Spot urine sodium in acute heart failure: differences in prognostic value on admission and discharge.

AIMS

Most studies examined spot urine sodium's (sUNa ) prognostic utility during the early phase of acute heart failure (AHF) hospitalization. In AHF, sodium excretion is related to clinical status; therefore, we investigated the differences in the prognostic information of spot UNa throughout the course of hospitalization for AHF (admission vs. discharge).

METHODS AND RESULTS

The study population were AHF patients (n = 172), who survived the index hospitalization. We compared the relationship between early (on admission, at 24 and 48 h) and discharge sUNa measurements with post-discharge study endpoints: composite of 1 year all-cause mortality and AHF rehospitalization (with time to first event analysis) as well as with each event in separation. There were 49 (28.5%) deaths, 40 (23.3%) AHF rehospitalizations, while the composite endpoint occurred in 69 (40.1%) during 1 year follow-up. The sUNa had prognostic significance for the composite endpoint when assessed on admission, at 24 and at 48 h: hazard ratios (HRs) with 95% confidence intervals (CIs) (per 10 mmol/L) were 0.88 (0.82-0.94); 0.87 (0.81-0.91); 0.90 (0.84-0.96), all P < 0.005. In contrast to early, active decongestion phase, discharge sUNa had no prognostic significance HR (95% CI) (per 10 mmol/L): 0.99 (0.93-1.06) P = 0.79 for the composite endpoint, which was independent from the dose of oral furosemide prescribed at that timepoint (average causal mediation effects: -0.38; P = 0.71). Similarly, discharge sUNa was neither associated with 1 year mortality HR (95% CI) (per 10 mmol/L): 0.97 (0.89-1.05) P = 0.48 nor with AHF rehospitalizations HR (95% CI) (per 10 mmol/l): 1.03 (0.94-1.12), P = 0.56. The comparison of longitudinal profiles of sUNa during hospitalization showed significantly higher values within the early, active decongestive phase in those who did not experience composite endpoint when compared with those who did: admission: 94 ± 34 vs. 76 ± 35; Day 1: 85 ± 36 vs. 65 ± 37; Day 2: 84 ± 37 vs. 67 ± 35, all P < 0.005 (mmol/L), respectively. There was no difference between those groups in discharge sUNa : 73 ± 35 vs. 70 ± 35 P = 0.82 (mmol/L).

CONCLUSIONS

Spot UNa assessed at early phase of hospitalization and at discharge have different prognostic significance, which confirms that it should be always interpreted along with clinical context.