Effect of lipid exposure on graft patency and clinical outcomes: arteries and veins are different.

Objectives: We evaluated the influence of lipid exposure upon conduit patency in long-term follow-up after primary CABG.

Methods: From a prospectively compiled database, we identified 1207 grafts (436 SV and 771 mixed arterial grafts) among 413 CABG patients with 9.4 ± 2.4 years of follow-up (range 3-13). Surveillance angiography was performed as part of a randomized trial. All available lipid assays were collected from pathology laboratories, and from these, mean annualized lipid exposure was calculated for total cholesterol, HDL, LDL and triglycerides. Angiographical and clinical data were analysed against lipid exposure. Graft failure was defined as occlusion, string sign or >80% stenosis.

Results: Six thousand and seventy-seven lipid measurements were obtained, and there were 154 failed grafts. Three hundred and eleven patients received at least one vein graft, and all 413 patients received at least one arterial graft. Overall, only HDL levels were inversely correlated with graft failure, with total cholesterol and LDL showing no associations in a mixed pool of arterial and venous grafts. To assess whether total/LDL cholesterol had no effect or were exerting competing effects in arteries and veins, separate multivariate analyses were performed. Venous graft failure was associated with increased total cholesterol/HDL (P=0.006) and LDL/HDL (P=0.032). By contrast, elevated total cholesterol was correlated with a reduced risk of arterial graft failure (OR for graft failure 0.705, P 0.023) with increasing LDL cholesterol following a similar trend (OR for graft failure 0.729, P=0.051).

Conclusion: Sub-fractions of dyslipidaemia known to be risk factors for native vessel disease appear to similarly influence vein grafts. Arterial conduits are at least more resistant to the effects of high lipid exposure, and appear to be protective. These results favour the use of arterial grafts in patients with poorly controlled dyslipidaemia.