Hyponatremia Associated with Congestive Heart Failure: Involvement of Vasopressin and Efficacy of Vasopressin Receptor Antagonists

Hyponatremia is frequently found in patients with congestive heart failure. A reduction in effective circulatory blood volume in a volume-expanded patient with decreased cardiac output is linked to a baroreceptor-mediated non-osmotic release of arginine vasopressin (AVP). The increased production of AVP and salt and water retention in the proximal and distal tubules of the kidney by humoral, hemodynamic, and neural mechanisms increase circulatory blood volume and contribute to hyponatremia. Recent studies have indicated that hyponatremia predicts the short-term and long-term prognosis of heart failure by increasing cardiac death and rehospitalization. In addition, the early development of hyponatremia in acute myocardial infarction also predicts the long-term prognosis of worsening heart failure. AVP V2 receptor antagonism may relieve water retention, but it is unknown whether the V2 receptor inhibitor, tolvaptan, improves the long-term prognosis of congestive heart failure. The newly identified natriuretic factor in renal salt wasting has the potential of improving clinical outcomes when combined with a distal diuretic.