Activity with ambulation attenuates diuretic responsiveness in chronic heart failure

Renal, Cardiac, and Autonomic Effects of Catheter-Based Renal Denervation in Ovine Heart Failure

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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.

Baroreflex activation therapy: a new approach to the management of advanced heart failure with reduced ejection fraction

Chronic heart failure is a common clinical condition characterized by persistent excessive sympathetic nervous system activation. The derangement of the sympathetic activity has relevant implications for disease progression and patient survival. Aiming to positively impact patient outcome, autonomic nervous system modulatory therapies have been developed and tested in animal and clinical studies. As a general gross assumption, direct vagal stimulation and baroreflex activation are considered equivalent. This assumption does not take into account the fact that direct cervical vagal nerve stimulation involves activation of both afferent and efferent fibers innervating not only the heart, but the entire visceral system, leading to undesired responses to and from this compartment. The different action of baroreflex activation is based on generating a centrally mediated reduction of sympathetic outflow and increasing parasympathetic activity to the heart via a physiological reflex pathway. Thus, baroreflex activation rebalances the unbalanced autonomic nervous system via a specific path. Independent and complementary investigations have shown that sympathetic nerve activity can be rebalanced via control of the arterial baroreflex in heart failure patients.

Results from recent pioneering research studies support the hypothesis that baroreflex activation can add significant therapeutic benefit on top of guideline-directed medical therapy in patients with advanced heart failure. In the present review, baroreflex activation therapy results are discussed, focusing on critical aspects like patient selection rationale to support clinician orientation in opting for baroreflex activation therapy when, on top of current guideline-directed medical treatment, other therapies are to be considered.

Renal Denervation to Modify Hypertension and the Heart Failure State

Sympathetic overactivation of renal afferent and efferent nerves have been implicated in the development and maintenance of several cardiovascular disease states, including resistant hypertension and heart failure with both reduced and preserved systolic function. With the development of minimally invasive catheter-based techniques, percutaneous renal denervation has become a safe and effective method of attenuating sympathetic overactivation. Percutaneous renal denervation, therefore, has the potential to modify and treat hypertension and congestive heart failure. Although future randomized controlled studies are needed to definitively prove its efficacy, renal denervation has the potential to change the way we view and treat cardiovascular disease.

Statins and the autonomic nervous system

Statins (3-hydroxy-3-methylglutaryl-CoA reductase inhibitors) reduce plasma cholesterol and improve endothelium-dependent vasodilation, inflammation and oxidative stress. A ‘pleiotropic’ property of statins receiving less attention is their effect on the autonomic nervous system. Increased central sympathetic outflow and diminished cardiac vagal tone are disturbances characteristic of a range of cardiovascular conditions for which statins are now prescribed routinely to reduce cardiovascular events: following myocardial infarction, and in hypertension, chronic kidney disease, heart failure and diabetes. The purpose of the present review is to synthesize contemporary evidence that statins can improve autonomic circulatory regulation. In experimental preparations, high-dose lipophilic statins have been shown to reduce adrenergic outflow by attenuating oxidative stress in central brain regions involved in sympathetic and parasympathetic discharge induction and modulation. In patients with hypertension, chronic kidney disease and heart failure, lipophilic statins, such as simvastatin or atorvastatin, have been shown to reduce MNSA (muscle sympathetic nerve activity) by 12–30%. Reports concerning the effect of statin therapy on HRV (heart rate variability) are less consistent. Because of their implications for BP (blood pressure) control, insulin sensitivity, arrhythmogenesis and sudden cardiac death, these autonomic nervous system actions should be considered additional mechanisms by which statins lower cardiovascular risk.

The role of renal denervation in the treatment of heart failure

The heart and kidney interact in terms of hemodynamics and neurohumoral regulatory mechanisms, and this helps to maintain circulatory homeostasis under normal conditions. However, the normal regulatory mechanisms become inappropriate in the setting of congestive heart failure (CHF), and significant renal dysfunction often develops in CHF patients. Activation of renal sympathetic efferent nerves causes renin release, sodium and water retention, and reduced renal blood flow, all hallmarks of the renal manifestations of CHF. An increase in plasma levels of angiotensin II that is mediated in part by renal sympathetic activation has an effect on the central nervous system to further increase global sympathetic tone. Renal sympathetic activity can be assessed clinically by renal norepinephrine spillover, and an increase in renal norepinephrine spillover in CHF predicts reduced survival. In addition to efferent sympathetic activation, activation of renal sensory nerves in CHF may cause a reflex increase in sympathetic tone that contributes to elevated peripheral vascular resistance and vascular remodeling as well as left ventricular remodeling and dysfunction. In animal models of heart failure, surgical renal denervation has been shown to improve both renal and ventricular function. Although surgical renal denervation has long been known to lower blood pressure and improve survival in patients with hypertension, the invasive nature of this approach and its associated complications has limited its appeal. However, a novel catheter-based device has recently been introduced that specifically interrupts both efferent and afferent renal nerves, and there is significant interest in the use of this device to treat both hypertension and CHF. Several ongoing clinical trials are investigating the safety and efficacy of renal denervation in patients with CHF.