The impact of obesity on late patency of left internal mammary artery grafts.

Background: Arterial conduits having long-term patency rates have been increasingly used for bypass of coronary arteries although some risk factors for their occlusion such as recipient vessel size, older age, and hyperlipidaemia have been described. Obesity, on the other hand, has been well established as a coronary risk factor. However, the effects of obesity on patency of arterial conduits, especially the internal mammary artery, have not been studied previously.
Aim: To assess the long-term effects of obesity on left internal mammary artery (LIMA) patency.
Methods: Angiograms of all patients with a LIMA conduit only were analysed. Two groups were formed according to the LIMA patency: group 1 - patients with occluded LIMA (n = 59), and group 2 - patients with patent LIMA (n = 68). Baseline demographic, haemodynamic, and laboratory characteristics of patients in both groups were compared. Obesity was defined as body mass index > or = 30 kg/m2.
Results: The mean BMI value in group 1 was significantly higher than in group 2 (30.4 +/- 3.1 vs. 28.7 +/- 4.7, p = 0.025). The two groups differed in time from surgery, drug use, and HDL cholesterol level. In addition, patients in both groups were categorised by BMI, and obese and non-obese groups were formed. Higher BMI was significantly associated with LIMA occlusion such that 71% of patients in group 1 had increased BMI, compared with 25% of patients in group 2 (p < 0.001). Multivariate analysis showed that multiple adjusted OR of the risk of LIMA occlusion was 7.41 (95% CI 3.38-16.28) for patients with increased BMI.
Conclusions: Obesity (> or = 30 kg/m2) has a significant and independent negative effect on the patency of the LIMA graft.