Materials and Methods: In this cross-sectional study 200 consecutive patients, who underwent elective angiography in Madani Heart hospital, Tabriz, Iran, were selected and their blood samples were measured for total, direct, and indirect bilirubin level, with Diazo method using colorimetric technique. Following angiography, comparisons were made between the severity and location of CAS and therapeutic follow-up plan with total, direct, and indirect bilirubin level.

Results: Of 200 studied patients, 129 (64.5%) and 71 (35.5%) subjects were male and female, respectively. The cases were classified into 5 subgroups based on angiography results as follows: 59 (29.5%) cases with normal angiography, 11 cases (5.5%) with minimal CAD, 56 cases (28%) with single vessel involvement, 35 (17.5%) cases with two vessel involvement and 39 cases (19.5%) with three vessel involvement. The mean total bilirubin level was 1.47 ± 0.8 mg/dl, 1.27 ± 0.12 mg/dl, 1.27 ± 0.06 mg/dl, 1.6 ± 0.04 mg/dl and 0.98 ± 0.05 mg/dl, respectively for the cases with above order. The mean difference in serum total bilirubin between normal angiography group and three-vessel involvement group was 0.49 mg/dl (P < .0001). There was a significant inverse relation between bilirubin level (total, direct and indirect) and number of involved vessels and involvement intensity increased as serum bilirubin level decreased. Severity of coronary arteries stenosis as well as the number of involved vessels increased as serum bilirubin level decreased.

Conclusion: According to results, there was a significant inverse relation between serum bilirubin level and coronary involvement (type and intensity). Higher bilirubin serum levels played a protective role against CAD, even in the presence of other risk factors. Therefore, bilirubin level can be used as a predictor of CAD in the future.