Background: In the last decade there has been strong evidence that bilirubin is a potent endogenous antioxidant that protects against atherosclerosis. A handful of studies have reported an inverse relationship between serum bilirubin level and severity of stable coronary artery disease. However these studies are new, have small populations, and have not been validated by other studies, hence there is need for more research on this topic.
Methods: This was a cross-sectional study where adult patients admitted for elective coronary angiography at our institution had blood extracted and sent for total and direct serum bilirubin level. Bilirubin levels were then statistically correlated with angiographic severity of stable coronary artery disease as measured by anatomic lesion involvement and TIMI flow grade.
Results: A total of 160 patients were included in this study, with a mean age of 58 years and a 2:1 male-to-female ratio. Seventy-nine percent were hypertensive and 38% were diabetic. Liver function tests were within normal range. Participants with a high TIMI flow grade of 3 had a mean serum total bilirubin level of 13.00 mmol/L and serum direct bilirubin level of 6.83 mmol/L, while patients with a TIMI flow grade of 2 had levels of 14.28 mmol/L and 5.58 mmol/L for total bilirubin and direct bilirubin, respectively. Participants with normal coronaries had a mean total bilirubin level of 14.43 mmol/L and a mean direct bilirubin level of 7.04 mmol/L, while those with non-obstructive CAD had a mean total bilirubin level of 13.03 mmol/L and a mean direct bilirubin level of 7.39 mmol/L. Mean total bilirubin levels for l-vessel, 2-vessel, and 3-vessel coronary artery disease were 13.72 mmol/L, 12.46 mmol/L, and 11.90 mmol/L, respectively while mean direct bilirubin levels were 7.60 mmol/L, 7.73 mmol/L, and 6.34 mmol/L, respectively. None of these results are statistically significant.
Conclusion: Serum bilirubin level is not associated with the extent and severity of stable coronary artery disease. However, none of our study results are statistically significant. More participants are needed to provide further power for our study to detect a statistically significant effect.