Apolipoprotein E polymorphism is not a predictor for repeated coronary artery bypass surgery

Factors leading to the occlusion of coronary grafts are diverse and may at least partially be inherited. We aimed to study the possible genetic predisposition and especially the role of apoE epsilon4 allele as a risk factor for repeated coronary artery bypass grafting (CABG) in a case-control setting.

All patients (n=184) who underwent repeated CABG between 1990 and 1998 were identified in the computed registry of the Department of Cardiothoracic Surgery in Tampere University Hospital. Age, sex and operation date matched controls with first time CABG were selected from the same registry. DNA samples were collected by sample stick sent via the mail for buccal smear. The final analysis included 137 surviving matched pairs.

In patients <62 years of age (median age), family history emerged as the only significant (OR=3.4; 95% CI=1.5-7.8, p=0.004) predictor for repeated surgery. Among older patients, repeated CABG was no longer predicted by family history but by hypercholesterolemia (OR=2.1; 95% CI=1.1-4.0, p=0.027), modified by apoE genotype.

Our results suggest that medium-term survivors after redo CABG have a strong genetic predisposition unrelated to hypercholesterolemia or apoE genotype, leading to more severe coronary artery disease at earlier age. In the older age group, redo coronary artery bypass surgery is associated with hypercholesterolemia, which, although modified by apoE genotype, may mainly be due to other genetic or acquired factors.