Serum direct bilirubin predicts severe tricuspid regurgitation in atrial fibrillation.

Aims: Moderate-to-severe tricuspid regurgitation (TR) often coexists with atrial fibrillation (AF) and is associated with poor prognoses. Although inflammation is elevated in TR patients, whether bilirubin predicts moderate-to-severe TR in AF remains unclear. This study aims to evaluate serum bilirubin as an early diagnostic marker for TR in AF. Method and results: We enrolled 344 AF patients between 2020 and 2023 and collected clinical data, including diagnoses, blood tests, medication history, and transthoracic echocardiography parameters. Patients were grouped by TR severity (AF with vs. without moderate-to-severe TR) or antibiotic use (users vs. non-users). After adjusting for confounders, univariate and multivariate Cox regression analyses were performed to gauge variable associations with TR occurrence. A receiver operating characteristic (ROC) analysis assessed the predictive accuracy of direct bilirubin (DBIL) for TR, and Kaplan-Meier curves depicted the cumulative 48-month TR incidence in patients with DBIL >3.5 µmol/L. Patients with moderate-to-severe TR had higher DBIL (5 vs. 3 µmol/L, Conclusions: Serum DBIL levels serve as a potential early diagnostic marker for moderate-to-severe TR in AF patients, and anti-infective therapy lowers TR incidence.