Serum Lp(a) level as a predictor of vein graft stenosis after coronary artery bypass surgery in patients.

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Abstract
Although the serum lipoprotein fraction Lp(a) has been associated with coronary artery atherosclerosis, its relationship to narrowing of saphenous vein grafts has not previously been elucidated. We therefore measured serum Lp(a) levels in 167 symptomatic patients undergoing cardiac catheterization who had had coronary artery bypass surgery 0.7 to 14.3 years earlier. Lp(a), total cholesterol, and total triglyceride levels were compared with the degree of saphenous vein graft stenosis to test for any association. Serum Lp(a) levels were significantly associated with the degree of stenosis of saphenous vein grafts (r = .24, p = .002). Mean Lp(a) levels (mg/dl) in the 135 patients with stenosis were almost double (32.0 +/- 32.7, mean +/- SD) those in the 32 patients with no graft stenosis (16.7 +/- 22.6; p = .002). Graft stenosis was not associated with previous myocardial infarction, hypertension, obesity, diabetes, or smoking. Serum cholesterol levels (mg/dl) were slightly higher in the stenosis group (251.3 +/- 69) than in the no-stenosis group (231.8 +/- 48.8), but the difference was of borderline significance (p = .06). A stepwise increase in mean Lp(a) was found in groups of patients with increasing vein graft stenosis. At a serum Lp(a) level of 31.6 mg/dl or above, 92% of the patients demonstrated vein graft stenosis. Thus, patients with elevated Lp(a) levels have an increased risk of developing saphenous vein graft stenosis after coronary bypass surgery.