Plasma lipoprotein(a) is an independent risk factor for carotid atherosclerosis especially in the presence of high LDL-cholesterol levels

Clinical studies have suggested that elevated plasma Lp(a) levels may be considered as an independent risk factor for vascular disease especially in the presence of elevated concentrations of LDL-cholesterol, which are themselves atherogenic. In order to evaluate whether high levels of low density lipoprotein cholesterol (LDL-C) may contribute to the atherogenic effect of lipoprotein(a) [Lp(a)], the association between elevated Lp(a) levels and thickening of the intima plus media in the common carotid artery (CC-IMT) in patients with different degrees of hypercholesterolemia was investigated. 100 type II hypercholesterolemic patients and 25 normolipidemic subjects were enrolled in the study. Plasma lipid and lipoprotein levels were determined enzymatically, Lp(a) levels by ELISA. Patients were arbitrarily divided into two groups according to plasma Lp(a) concentration (Lp(a) < 30 or >=30 mg/dl). For each patient mean CC-IMT was determined by B-mode ultrasound using a Biosound 2000 II; in 60 patients and in the controls, the maximal IMT (Max-IMT) in the whole carotid tree was also determined. CC-IMT values were higher in hypercholesterolemic patients with plasma Lp(a) levels >= 30 mg/dl than in those with lower levels (p<0.002). The CC-IMT and the Max-IMT were directly and independently correlated with plasma levels of Lp(a) (r= 0.33 and r=0.25 respectively; both p<0.05). The effect of LDL-C concentrations on the relationship between IMT and Lp(a) was investigated by dividing the patients into quartiles of plasma LDL-C. After stratification CC-IMT significantly correlated with plasma Lp(a) levels in the patients with severe hypercholesterolemia (LDL-C > 5.2 mmol/L) but not in patients in the lowest quartile of LDL-C, i.e. those with moderate hypercholesterolemia. No correlation between CC-IMT and Lp(a) was found in normolipidemic subjects. Thus elevated plasma levels of Lp(a) can be considered as an additional, independent factor associated with the thickening of common carotid arteries in patients with severe but not in those with moderate hypercholesterolemia or in normocholesterolemic subjects.