ObjectiveTo explore the prognostic value of serum cystatin C (Cys C) in patients with congenital heart disease-associated pulmonary arterial hypertension (PAH-CHD).MethodsA retrospective cohort study was conducted on adult PAH-CHD patients who were hospitalized for the first time in the First Affiliated Hospital of Xinjiang Medical University from January 2010 to January 2020. The serum Cys C and other related data of patients were collected. The median follow-up time was 57 months. The main end event was all-cause death. According to the prognosis, the patients were divided into a survival group and a death group. Cox regression was used to analyze the risk factors for all-cause death in patients with PAH-CHD.ResultsA total of 456 patients were enrolled, including 160 males and 296 females, aged 38.99±14.72 years. The baseline data showed that there were statistical differences in resting heart rate, serum Cys C, creatinine, NT-proB-type natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin T (hs-cTnT), high-sensitivity C reactive protein (hs-CRP), New York Heart Association (NYHA) cardiac function classification and serum potassium between the survival group and the death group. Univariate Cox regression analysis showed that serum Cys C, NT-proBNP, hs-cTnT, creatinine and NYHA cardiac function classification were related risk factors for all-cause death in patients with PAH-CHD. Multivariate Cox regression analysis showed that serum Cys C (HR=3.820, 95%CI 2.053-7.108, P<0.001), NYHA grade Ⅲ (HR=2.234, 95%CI 1.316-3.521, P=0.010), NYHA grade Ⅳ (HR=4.037, 95%CI 1.899-7.810, P=0.002) and NT-proBNP (HR=1.026, 95%CI 1.013-1.039, P<0.001) were independent risk factors for all-cause death in patients with PAH-CHD and had a good predictive value.ConclusionAs a new cardiac marker, serum Cys C can predict all-cause death in patients with PAH-CHD and is an independent risk factor.