Involvement of Lipoprotein(a) in calcification of coronary arteries and thoracic aorta as detected by X-ray computed tomography

Abstract

The authors compared the severity of coronary calcification and thoracic aortic calcification as detected by x-ray computed tomography (X-ray CT) with Lipoprotein(a) [Lp(a)], and investigated whether Lp(a) is more important than total cholesterol (TC) or HDL-cholesterol (HDLC) as a risk factor for arteriosclerosis. Subjects were 64 patients (47 males, mean age 57.1 ± 8.4 years) comprising 43 cases of ischemic heart disease, 9 cases of chest pain syndrome, 7 of valvular heart disease, and 5 of dilated cardiomyopathy. Fasted blood samples were collected early in the morning and values before medication were used. Lp(a) was measured by ELISA. Evaluation of coronary calcification by X-ray CT was performed in accordance with the procedure described in the authors' previous reports. Coronary calcification was assessed in all slices (slice thickness: 1 cm; scoring system: no coronary calcification, 0 points; coronary calcification less than 1 cm in length, 1 point; 1–2 cm, 2 points; over 2 cm, 3 points). The total score was used as coronary calcification score. For the aortic calcification score, the total number of aorta (slice thickness: 1 cm) with calcification from the superior margin of the aortic arch to the inferior cardiac margin was used. Mean scores of coronary and aortic calcification were 6.1 ± 7.9 and 4.5 ± 5.2 points, and Lp(a), TC, and HDLC, 23.7 ± 23.3, 213 ± 37, and 49.9 ± 15.1 mg/dl, respectively. No correlation was seen between the scores of both coronary calcification and aortic calcification and any of the three lipid parameters, but for cases without coronary calcification, Lp(a) (10.6 ± 8.5 mg/dl) was significantly lower (p < 0.1) than that for cases with coronary calcification (1 vessel, 29.4 ± 24.4; 2 vessels, 26.5 ± 16.7; 3 vessels, 32.6 ± 31.0 mg/dl).

No significant difference was observed, however, for TC and HDLC between patients with and without coronary calcification/aortic calcification. It is suggested that Lp(a) may be a risk factor for coronary calcification. There is no correlation, however, between Lp(a) and the severity of coronary calcification. Aortic calcification is not related to the serum Lp(a) level.