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

Investigation of the effects of diabetes mellitus on left internal thoracic artery flow patterns in patients scheduled to undergo coronary bypass graft surgery

PURPOSE

Diabetes mellitus (DM) plays a key role in the formation and prognosis of cardiovascular diseases. In this study, we aimed to investigate the effects of DM and glycemic control on left internal thoracic artery (LITA) Doppler flow in patients scheduled to undergo coronary artery bypass graft (CABG) surgery.

METHODS

Patients who were hospitalized with a planned isolated CABG operation to our clinic between October 1, 2019 and March 1, 2020 were consecutively included in this prospective study. The patients were divided into three groups as those without DM (Group 1), those with DM and HbA1c values of below 7.5 (Group 2), and those with DM and HbA1c values of 7.5 and above (Group 3). The differences between the LITA Doppler flow patterns of the patients were analyzed.

RESULTS

The mean ages of Group 1 (n = 103), Group 2 (n = 42), and Group 3 (n = 47) were 59.8 ± 9.6 years, 60.5 ± 9.3 years, and 61.9 ± 8.1 years, respectively. The groups differed in terms of diameter, volume, Vmax, pulsality index (PI), and resistive index (RI) values, both when the groups were compared among themselves (P < .001, for all), and when they were compared between those with (Groups 2 and 3) and without DM (Group 1) (P < .001, for all). Volume (R = -0.627, P < .001) and Vmax (R = -.450, P < .001) were moderately negatively correlated, while PI (R = .523, P < .001) and RI (R = 0.598, P < 0.001) were moderately positively correlated with HbA1c levels.

CONCLUSION

In this study, we showed that increased HbA1c levels may be associated with significant functional and structural changes of LITA.

Impact of type 2 diabetes on vascular reactivity to cGMP generators in human internal thoracic arteries

OBJECTIVE

The balance between nitric oxide (NO)-sensitive and -insensitive forms of soluble guanylate cyclase (sGC) has been demonstrated to be disrupted in certain lifestyle-related diseases. However, it remains unclear whether type 2 diabetes results in a shift of sGC to the NO-insensitive form. This study addressed this issue in the human blood vessel.

METHODS

Internal thoracic arteries were obtained from patients undergoing coronary artery bypass grafting. Helically cut strips of the arteries were suspended in organ chambers, and relaxant responses to nitroglycerin (NO-sensitive sGC stimulant) and BAY 60-2770 (NO-insensitive sGC stimulant) were assessed.

RESULTS

The patients were divided into two groups according to the presence of type 2 diabetes (HbA1c: 7.0±0.3%) or its absence (HbA1c: 5.6±0.1%). Nitroglycerin-induced relaxation was not different in the arteries obtained from type 2 diabetic and non-diabetic patients. In addition, the relaxant response to BAY 60-2770 in type 2 diabetics was comparable to that observed in non-diabetics. Although the patients enrolled often had vascular risk factors other than type 2 diabetes, the relaxant responses were still in the same range in a comparison based on the number of risk factors. However, in separate experiments, the relaxant response to nitroglycerin was attenuated by pre-incubation of the arteries with ODQ (sGC imbalance inducer), whereas the relaxant response to BAY-60-2770 was augmented.

CONCLUSIONS

These findings suggest that type 2 diabetes does not affect the balance between NO-sensitive and -insensitive sGC in human internal thoracic artery grafts.

Concomitant grafting of both postbifurcation internal thoracic artery branches

OBJECTIVE

We aimed to assess the clinical outcome and graft patency after concomitant grafting of both postbifurcation internal thoracic artery (ITA) branches.

METHODS

Between 2007 and 2013, 17 patients (14 men; mean [SD] age, 60 [9.3] years) underwent skeletonized bifurcated ITA grafting. Respective targets were restricted to non-left anterior descending (LAD) area. In all patients, a complementary standard ITA was used to graft the LAD artery. Graft patency was assessed by standard coronary angiography or serial multidetector computed tomography.

RESULTS

Of the bifurcated conduits, 94% were right ITA. Respective right ITA target sets were first and second obtuse marginal arteries (M1-M2) (n = 12), ramus-M1 (n = 2), and distal right coronary artery-posterior descending artery (n = 2). Right ITAs were mobilized retroaortic (via the transverse sinus) in 14 patients (82%) (to circumflex artery targets). Circumflex artery targets comprised 88.2% of all anastomoses (30/34). There were no early mortalities, myocardial infarctions, or hypoperfusion syndromes. During median follow-up of 44 months (range, 3-63), there was no late mortality. Overall reintervention rate was 11.7%, and bifurcated ITA-related reintervention rate was 5.8%. At 5 years, freedom from major adverse cardiac or cerebrovascular event related to bifurcated ITA respective territory was 87% (Kaplan-Meier). Coronary imaging was achieved in 76% of the patients (elective multidetector computed tomography, n = 9; symptoms-directed coronary catheterization, n = 4). Bifurcation branch patency rate was 88.4% (23/26) at a median of 3.5 years.

CONCLUSIONS

Grafting both postbifurcation ITA branches is technically feasible and may be selectively considered. Current observations are valid for skeletonized conduits and limited to non-LAD targets. These preliminary findings should be corroborated by larger data sets.

Radial artery as graft for coronary artery bypass surgery: Advantages and disadvantages for its usage focused on structural and biological characteristics

Radial artery (RA) is the most popular arterial graft after the left internal thoracic artery in both low- and high-risk patients undergoing coronary artery bypass grafting. Various arterial grafts such as the right internal thoracic artery, the right gastroepiploic artery, and the inferior epigastric artery have also gained ground over the past 30 years because of the intimal hyperplasia and atherosclerosis of the saphenous vein leading to late graft occlusion. In this review article we would like to present the utility of the RA as a graft, focused mainly on its structural and biological characteristics.

Radial artery graft flowmetry is better than saphenous vein on postero-lateral wall

BACKGROUND

Although general agreement exists on internal mammary graft as the first conduit, the second choice is still questioned. Despite radial artery (RA) grafting has been suggested, saphenous veins (SV) continue to be extensively used.

METHODS

A prospective series of isolated RA-CABG (150 patients) or SV-CABG (180 patients), performed either off-pump (OP-CABG) and on-pump (CPB-CABG), in diabetics and non-diabetics, in elderly and young patients, during the last 5-years at a single institution were evaluated. RA was harvested with harmonic scalpel, flowmetry was performed with a transit-time flowmeter (TTF). Graft flow reserve (GFR) was calculated with intra-aortic balloon-pump. Follow-up was collected by outpatient clinic database or by telephone interview with general practitioners.

RESULTS

The 2 groups showed comparable preoperative and intraoperative variables. Mortality, morbidity, myocardial infarction, troponin I leakage, and echocardiographic parameters were comparable (p=NS). RA-CABG demonstrated significantly higher TTF maximum, mean and minimum flow (p<.001) with lower Pulsatility Index (p<.001), either in the circumflex and the right coronaries. Compared to SVG-grafting, significantly higher GFR was found in RA-CABG on the circumflex (p=.001) and right (p=.028) coronaries. 38.1+/-0.9 SE months follow-up resulted in higher survival and freedom from cardiac events in RA-CABG. Better TTF and GFR were demonstrated in OP-CABG, CPB-CABG, diabetics, non-diabetics, either on the circumflex and right coronary systems (p<.05). Better mean flow was detected in RA-CABG on the circumflex in the elderly (p=.04) and the young (p=.05).

CONCLUSIONS

RA-CABG demonstrated better TTF and GFR results compared to SV-CABG. These data may contribute to explain the survival benefit of arterial revascularization already reported.

Does bilateral internal thoracic artery grafting increase long-term survival of diabetic patients?

BACKGROUND

The purpose of the present study was to determine whether long-term survival in diabetic patients increased after bilateral internal thoracic artery (BITA) coronary bypass compared with matched patients with single internal thoracic artery (SITA) coronary bypass.

METHODS

The propensity for BITA was determined using logistic regression analysis and each BITA patient was matched with one SITA patient. Between January 1992 and March 2002, 980 matched diabetic patients (490 BITA versus 490 SITA) underwent coronary artery bypass surgery. Long-term survival data were obtained from the National Death Index (mean follow-up, 4.7 +/- 3.0 years). Groups were compared by Cox proportional hazard models and Kaplan-Meier survival plots.

RESULTS

Multivariate Cox regression analysis determined that BITA grafting had no significant effect on long-term survival (hazard ratio 0.89, 95% confidence interval: 0.69 to 1.14, p = 0.343). There were no differences in 30-day mortality (3.9% for BITA versus 3.7%, p = 0.999) and major postoperative complications except for length of stay (11.4 days for BITA versus 12.7 days, p < 0.001). Five-year survival rate was 79.9% in the BITA group and 75.7% in the SITA group (p = 0.252). There was no difference in 5-year survival rate between matched patients younger than 60 or from 70 to 79 years old. However, BITA patients aged 60 to 69 years had better 5-year survival rates (84.1% versus 71.0%, p = 0.0196), whereas the opposite was observed in patients aged more than 79 years (5-year survival for BITA 43.1% versus 70.0%, p = 0.016).

CONCLUSIONS

Bilateral internal thoracic artery grafting had no significant effect on long-term survival for diabetic patients, but it may increase long-term survival in patients aged 60 to 69 years, whereas SITA grafting may be beneficial for patients more than 79 years old.

[Arterial grafts in coronary surgery for diabetic patients]

Surgical revascularization allows especially for the diabetic patient with coronary multi-vessel disease a superior long-termperspective compared to percutaneous coronary interventions. However, the specific advantages and also risks associated with the expanded use of arterial grafts as coronary conduits in diabetics are not clearly answered. A systemic analysis of the current literature underlines the following statements: The radial artery is, compared to the internal mammary artery, to a higher extent prone to atherosclerosis, especially in diabetic patients. Better long-term survival for patients with bilateral IMA-grafts has also been assessed for diabetic patients. The risk of thoracic wound infections is not obligatory increased for diabetics with double IMA-grafts. Revascularization with radial arteries can be performed with low perioperative risks. Long-term results or studies on radial artery bypass grafting especially in diabetics are not available. In our own experience (3,548 isolated coronary operations, 01/2001 until 05/2005), diabetic patients have no increased perioperative mortality, even when using more complex arterial grafting. Conclusively, diabetic patients should also significantly benefit from the use of the second mammary artery. Regarding conduit quality, a second IMA appears favorable over the radial artery.

Does Diabetes Affect the Postoperative Outcomes After Total Arterial Off-Pump Coronary Bypass Surgery in Multivessel Disease?

BACKGROUND

Previous studies have reported conflicting results regarding the adverse effects of diabetes on surgical outcomes after coronary artery bypass grafting (CABG). We reviewed our experience to determine the impact of diabetes on early and midterm surgical outcomes of patients with multivessel disease who underwent total arterial revascularization with avoidance of cardiopulmonary bypass.

METHODS

Between January 1998 and December 2003, 517 patients with multivessel disease underwent total arterial off-pump CABG; 214 were diabetic (DM group) and 303 were nondiabetic (NDM group). The DM group was sicker than the NDM group (more left ventricular dysfunction, postinfarction angina, previous myocardial infarction, and chronic renal failure). Mean follow-up period was 34 +/- 17 months. The multivariate risk factors for operative mortality, one-year angiographic patency, and midterm survival were analyzed.

RESULTS

Mean numbers of distal anastomoses were not different between the two groups (DM, 3.1 +/- 0.9; NDM, 3.0 +/- 0.8). Operative mortality was 1.4% (DM, 1.4% vs NDM, 1.3%; p = not significant [ns]). No differences were found in the incidences of postoperative morbidities, including mediastinitis and superficial wound problems, between the two groups. In immediate postoperative angiography, the patency rates were 99.2% in the DM and 98.9% in the NDM group (p = ns). One-year patency rates in angiography were also similar between the two groups (DM, 96.0%; NDM, 95.4%; p = ns). Multivariate analysis indicated that diabetes was not an independent risk factor of steno-occlusion at one-year follow-up angiography. Five-year cumulative survival was 87.7 +/- 4.1% in the DM, and 94.2 +/- 1.4% in NDM (p = ns) group. Five-year freedom from cardiac death was 99.0 +/- 0.7% in the DM, and 97.4 +/- 1.0% in the NDM (p = ns) group. Old age (age > 75 years) and chronic renal failure were independent risk factors for lower midterm survival. Our study failed to demonstrate that diabetes was an independent risk factor for lower midterm survival.

CONCLUSIONS

Diabetes mellitus did not affect the early postoperative and midterm results, including one-year graft patency, in patients with multivessel disease undergoing total arterial and off-pump CABG.

Compromised arterial function in human type 2 diabetic patients

Diabetes is associated with a perturbation of signaling pathways in vascular tissue, which causes vasomotor dysfunction such as hypertension and accelerated atherosclerosis. In the present study, the mechanisms of vasomotor dysfunction, Akt (Thr308 and Ser473) phosphorylation and expression of endothelial NO (nitric oxide) synthase, and inducible NO synthase were investigated in human diabetic internal mammary arteries. The phospho-Akt (Thr308) level in arteries from diabetic patients was reduced to about one-half of the level in nondiabetic patients, suggesting impaired insulin signaling in human diabetic vascular tissue. Augmented vasoconstriction was observed in diabetic arteries, due in part to deficiency of basal and stimulated NO production. This correlated with decreased endothelial NO synthase expression and activity in diabetic vessels. The sensitivity of diabetic vessels to the NO donor, sodium nitroprusside, was reduced as well, suggesting that NO breakdown and/or decreased sensitivity of smooth muscle to NO are also responsible for abnormal vasoconstriction. In addition, the abnormal vasoconstriction in diabetic vessels was not completely abolished in the presence of Nomega-nitro-L-arginine methyl ester, revealing that NO-independent mechanisms also contribute to vasomotor dysfunction in diabetes. In conclusion, diabetes downregulates the Akt-signaling pathway and compromises human arterial function through a decrease in NO availability as well as through NO-independent mechanisms.

Bilateral versus single internal thoracic artery grafting in oral-treated diabetic subsets: comparative seven-year outcome analysis

BACKGROUND

Recent interest has focused on the use of arterial conduits in diabetic subsets. To date, the long-term benefits of bilateral internal thoracic artery (BITA) grafting in this subgroup remain in question.

METHODS

Two hundred eighty-five consecutive oral-treated diabetics operated on nonemergent basis (1996 to 1998) were compared according to the surgical technique, left-sided skeletonized BITA (n = 228) or single internal thoracic artery- saphenous veins (SITA) (n = 57). Patients with chronic lung disease, usually preselected to SITA grafting, were not included.

RESULTS

The respective grafts to patient ratio was 3.1 +/- 1 and 3.2 +/- 0.8 for the SITA and BITA groups (p = NS). Complementary conduits used in the BITA group were gastroepiploic arteries (25%) and saphenous veins (13%). Early outcome was comparable, including the incidence of deep sternal infections (1.8% in both groups). During follow-up (range, 4 to 7.5 years; median, 5), there were less repeat revascularizations (4.4% vs 12.3%, p = 0.025) and major adverse cardiac events (MACE) (11.2% vs 36.8%, p < 0.0001) in the BITA group. At 7 years, survival (Kaplan-Meier) (75% vs 59%, p = 0.006, log-rank), freedom from cardiac mortality (92% vs 68%, p < 0.0001), and freedom from MACE (70% vs 59%, p = 0.004) were superior in the BITA group. Multivariate analysis identified the use of BITA as a protective factor against the occurrence of late cardiac mortality (odds ratio [OR] 0.2) and MACE (OR 0.3); conversely, SITA-saphenous vein arrangements increased the risk by fivefold (OR 5, confidence interval limits [CL] 1.6 to 16.6, p = 0.005) and threefold (OR 3.3, CL 1.5 to 9, p = 0.005), respectively.

CONCLUSIONS

Left-sided BITA grafting confers improved long-term survival and event-free survival in oral-treated diabetics. We, therefore, recommended this approach in this diabetic subset.

Should the internal thoracic artery be skeletonized?

Traditionally, the internal thoracic artery is harvested as a pedicle. In contemporary cardiac surgical practice, however, certain surgeons practice the internal thoracic artery-skeletonization technique. A systematic review of clinical studies reporting on the use of skeletonized internal thoracic arteries (SKT-ITA) has not yet been performed. The primary aim of this review article is to examine comprehensively the entire body of evidence regarding the use of SKT-ITA. In particular, we aimed to analyze the effects of skeletonization on sternal blood supply, wall damage and blood flow in the harvested vessel, postoperative graft patency, and clinical outcome. Advantages and disadvantages of the skeletonization technique are highlighted and discussed.

Bilateral internal thoracic artery grafting in diabetic patients: short-term and long-term results of a 515-patient series

BACKGROUND

Despite potential long-term benefits, bilateral internal thoracic artery grafting in diabetics remains controversial because of the risk of sternal infection. We sought to assess the short- and long-term outcome after left-sided bilateral internal thoracic artery grafting and to determine the configuration of choice in diabetic subsets.

METHODS

Between 1996 and 2001, 515 diabetics underwent isolated left-sided skeletonized bilateral internal thoracic artery grafting. The outcome of 468 consecutive oral-treated diabetics and 47 selective insulin-treated patients was analyzed. Patients undergoing T-grafting were compared with those undergoing in situ bilateral internal thoracic artery arrangements.

RESULTS

The respective rates for early mortality and sternal infections were 2.4% and 1.9% in oral-treated diabetics and 6.3% and 4.3% in insulin-treated diabetics. Multivariate correlates of sternal infection were chronic lung disease (odds ratio, 10), obesity (odds ratio, 7), reoperation (odds ratio, 22), and a creatinine level of 2 mg/dL or more (odds ratio, 8). Five-year survival was 82%. The T-graft (n = 437) and in situ (n = 162) subgroups had comparable baseline profiles. Freedom from cardiac mortality at 6.5 years was 95.6% and 87.6% (P =.277), and freedom from repeat revascularization was 91.5% and 92.7% (P =.860), respectively. The choice of bilateral internal thoracic artery configuration did not appear as a correlate of mortality, cardiac mortality, or major adverse cardiac events. Complementary right-sided gastroepiploic artery (hazard ratio, 0.36) and sequential (hazard ratio, 0.55) grafting were identified as protective factors against the occurrence of major adverse cardiac events.

CONCLUSIONS

Routine skeletonized bilateral internal thoracic artery grafting can be implemented safely in oral-treated diabetics. This strategy is associated with a favorable late cardiac outcome and is thus recommended. Both left-sided bilateral internal thoracic artery configurations provide comparable short- and long-term outcomes.

Influence of type 2 diabetes on functional and structural properties of coronary artery bypass conduits

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.

Bilateral internal thoracic artery grafting in insulin-treated diabetics: should it be avoided?

BACKGROUND

It has been advocated that skeletonized bilateral internal thoracic artery (BITA) grafting may be implemented safely in diabetics, thus bestowing these patients with the long-term benefits of this strategy. However, the feasibility of this approach in insulin-treated patients has yet to be determined.

METHODS

One-hundred twenty-four insulin-treated diabetics, operated on between April 1996 and December 2001, were compared according to the surgical technique used: BITA (n = 50) or single internal thoracic artery (SITA; n = 74). In the latter, complementary grafts used were saphenous veins and radial arteries.

RESULTS

The groups had comparable risk profiles, with the exception of more neurologic events in the SITA group (21% vs 4%, p = 0.008). There was no significant difference in 30-day mortality (6% vs 4%, p = 0.684), nor in the incidence of neurologic complications (2% vs 8%, p = 0.240). The rate of sternal infection was comparable (4% vs 2.7%, p = 1.000). Use of BITAs was associated with a lower return of angina (4% vs 20%, p = 0.025), less cardiac events (17% vs 38%, p = 0.01), and reduced cardiac mortality (none vs 10%, p = 0.04). Despite the similar 6-year survival (80.5% and 77.4%, p = NS), cardiac-related event-free survival was better in BITA patients (69% vs 23%, p < 0.0001). Multivariate analysis identified use of BITA as a protective factor resulting in less return of angina (p = 0.007) and improved cardiac-related event-free survival (p = 0.001).

CONCLUSIONS

Skeletonized BITA grafting can be performed in insulin-treated diabetics at acceptable risk. This approach may confer improved cardiac outcome. Thus, it should be considered in selected patients.