Aims: To compare the performance of apolipoproteins (Apo) and oxidized LDL against routine clinical lipid profiles in the discrimination of atherosclerotic burden and cardiac function in stable coronary artery disease (CAD) patients.
Methods and results: Using a cross-sectional approach, we measured oxidized LDL, Apo AI and B in 199 patients (34-81 years) with stable symptomatic CAD. The discrimination of (i) atherosclerotic burden (coronary atheroma scores, the number of diseased coronary vessels), and (ii) cardiac function [NYHA classification, left-ventricular systolic dysfunction (LVSD)] were judged using receiver operating characteristic (ROC) curves. The ratio of Apo AI to B was correlated to oxidized LDL (Spearman, r = 0.37, P < 0.001); however, oxidized LDL was unrelated to measures of cardiac function or CAD severity. Concentrations of Apo AI decreased from 1.38 to 1.20 g/L with increasing atheroma scores (P = 0.02), while triglyceride levels increased from 1.50 to 2.23 mmol/L (P = 0.016). High-density lipoprotein (HDL) cholesterol and Apo AI levels were higher among those with heart failure (P = 0.002), and increased ordinally with NYHA class (P = 0.005). On ROC analysis, reduced levels of Apo AI and HDL cholesterol were discriminators for patients in the upper quartile for atheroma score (P < 0.004). Raised indices of HDL were associated with heart failure (P < 0.002).
Conclusion: Apo AI levels are a consistent discriminator of atherosclerotic burden among patients with stable CAD. However, heart failure presents an element of confounding in the diagnostic and prognostic utility of Apo monitoring among these patients.