Abstract Background/Introduction Episodes of acute heart failure (AHF) unfavorably affect extra-cardiac organs such as the liver due to altered hemodynamics and neurohormonal activation. In AHF, elevated levels of levels of alanine aminotransferase (ALT) and total bilirubin (tBil) may reflect congestion and impaired liver function, while lower levels of ALT (which is also produced in muscle cells) correlate with malnutrition and sarcopenia. Thus, the clinical importance of these markers in AHF and the post-discharge period is unclear. Purpose To assess circulating concentrations of ALT and tBil in patients with AHF before discharge and during high-intensity care (HIC) vs usual care follow-up in association with clinical outcomes. Methods ALT and tBil concentrations were measured 1-2 days before discharge in patients hospitalized for AHF (baseline), and again after 90 days of either HIC or usual care according to the STRONG-HF protocol. Baseline values and changes in ALT and tBil were analyzed in association with the primary outcome of all-cause death or HF readmission by day 180. Results At baseline, the median (Q1-Q3) concentrations of ALT and tBil were 21 (15-32) U/L and 14 (10-21) umol/L, respectively. Lower levels of both ALT and tBil were associated with female sex, Black race, lower BMI, higher LVEF, lower hemoglobin, lower creatinine and less frequent atrial fibrillation/flutter, while there were no significant associations with age. Patients with lower ALT, but not tBil, were more likely to have edema, elevated JVP and orthopnea, and used higher loop diuretic doses and less beta-blockers, pre-randomization (Figure, panel A). ALT was inversely associated with risk for the primary outcome (HR 0.81 [95%CI 0.65,1.00) per log increment, p=0.05), while there was no association with risk for tBil (HR 1.04 [95%Ci 0.84-1.28], p=0.73) (Figure, panel B). After 90 days, ALT and tBil concentrations were lower than at baseline, with a greater reduction in tBil in the HIC group vs usual care group (mean -1.7 [95%CI -3.0,-0.4] umol/L, p=0.01), while there was no significant between-group differences in ALT changes (mean -0.6 [95%CI -4.7,3.4] U/L, p=0.75) (Figure, panel C). The treatment effect of HIC over usual care on the primary outcome was consistent across the range of baseline ALT (P-interaction=0.30) and tBil (P-interaction=0.80) (Figure, panel D). Conclusion Contrary to our hypothesis of higher liver function tests with hepatic congestion in AHF, lower ALT was associated with more congestion and worse outcomes among patients hospitalized for AHF in STRONG-HF. There was no prognostic value from tBil levels. This suggests that ALT may be a marker of sarcopenia in these patients. Importantly, the beneficial effect of HIC on clinical outcomes is consistent irrespective of ALT and tBil levels at discharge.Figure