Apolipoproteins: correlation with carotid intimamedia thickness and coronary artery disease.

BACKGROUND: Lower levels of plasma apolipoprotein AI (Apo A-I) and higher levels of ApoB, and the ratio of ApoB to ApoA-I are considered to be independent risk factors for coronary heart disease, and may assume importance in the definite subset of Indian patients with normal levels of traditional lipid risk factors and an early-onset of coronary artery disease (CAD). Carotid intima-media thickness is considered as a marker of atherosclerosis and in prediction of clinical coronary events and coronary artery disease. With increasing interest in the role of non-traditional lipid risk factors in CAD and few studies reported in Indian subjects, we undertook this study to correlate the apolipoprotein levels with CAD and their impact on arterial thickening utilizing the carotid intima-media thickness as a surrogate marker.

METHODS AND RESULTS: Traditional lipid profile, apolipoprotein A-I and B and carotid artery Intima-media thickness (IMT) with a B-mode scan were measured in 309 patients recruited for the study (age group 36-64 years), which included 193 males and 116 females. Mean of maximal IMT exceeding 0.8 mm at the far wall of common carotid artery, excluding plaques, was selected as the higher values for comparison. One hundred and twenty two subjects had evidence for CAD as diagnosed by documented hospitalization with myocardial infarction or acute coronary syndrome, coronary angiography when feasible or noninvasive cardiac evaluation. Prevalence of subjects with increased IMT was higher among subjects with an apolipoprotein B: apolipoprotein A-I ratio exceeding one compared to those with a ratio less than one (30.6% vs 16.5%, p = 0.005). Prevalence of CAD was significantly higher among subjects with apolipoprotein B: apolipoprotein A-I ratio exceeding one as compared to those with a ratio less than one (53.7% vs 30.3%, p = 0.0002). Subjects with apolipoprotein B: apolipoprotein A-I ratio exceeding one and carotid IMT more than 0.8 mm had a 2.7-fold prevalence for CAD as against those with a ratio less than one and IMT less than 0.8 mm. On multivariate logistic regression analysis, apolipoprotein B: apolipoprotein A-I ratio exceeding one was significantly associated with increased IMT (odds ratio 2.27) and CAD (odds ratio 2.50) even after inclusion of sex, smoking, body mass index, total cholesterol, LDL-cholesterol, HDL-cholesterol, total cholesterol:HDL-cholesterol ratio and serum triglycerides into the model.

CONCLUSIONS: We conclude that apolipoprotein B to A-I ratio shows a strong association with carotid intimal medial thickening and coronary artery disease in this Western Indian population and may play an important role is assessment of coronary risk in addition to traditional coronary risk factors.