Difference in acetylcholine-induced nitric oxide release of arterial and venous grafts in patients after coronary bypass operations

Coronary artery bypass grafting transiently improves myocardial flow reserve in patients with impaired left ventricular function

BACKGROUND

Myocardial flow reserve (MFR) derived from 13N-ammonia positron emission tomography is an index used to evaluate ischemic cardiomyopathy and predict the prognosis of patients with coronary artery disease (CAD). This study aimed to evaluate the short-term changes in MFR in patients who underwent coronary artery bypass grafting (CABG). In addition, as a reference, we showed the changes in MFR in the percutaneous coronary intervention (PCI) and optimal medical therapy (OMT) patient groups.

METHODS

To determine the short-term effects of CABG in CAD with left ventricular dysfunction, myocardial blood flow (MBF) and MFR were measured before and after CABG. Additionally, we showed changes in MBF and MFR of the PCI and OMT patient groups during treatment.

RESULTS

We observed that resting MBF did not significantly increase from baseline to post-CABG (0.84 ± 0.32 vs. 0.83 ± 0.23, P = 0.958); however, stress MBF increased significantly from baseline to post-CABG (1.23 ± 0.64 vs. 1.49 ± 0.42, P < 0.001). The global MFR increased significantly from baseline to post-CABG (1.49 ± 0.42 mL/g/min vs. 1.91 ± 0.51 mL/g/min, P < 0.001). Additionally, stress and resting ejection fraction (EF) significantly increased (stress EF: 42 ± 18.7% vs. 50.9 ± 18%, P = 0.005; resting EF: 45.8 ± 19.5% vs. 52.1 ± 19.4%, P = 0.031).

CONCLUSIONS

This study demonstrated that CABG significantly improved MFR in a short period of time with left ventricular dysfunction. These findings suggest that epicardial coronary artery patency restores myocardial microcirculatory dysfunction in the short term.

Multi-Omics Profiling of Human Endothelial Cells from the Coronary Artery and Internal Thoracic Artery Reveals Molecular but Not Functional Heterogeneity

Major adverse cardiovascular events occurring upon coronary artery bypass graft surgery are typically accompanied by endothelial dysfunction. Total arterial revascularisation, which employs both left and right internal thoracic arteries instead of the saphenous vein to create a bypass, is associated with better mid- and long-term outcomes. We suggested that molecular profiles of human coronary artery endothelial cells (HCAECs) and human internal mammary artery endothelial cells (HITAECs) are coherent in terms of transcriptomic and proteomic signatures, which were then investigated by RNA sequencing and ultra-high performance liquid chromatography-mass spectrometry, respectively. Both HCAECs and HITAECs overexpressed molecules responsible for the synthesis of extracellular matrix (ECM) components, basement membrane assembly, cell-ECM adhesion, organisation of intercellular junctions, and secretion of extracellular vesicles. HCAECs were characterised by higher enrichment with molecular signatures of basement membrane construction, collagen biosynthesis and folding, and formation of intercellular junctions, whilst HITAECs were notable for augmented pro-inflammatory signaling, intensive synthesis of proteins and nitrogen compounds, and enhanced ribosome biogenesis. Despite HCAECs and HITAECs showing a certain degree of molecular heterogeneity, no specific markers at the protein level have been identified. Coherence of differentially expressed molecular categories in HCAECs and HITAECs suggests synergistic interactions between these ECs in a bypass surgery scenario.

Impact of the no-touch harvesting technique on the vessel diameter of saphenous vein grafts for coronary artery bypass grafting

Objectives

To explore the impact of the no-touch harvesting technique on the vessel diameter of saphenous vein grafts.

Methods

This retrospective, single-center study enrolled 166 patients who underwent isolated coronary artery bypass grafting using saphenous vein grafts. Saphenous vein grafts were harvested conventionally in 83 patients (conventional group) and using the no-touch technique in 83 patients (no-touch group). We analyzed graft patency and the vessel diameters of saphenous vein grafts in the pre- and postoperative states. The diameter mismatch between the saphenous vein grafts and the coronary artery at the anastomotic site was also measured; preoperative diameter was measured using ultrasound imaging, and the postoperative diameter was measured using electrocardiogram-gated enhanced computed tomography.

Results

A total of 135 saphenous vein grafts (66 and 69 grafts in the conventional and no-touch groups, respectively) were evaluated for postoperative patency. Graft patency was equivalent in the 2 groups (conventional, 96.9% vs no-touch, 100%; P = .24). A detailed evaluation was performed in 109 saphenous vein grafts (52 and 57 grafts in the conventional and no-touch groups, respectively). Saphenous vein graft diameter was significantly distended in the conventional group (preoperative, 2.6 ± 0.7 mm vs postoperative, 3.4 ± 0.5 mm; P < .0001). However, saphenous vein graft diameter did not change in the no-touch group (preoperative, 2.9 ± 0.4 mm vs postoperative 2.8 ± 0.4 mm, P = .33). The diameter mismatch was significantly smaller in the no-touch group (conventional 1.4 ± 0.6 mm vs no-touch 1.0 ± 0.4 mm, P < .0001).

Conclusions

The no-touch technique avoids the expansion of graft diameter and diameter mismatch between the saphenous vein grafts and coronary artery.

Additional survival benefit of bilateral in situ internal thoracic artery grafting with composite radial artery graft in total arterial off-pump coronary artery bypass grafting

OBJECTIVE

This study aimed to elucidate whether the use of bilateral internal thoracic arteries (BITAs) confers additional survival benefits compared with a single internal thoracic artery (SITA) in total arterial grafting with the radial artery.

METHODS

Between 2002 and 2016, 617 patients underwent a bilateral in situ internal thoracic artery grafting with the radial artery as a composite I-graft (BITA-I group) and 516 patients underwent single in situ internal thoracic artery grafting with the radial artery as a composite Y-graft (SITA-Y group). All anastomoses were performed without cardiopulmonary bypass and aortic manipulation. Propensity score matching was performed to adjust covariates and compared the outcomes between the 2 groups. Subanalysis was also performed to evaluate the effects of the BITA-I group on survival according to the covariates using Cox proportional hazards regression analysis.

RESULTS

Propensity score matching yielded 348 well-matched pairs. Early postoperative outcomes were similar in the 2 groups. The BITA-I group showed significantly better survival than the SITA-Y group (79.3% vs 70.2% at 10 years, P = .015). The subanalysis revealed a significantly better survival in the BITA-I group among overall patients (hazard ratio, 0.68; 95% confidence interval, 0.49-0.93). There was a significant positive effect on survival in the BITA-I group among patients without comorbidities or those aged <77 years.

CONCLUSIONS

BITA grafting with the radial artery provides better long-term survival than SITA grafting with the radial artery, which is enhanced among patients aged <77 years with minimum comorbidities.

Conduits' Biology Regulates the Outcomes of Coronary Artery Bypass Grafting

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Accelerated atherosclerosis is common when SVGs, but not arterial grafts, are used for myocardial revascularization during CABG.

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This review will provide an overview of the available data on the most commonly used conduits in CABG, highlighting the differences in their cellular biology, mechanical, biochemical, and vasoconstrictive properties.

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Clinical and scientific evidence support the use of arterial grafts over venous conduits at the time of CABG. These arterial conduits seem to be more protected toward the development of atherosclerosis. Exploring the molecular and cellular mechanisms, of the various cell populations within these conduits, will help unveil the pathways responsible for these protective effects.

Coronary artery bypass graft (CABG) is the gold standard for coronary surgical revascularization. Retrospective, prospective, and meta-analysis studies looking into long-term outcomes of using different conduits have pointed to the superiority of arterial grafts over veins and have placed the internal mammary artery as the standard conduit of choice for CABG. The superiority of the internal mammary artery over other conduits could be attributable to its intrinsic characteristics; however, little is known regarding the features that render some conduits atherosclerosis-prone and others atherosclerosis-resistant. Here, an overview is provided of the available data on the most commonly used conduits in CABG (internal mammary artery, saphenous vein, radial artery, gastroepiploic artery), highlighting the differences in their cellular biology, mechanical, biochemical, and vasoconstrictive properties. This information should help in furthering our understanding of the clinical outcomes observed for each of these conduits.

Implications of coronary artery bypass grafting and percutaneous coronary intervention on disease progression and the resulting changes to the physiology and pathology of the native coronary arteries

Myocardial revascularization can be achieved through 2 different methods: coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). Clinical trials comparing PCI and CABG generally use the composite end points of death, stroke, myocardial infarction and target vessel revascularization to determine superiority. Other effects of these interventions, including the preservation of normal coronary physiology, the response of the coronary tree to stressors and the response of the vessel wall to the revascularization intervention, are not routinely considered, but these may have significant implications for patients in the medium and long term. For PCI, relatively small differences in clinical outcomes have been reported between bare metal and drug-eluting stents, and the latter seems to have inconsistent and somewhat unpredictable effects on the vascular biology of the coronary arteries. In coronary bypass, the use of arterial conduits is associated with superior clinical outcomes, better long-term patency and the preservation of essentially normal coronary function after intervention. This review assembles the clinical, physiological, angiographic and pathological literature currently available and attempts to provide a more complete picture of the effects of CABG and PCI on coronary arteries.

Bilateral vs unilateral internal mammary revascularization in patients with left ventricular dysfunction

AIM

To investigate the survival benefit of bilateral internal mammary artery (BIMA) grafts in patients with left ventricular dysfunction.

METHODS

Between 1996 and 2009, we performed elective, isolated, primary, multiple cardiac arterial bypass grafting in 430 consecutive patients with left ventricular ejection fraction ≤ 40%. The early and long-term results were compared between 167 patients undergoing BIMA grafting and 263 patients using left internal mammary artery (LIMA)-saphenous venous grafting (SVG).

RESULTS

The mean age of the overall population was 60.1 ± 15 years. In-hospital mortality was not different between the two groups (7.8% vs 10.3%, P = 0.49). Early postoperative morbidity included myocardial infarction (4.2% vs 3.8%, P = 0.80), stroke (1.2% vs 3.8%, P = 0.14), and mediastinitis (5.3% vs 2.3%, P = 0.11). At 8-year follow-up, Kaplan-Meier-estimated survival (74.2% vs 58.9%, P = 0.02) and Kaplan-Meier-estimated event-free survival (all cause deaths, myocardial infarction, stroke, target vessel revascularization, heart failure) (61.7% and 41.1%, P < 0.01) were significantly higher in the BIMA group compared with the LIMA-SVG group in univariate analysis. The propensity score matching analysis confirmed that BIMA grafting is a safe revascularization procedure but there was no long term survival (P = 0.40) and event-free survival (P = 0.13) in comparison with LIMA-SVG use.

CONCLUSION

Our longitudinal analysis suggests that BIMA grafting can be performed with acceptable perioperative mortality in patients with left ventricular dysfunction.

Coronary Artery Bypass Graft Versus Percutaneous Coronary Intervention

Background:

Multiple studies have compared coronary artery bypass graft (CABG) with percutaneous coronary interventions (PCI) for coronary revascularization. There is considerable evidence that adherence to medical therapy can affect the outcomes of therapeutic interventions. However, the long-term influence of compliance with recommended medical therapy on the comparative outcomes of CABG versus PCI remains to be defined.

Methods:

All non–ST-segment–elevation myocardial infarction patients undergoing coronary revascularization in an 8-hospital network were followed for up to 8 years to determine medication history and major adverse cardiac events: all-cause mortality, nonfatal myocardial infarction, and reintervention. All mortalities were checked against the Social Security Death Index. Survival curves were derived with Kaplan-Meier methods; hazard ratios were calculated with the Cox proportional hazard model; and propensity score matching was used to account for differences in patient selection.

Results:

Among the 973 CABG and 2255 PCI patients, Kaplan-Meier major adverse cardiac event–free survival curves demonstrated a significant benefit for antiplatelet, lipid-lowering, and β-blocker therapy in both the CABG and PCI groups ( P =0.001 for all 3 medications). Cox regression identified compliance with optimal medical therapy as a more powerful predictor of major adverse cardiac event–free survival than choice of therapy (hazard ratio for noncompliance=2.79; 95% confidence limits, 2.19–3.54; P <0.001; hazard ratio for PCI versus CABG=1.68, 95% confidence limits, 138–2.04; P <0.001). In propensity-matched patients, CABG outcomes were superior to PCI outcomes in patients nonadherent to optimal medical therapy ( P =0.001) but were not different in patients adherent to optimal medical therapy ( P =0.574).

Conclusions:

Regardless of coronary revascularization strategy, medication adherence has a dramatic effect on long-term outcome. Among comparable patients who adhere to optimal medical therapy, outcomes of PCI and CABG may not differ; however, among nonadherent patients, CABG affords better major adverse cardiac event–free survival. Therefore, patient compliance with medical therapy may inform clinical decision making and should be incorporated into all future comparative studies of comparative coronary revascularization strategies.

Simultaneous Noninvasive Assessment of Systemic and Coronary Endothelial Function

BACKGROUND

Normal endothelial function is a measure of vascular health and dysfunction is a predictor of coronary events. Nitric oxide-mediated coronary artery endothelial function, as assessed by vasomotor reactivity during isometric handgrip exercise (IHE), was recently quantified noninvasively with magnetic resonance imaging (MRI). Because the internal mammary artery (IMA) is often visualized during coronary MRI, we propose the strategy of simultaneously assessing systemic and coronary endothelial function noninvasively by MRI during IHE.

METHODS AND RESULTS

Changes in cross-sectional area and blood flow in the right coronary artery and the IMA in 25 patients with coronary artery disease and 26 healthy subjects during IHE were assessed using 3T MRI. In 8 healthy subjects, a nitric oxide synthase inhibitor was infused to evaluate the role of nitric oxide in the IMA-IHE response. Interobserver IMA-IHE reproducibility was good for cross-sectional area (R=0.91) and blood flow (R=0.91). In healthy subjects, cross-sectional area and blood flow of the IMA increased during IHE, and these responses were significantly attenuated by monomethyl-l-arginine (P<0.01 versus placebo). In patients with coronary artery disease, the right coronary artery did not dilate with IHE, and dilation of the IMA was less than that of the healthy subjects (P=0.01). The blood flow responses of both the right coronary artery and IMA to IHE were also significantly reduced in patients with coronary artery disease.

CONCLUSIONS

MRI-detected IMA responses to IHE primarily reflect nitric oxide-dependent endothelial function and are reproducible and reduced in patients with coronary artery disease. Endothelial function in both coronary and systemic (IMA) arteries can now be measured noninvasively with the same imaging technique and promises novel insights into systemic and local factors affecting vascular health.

Multiple arterial grafting for coronary revascularization: "A guide for the perplexed"

The surgical literature abounds with articles extolling the benefits of arterial grafting for patients with advanced coronary artery disease in need of surgical revascularization. However, examination of clinical performance demonstrates that extensive use of arterial grafting is highly selective and generally uncommon. Rather than to merely repeat multiple excellent recent literature reviews, the goal herein is to provide the reader with a guide to the evaluation of the current literature as well as to suggest fruitful areas for further research. More circumspect understanding of the strengths and weaknesses of our current knowledge base will not only help to explain the current apparent disparity between theory and practice but will hopefully inform future decision-making and patient care.

Bilateral internal mammary artery grafting enhances survival in diabetic patients: a 30-year follow-up of propensity score-matched cohorts

BACKGROUND

The prevalence of diabetes mellitus is increasing at an unprecedented rate, affecting nearly 8% of the population. Previous studies have demonstrated a potential benefit for surgical over interventional revascularization in this group of patients. Similarly, studies have shown the superiority of bilateral internal mammary artery (BIMA) grafting over single internal mammary artery (SIMA) grafting in select populations. However, concerns about sternal wound infection have discouraged the use of BIMA grafting in diabetics. Therefore, we studied the long-term results of BIMA versus SIMA grafting in a large population of diabetic patients in whom BIMA grafting was broadly applied.

METHODS AND RESULTS

Between February 1972 and May 1994, 1107 consecutive diabetic patients underwent coronary artery bypass grafting with either SIMA (n=646) or BIMA (n=461) grafting. Optimal matching with the propensity score was used to create matched SIMA (n=414) and BIMA (n=414) cohorts. Cross-sectional follow-up (6 weeks to 30.1 years; mean, 8.9 years) determined long-term survival. There was no difference in operative mortality, sternal wound infection, or total complications between matched SIMA and BIMA groups (operative mortality, 10 of 414 [2.4%] versus 13 of 414 [3.1%]; P=0.279; sternal wound infection, 7 of 414 [1.7%] versus 13 of 414 [3.1%]; P=0.179); total complications, 71 of 414 [17.1%] versus 71 of 414 [17.1%]; P=1.000). Late survival was significantly enhanced with the use of BIMA grafting (median survival: SIMA, 9.8 years versus BIMA, 13.1 years; P=0.001). Use of BIMA was found to be associated with late survival on Cox regression (P=0.003).

CONCLUSION

Compared with SIMA grafting, BIMA grafting in propensity score-matched patients provides diabetics with enhanced survival without any increase in perioperative morbidity or mortality.

Physiological and metabolic effects of grafts in coronary artery bypass surgery

The internal thoracic artery (ITA) has become the gold standard graft material for modern coronary artery bypass grafting (CABG) because of its excellent long-term patency. The use of ITA grafts has also prolonged the postoperative survival of patients when applied to the left anterior descending artery or used bilaterally as 2 grafts for the left coronary system. Moreover, recent large-scale randomized clinical trials comparing the survival rates between CABG and percutaneous coronary intervention (PCI) with stents have shown that CABG is more effective for improving the survival of patients with severe coronary artery disease and/or in those with diabetes mellitus. The fundamental principle underlying these clinical benefits of CABG is the excellent endothelial function of the ITA, which provides physiological and metabolic effects that are beneficial not only for the graft itself, but also for the recipient coronary system. The production of nitric oxide and prostanoids by the ITA endothelium and their beneficial effects on the downstream coronary artery should therefore be taken into consideration when debating the merits of CABG vs. PCI.

First evaluation of real-time nitric oxide changes in the coronary circulation in patients with non-ischaemic dilated cardiomyopathy using a catheter-type sensor

AIMS

No direct method has yet been developed to measure real-time plasma nitric oxide (NO) concentration in humans. In this study, we evaluated a new method for measuring plasma NO concentration in patients with dilated cardiomyopathy (DCM) and in normal controls using a catheter-type sensor.

METHODS AND RESULTS

We simultaneously measured average peak velocity (APV) of the coronary artery flow and change in plasma NO concentration using the NO sensor placed in the great cardiac vein of 10 DCM patients and 10 control subjects. These evaluations were performed in response to sequential intracoronary infusions of acetylcholine (ACh, 10⁻⁸-10⁻⁶ M), N(G)-monomethyl-l-arginine (l-NMMA, 200 µmol) and co-infusion of ACh and l-NMMA. The change in plasma NO concentration in DCM patients was significantly impaired compared with the control group (P < 0.01). Pretreatment with l-NMMA completely suppressed the ACh-induced NO concentration, whereas APV in the left anterior descending coronary artery was partially suppressed in both groups. Plasma NO concentration reached its peak value later than the maximum APV following the injection of ACh (10⁻⁶ M) in both groups.

CONCLUSION

The catheter-type NO sensor could be applied to clinically evaluate the endothelial function (i.e. reduced endothelium-derived NO bioavailability) in patients with cardiovascular diseases.

Impact of purely internal thoracic artery T-graft technique on the mode and quality of surgical myocardial revascularization evaluated by early postoperative coronary angiography

BACKGROUND

The use of the internal thoracic artery for coronary artery bypass has improved the results of such surgery. However, bypass using only the internal thoracic arteries sometimes requires a T-graft. This purely internal thoracic artery T-graft technique has progressively become part of our surgical protocol for coronary artery bypass surgery.

AIMS

The aim of the study was to analyse the impact of this surgical technique on the degree and quality of coronary revascularization using early postoperative angiography.

METHODS

Between January 2004 and December 2006, 148 patients underwent coronary artery bypass surgery exclusively using both internal thoracic arteries in a T-graft configuration. Systematic postoperative angiography was offered to all 148 patients; it was accepted by 108 patients and refused by 40 patients.

RESULTS

There were no statistically significant differences between the two groups. In-patient mortality was 2.02% (n=3) for the whole population studied, and 1.49% (n=2) for the 134 patients who received only coronary artery bypass grafts. The revascularization rate was 89% and 3.46 coronary anastomoses were constructed per patient (range 2-6). Angiography was performed on 108 right internal thoracic artery to left internal thoracic artery anastomoses, 374 anastomoses of internal thoracic arteries to coronary arteries and 382 inter-anastomosis segments: 98% of the anastomoses and segments were patent.

CONCLUSION

The exclusive recourse to the purely internal thoracic artery T-graft technique meant that it has been possible to dispense with other types of graft while achieving complete and effective revascularization of the coronary artery.

Effects of ultrasonic skeletonization of the gastroepiploic artery on endothelial nitric oxide production

OBJECTIVE

: The right gastroepiploic artery (GEA) is a reliable conduit for coronary artery bypass grafting. Recently, ultrasonic skeletonization in graft harvesting has attracted attention as an alternative technique to increase the length and caliber size of grafts. The influence of GEA skeletonization using an ultrasonically activated device with that using an electrosurgical unit was compared from the viewpoint of production of nitric oxide (NO).

METHODS

: Fourteen pigs were used in this study. The GEA were harvested using an ultrasonically activated device (group ultrasonically activated device [USAD], n = 7) or electrocautery (group E, n = 7). Blood sampling was performed at the following three times from the distal end of the GEA: (1) preskeletonization, (2) pedicle, and (3) postskeletonization. Plasma NOx (NO metabolites) levels were measured by chemiluminescent assay. Moreover, in excised specimens, the expression of nitric oxide synthase was examined immunohistologically.

RESULTS

: In group USAD, the preskeletonization basal level of plasma NOx in GEA was 25.7 ± 10.9 μmol/L, which then increased to 26.9 ± 10.5 μmol/L (pedicle) and 32.2 ± 12.1 μmol/L (postskeletonization). In group E, the preskeletonization basal plasma NOx level in GEA was 28.9 ± 11.4 μmol/L, which changed to 27.5 ± 8.9 μmol/L (pedicle) and 21.8 ± 8.3 μmol/L (postskeletonization). The results of multivariate analysis indicated that the patterns of changes in plasma NOx level were significantly different in both groups (P = 0.024). In group USAD, post hoc multiple comparison tests revealed a significant difference between preskeletonization and postskeletonization (P = 0.037).

CONCLUSIONS

: Ultrasonically skeletonized GEA showed increased effective graft length, higher free flow capacity, and increased endothelial NO production than that prepared using an electrosurgical unit.

Early remodeling of lower extremity vein grafts: inflammation influences biomechanical adaptation

BACKGROUND

The remodeling of vein bypass grafts after arterialization is incompletely understood. We have previously shown that significant outward lumen remodeling occurs during the first month of implantation, but the magnitude of this response is highly variable. We sought to examine the hypothesis that systemic inflammation influences this early remodeling response.

METHODS

A prospective observational study was done of 75 patients undergoing lower extremity bypass using autogenous vein. Graft remodeling was assessed using a combination of ultrasound imaging and two-dimensional high-resolution magnetic resonance imaging.

RESULTS

The vein graft lumen diameter change from 0 to 1 month (22.7% median increase) was positively correlated with initial shear stress (P = .016), but this shear-dependent response was disrupted in subjects with an elevated baseline high-sensitivity C-reactive protein (hsCRP) level of >5 mg/L. Despite similar vein diameter and shear stress at implantation, grafts in the elevated hsCRP group demonstrated less positive remodeling from 0 to 1 month (13.5% vs 40.9%, P = .0072). By regression analysis, the natural logarithm of hsCRP was inversely correlated with 0- to 1-month lumen diameter change (P = .018). Statin therapy (beta = 23.1, P = .037), hsCRP (beta = -29.7, P = .006), and initial shear stress (beta = .85, P = .003) were independently correlated with early vein graft remodeling. In contrast, wall thickness at 1 month was not different between hsCRP risk groups. Grafts in the high hsCRP group tended to be stiffer at 1 month, as reflected by a higher calculated elastic modulus (E = 50.4 vs 25.1 Mdynes/cm2, P = .07).

CONCLUSIONS

Early positive remodeling of vein grafts is a shear-dependent response that is modulated by systemic inflammation. These data suggest that baseline inflammation influences vein graft healing, and therefore, inflammation may be a relevant therapeutic target to improve early vein graft adaptation.

Saphenous Vein Grafts Display Poor Endothelium-Dependent and Endothelium-Independent Dilation—Implications for the Pathogenesis of Vein Graft Atherosclerosis

OBJECTIVE

As endothelial dysfunction has been implicated in the pathogenesis of late failure of saphenous vein grafts (SVG), we assessed endothelium-dependent and endothelium-independent vascular responses of SVG in humans.

METHODS

Subjects undergoing angiography after bypass grafting had selective infusions of acetylcholine (ACh, an endothelium-dependent dilator) and sodium-nitroprusside (SNP, an endothelium-independent dilator) into a non-obstructed vein graft. SVG diameters were measured by quantitative coronary angiography. Two matched groups of control subjects, with or without coronary artery disease (CAD), were studied after similar infusions into their femoral arteries.

RESULTS

We assessed 10 subjects with SVG, 8 controls with and 8 without CAD. SVG dilatation to high-dose ACh was 5+/-3%, similar to the femoral arteries of subjects with CAD (10+/-5%), but significantly less than the ACh-related arterial dilatation in the non-CAD group (16+/-2%, p=0.02). Similarly, dilatation of SVG after SNP infusion was 9+/-3%, which was not significantly different from the nitrate responses of femoral arteries in the CAD group (21+/-5%), but significantly poorer than in the non-CAD subjects (27+/-5%, p=0.02).

CONCLUSION

Saphenous vein bypass grafts display poor endothelium-dependent and endothelium-independent vascular responses in vivo, compared with healthy systemic arteries. This may contribute to the pathogenesis of accelerated atherosclerosis seen in SVG.

Coronary bypass surgery in kawasaki disease in a four-year-old patient: case report

Kawasaki disease is an acute vasculitis syndrome of unknown etiology that mainly affects small and medium-sized arteries, particularly the coronary arteries. This disease is rarely seen in infants and young people in Turkey. In this short report, we present a four-year-old patient who has Kawasaki disease associated with coronary artery aneurysm and underwent coronary bypass grafting.

Lower extremity vein graft failure: a translational approach

Abstract

Patients with the most severe manifestations of lower extremity arterial occlusive disease often require peripheral bypass surgery for limb salvage and preservation of function. Although good quality saphenous vein offers the most durable conduit for reconstruction, 5-year failure rates are 30–50% and have remained largely unchanged for the past two decades. The majority of these failures occur within the first year of implantation, which is regarded as the most biologically active time during which the vein graft adapts to the arterial environment. Although intimal hyperplasia is generally regarded as the primary culprit of vein graft failure, geometric remodeling of the healing vein graft has recently emerged as a potentially significant contributing factor. While hemodynamic forces, including an increase in shear stress and wall tension, are undoubtedly central to the magnitude and direction of vein graft remodeling, we have determined that these forces alone cannot account for the extent of variability noted in early remodeling patterns. Therefore, we hypothesize that circulating factors, such as mediators of inflammation, may modulate the vein graft response to mechanical forces. This article reviews the definition and diagnosis of vein graft failure and summarizes our current efforts to understand the mechanisms of normal and abnormal vein graft adaptation to the arterial environment.

Early results of off-pump coronary artery bypass grafting for patients on chronic renal dialysis

OBJECTIVE

Renal dialysis is one of the independent risk factors for coronary artery bypass graft surgery. Off-pump coronary artery bypass grafting (OPCAB) may become a good option for these patients. In this study, early results as well as surgical techniques of OPCAB in dialysis patients were analyzed compared with non-dialysis patients.

METHODS

Between July 1997 and December 2002, 471 consecutive patients who underwent OPCAB were enrolled in this study. Among them, 20 patients (4.2%) had received hemodialysis regularly for more than 3 months until the operation. Severity of coronary artery disease or clinical presentations had no significant difference, however, left ventricular function was significantly impaired in dialysis patients.

RESULTS

The average number of anastomosis was 2.8 +/- 1.0 in the dialysis group and 3.2 +/- 1.0 in the non-dialysis group (p=0.056). Twelve patients (60.0%) received 3 or more bypass grafts in the dialysis group. Among them, 6 patients were revascularized only by in-situ or composite arterial conduits using bilateral internal thoracic arteries with or without the gastroepiploic artery. No patients required aortic clamping in the dialysis group. There was no mortality or morbidity in dialysis patients. Perioperaitve bleeding and mechanical ventilation time in the intensive care unit was similar in both groups. No dialysis patients required prolonged mechanical ventilation and hemodialysis from the beginning of the operation to extubation.

CONCLUSION

The rationale for OPCAB for dialysis patients has been established. Total arterial revascularization without aortic clamping is applicable for dialysis patients who require multivessel bypass grafts.

Accelerated graft disease in a composite saphenous vein with internal thoracic artery in a chronic renal dialysis patient

A 59-year-old man with 18-year history of renal dialysis due to chronic nephritis suffered coronary artery disease, which was complete occlusion of the right coronary artery and diffuse 90% stenosis of the proximal left anterior descending artery. Off-pump coronary artery bypass grafting was performed. Saphenous vein (SV) was anastomosed with left internal thoracic artery (ITA) as a T-graft. Left ITA was anastomosed to the left anterior descending artery. The end of SV was sewn on the posterior descending artery. Coronary and graft angiography performed 2 weeks after the operation showed good patency with good distal run-off of both left ITA and SV. Three months after the operation, he was admitted with unstable angina. Angiography revealed accelerated SV graft stenosis without any change of prior coronary disease. However, angiography 7 months after the operation revealed complete obstruction of the SV graft when he was admitted because of recurrent anginal pain.

Coronary revascularization in the 21st century. Emphasis on contributions by Japanese surgeons

The first three decades of coronary artery surgery have provided the foundation for the next century of this evolution. It is apparent that a multitude of events including the development of cardioplegia, improving surgical instrumentation, technological advances including endoscopic approaches and computer assisted robotics and biologic discoveries such as the role of the endothelium have provided the underpinnings for improved surgical outcomes. However, the single most important determinant of late results is the type of bypass conduit used for grafting. Thus, use of the left internal thoracic artery (ITA) grafted to the left anterior descending coronary is a more important determinant of survival than is any other factor (progression of coronary artery disease, increased age, poor left ventricular function, diabetes, female gender and off-pump operations). Use of two ITAs provides further benefit and it is likely that three or more arterial conduits will be shown to be advantageous in this regard in due time. Japanese cardiothoracic surgeons have made significant contributions to the continuing evolution of coronary bypass surgery and particularly to the advance of arterial conduits. This report will address those contributions to this evolution.

Comparison of endothelium-dependent vasoactivity of internal mammary arteries from hypertensive, hypercholesterolemic, and diabetic patients

BACKGROUND

Endothelium-dependent relaxation is abnormal in a variety of diseased states. Despite the widespread use of the internal mammary artery (IMA) in coronary artery bypass grafting, there is a lack of comparative studies on IMA endothelial-dependent function in patients with major cardiovascular risk factors.

METHODS

An IMA segment from 48 selected patients undergoing coronary artery bypass grafting was harvested intraoperatively and assigned to one of four groups (n = 12): diabetics requiring therapy, hypertensives, hypercholesterolemic, and nondiabetic-normotensive-normocholesterolemic patients. Internal mammary artery specimens were cut into rings and suspended in organ bath chambers, and the isometric tension of vascular tissues was recorded. The IMA rings were (1) precontracted with norepinephrine, and the endothelium-derived relaxation was evaluated by cumulative addition of acetylcholine, (2) contracted with cumulative concentrations of endothelin-1, and (3) contracted with the nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine. Furthermore, the release of prostacyclin by the IMA rings was directly measured during basal tone conditions and at the end of the various pharmacologic interventions. Histology of IMA rings was randomly performed.

RESULTS

The results obtained in these experiments showed that IMA rings harvested from hypertensive patients have the greatest impairment of endothelium-dependent response to relaxant and contracting stimuli (p < 0.01 versus nondiabetic-normotensive-normocholesterolemic tissues; p < 0.05 versus hypercholesterolemic and diabetic tissues) and prostacyclin release in normal and stimulated conditions. To a lesser extent, hypercholesterolemic and diabetic tissues show similar depression (diabetic > hypercholesterolemic) both of relaxation and prostacyclin production, with respect to nondiabetic-normotensive-normocholesterolemic specimens (p < 0.05). Histology findings (scanning electron microscopy) did not differ in multiple sections from vessel studies.

CONCLUSIONS

Major cardiovascular risk factors affect the endothelium-dependent vasoactive homeostasis of human IMA differently. Depression of relaxation is highest in patients with a history of hypertension. These findings may be pertinent to early and long-term treatment of patients undergoing coronary artery bypass grafting.

Adenovirus-mediated gene transfer of human inducible nitric oxide synthase in porcine vein grafts inhibits intimal hyperplasia

OBJECTIVE

The aim of this study is to determine whether adenoviral inducible nitric oxide synthase (iNOS) gene transfer could inhibit intimal hyperplasia (IH) in porcine internal jugular veins interposed into the carotid artery circulation.

METHODS

Porcine internal jugular veins were transduced passively with 1 x 10(11) particles of an adenoviral vector carrying either the human iNOS (AdiNOS) or beta-galactosidase (AdlacZ) cDNA for 30 minutes and then interposed into the carotid artery circulation. Segments of each vein graft were maintained in an ex vivo organ culture to measure nitrite accumulation, a marker of nitric oxide synthesis. The grafts were analyzed immunohistochemically for the presence of neutrophils, macrophages, and leukocytes by staining for myeloperoxidase, ED1, and CD45, respectively, at 3 (n = 4) and 7 (n = 4) days. Morphometric analyses and cellular proliferation (Ki67 staining) were assessed at 3 (n = 4), 7 (n = 4), and 21 days (n = 8).

RESULTS

AdlacZ-treated vein grafts demonstrated high levels of beta-galactosidase expression at 3 days with a gradual decline thereafter. Nitrite production from AdiNOS-treated vein grafts was approximately fivefold greater than AdlacZ-treated grafts (P =.00001). AdiNOS or AdlacZ treatment was associated with minimal graft inflammation. Cellular proliferation rates were significantly reduced in AdiNOS-treated grafts as compared with controls at both 3 (41%, P =.000004) and 7 days (32%, P =.0001) after bypass. This early antiproliferative effect was most pronounced at the distal anastomosis (65%, P =.0005). The iNOS gene transfer reduced the intimal/medial area ratio in vein grafts at 7 (36%, P =.009) and 21 days (30%, P =.007) versus controls. This inhibition of IH was again more prominent in the distal segments of the grafts (P =.01).

CONCLUSION

Adenovirus-mediated iNOS gene transfer to porcine internal jugular vein grafts effectively reduced cellular proliferation and IH. Although iNOS gene transfer reduced IH throughout the entire vein graft, the most pronounced effect was measured at the distal anastomosis. These results suggest potential for iNOS-based genetic modification of vein grafts to prolong graft patency.

S-nitrosothiols cause prolonged, nitric oxide-mediated relaxation in human saphenous vein and internal mammary artery: therapeutic potential in bypass surgery

1. Reduced endothelial nitric oxide (NO) production in conduit vessels for coronary artery bypass grafting (CABG) has been implicated in post-operative complications, including spasm. 2. The brief effects of existing NO donors limits their applicability to improving patency of graft vessels. RIG200 is a novel S-nitrosothiol that might have advantages over conventional drugs because it has sustained effects in areas of endothelial damage. 3. Here we tested the hypothesis that RIG200 and S-nitrosoglutathione (GSNO) have prolonged, NO-mediated effects in human saphenous vein (SV) and internal mammary artery (IMA), compared with glyceryl trinitrate (GTN) and sodium nitroprusside (SNP). 4. 84 SV and 80 IMA rings from 64 patients undergoing CABG were studied in vitro. Rings were precontracted with phenylephrine (EC(80) concentration) and the functional integrity of the endothelium tested with acetylcholine (10 microM). 5. Relaxation of precontracted SV and IMA rings to GTN and SNP (0.01 - 10 microM) generally recovered fully on washout. In contrast, responses to RIG200 and GSNO were sustained during washout (30 min). Sustained relaxation was reversed by the NO scavenger, ferrohaemoglobin (10 microM) but not by the NO synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (100 and 250 microM in SV and IMA respectively). 6. Pretreatment (30 min) of SV with both S-nitrosothiols (10 microM) inhibited phenylephrine-induced contraction for >180 min, compared with <90 min for GTN. In IMA, contractility was suppressed to 49+/-4% (GSNO) and 26+/-4% (RIG200) of baseline after 240 min washout. 7. Pretreatment of bypass conduits with S-nitrosothiols might improve their patency in the early post-operative period.

Benefits accruing to grafting of the right internal thoracic artery to the left anterior descending artery in coronary artery bypass grafting

OBJECTIVES

We have investigated the effects and outcome from grafting the right internal thoracic artery to the left anterior descending artery in coronary artery bypass grafting.

METHODS

We analyzed the findings in 185 patients who underwent coronary artery bypass grafting involving right internal thoracic artery-left anterior descending artery bypass. The survival rate, cardiac events related to the right internal thoracic artery-left anterior descending artery graft, and graft patency were investigated. In cardiac catheterization, the production of nitric oxide from the endothelium of the internal thoracic artery was measured as the plasma nitrite and nitrate levels by the Griess reaction. The reactions to acetylcholine infusion (5 micrograms) in the right internal thoracic artery (n = 4) were compared to those in the left internal thoracic artery (n = 9) grafts.

RESULTS

The hospital mortality rate was 0.5%. The actuarial survival rate at 11 years after operation was 98.81%. The rate of freedom from cardiac events at 11 years after operation was 92.08%. The rate of patency of the right internal thoracic artery-left anterior descending artery was 97.0% in 133 patients. Nitric oxide production was calculated as (total nitrite plus nitrate production in response to stimulation by acetylcholine-total nitrite plus nitrate level before acetylcholine load)/(total nitrite plus nitrate level before acetylcholine load). There was no significant difference in changes in plasma concentration in response to acetylcholine stimulation between the right internal thoracic artery-left anterior descending artery and left internal thoracic artery-left anterior descending artery groups (20 +/- 29% versus 5 +/- 10%).

CONCLUSIONS

The right internal thoracic artery-left anterior descending artery grafts exhibited good patency and release of nitric oxide in response to acetylcholine loading, similar to left internal thoracic artery-left anterior descending artery grafts.