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Cardiac afferents and neurohormonal activation in congestive heart failure
D F Davila1, J H Donis, G Bellabarba
1Centro de Investigaciones Cardiovasculares, Departamento de Pediatria, Universidad de Los Andes, Merida, Venezuela. diegod@ing.ula.ve
Insights
Cardiac afferents play a key role in heart failure. Understanding their interaction with the nervous system and neurohormonal systems is crucial for developing effective treatments for congestive heart failure.
Area of Science:
- Cardiovascular Physiology
- Neurocardiology
- Heart Failure Pathophysiology
Background:
- Cardiac chambers possess afferent nerve connections to the brainstem and spinal cord.
- Vagal and sympathetic afferents exhibit distinct activation patterns in response to physiological and pathological stimuli.
- Dysregulation of these afferent pathways contributes to the neurohormonal imbalances seen in heart disease.
Purpose of the Study:
- To elucidate the distinct roles of vagal and sympathetic cardiac afferents in heart failure.
- To explain the dissociation of neurohormonal profiles in progressive cardiac disease.
- To identify potential therapeutic targets for congestive heart failure.
Main Methods:
- Review of existing literature on cardiac afferent function.
- Analysis of neurohormonal responses in cardiac disease progression.
- Examination of drug mechanisms affecting cardiac adrenergic drive.
Main Results:
- Vagal afferents are activated by volume expansion and atrial natriuretic factor, mediating depressor responses.
- Sympathetic afferents are activated by ischemia and cardiac enlargement.
- Progressive heart failure involves a complex interplay of afferent activation, leading to neurohormonal dysregulation and fluid retention.
Conclusions:
- Cardiac afferent activity is central to the pathophysiology of congestive heart failure.
- Heart size and afferent nerve function are critical factors for understanding and treating heart failure.
- Targeting cardiac afferents may offer a common mechanism for drugs like digitalis, ACE inhibitors, and beta-blockers.
Abstract:
Cardiac chambers have afferent connections to the brainstem and to the spinal cord. Vagal afferents mediate depressor responses and become activated by volume expansion, increased myocardial contractility and atrial natriuretic factor. Sympathetic afferents, on the contrary, are activated by metabolic mediators, myocardial ischemia and cardiac enlargement. These opposite behaviors may lead to activation or suppression of the sympathetic nervous system and of the renin-angiotensin-aldosterone system. As cardiac diseases progress, the heart dilates, plasma norepinephrine increases, atrial natriuretic factor is released and the renin-angiotensin-aldosterone system is suppressed to maintain water and sodium excretion. This dissociation of the neurohormonal profile of cardiac patients, may be explained by coactivation of sympathetic afferents, by cardiac dilatation, and of vagal afferents by atrial natriuretic factor. In more advanced stages, atrial natriuretic factor suppression of the renin-angiotensin-aldosterone system is overridden by overt sympathetic activation and sodium and water retention ensues. Digitalis, angiotensin-converting enzyme inhibitors and beta-blockers selectively decrease cardiac adrenergic drive. A common mechanism of action, to all three groups of drugs, would be attenuation of sympathetic afferents and partial normalization of vagal afferents. Consequently, heart size and cardiac afferents emerge as the key factors to understand the pathophysiology and treatment of the syndrome of congestive heart failure.