Association Between Serum Total Bilirubin And Coronary Plaque Vulnerability

Objectives:Bilirubin has emerged as an important endogenous antioxidant molecule,previous studies have reported a relationship between serum bilirubin levels and coronary artery disease(CAD),and increasing evidence shows that serum total bilirubin provides some protection against CAD.However,data regarding the relation between serum levels of total bilirubin and coronary plaque characteristics are rare up to now.The purpose of this study was to estimate whether serum total bilirubin(STB)levels was related to tissue characterization and vulnerability of coronary plaque by optical coherence tomography(OCT)in patients with CAD.Methods:In total of 129 patients who underwent OCT immediately after coronary angiography were included in this study.The patients according to symptoms and clinical examinations were divided into stable angina pectoris(SAP)group [N=58] and acute coronary syndrome(ACS)group [N=71].We measured STB in all participants.The ACS group and SAP group were further divided into 2subgroups respectively according to the median baseline STB of the two groups(11.10μmol/L and 11.48 μmol/L): a high-STB-ACS group(STB≥11.10 μmol/L)and a low-STB-ACS group(STB<11.10 μmol/L),a high-STB-SAP group(STB≥11.48 μmol/L)and a low-STB-SAP group(STB<11.48 μmol/L).The features of coronary plaque in ACS group were compared between 2 subgroups,the same in the SAP group also compared between 2 subgroups.The relationship between serum levels of total bilirubin and the stability of coronary plaque was analyzed.Results:STB was similar in the ACS group and SAP group.The types of plaque distribution/thickness of fibrous cap/infiltration degree of macrophages and lipid index were not significantly different between the subgroups of SAP group.The proportion of vulnerable plaque in the high-STB-ACS group weresignificantly higher compared with low-STB-ACS group(P<0.01).The thickness of fibrous cap of plaques in the high-STB-ACS group were lower than those in the low-STB-ACS group(P<0.05)and the infiltration degree of macrophages in the high-STB-ACS group were more heavily than those in the low-STB-ACS group(P<0.05).In ACS group,Pearson’s correlation analyses evidenced that STB were negatively associated with the thickness of fibrous cap(R=-0.31,P < 0.05).Furthermore,in ACS group,multivariate regression analysis showed that STB [OR: 1.145(95% CI:1.019-1.286),P = 0.022] and LDL-C [OR: 2.615(95% CI: 1.047-6.528),P = 0.039] were significant indicator of thick cap fibroatheroma(TCFA),and the optimal cut-off point of the STB predicting TCFA is 11.11μmol/L,with a sensitivity of 84.20% and specificity of65.42% in ACS group.Conclusion:STB were found positively associated with coronary plaque vulnerability in the ACS patients,increased STB in the ACS patients may be an important factor for the more heavily infiltrated by macrophages and the more thinner fibrous cap of plaques.STB may serve as a useful marker in reflecting plaque vulnerability and predicting TCFA in the ACS patients.