Moderate to severe hypochloremia is associated with shortened survival in dogs with stable congestive heart failure

To retrospectively evaluate hypochloremia as a predictor of poor outcomes for dogs with congestive heart failure (CHF).

A single-institution retrospective study including dogs diagnosed with CHF between 2014 and 2024. Biochemical variables, medications, and outcome data were extracted from medical records at the first recheck after the initial CHF episode. Exclusion criteria were active CHF, absence of serum chloride concentration (s[Cl]) on bloodwork, reliance on point-of-care bloodwork alone, major interventional procedures (eg, mitral valve repair), and clinically important vomiting or diarrhea. Dogs were grouped by s[Cl] < 100 or ≥ 100 mEq/L. Associations between s[Cl] < 100 mEq/L, biochemical variables, medications, and risk of death were evaluated with a Cox proportional hazards model. Survival was assessed with a Kaplan-Meier analysis and compared with a log-rank test.

A total of 292 stable CHF dogs were included (229 degenerative valve disease, 31 dilated cardiomyopathy, 21 congenital heart disease, 6 pulmonary hypertension, and 5 arrhythmogenic cardiomyopathy). Median s[Cl] was 106.5 mEq/L (range, 85.0 to 119.0 mEq/L). Dogs with s[Cl] < 100 mEq/L had a significantly increased risk of death (HR, 2.649; 95% CI, 1.265 to 5.311) and shortened survival (median survival, 115 days) compared to dogs with s[Cl] ≥ 100 mEq/L (median survival, 196 days). No other biochemical variables or medications were significantly associated with survival.

Moderate to severe hypochloremia (s[Cl] < 100 mEq/L) in dogs with stable CHF is associated with worse survival compared to dogs with s[Cl] ≥ 100 mEq/L.

These findings support clinical efforts to correct and maintain serum chloride concentrations above 100 mEq/L in dogs with CHF.