Hyponatremic hypervolemia in heart failure--the hot spot for vasopressin receptor antagonists?

Dilutional hyponatremia is the most common electrolyte disorder occurring in heart failure (HF). The relation between hyponatremia and increased morbidity and mortality is widely evidenced. Treatment of this condition is circumscribed by strict correlation of electrolyte and water balance, though. Neurohormonal activation in HF is the effect of compensatory mechanisms due to insufficient effective blood volume. One of the factors is increased serum argininovasopressin (AVP) concentration. The principal effects of this action are free water retention via V2 receptor and vasoconstriction by V(1A) receptor. Stimulation of V(1A) receptor also contributes to heart muscle remodeling. Diuretics are still the basic treatment of hypervolemia. At the same time they have a very unfavorable side effect in the form of exacerbating hyponatremia. The new direction of investigations occurred after noticing the spectacular aquaretic effect of antagonizing AVP receptors. The effect is new group of drugs--vasopressin receptor antagonists called the vaptans. Unlike the diuretics, they cause free water excretion without electrolyte loss. The registration includes in-hospital treatment of states of hyponatremia (conivaptan, tolvaptan, mozavaptan), the two other (lixivaptan, satavaptan) are undergoing research. Apart from improving clinical status, there is still no evidence of improving the patients' survival. Further research in this field is necessary to demonstrate whether there is prognosis amelioration in short-term and long-term patients' observation.