Subcommittee on Clinical Trials: Registry of Multicenter Clinical Trials

Influence of serum lipoprotein(a) and homocyst(e)ine levels on graft patency after coronary artery bypass grafting

High serum levels of lipoprotein(a) and homocyst(e)ine are considered independent risk factors for atherothrombotic disease. In a prospective study in patients undergoing coronary artery bypass grafting, the preoperatively determined lipoprotein(a) and homocyst(e)ine levels were related to the frequency of 1-year graft occlusion. A cohort of 610 patients who underwent coronary artery bypass surgery was followed through the first postoperative year. Shunt angiography was performed in 581 patients (95%) at a mean of 12.1 +/- 1.5 months after the operation. The serum levels of lipoprotein(a) (n = 570) and homocyst(e)ine (n = 565) in patients with occluded internal mammary artery (IMA) grafts were not significantly different from the levels in those with open IMA grafts. Also, the serum lipoprotein(a) and homocyst(e)ine levels in patients with > or = 1 occluded vein graft were not significantly different from those in patients with all vein grafts patent. This study also determined the incidence of graft occlusion in quartiles of the lipoprotein(a) and homocyst(e)ine levels, respectively, and tested for linear trends. No significant trends in the incidence of graft occlusion were found, but the number of patients with vein graft occlusions was higher in the lowest quartile of lipoprotein(a) than that in the upper 3 quartiles (odds ratio, 1.82, 95% confidence interval, 1.21 to 2.74, p = 0.0025). Controlling for background variables in multivariate models only slightly modified the results. Thus, apart from an unexplained excess of vein graft occlusions in the lowest quartile of lipoprotein(a) levels, no association between the preoperative serum lipoprotein(a) or homocyst(e)ine levels and the frequency of 1-year graft occlusion could be demonstrated.

Long-term effects of n-3 fatty acids on serum lipids and glycaemic control

The long-term influence of n-3 polyunsaturated fatty acids (n-3 PUFAs) on serum lipids and glucose homeostasis was studied in a group of non-diabetic, moderately hypertriglyceridaemic patients undergoing coronary artery bypass grafting. They were investigated according to the same procedure before and 6 months after the operation. Following randomization postoperatively, 28 patients received 3.4 g eicosapentaenoic and docosahexaenoic acid per day, whereas 29 patients comprised the control group. The decline in serum triglycerides after 6 months was significantly greater in the n-3 PUFA group than in the control group (median decline, -33.2% vs. -11.1%, p = 0.002), while no group difference was noted in serum total, HDL, or LDL cholesterol levels. Fasting plasma glucose levels decreased less in the n-3 PUFA group compared with the control group (median change, -0.2 mmol l-1 vs. -0.5 mmol l-1, p = 0.054). The corresponding changes in fasting insulin levels were -2 mIU ml-1 in the n-3 PUFA group and no change in the control group (p = 0.039). In both groups combined, the recorded changes in serum triglyceride and serum insulin levels were negatively correlated with the change in serum phospholipid n-3 fatty acids (r = -0.35, p = 0.008 and r = -0.32, p = 0.016, respectively). An oral glucose tolerance test revealed no significant group differences after 6 months, neither in the peak levels, nor in the areas under the curves between 0 and 3h after the glucose load for glucose, insulin, and C-peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Low molecular weight heparin in prevention of perioperative thrombosis

OBJECTIVE

To determine whether prophylactic treatment with low molecular weight heparin reduces the incidence of thrombosis in patients who have had general or orthopaedic surgery.

DESIGN

Meta-analysis of results from 52 randomised, controlled clinical studies (29 in general surgery and 23 in orthopaedic surgery) in which low molecular weight heparin was compared with placebo, dextran, or unfractionated heparin.

SUBJECTS

Patients who had had general or orthopaedic surgery.

INTERVENTION

Once daily injection of a low molecular weight heparin compared with placebo, dextran, or unfractionated heparin.

MAIN OUTCOME MEASURES

Incidence of deep venous thrombosis, pulmonary embolism, major haemorrhages, and death.

RESULTS

The results confirm that low molecular weight heparins are more efficacious for the prophylactic treatment of deep venous thrombosis than placebo (common odds ratio 0.31, 95% confidence interval 0.22 to 0.43; p < 0.001) and dextran (0.44, 0.30 to 0.65; p < 0.001). The results suggest that low molecular weight heparins are also more efficacious than unfractionated heparin (0.85, 0.74 to 0.97; p = 0.02), with no significant difference in the incidence of major haemorrhages (1.06, 0.93 to 1.20; p = 0.62).

CONCLUSIONS

Low molecular weight heparins seem to have a higher benefit to risk ratio than unfractionated heparin in preventing perioperative thrombosis. However, it remains to be shown in a suitably powered clinical trial whether low molecular weight heparin reduces the risk of fatal pulmonary embolism compared with heparin.