PATIENTS UNDERGOING CORONARY-ARTERY BYPASS GRAFT-SURGERY ARE AT HIGH-RISK OF IMPAIRED GLUCOSE-TOLERANCE AND DIABETES-MELLITUS DURING THE FIRST POSTOPERATIVE YEAR

This study demonstrates that patients who have undergone coronary arte ry bypass graft (CABG) surgery have a high prevalence of abnormal gluc ose tolerance 3 months and 1 year later. Although only 6% were known t o have diabetes mellitus (DM) preoperatively, a further 4% were classi fied DM at two oral glucose tolerance tests (OGTTs) over the subsequen t year and a further 18% were classified as having impaired glucose to lerance (IGT) at 12 months, Reproducibility of the 120-minute plasma g lucose level in the 75-g OGTT was estimated from a repeat test perform ed within 10 days. The coefficient of variation (CV) of 120-minute glu cose was between 14% and 18%. The observed changes in class of glucose tolerance observed at OGTTs repeated 6 and 12 months after surgery di ffered from the predicted changes based purely on the estimated variab ility of 120-minute glucose measurement. There was evidence of regress ion to the mean for the IGT group. However, there was also evidence of deteriorating glucose tolerance in some subjects. Between 4% and 9% o f those with IGT 3 months after CABG surgery developed DM by 12 months , and 26 (13%) of those with initially normal glucose tolerance (NGT) developed IGT. Insulin and glucose responses in the OGTT and estimates of insulin resistance and B-cell function from fasting samples show t hat insulin resistance was the principal abnormality in IGT subjects, whereas in DM subjects, both insulin resistance and B-cell dysfunction contributed. Analysis of preoperative patient characteristics showed that the presence of either a systolic blood pressure of 140 mm Hg or body mass index (BMI) of more than 25 kg/m(2) identified 51% of the su bjects who would at 1 year after surgery include all those who would b e classified DM and 67% of those who would have IGT. Further analyses including insulin levels identified groups at particularly high risk o f DM, but no combination of readily available preoperative measures id entified all those destined to be classified IGT. Copyright (C) 1995 b y W.B. Saunders Company