Outcome Differences in Community- Versus Hospital-Acquired Hyponatremia in Patients With a Diagnosis of Heart Failure

Abstract

Background— Hyponatremia at hospital admission is a well-known risk factor of morbidity and mortality in patients with heart failure (HF). However, there are few data about hyponatremia developing during hospitalization in patients with HF. The present study compares hospital-acquired hyponatremia (HAH) with community-acquired hyponatremia (CAH) in HF patients with respect to outcome. Methods and Results— A total of 5347 consecutive hospitalized patients with a diagnosis of HF were analyzed. CAH was defined as a serum sodium value of ≤135 mEq/L at the time of hospital admission. HAH was defined as development of a serum sodium level of ≤135 mEq/L during hospitalization in the setting of a serum sodium value >135 mEq/L on admission. In-hospital mortality, length of stay, worsening kidney function, and discharge to short-/long-term care facilities were analyzed. CAH and HAH were identified in 1039 patients (19.4%) and in 1302 patients (24.4%) of the 5347 patients admitted, respectively. Both types of hyponatremia were associated with increased mortality, length of stay, rate of discharge to short-/long-term care facilities, and worsening kidney function. In-hospital mortality did not differ between CAH and HAH, but differences in demographics and comorbidities were present. Conclusions— The present results identified HAH as a risk factor for increased mortality in HF as has been previously described for CAH. HAH was associated with increased length of stay, discharge to short-/long-term care facilities, and development of cardio-renal failure. Thus, hyponatremia in hospitalized patients with a diagnosis of HF, either on admission or during hospitalization, is a prognostic marker for poor outcomes.