Association of serum total bilirubin levels with the severity, extent and subtypes of coronary atherosclerotic plaques detected by coronary CT angiography

In this study, we aimed to evaluate whether serum total bilirubin was associated with the severity and morphology of coronary atherosclerotic plaques detected by computed tomography angiography (CTA). The study population consisted of 1,115 patients (55.2 % men) who underwent dual-source 64-slice CTA for the assessment of coronary artery disease (CAD). Coronary arteries were evaluated on 16 segment basis and critical coronary plaque was described as luminal narrowing >50 %, whereas plaque morphology was assessed on per segment basis. Serum bilirubin levels were determined using commercially available assay kits. The critical atherosclerotic lesions were detected in 431/1,115 (38.6 %) subjects by CTA. Serum total bilirubin levels were found to be lower in patients with any coronary plaque (0.62 ± 0.21 vs. 0.70 ± 0.25 mg/dL, p = 0.002). Also bilirubin level was lower in patients with critical stenosis compared to non-critical stenosis (0.57 ± 0.18 vs. 0.70 ± 0.24 mg/dL, p < 0.001). Subjects having primarily noncalcified plaque (NCP) and mixed plaque (MP) have lower bilirubin levels compared to calcified plaque (CP) and normal subjects (0.62 ± 0.20 for NCP and 0.60 ± 0.19 for MP, 0.65 ± 0.26 for CP and 0.71 ± 0.25 for normal subjects, p < 0.001). This independent association was remained for NCP after multinominal regression analysis (OR: 0.76; 95 % CI 0.58–0.88; p < 0.001). Our study demonstrated that serum bilirubin level was significantly associated with the presence, severity and the noncalcified morphology of atherosclerotic plaques detected by CTA. Further prospective clinical studies are needed to clarify the exact physiopathologic and prognostic role of bilirubin in CAD.