Significance of Hyponatremia in Heart Failure

Hyponatremia is a common clinical condition among hospitalized heart failure patients, associated with increased morbidity and mortality. The pathophysiological mechanisms that relate heart failure with hyponatremia are complex, involving beyond renal dysfunction, neurohormonal activation and diuretic treatment. The pituitary hormone vasopressin seems to play a central role leading to renal water retention and hyponatremia. Although therapeutic strategies (water restriction, hormone inhibition) have been shown to increase serum sodium concentration and improve symptoms, no beneficial effect has been detected on clinical outcome. This fact urges the need for the conduction of further clinical trials, in order to determine the causality between shortand long-term outcome and serum sodium concentration in heart failure patients. I N T R O D U C T I O N Hyponatremia represents one of the most common clinical metabolic disorders in patients with chronic heart failure. Hyponatremia, which is generally defined as Na concentrations below 135 meq/l, occurs in 10-20% of heart failure (HF) patients. Several studies have revealed the prognostic role of serum Na concentrations on the clinical course of HF. The Acute Decompensated Heart Failure registry (ADHERE), which included 158,168 HF patients, showed a prevalence of 5% among patients on admission with serum sodium levels <130 meq/L. Those low Na concentrations were associated with increased mortality and morbidity. In the Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure (OPTIMIZE-HF) registry, including 48,162 HF patients, 19.7% of the patients had hyponatremia on admission, which was also associated with prolonged hospitalization and higher inhospital mortality. Recently, from the Duke Databank for Cardiovascular Diseases, 10% of the 1,045 patients, who were indentified with HF and systolic dysfunction, had hyponatremia. Those hyponatremic patients were older, more likely to have anemia, higher heart rate and levels of blood urea nitrogen, lower blood pressure, and more severe HF; while the multiadjusted analysis revealed that low serum Na was associated with poor cardiovascular outcome. Although the incidence of hyponatremia in hospitalized patients is well described, in stable outpatients the available data are limited. In REVIEW First Cardiology Department, School of Medicine, University of Athens, Athens, Greece HOSPITAL CHRONICLES 2012, 7(2): 91–95 Corresponding author Christina Chrysohoou, MD, PhD 46 Paleon Polemiston St., 166 74, Attica, Greece Tel. +30-210-9603116, Fax. +30-210-9600719 E-mail: [email protected] Manuscript received February 5, 2012; revised manuscript received February 29, 2012; re-revised manuscript received March 13, 2012; accepted March 16, 2012