Cardiorenal Syndrome: Role of Arginine Vasopressin and Vaptans in Heart Failure.

Heart and kidney failure continued to be of increasing prevalence in today's society, and their comorbidity has synergistic effect on the morbidity and mortality of patients. Cardiorenal syndrome (CRS) is a complex disease with multifactorial pathophysiology. Better understanding of this pathophysiological network is crucial for the successful intervention to prevent advancement of the disease process. One of the major factors in this process is neurohormonal activation, predominantly involving renin-angiotensin-aldosterone system (RAAS) and arginine vasopressin (AVP). Heart failure causes reduced cardiac output/cardiac index (CO/CI) and fall in renal perfusion pressures resulting in activation of baroreceptors and RAAS, respectively. Activated baroreceptors and RAAS stimulate the release of AVP (non-osmotic pathway), which acts on V2 receptors located in the renal collecting ducts, causing fluid retention and deterioration of heart failure. Effective blockade of AVP action on V2 receptors has emerged as a potential treatment option in volume overload conditions especially in the setting of hyponatremia. Vasopressin receptor antagonists (VRAs), such as vaptans, are potent aquaretics causing electrolyte-free water diuresis without significant electrolyte abnormalities. Vaptans are useful in hypervolemic hyponatremic conditions like heart failure and liver cirrhosis, and euvolemic hyponatremic conditions like syndrome of inappropriate anti-diuretic hormone secretion. Tolvaptan and conivaptan are pharmaceutical agents that are available for the treatment of these conditions.