Direct Bilirubin, but not Indirect Bilirubin, is Associated with Short-term Adverse Events in HFpEF

Objective: Abnormal live function tests have been identified as independent risk factors for ominous prognosis in patients with heart failure. However, most of the previous studies have failed to determine the contribution of direct bilirubin (DBIL) and indirect bilirubin (IBIL) separately. Hence, we aimed to explore whether DBIL or IBIL is correlated with the prognosis of heart failure with preserved ejection fraction (HFpEF). Methods: A total of 19837 patients were hospitalized for HFpEF between January 2012 and January 2022 in Fuqing City Hospital affiliated with Fujian Medical University. The primary endpoint was in-hospital all-cause mortality. Secondary endpoints included in-hospital cardiovascular mortality and 30-day re-admission for heart failure. Results: Univariable analysis indicated that patients with elevated DBIL or IBIL were exposed to a higher risk of mortality and re-admission. However, in multivariable models, both ln-transformed DBIL and TBIL, but not IBIL, were independent risk factors for in-hospital all-cause mortality [hazard ratio (HR)=1.796, 95% confidential interval (CI)=1.477-2.183, P＜0.001; HR=1.854, 95% CI=1.461-2.352, P＜0.001; HR=1.161, 95% CI=0.959-1.407, P=0.126] and in-hospital cardiovascular mortality (HR=1.831, 95% CI=1.345-2.492, P＜0.001; HR=1.899, 95% CI=1.300-2.773, P=0.001; HR=1.145, 95% CI=0.841-1.561, P=0.389). Only DBIL remained independently associated with 30-day readmission for heart failure (HR=1.361, 95% CI=1.036-1.787, P=0.027). Adding ln-transformed DBIL to model 1 increased its discriminatory capacity (C-statistic: 0.851 to 0.869, respectively), whereas adding ln-transformed IBIL yielded little increment (C-statistic: 0.851 to 0.852, respectively). Conclusion: DBIL, but not IBIL, was associated with short-term ominous prognosis in patients with HFpEF. Hence, DBIL may be the superior predictor for prognosis in HFpEF.