Neuroendocrine System

Activation of the sympathetic nervous system (SNS) is often one of the first responses to a failing left ventricle.  As the pumping action of the left ventricle decreases, cardiac output and blood pressure decrease.  These actions activate the baroreceptors and vasomotor regulatory centers in the medulla.  This increases the level of catecholamines, which in turn stimulate alpha- and beta-adrenergic receptors.  This action increases the heart rate, increases peripheral vasoconstriction, thus increasing afterload (SVR), and an increase in contractility.  A person with chronic heart failure is unable to respond to the circulating catecholamines.  The heart does this in an attempt to protect the heart.  This inability to respond to circulating catecholamines leads to the exercise intolerance that heart failure patient’s experience.

ACE Inhibitors are an important part of the treatment of heart failure.  ACE Inhibitors are angiotensin converting enzymes.  Please see the page concerning ACE Inhibitors.  Patients that are unable to take ACE Inhibitors due to side effects or decreased renal function may be placed on ARB’s instead.