We examined the acute and long-term effects of coronary artery bypass (CABG) surgery on serum lipid, lipoprotein and apolipoprotein levels. One series of 34 patients having CABG surgery was studied pre-operatively and for six weeks afterwards, and another 22 patients were investigated before and two years after CABG surgery. None of the patients studied received any lipid-lowering drug therapy or specific dietary advice. In both groups, pre-operative serum lipoprotein (a) (Lp(a)) and serum triglyceride concentrations were raised and serum high-density lipoprotein (HDL) cholesterol and apolipoprotein Al (apo Al) were low compared to healthy people. Acutely, there were profound decreases of 40–60in the serum levels of cholesterol (p<0.001), low-density lipoprotein cholesterol (p<0.05), triglycerides (p<0.01), Lp(a) (p<0.05) and apolipoprotein B (apo B) (p<0.05). There was a small decrease in serum apo A1 (p<0.05), and serum HDL cholesterol showed no change. All these variables regained their pre-operative values within six weeks. Two years postoperatively, serum Lpa was 40less than its pre-operative concentration (p<0.001) and HDL cholesterol had increased (p<0.001 ). Triglyceride levels decreased (p<0.02) whenβ-blockade was withdrawn. The long-term decrease in Lp(a) following surgery is unlikely to be due either to stopping beta-blockers or to life-style changes. Myocardial ischaemia relieved by the operation may have been partially responsible for its previously raised concentrati
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