Additive Effects of β 1 389 Arg/Gly α 2c 322–325 Wt/Del Genotype Combinations on Adjudicated Hospitalizations and Death in the Beta-Blocker Evaluation of Survival Trial (BEST)

The sympathetic nervous system and heart failure

Heart failure (HF) is a syndrome characterized by upregulation of the sympathetic nervous system and abnormal responsiveness of the parasympathetic nervous system. Studies in the 1980s and 1990s demonstrated that inhibition of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors improved symptoms and mortality in HF resulting from systolic dysfunction, thus providing a framework to consider the use of β-blockers for HF therapy, contrary to the prevailing wisdom of the time. Against this backdrop, this article reviews the contemporary understanding of the sympathetic nervous system and the failing heart.

Treatment of chronic heart failure with β-adrenergic receptor antagonists: a convergence of receptor pharmacology and clinical cardiology

Despite the absence of a systematic development plan, β-blockers have reached the top tier of medical therapies for chronic heart failure. The successful outcome was due to the many dedicated investigators who produced, over a 30-year period, increasing evidence that β-blocking agents should or actually did improve the natural history of dilated cardiomyopathies and heart failure. It took 20 years for supportive evidence to become undeniable, at which time in 1993 the formidable drug development resources of large pharmaceutical companies were deployed into Phase 3 trials. Success then came relatively quickly, and within 8 years multiple agents were on the market in the United States and Europe. Importantly, there is ample room to improve antiadrenergic therapy, through novel approaches exploiting the nuances of receptor biology and/or intracellular signaling, as well as through pharmacogenetic targeting.

Influence of global region on outcomes in heart failure β-blocker trials

OBJECTIVES

We sought to describe the United States and the rest of the world (ROW) outcomes from the major β-blocker heart failure (HF) trials.

BACKGROUND

HF trials have demonstrated differences in outcomes by geographic region.

METHODS

Randomized, double-blind, placebo-controlled studies that evaluated β-blockers in HF patients, had a primary endpoint of mortality, and enrolled U.S. patients were included. Relative risk (RR) was calculated for patients enrolled in the United States and ROW. Meta-analysis of the combined mortality rates was performed using the Cochran-Mantel-Haenszel statistic, stratified by study.

RESULTS

A total of 8,988 patients were enrolled in the MERIT-HF (Metoprolol Controlled-Release Randomized Intervention Trial in Heart Failure), COPERNICUS (Carvedilol Prospective Randomized Cumulative Survival trial), and BEST (β-Blocker Evaluation of Survival Trial) combined; 4,198 (46.7%) were from the United States. In the U.S. cohort, the RR reduction for each β-blocker was of smaller magnitude than in the overall cohort and no longer significant, whereas in the ROW subgroup, the mortality benefit for β-blockade persisted. In the pooled analysis (n = 11,635), the RR of death was reduced by 23% (p < 0.001) with β-blockade compared with placebo. In contrast, the mortality reduction associated with β-blockade in the U.S. cohort was small and not statistically significant (RR: 0.92, 95% confidence interval [CI]: 0.82 to 1.02, p = 0.11). The survival benefit persisted in the ROW cohort (RR: 0.64, 95% CI: 0.56 to 0.72, p < 0.001).

CONCLUSIONS

Among patients enrolled in the United States, β-blockade was associated with a lower magnitude of survival benefit, whereas the ROW response was similar to the total study population. This geographic difference in treatment response may be a reflection of population differences, genetics, cultural or social differences in disease management, or low power and statistical chance.

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.

Cardiovascular nursing on human genomics: what do cardiovascular nurses need to know about congestive heart failure?

This paper presents the main causes of heart failure (HF) and an update on the genetics studies on each cause. The review includes a delineation of the etiology and fundamental pathophysiology of HF and provides rational for treatment for the patient and family. Various cardiomyopathies are discussed, including primary cardiomyopathies, mixed cardiomyopathies, cardiomyopathies that involve altered cardiac muscle along with generalized multiorgan disorders, and various cardiovascular conditions, such as coronary artery disease (ischemic cardiomyopathy) and hypertension (hypertensive cardiomyopathy). A brief review of pharmacogenetics and HF is presented. The application of the genetic components of cardiomyopathy and pharmacogenetics is included to enhance cardiovascular nursing care.