Prognostic Role of Hyponatremia in Heart Failure Patients Depending on Renal Disease: Clinical Evidence

Aim: Hyponatremia is very often associated with renal disease in patients with heart failure (HF) and, when present, determines a poor outcome. We investigated the role of hyponatremia in HF patients in whom the presence or absence renal insufficiency was accurately predefined. Methods: This was a cohort study based on the Spanish National Registry on Heart Failure (RICA), a multicenter, prospective registry that enrolls patients admitted for decompensated HF who were subsequently followed up for 1 year. We classified patients into 4 groups according to the presence or absence of renal disease defined by the hematocrit, urea, and gender formula (HUGE) and then according to the presence of hyponatremia (Na ≤135 mEq/L). Results: A total of 3,478 patients were included. Hyponatremia was more prevalent in the group with renal disease (22.1%) than without (18.4%). During admission, both groups with hyponatremia had more complications than those with normal serum sodium. During the 1-year follow-up, patients with hyponatremia and renal disease had a significantly worse outcome (HF mortality and readmission), HR 1.87, 95% CI 1.54–2.29, p < 0.001, compared to those with hyponatremia without renal disease, HR 1.01, 95% CI 0.79–1.3, p = 0.94. Conclusions: Hyponatremia is more prevalent in patients with renal insufficiency, and outcome is poorest when both renal disease and hyponatremia coexist. Patients with hyponatremia without renal disease show no differences in outcome compared to those without hyponatremia.