Lysine-binding species of lipoprotein(a) in coronary artery disease

Elevated levels of plasma lipoprotein(a) [Lp(a)] have frequently been associated with coronary artery disease (CAD). Recently Lp(a) was fractionated into two species with different affinities for Lysine-Sepharose. The influence of lysine-binding heterogeneity of Lp(a) on its cardiovascular pathogenicity has not previously been studied. The authors have determined plasma levels of total Lp(a), its lysine-binding [lys+] and unretained [lys-] species in 67 male CAD patients undergoing cardiac catheterization. Forty-three patients have severe CAD (two- or three-vessel disease) and 24 patients have less pronounced CAD (one-vessel disease or less than 50% narrowing of coronary vessels). All patients were ranked in order of their Lp(a) levels and then grouped into quartiles. The prevalence of severe CAD was significantly higher in the upper Lp(a) quartile as compared with the other three quartiles (odds ratio 10-5; chi-square 11.2; P = 0.0008). Similar results were obtained when the same analysis was carried out for [lys+] and [lys-] species of Lp(a) (odds ratio 11.52 and 3.3, respectively; chi-square 12.3 and 4.34, respectively; P = 0.0004 and 0.037, respectively). Thus, measurement of either species of Lp(a) does not provide any additional improvement in the prediction of CAD as compared to the estimation of total Lp(a) levels.