Serum direct bilirubin predicts severe tricuspid regurgitation in atrial fibrillation

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.

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, p < 0.001), direct bilirubin, B-type natriuretic peptide, and γ-GGT values. A multivariate Cox regression showed that elevated DBIL independently predicted TR (HR = 1.104, p = 0.039). The ROC analysis identified DBIL ≥3.5 µmol/L as an optimal cutoff for distinguishing TR (AUC = 0.846, sensitivity 91.2%, specificity 68.8%). Among patients with DBIL >3.5 µmol/L, antibiotic use reduced TR risk (HR = 0.214, p < 0.001).

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.