A PROSPECTIVE-STUDY OF SERUM-LIPOPROTEINS AFTER CORONARY-ARTERY BYPASS-SURGERY

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-operativ ely and for six weeks afterwards, and another 22 patients were investi gated before and two years after CABG surgery. None of the patients st udied received any lipid-lowering drug therapy or specific dietary adv ice. In both groups, pre-operative serum lipoprotein (a) (Lp(a)) and s erum triglyceride concentrations were raised and serum high-density li poprotein (HDL) cholesterol and apolipoprotein AI (ape AI) were low co mpared to healthy people. Acutely, there were profound decreases of 40 -60% in the serum levels of cholesterol (p<0.001), low-density lipopro tein 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 thes e variables regained their pre-operative values within six weeks. Two years postoperatively, serum Lpa was 40% less than its pre-operative c oncentration (p<0.001) and HDL cholesterol had increased (p<0.001). Tr iglyceride levels decreased (p<0.02) when beta-blockade was withdrawn. The long-term decrease in Lp(a) following surgery is unlikely to be d ue either to stopping beta-blockers or to life-style changes. Myocardi al ischaemia relieved by the operation may have been partially respons ible for its previously raised concentration.