In Patients Hospitalized for Heart Failure, Hyponatremia Predicts Complications, But Not Mortality

In a real-world sample of patients hospitalized for heart failure (HF), hyponatremia predicted clinical complications during admission, but it was not linked to short-term mortality or readmission, according to a recent study published in the Cardiology Journal.

Using the National Registry of Heart Failure (RICA) cohort, Jose Carlos Arévalo Lorido, MD, and a team of internists throughout Spain recruited 973 acute decompensated HF patients, 15% of whom had hyponatremia defined as a serum sodium level <135 mmol/L.

With an aim to determine the association between hyponatremia and health outcomes in HF patients, the researchers used all-cause readmission or death as the primary endpoint, while the secondary endpoints focused on the presence of complications, including “worsening of renal function, hyperpotasemia, acute confusional syndrome, urinary tract infections (UTIs), pneumonia, and a need for blood transfusion, hemofiltration, or inotropic or hypotensive drugs.”

After comparing comorbidities and complications between the HF patients with hyponatremia and those with sodium levels ≥135 mmol/L, the authors found “clinical complications and pleural effusion during admission were higher in the patients with hyponatremia (35.41%, P< 0.001).” The hyponatremia group also experienced “more worsening of basal renal function, more hyperpotasemia, more need for vasoactive and hypotensive drugs, more need for hemofiltration, more frequency of acute confusional status, and more frequency of UTIs” than the group with normal serum sodium levels.

Although death and hospital readmission occurred more frequently among the hyponatremia patients in the 90-day period following discharge, the investigators found low serum sodium was not associated with short-term mortality or readmission when they adjusted the primary endpoint through a multivariate Cox regression analysis that assessed comorbidity. As a result, the authors noted “comorbidity could play an important role in the presence or absence of hyponatremia and could even influence the 90-day mortality or readmission attributed to lower serum sodium.”

“Hyponatremia has (been) shown to be a prognostic indicator of increased mortality in a determined group of patients with HF, as (previous) clinical trials (have focused) on a relatively small segment of the HF population. However, in wider population like ours with older people who have more comorbidity … this question remains to be investigated,” the researchers concluded. “Future trials with hyponatremic patients and HF should include data of comorbidity to validate the results that we have obtained in this study.”