Serum gamma-glutamyltransferase activity: a new marker for coronary artery bypass graft disease

OBJECTIVES
Serum gamma-glutamyltransferase (GGT) activity has been shown to be related to the development of atherosclerosis and cardiovascular events. We evaluated the association between GGT and severe graft disease in patients undergoing coronary artery bypass graft (CABG) surgery.

STUDY DESIGN
We evaluated 113 patients (mean age 62±9 years; range 21 to 81 years) who underwent control coronary angiography after a mean of 39 months (range 18 to 84 months) following CABG surgery. A graft was considered patent if there was <70% stenosis or severely diseased if there was ≥70% stenosis on coronary angiography. Preoperative serum GGT levels were measured in all the patients and none had severe systemic or hepatobiliary disease. The association between serum GGT level and severe graft disease was investigated. The grafts were also evaluated separately.

RESULTS
Coronary angiography showed severe graft disease involving at least one graft in 65 patients (57.5%). Serum GGT level was significantly higher in patients with severe graft disease (p=0.001). ROC curve analysis yielded a cut-off value of 29.5 U/l for serum GGT level to predict severe graft disease (area under the curve: 0.69) with 48% sensitivity and 82% specificity. While GGT levels were similar for internal mammary artery grafts (p>0.05), radial artery grafts and saphenous vein grafts (SVG) with severe graft disease were associated with significantly higher GGT levels (p=0.003 and p<0.001, respectively). In multivariate analysis, family history of coronary artery disease at a young age (OR 2.46, 95% CI 1.08-5.61, p=0.03) and serum GGT (OR 1.03, 95% CI 1.00-1.07, p=0.05) were independent predictors of severe graft disease. Separate analysis based on the graft types showed that GGT was an independent predictor of severe graft disease for only SVG (OR 1.02, 95% CI 1.00-1.04, p=0.03).

CONCLUSION
Serum GGT level may be an independent marker for the development of severe SVG disease in patients undergoing CABG surgery.