Low sodium levels are strongly associated with poor prognosis in acute heart failure (AHF); however, the prognostic impact of the sodium level trajectory overtime has not been determined. A secondary analysis of the AQUAMARINE study in which patients with AHF and renal impairment were randomized to receive either tolvaptan or conventional treatment was performed. Sodium levels were evaluated at the baseline and at 6, 12, 24, and 48 h. We defined 'sodium dipping' as sodium level falling below the baseline level at any time point. The primary endpoint was the combined event of all-cause death and heart failure rehospitalization during follow-up. The analysis included 184 patients with a median follow-up of 21.1 months. Sodium levels more steeply increased during the 48 h in patients without events as compared to sodium levels in patients with events (P = 0.018 in linear-mixed effect model). The sodium dipping group (n = 100; 54.3%) demonstrated significantly less urine output, less body weight reduction, and poorer diuretic response within 48 h compared to the non-dipping group. The sodium dipping group was also significantly associated with a low combined-event-free survival after adjustment for other prognostic factors (HR 1.97; 95% CI 1.06-3.38; P = 0.033). The trajectory of sodium levels during the acute phase is associated with the prognosis of patients with AHF independently of the baseline sodium level.
Keywords: Acute heart failure; Prognosis; Serum sodium.