Relationship between plasma oxidized low-density lipoprotein and the coronary vasomotor response to acetylcholine in patients with coronary artery disease

The present study examined the relation of plasma oxidized low-density lipoprotein (LDL) levels to plasma LDL cholesterol levels and the impairment of endothelium-dependent coronary vasorelaxation in patients with coronary artery disease (CAD). In the first study, the relationship between plasma levels of oxidized LDL and LDL cholesterol were investigated in 88 patients with CAD. In the second study, the changes in the diameter of the left anterior descending (LAD) and the left circumflex (LCX) coronary arteries were measured after intracoronary administration of acetylcholine (15 microg) and isosorbide dinitrate (2.5 mg) in 15 patients with CAD. Plasma oxidized LDL levels were determined with a sandwich enzyme-linked immunosorbent assay. Plasma oxidized LDL levels did not correlate with plasma LDL cholesterol levels (r=-0.03, p=NS). The % diameter changes (mean+/-SEM) in the LAD and LCX after intracoronary acetylcholine were -8.3+/-3.5% and -10+/-4.2%, respectively. The % diameter changes in the LAD and LCX after intracoronary isosorbide dinitrate were 23+/-4.8% and 23+/-5.1%, respectively. The % diameter changes in the LAD and LCX inversely correlated with plasma oxidized LDL levels after intracoronary acetylcholine (LAD: r=-0.55, p=0.03; LCX: r=-0.59, p=0.02), but were not after intracoronary isosorbide dinitrate. Plasma LDL cholesterol, triglyceride, and high-density lipoprotein cholesterol levels did not correlate with the coronary vasoreaction to acetylcholine. In conclusion, plasma oxidized LDL levels do not correlate with plasma LDL-cholesterol levels and are related to impairment of endothelium-dependent coronary vasodilation in patients with CAD.