Hyponatremia Associated with Increased Long-term Mortality for Heart Failure Patients

Hyponatremia is independently associated with a long-term increase in mortality and rehospitalization for chronic heart failure (HF) patients, researchers at the Duke Clinical Research Institute have found.

The researchers studied 1,045 patients from the Duke Databank for Cardiovascular Diseases with chronic HF due to left ventricle systolic dysfunction who underwent cardiac catheterization between 2000 and 2008. Of these subjects, 107 (10.2%) had hyponatremia, defined as serum sodium plasma levels under 135 mmol/L. The patients were followed for an average of 4.5 years, their baseline median age was 62, and males made up 67% of participants.

At eight years, 397 of the participants had died and 675 had experienced cardiovascular death or rehospitalization. Based on an unadjusted analysis, hyponatremia was associated with an 89% increase in risk of death from any cause and a 40% increase in risk of cardiovascular death or rehospitalization. Based on multivariable analysis, it was associated with a 42% increase in risk of death from any cause and a 45% increase in risk of cardiovascular death or rehospitalization.

“Kaplan-Meier curves show that the increased risk associated with hyponatremia persists for at least 2—3 years with the survival curves of hyponatremic and nonhyponatremic patients, which continue to diverge for the first years and then run parallel,” the researchers write.

The researchers note that there is a strong association between HF and hyponatremia and, though there is no definite proof, hyponatremia may play a role in causing HF. “There are several possibilities through which hyponatremia might be associated with HF,” they write, “including myocardial remodeling in response to excessive water reabsorption expanding ventricular preload and alterations in gap junction function owing to lower osmolality, or, possibly, hyponatremia might simply be a marker for high vasopressin levels, which, through the stimulation of V1a receptors, could alter outcomes in chronic HF.”

The researchers note that the study’s limitations include the fact that it was conducted retrospectively, based on patients from a single center, and, as it included patients undergoing cardiac catheterization, may not represent all HF patients. They recommend that further studies be undertaken to determine how prompt correction of hyponatremia would affect outcomes for HF patients.

The study appears in the January edition of the Journal of Cardiac Failure.