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A prospective study of serum lipoproteins after coronary artery bypass surgery
N Shaukat1, S S Ashraf, M I Mackness
1University Department of Medicine, Manchester Royal Infirmary, UK.
Insights
Coronary artery bypass surgery temporarily alters lipid levels, but long-term, it significantly reduces lipoprotein (a) and increases HDL cholesterol. These changes suggest myocardial ischemia relief may influence lipid profiles post-CABG.
Area of Science:
- Cardiovascular Surgery
- Clinical Biochemistry
- Lipid Metabolism
Background:
- Patients undergoing coronary artery bypass grafting (CABG) often present with dyslipidemia, including elevated serum lipoprotein (a) [Lp(a)] and triglycerides, and low high-density lipoprotein (HDL) cholesterol and apolipoprotein AI (apo AI).
- Understanding the impact of CABG on these lipid parameters is crucial for assessing cardiovascular risk and patient outcomes.
Purpose of the Study:
- To investigate the acute and long-term effects of CABG surgery on serum lipid, lipoprotein, and apolipoprotein levels.
- To compare pre-operative lipid profiles with those measured acutely post-surgery and at two years follow-up.
Main Methods:
- Serum lipid profiles were analyzed in 34 patients pre-operatively and six weeks post-CABG.
- A separate cohort of 22 patients was studied pre-operatively and two years after CABG.
- Patients received no lipid-lowering therapy or dietary interventions.
Main Results:
- Acutely post-CABG, significant reductions (40-60%) were observed in total cholesterol, LDL cholesterol, triglycerides, Lp(a), and apo B levels (p < 0.05).
- Serum apo AI decreased slightly (p < 0.05), while HDL cholesterol remained unchanged acutely.
- Within six weeks, all acute changes reverted to pre-operative levels. However, at two years, Lp(a) was significantly reduced by 40% (p < 0.001) and HDL cholesterol increased (p < 0.001). Triglyceride levels also decreased (p < 0.02) upon beta-blocker withdrawal.
Conclusions:
- The acute lipid alterations following CABG are transient, returning to baseline within six weeks.
- Long-term, CABG is associated with a sustained reduction in Lp(a) and an increase in HDL cholesterol.
- The persistent decrease in Lp(a) suggests that relief of myocardial ischemia may be a contributing factor, independent of beta-blocker use or lifestyle changes.
Abstract:
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 AI (apo AI) were low compared to healthy people. Acutely, there were profound decreases of 40-60% in 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 40% less than its pre-operative concentration (p < 0.001) and HDL cholesterol had increased (p < 0.001). Triglyceride levels decreased (p < 0.02) when beta-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 concentration.