Small Animal Rotating Intern University of Florida College of Veterinary Medicine Gainesville, FL, United States
Background: Hypochloremia is the most common electrolyte abnormality in cats with acute congestive heart failure (CHF). Although associated with poor outcomes in people, its impact on survival in cats with CHF is unclear. Hypothesis/Objectives: We hypothesized that hypochloremia, but not medication use, would be associated with outcomes in cats with stable CHF. Animals: 86 client-owned cats. Methods: Retrospective study. Records of 178 cats (2014–2024) were reviewed. Cats with stable CHF (>1-week post-hospitalization) and chemistry panels including serum chloride concentrations (s[Cl⁻]) from the UF Laboratory were included; those with significant gastrointestinal disease were excluded. Data included clinical, echocardiographic, medication, and outcome variables. Cats were categorized as normochloremic (≥112 mEq/L) or hypochloremic (<112 mEq/L). Group comparisons were made using Mann-Whitney U or Fisher’s exact tests. Correlation between loop diuretic dosage and s[Cl⁻] was assessed with Spearman’s test. Survival was analyzed using Kaplan-Meier and Cox regression. Pimobendan survival effects were also evaluated, and % CHF time on pimobendan was calculated to assess potential confounding. Results: Median s[Cl⁻] was 115.3 mEq/L (range 100.0–121.6). Hypochloremia was associated with increased risk of death (HR 4.584; CI 1.327–14.94) and shorter survival (159 vs. 416 days, P < 0.0001). Pimobendan was also associated with higher risk of death (HR 2.227; CI 1.220–4.112) and shorter survival (210 vs. 559 days, P = 0.014), even when excluding cats with LVOTO (P = 0.004). Conclusions and Clinical Importance: Hypochloremia and pimobendan use are risk factors for death in CHF cats. Strategies to normalize s[Cl⁻] may improve outcomes.
