Influence of Type 2 Diabetes on Functional and Structural Properties of Coronary Artery Bypass Conduits

Abstract

Recent studies have reported a high incidence of postoperative unfavorable cardiac-related events in patients with diabetes who underwent coronary artery bypass grafting (CABG). Structural and functional characteristics of CABG conduits, which have been shown to play an important role in patient outcome after myocardial revascularization, have not been fully investigated in diabetic subjects. Therefore, we sought to determine the influence of adult-onset diabetes on vasoreactivity and morphological profile of venous and arterial grafts. Of the 160 consecutive patients enrolled in the study, 90 were diagnosed with type 2 diabetes and 70 did not have diabetes (control group). All patients underwent evaluation of glucose control before surgery. Tissue specimens were collected from left internal thoracic artery (LITA) and saphenous vein (SV) grafts harvested during elective CABG. Functional tests were performed to assess contractile and vasodilative responses of bypass conduits. Histological evaluation was carried out to examine vessel wall structure. Univariate and multivariate analyses were performed to correlate the preoperative factors related to the control of the endocrine disorder with histological findings. Patient medical history and demographics did not differ between the groups. Diabetic patients showed significant microalbuminuria and higher plasma levels of C-peptide and GHb as compared with nondiabetic subjects. Functional tests of the LITA segments revealed no difference between groups with regard to contractile and vasodilative responses. In contrast, significant impairment in the endothelium-related vasodilation of the SV grafts was observed in diabetic subjects. Histological studies showed structural preservation of the arterial conduits in both groups. However, marked intimal abnormalities (also atherosclerotic calcified plaques) were detected in SV grafts harvested from diabetic patients. Logistic regression analysis showed that high levels of proteinuria and GHb were independent predictors of advanced structural degeneration of SV conduits. Treatment modality, duration of diabetes, and other demographic or metabolic factors were found to have no influence on the morphological characteristics of SV conduits. In conclusion, biological properties of LITA conduits for CABG were preserved in diabetic patients. However, these patients frequently showed impairment of the endothelium-dependent vasorelaxation and intimal degeneration of SV grafts. The extent of structural abnormalities of SV grafts was inversely correlated with the efficacy of the metabolic control of the endocrine disorder. Further studies are required to conclusively correlate preoperative SV graft abnormalities with postoperative conduit patency rate and the occurrence of adverse cardiac-related events in diabetic subjects.

Type 2 Diabetes Mellitus Is Associated With Faster Degeneration of Bioprosthetic Valve

“…Total cholesterol levels are not included in the definition of the MS and are not correlated with the presence of type 2 DM because they are not significantly affected by insulin resistance. 20 Therefore, the fact that total cholesterol was associated with SVD independent of DM appears to confirm findings from previous studies 1,2 and to suggest that an accelerated atherosclerotic process, of which hyperglycemia and hypercholesterolemia 21 are among the main determinants, may play a key role in SVD.…”

Effects of elevated perfusion pressure and pulsatile flow on human saphenous veins isolated from diabetic and non-diabetic patients

“…11 -13 In addition, many authors described the presence of endothelial denudation and venous lumen dilation under distention pressure without flow. 5,7,10 The histological data Unlike previous studies that reported increased luminal area 9 and increased inner diameter of the saphenous vein, 10 the luminal area in the present study did not differ among experimental groups. The area and lumen diameter increased when the saphenous vein was distended.…”

“…In diabetic patients, saphenous vein grafts exhibit reduced endothelium-dependent vasodilatation. 10 Our previous studies have shown that HSV segments perfused with nonpulsatile flow and increased pressures for 3 h exhibit greater morphological changes in the presence of higher perfusion pressures. 11 The present study extends our previous work by utilizing pulsatile flow for perfusion of HSV segments and by comparing veins isolated from diabetic and nondiabetic patients.…”

Secondary Prevention After Coronary Artery Bypass Graft Surgery

“…279 This may relate to the association between type 2 diabetes mellitus and impaired endothelial function and intimal degeneration of saphenous vein grafts, changes that inversely correlate with the metabolic control of the diabetes mellitus. 280 Interestingly, diabetes mellitus has much less effect on the properties of the internal mammary artery.…”