Complete arterial revascularization using T-graft technique in diabetics with coronary three-vessel disease

[Diabetes mellitus and coronary artery disease--a high risk combination]

Patients with diabetes mellitus are often not recognized in clinical routine, but also not well characterized in clinical trials. As a diagnostic approach it is recommended to test fasting glucose and glycosylated hemoglobin (HbA1c) in every patient with coronary artery disease (CAD). HbA1c, in addition, provides important prognostic information. Patients with diabetes mellitus do have an enhanced cardiovascular risk in all stages and during all kind of interventions of CAD. However, diabetes is not equal to diabetes; risk modifying factors such as HbA1c, concomitant diseases and medication have to be considered. Absolute benefit of pharmacological therapies is also enhanced in patients with diabetes compared to non-diabetics. However, statins or anti-hypertensive treatment seem to be even more effective in reducing cardiovascular events than pure control of glucose levels alone. During percutaneous interventions (PCI) glycoprotein IIb/IIIa-inhibitors reduce mortality in diabetics, an effect which may be partially also achieved by Clopidogrel. Glitazones reduce restenosis rates; however, clinical end point studies are still ongoing. After PCI, restenosis may be a predictor of mortality in patients with diabetes. Whether drug eluting stents, besides effectively reducing restenosis, may also reduce hard clinical events in patients with diabetes remains to be demonstrated. Current available studies comparing PCI with bypass are limited due to not considered factors (stenosis morphology), randomization bias, and faster progress of technology compared to study termination. During an acute coronary syndrome/myocardial infarction, hyperglycemia is an adverse prognostic marker. However, so far studies using glucose-insulin-potassium (GIK) infusion have not been convincingly demonstrate to be beneficial.

[Coronary artery surgery in diabetic patients]

Currently, 15% to 30% of the patients that undergo coronary artery surgery are diabetics. As a group, they have less favorable anatomic and clinical characteristics than the general population. Specifically, diabetics have more extensive coronary disease, more vessels involved, and more diffuse stenosis, so they need a higher number of distal anastomoses to achieve complete revascularization. In spite of these drawbacks, they can undergo coronary artery bypass procedures with an operative mortality similar to that of non-diabetic patients. However, some postoperative complications are significantly more prevalent among diabetics, mainly renal failure, neurological accidents, sternal dehiscence, and infection. In early studies of the late results of surgical revascularization, mainly based on venous grafts, late survival and clinical improvement were less satisfactory in diabetics than in non-diabetics. However, in recent experiences, in which the internal mammary artery has been used extensively, the clinical outcome of diabetics has been similar to that of non-diabetics, confirming this procedure as the preferred one in revascularizing the coronary arteries of diabetics with multivessel disease. Off-pump surgery and extensive use of arterial grafts are becoming established strategies for reducing operative risk and improving long-term clinical results. However, continuous, strict medical management of hyperglycemia and other known coronary risk factors, especially lipid levels, is essential.

Vasoreactivity of arterial grafts in the patient with diabetes mellitus: investigations on internal thoracic artery and radial artery conduits

OBJECTIVE

Arterial revascularization with either internal thoracic artery (ITA) or radial artery (RA) appears to be particularly attractive in diabetic patients. Previous investigations have shown that endothelial dysfunction and artherosclerosis are seen more often in these patients. The aim of this study was to compare the vasoreactive properties of ITA and RA grafts in diabetic and non-diabetic patients.

METHODS

Arterial rings were harvested from 57 patients who underwent complete arterial revascularization. The patients were divided into a non-diabetic group (I: n = 30) and patients with diabetes mellitus (II: n = 27). Arterial rings of the ITA (I: n = 30; II: n = 27) and RA (I: n = 28; II: n = 19) were mounted on a strain gauge in oxygenated, normothermic Krebs's--Henseleit solution at optimal resting tension. With KCL (80 mM) serving as the control, assessment of force of contraction (norepinephrine), endothelium-dependent relaxation (acetylcholine) and smooth muscle-dependent relaxation (glyceroltrinitrate) were obtained.

RESULTS

After KCL, the RA showed a trend to lower maximum contraction forces in diabetics (I: 76 +/- 25 mN; II: 69 +/- 29 mN), which was pronounced in patients with diabetes of more than 10 years duration (55 +/- 23 mN; P = 0.1). Maximum contraction force of the ITA was similar in both groups (I: 41 +/- 20 mN; II: 34 +/- 19 mN) and not influenced by the duration of diabetes. The two groups showed no significant differences of the relative vasoconstriction after norepinephrine in RA (I: 53 +/- 18%; II: 61 +/- 19%) and ITA rings (I: 70 +/- 23%; II: 69 +/- 25%). Also, endothelium-dependent relaxation with acetylcholine in RA (I: 53 +/- 14%; II: 57 +/- 16%) and ITA rings (I: 42 +/- 17%; II: 44 +/- 20%), and smooth muscle relaxation with glyceroltrinitrate of RA (I: 72 +/- 8%; II: 73 +/- 12%) and ITA rings (I: 64 +/- 12%; II: 58 +/- 20%) was comparable in both groups. No influence of duration of the diabetic disease was noted.

CONCLUSIONS

Although RA rings of patients with a long duration of diabetes have decreased maximum contraction forces, their relative vasoconstriction after norepinephrine, endothelium-dependent relaxation and smooth muscle relaxation was similar to non-diabetic patients. We thus conclude that the RA is an adequate arterial conduit in the patient with diabetes mellitus.