Hyponatremia at hospital admission for heart failure independently predicts an increased risk of death in Asian patients, according to a study published in the Korean Journal of Internal Medicine (2015;30:460-470).
Byung-Su Yoo, MD, of Yonsei University Wonju College of Medicine in Wonju, Korea and colleagues studied 1,470 hospitalized HF patients from 9 centers in 3 countries. Patients had a mean sodium level of 138 mmol/L at admission. Of the 1,470 patients, 247 (16.8%) had hyponatremia, defined as a sodium level below 135 mmol/L.
The 12-month mortality rate was significantly higher in the patients with than without hyponatremia (27.9% vs. 14.6%). Hyponatremia was independently associated with a 72% increased risk of 12-month mortality.
Hyponatremia improved in 57% of the patients with the condition during their hospital stay, but this was not associated with improved outcomes. Adherence to optimal medical therapy (OMT) was lower in hyponatremic patients than the normonatremia group. The proportion of patients with OMT was only 25.5% at admission and 44.2% at discharge.
The researchers defined as OMT as the combined use of ACE inhibitor/angiotensin receptor blocker and beta-blocker.
The investigators noted that their study was limited by the fact that it was not a prospective, randomized trial. “Although we tried to adjust for significant clinical variables and performed propensity score matching for the analysis,” they wrote, “unmeasured confounding factors may have biased the study result.”
In the first 12 months, 247 patients died. These patients were significantly older (mean 71.9 vs. 65.2 years) and had significantly lower mean body mass index (22.2 vs. 24.2 kg/m2 ) than those who did not die. Significantly higher proportions of deceased patients had diabetes, hypertension, coronary artery disease, and chronic kidney disease.