U-Shaped Relationship of Sodium-to-chloride Ratio on admission and Mortality in Elderly Patients with Heart Failure: A Retrospective Cohort Study

Serum sodium and chloride have clinical significance in the prognosis of heart failure. Little is known regarding the prognostic value of sodium-to-chloride (Na/Cl) ratio in patients with heart failure. This study sought to investigate the association between Na/Cl ratio on admission and mortality risk of elderly patients with acute heart failure in a retrospective cohort. We included 1819 patients (aged over 60) from the Zigong Heart Failure Study. Patients were grouped according to Na/Cl ratio and followed up for all-cause mortality at 3 months. Restricted cubic spline, cox proportional hazard regression and Kaplan-Meier curve were used to examine the correlation between serum Na/Cl ratio on admission and mortality risk. Restricted cubic spline analysis suggested a U-shaped association between Na/Cl ratio on admission and 3 months mortality risk (P nonlinearity <0.001), with the nadir of risk at 1.34. After adjustment for multivariate, patients with Na/Cl ratio <1.3 or ≥ 1.4 had hazard ratios for mortality of 3.58 (95% CI, 1.63-7.84) and 2.66 (95% CI, 1.23-5.72) compared with those with Na/Cl ratio of 1.3-1.4. The cumulative hazard of mortality estimates significantly differed across Na/Cl ratio groups (log-rank P<0.001). Subgroup analysis showed there were no interactions with absent or present of hyponatremia and hypochloremia (P for interaction all >0.05). Both low and high Na/Cl ratios were associated with an increased mortality risk in elderly patients with acute heart failure. Further studies need to verify these 2 biochemical phenotypes and develop corresponding treatment strategies.