the renin–angiotensin–aldosterone system, this devastating disease still carries tremendous morbidity and mortality in the western world. G protein-coupled receptors, such as β-adrenergic and angiotensin II receptors, located in the membranes of all three major cardiac cell types, ie, myocytes, fibroblasts, and endothelial cells, play crucial roles in regulation of cardiac function in health and disease. Their importance is reflected by the fact that, collectively, they represent the direct targets of over one-third of the currently approved cardiovascular drugs used in clinical practice. Over the past few decades, advances in elucidation of the signaling pathways they elicit, specifically in the heart, have led to identification of an increasing number of new molecular targets for heart failure therapy. Here, we review these possible targets for heart failure therapy that have emerged from studies of cardiac G protein-coupled receptor signaling in health and disease, with a particular focus on the main cardiac G protein-coupled receptor types, ie, the β-adrenergic and the angiotensin II type 1 receptors. We also highlight key issues that need to be addressed to improve the chances of success of novel therapies directed against these targets.

Stretch current-induced abnormal impulses in CaMKIIδ knockout mouse ventricular myocytes

BACKGROUND

CaMKII activation is proarrhythmic in heart failure where myocardium is stretched. However, the arrhythmogenic role of CaMKII in stretched ventricle has not been well understood.

OBJECTIVE

We tested abnormal impulse inducibility by stretch current in myocytes isolated from CaMKIIδ knockout (KO) mouse left ventricle (LV) where CaMKII activity is reduced by ≈ 62%.

METHODS AND RESULTS

Action potentials were recorded by whole-cell patch clamp, and abnormal impulses were induced in LV myocytes by a simulation of stretch-activated channel (SAC) current. SAC activation failed to induce abnormal impulses in wild type (WT) myocytes but steadily produced early after-depolarizations and automaticity in KO myocytes in which an increase in L-type calcium channel (LTCC) current (I(Ca)) and a reduction of sarcoplasmic reticulum Ca(2+) leak and action potential duration (APD) were observed. The abnormal impulses were not suppressed by CaMKII inhibitor AIP whereas a low concentration of nifedipine eliminated abnormal impulses without shortening APD, implicating I(Ca) in promoting stretch-induced abnormal impulses. In addition, APD prolongation by LTCC opener S(-)Bay K 8644 or isoproterenol facilitated abnormal impulse induction in WT ventricular myocytes even in the presence of CaMKII inhibitor AIP, whereas APD prolongation by K(+) channel blocker 4-aminopyridine promoted abnormal impulses in KO myocytes but not in WT myocytes.

CONCLUSION

I(Ca) activation plays a central role in stretch-induced abnormal impulses and APD prolongation is arrhythmogenic only when I(Ca) is highly activated. At increased I(Ca) activation, CaMKII inhibition cannot suppress abnormal impulse induction.

The effect of beta-blockade on myocardial remodelling in Chagas' cardiomyopathy

OBJECTIVE

Chagas' disease has spread throughout Latin America because of the high rate of migration among these countries. Approximately 30% of Chagas' patients will develop cardiomyopathy, and 10% of these will develop severe cardiac damage leading to heart failure. Beta-blockade improves symptoms and survival in heart failure patients; however, its efficacy has not been well established in Chagas' disease. We evaluated the role of carvedilol in cardiac remodeling and mortality in a Chagas' cardiomyopathy animal model.

METHODS

We studied Trypanosoma cruzi infection in 55 Syrian hamsters that were divided into three groups: control (15), infected (20), and infected + carvedilol (20). Animals underwent echocardiography, electrocardiography, and morphometry for collagen evaluation in ventricles stained with picrosirius red.

RESULTS

The left ventricular diastolic diameter did not change between groups, although it was slightly larger in infected groups, as was left ventricular systolic diameter. Fractional shortening also did not change between groups, although it was slightly lower in infected groups. Collagen accumulation in the interstitial myocardial space was significantly higher in infected groups and was not attenuated by carvedilol. The same response was observed in the perivascular space. The survival curve showed significantly better survival in the control group compared with the infected groups; but no benefit of carvedilol was observed during the study. However, in the acute phase (up to 100 days of infection), carvedilol did reduce mortality.

CONCLUSION

Carvedilol did not attenuate cardiac remodeling or mortality in this model of Chagas' cardiomyopathy. The treatment did improve survival in the acute phase of the disease.

Drug therapy for ventricular tachyarrhythmia in heart failure

Sudden cardiac death (SCD) accounts for approximately one-third of all deaths in patients with heart failure, and is generally the result of ventricular tachycardia (VT) and/or ventricular fibrillation (VF). The mechanisms of VT/VF associated with heart failure are complex and heterogeneous; they include functional and structural remodeling, as well as neurohormonal activation. The implantable cardioverter-defibrillator is very useful for preventing SCD, but the improvement of outcome is limited in patients with cardiac dysfunction and advanced heart failure. This article reviews the current status of drug therapy for the treatment of VT/VF in patients with heart failure. Chronic beta-blocker therapy reduces SCD and improves survival. Angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers and aldosterone antagonists are thought to reduce SCD by preventing ventricular remodeling. Amiodarone is potentially effective for preventing VT/VF in patients at high risk, especially those with nonischemic heart failure. This may be a result of the complex pharmacodynamics of amiodarone, which affects many kinds of ion channels/transporters, as well as thyroid function. The pure class III antiarrhythmic drug, nifekalant, is useful in the emergency treatment of VT/VF.

The sympathetic nervous system in heart failure physiology, pathophysiology, and clinical implications

Heart failure is a syndrome characterized initially by left ventricular dysfunction that triggers countermeasures aimed to restore cardiac output. These responses are compensatory at first but eventually become part of the disease process itself leading to further worsening cardiac function. Among these responses is the activation of the sympathetic nervous system (SNS) that provides inotropic support to the failing heart increasing stroke volume, and peripheral vasoconstriction to maintain mean arterial perfusion pressure, but eventually accelerates disease progression affecting survival. Activation of SNS has been attributed to withdrawal of normal restraining influences and enhancement of excitatory inputs including changes in: 1) peripheral baroreceptor and chemoreceptor reflexes; 2) chemical mediators that control sympathetic outflow; and 3) central integratory sites. The interface between the sympathetic fibers and the cardiovascular system is formed by the adrenergic receptors (ARs). Dysregulation of cardiac beta(1)-AR signaling and transduction are key features of heart failure progression. In contrast, cardiac beta(2)-ARs and alpha(1)-ARs may function in a compensatory fashion to maintain cardiac inotropy. Adrenergic receptor polymorphisms may have an impact on the adaptive mechanisms, susceptibilities, and pharmacological responses of SNS. The beta-AR blockers and the inhibitors of the renin-angiotensin-aldosterone axis form the mainstay of current medical management of chronic heart failure. Conversely, central sympatholytics have proved harmful, whereas sympathomimetic inotropes are still used in selected patients with hemodynamic instability. This review summarizes the changes in SNS in heart failure and examines how modulation of SNS activity may affect morbidity and mortality from this syndrome.

The burden of chronic obstructive pulmonary disease in patients hospitalized with heart failure

OBJECTIVES

Like chronic heart failure, chronic obstructive pulmonary disease (COPD) is an enormous public health problem in industrialized countries. Our aim was to determine the prevalence and clinical impact of COPD among patients hospitalized for heart failure in a community hospital serving a population of 125,000 people.

METHODS

Between 2001 and 2003 a total of 638 patients (73 +/- 10 years, 48% men, 74% NYHA class III) were identified with a discharge diagnosis of heart failure. Medical charts were reviewed and vital status was obtained from a Central Population Registry.

RESULTS

COPD was diagnosed in 106 (17%) patients whose age was similar to those without COPD (73 +/- 9 vs. 73 +/- 11 years, P = 0.35). Patients with COPD were more often males (65% vs. 45%, P < 0.001). There were no differences in arterial hypertension, atrial fibrillation, diabetes mellitus and most laboratory markers except hemoglobin (141 +/- 20 vs. 132 +/- 20 g/l, P < 0.001) and uric acid (453 +/- 136 vs. 414 +/- 139 mmol/l, P = 0.013). At discharge, patients with COPD were less likely to receive beta-blockers (12% vs. 28%, odds ratio 0.35, 95% CI0.19-0.64). During follow-up, patients with COPD had higher mortality (73% vs. 60%, P = 0.016, hazard ratio 1.48, 95% CI 1.15-1.90). Kaplan-Meier (log-rank test, P = 0.002) and Cox proportional hazard analysis, adjusted for age, sex, hemoglobin, uric acid, and treatment with beta-blockers and furosemide (hazard ratio 1.38, 95% CI1.04-1.83, P = 0.024) demonstrated the prognostic importance of COPD.

CONCLUSIONS

COPD is frequent among hospitalized patients with heart failure. Beta-blockers are largely underused, which is probably a major reason for the higher mortality observed in patients with concomitant chronic heart failure and COPD.

The potential beneficial effects of beta adrenergic blockade in the treatment of ventricular fibrillation

Cardiac arrest remains a major medical emergency in Western societies, with ventricular fibrillation being the initial rhythm in a significant proportion of cases. Adrenaline is generally accepted to improve the resuscitation outcome, since it improves coronary and cerebral blood flow during cardiopulmonary resuscitation, but several detrimental effects have been associated with its use, most of which are thought to be mediated by its beta adrenergic properties. Several animal studies suggest that beta adrenergic blockade during resuscitation, is associated with increased rates of resuscitation and improved post-resuscitation myocardial function. This article reviews the presence and function of beta-adrenoceptor subtypes in the intact and diseased human myocardium, as well as the differences observed in beta(1)- and beta(2) adrenoceptor subtypes in different species.

Reducing events in patients with chronic heart failure (REDUCEhf ) study design: continuous hemodynamic monitoring with an implantable defibrillator

BACKGROUND

The use of implantable cardioverter defibrillators (ICDs) has been proven effective in the prevention of sudden cardiac death (SCD) and constitutes standard of care in appropriate populations. Combining a pressure sensing system with ICD therapy represents the first attempt to provide continuous hemodynamic monitoring using a device previously designed exclusively for SCD protection.

METHODS

REDUCE is a prospective, multicenter, randomized, single-blind, parallel-controlled trial designed to assess the safety of the Chronicle ICD system (single chamber ICD with a hemodynamic monitoring system) and the effectiveness of a management strategy guided by intracardiac pressure information among ICD-indicated New York Heart Association (NYHA) Class II or III heart failure (HF) patients. Those successfully implanted with a Chronicle ICD will be randomized to the Chronicle group or Control group. All patients will receive optimal medical therapy, but the hemodynamic information from the device will be used to guide patient management only in the Chronicle group. Primary endpoints include freedom from system-related complications and relative risk reduction of one or more HF-related events (hospitalizations, and emergency department and urgent care visits requiring intravenous therapy for HF). Approximately 850 patients will be enrolled in at least 75 centers in the United States to accrue the 419 events needed to test the primary effectiveness endpoint. Enrollment began in April 2006, and is expected to end during 2009.

CONCLUSION

REDUCE will assess the safety of the Chronicle ICD system and the effectiveness of a patient management strategy based on remote access to continuous intracardiac pressures in reducing HF-related events.

A-kinase anchoring proteins as the basis for cAMP signaling

Common challenges to any cell are the processing of the extracellular stimuli it receives into intracellular signaling cascades that initiate a multitude of diverse biological functions. However, many of these stimuli act via a common signaling pathway, suggesting the cell must somehow discriminate between different stimuli and respond accordingly. Subcellular targeting through the association with adaptor and scaffolding proteins has emerged as a key mechanism by which cells maintain signaling specificity. Compartmentation of cAMP signaling is maintained by the clustering of cAMP signaling enzymes in discrete units by the scaffolding protein A-kinase anchoring proteins (AKAP). In doing so, AKAPs provide the molecular architecture for the cAMP micordomains that underlie the spacial-temporal control of cAMP signaling.

Researching a good death

Raises difficult issues, but many patients are keen to participate