Related Experiment Videos
[Metabolic changes in cardiac failure]
1Service de Cardiologie, Hôpital Pasteur, Nice.
Insights
The body activates compensatory mechanisms, including neurohumoral systems, to manage left ventricular dysfunction. While initially adaptive, persistent activation in chronic cardiac failure (CCF) becomes detrimental, increasing myocardial workload and worsening cardiovascular function.
Area of Science:
- Cardiology
- Neuroendocrinology
- Physiology
Context:
- Early left ventricular dysfunction triggers compensatory mechanisms.
- Neurohumoral systems, particularly the sympathetic nervous system, are central to these responses.
- Chronic cardiac failure (CCF) involves persistent, often detrimental, neurohormonal activation.
Purpose:
- To elucidate the role of neurohumoral systems in the progression of left ventricular dysfunction.
- To describe the hyperactivity of the noradrenergic sympathetic nervous system in CCF.
- To explain the impact of catecholamine changes and the Renin Angiotensin System (RAS) in CCF.
Summary:
- Hyperactivity of the noradrenergic sympathetic nervous system is observed in CCF, with elevated catecholamine levels.
- Arterial baroreceptors modulate noradrenaline release, affecting blood pressure and myocardial function.
- Downregulation of myocardial beta-receptors and activation of the Renin Angiotensin System (RAS) contribute to CCF pathophysiology.
Impact:
- Understanding these mechanisms is crucial for managing CCF.
- Identifies key pathways involved in cardiovascular adaptation and maladaptation.
- Highlights the dual role of neurohumoral responses in cardiac dysfunction.
Abstract:
As soon as there is evidence of left ventricular dysfunction, even before clinical signs of chronic cardiac failure (CCF) have developed, intrinsic and extrinsic compensatory mechanisms are brought into play by the body. The majority of these mechanisms are under the influence of neurohumoral systems. When neurohormonal responses persist, as in CCF, they take on a beneficial nature since they participate in adaptation of the cardiovascular system as a whole, but they are also harmful since they worsen the working conditions of the myocardium by their cardiac and peripheral effects. Hyperactivity of the noradrenergic sympathetic nervous system is seen in CCF with levels 2 to 3 times higher as compared with subjects with normal left ventricular function. The circadian rhythm of catecholamines is modified. The increase in circulatory catecholamines is all the greater when cardiac failure is advanced. This release of noradrenaline (NA) is under the control of arterial baroreceptors which normally send to the central nervous system inhibitory inflow from the sympathetic nervous system. Inhibitory tone is released in case of a fall in blood pressure. Noradrenaline acts on beta-predominant myocardial receptors (inotropic and tachycardic) and alpha-predominant vascular receptors, resulting in arteriolar vasoconstriction. There is rapid onset of down regulation of myocardial beta-receptors. This fall essentially concerns beta 1, but beta 2 also, since they may be affected according to the etiology of CCF (ischemia). The Renin Angiotensin System (RAS) is also activated by the fall in systemic blood pressure. This consists of a cascade of reactions leading to the synthesis of angiotensin II responsible for powerful vasoconstriction of all arterial areas, including the coronary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)