LIPOPROTEIN(A) IN PLASMA, ARTERIAL-WALL, AND THROMBUS FROM PATIENTS WITH AORTIC-ANEURYSM

The plasma concentration of lipoprotein(a) [Lp(a)] is highly correlate d with the incidence of cardiovascular and peripheral vascular disease . A positive physiological role for Lp(a) has not yet been clearly ide ntified, although elevated plasma levels in pregnant women, long-dista nce runners, subjects given growth hormone, patients after cardiovascu lar surgery, and patients with cancer, diabetes, or renal disease sugg est its involvement in tissue synthesis and repair. The hypothesis tha t Lp(a) is involved in repair/reinforcement of the aorta was tested in 38 patients undergoing surgery for aortic aneurysm. In 29 patients 1 day before surgery, the mean plasma Lp(a) protein level was 10.7 mg/dl . At about 1, 2, and 8 weeks after surgery, the level was 14.1, 15.1, and 15.2 mg/dl, respectively. These levels are significantly higher th an those of a comparable group of normal subjects (6.4 mg/dl; n = 274) . Specimens of resected aortic aneurysm showed extensive medial degene ration, discontinuous elastic fibers, and deposition of mucopolysaccha rides; these specimens were treated with a detergent-containing buffer to extract entrapped lipoproteins. The mean Lp(a) protein level in ao rtic wall extracts was 14.6 ng/mg tissue; these individual values were significantly associated with plasma Lp(a) levels before surgery (r(2 ) = 0.31, p = 0.0003). The mean Lp(a) protein level in aortic thrombus extracts was substantially higher at 69.6 ng/mg tissue; these individ ual levels also were significantly associated with plasma Lp(a) concen trations before surgery (r(2) = 0.68, p < 0.0001). The observations th at: (i) plasma Lp(a) protein is about 1.7-fold higher in patients with aortic aneurysms than in normal subjects; and (ii) that Lp(a) protein in the aneurysmic thrombus is about 4.8-fold higher than in the aorti c wall suggest that this lipoprotein plays a significant and direct ro le in thrombus formation and in reinforcement of the aneurysmic aortic wall.