AVP and congestive heart failure: The increase in total body sodium (Na) and water volume in CHF is due to a combination of a baroreceptor-mediated non-osmolar increase in arginine vasopressin (AVP) release and impaired renal sodium (Na) and water excretion via the activation of the sympathetic nervous system, increased renin, angiotensin and aldosterone production, and hemodynamic alterations.