Vein graft failure: from pathophysiology to clinical outcomes

Role of Perivascular Adipose Tissue in Vein Remodeling

Perivascular adipose tissue (PVAT) plays a crucial, yet underexplored, role in vein remodeling, which occurs after bypass surgery using a venous graft or creation of arteriovenous fistulae for hemodialysis access. PVAT exhibits significant heterogeneity in phenotype and tissue composition depending on the vascular bed, as well as its anatomic location within the vasculature. Through the excretion of adipokines, cytokines, and chemokines, PVAT can shape the vascular response to local and systemic perturbations. Moreover, the active exchange of cells reinforces the bidirectional cross talk between the vessel wall and PVAT. In this review, we describe the role of PVAT in relation to postinterventional vein remodeling, specifically focusing on the effect of surgery on the PVAT phenotype. Moreover, we discuss the pathophysiological mechanisms that ultimately affect clinical outcomes and highlight the therapeutic potential of PVAT to improve vein remodeling.

Myocardial Revascularization in Patients with Diabetes and Heart Failure-A Narrative Review

Heart failure and diabetes mellitus are major contributors to global morbidity and mortality, with their prevalence continuously rising, primarily due to aging populations and improvements in healthcare. These conditions often coexist or develop sequentially, leading to complex interactions that significantly influence the progression and management of both diseases. Furthermore, heart failure and diabetes are commonly associated with coronary artery disease, which presents a unique challenge in clinical management, particularly in the context of myocardial revascularization. The presence of diabetes exacerbates atherosclerotic progression and impairs endothelial function, while heart failure complicates the perfusion and recovery of myocardial tissue post-intervention. This narrative review delves into the underlying mechanisms contributing to revascularization failure in patients with heart failure and diabetes, emphasizing the importance of understanding these interactions for optimal treatment. The review also summarizes key findings from randomized controlled trials, examining evidence both in the general population and in specific subgroups, including the elderly and patients with left main coronary artery disease, chronic kidney disease, peripheral artery disease, and chronic obstructive pulmonary disease. Understanding these complexities is critical for improving patient outcomes.

Blockade of YAP Mechanoactivation Prevents Neointima Formation and Adverse Remodeling in Arterialized Vein Grafts

BACKGROUND

Bypass surgery using saphenous vein (SV) grafts is commonly performed to revascularize the ischemic heart and lower limbs. These interventions have limited success due to adverse remodeling caused by overproliferation of smooth muscle cells in the intima layer, leading to progressive bypass stenosis. We previously showed that cyclic strain deriving from exposure to coronary flow induces the expression of the matricellular protein thrombospondin-1 in the human SV, promoting activation of progenitor cells normally residing in the adventitia.

METHODS

We analyzed the data of an RNA-sequencing profiling of human SV progenitors subjected to uniaxial strain we previously performed by. Experiments in cell culture, ex vivo, and in vivo vein arterialization models were performed to substantiate findings with particular reference to the role of mechanically activated transcription factors. Validation was performed in vitro and in ex vivo/in vivo models of vein graft disease.

RESULTS

Results of bioinformatic assessment of the RNA-sequencing data indicated Yes-associated protein (YAP) as a possible mechanically regulated effector in pathologic evolution of SV progenitors. Inhibition of YAP by verteprofin-a drug that abolishes the interaction of YAP with Tea Domain DNA-binding proteins-reduced the expression of pathologic markers in vitro and reduced intima hyperplasia in vivo.

CONCLUSIONS

Our results reveal that desensitizing the SV-resident cells to mechanoactivation of YAP is feasible to reduce the graft disease progression.

Nanomedicine-based strategies for the treatment of vein graft disease

Autologous saphenous veins are the most frequently used conduits for coronary and peripheral artery bypass grafting. However, vein graft failure rates of 40-50% within 10 years of the implantation lead to poor long-term outcomes after bypass surgery. Currently, only a few therapeutic approaches for vein graft disease have been successfully translated into clinical practice. Building on the past two decades of advanced understanding of vein graft biology and the pathophysiological mechanisms underlying vein graft disease, nanomedicine-based strategies offer promising opportunities to address this important unmet clinical need. In this Review, we provide deep insight into the latest developments in the rational design and applications of nanoparticles that have the potential to target specific cells during various pathophysiological stages of vein graft disease, including early endothelial dysfunction, intermediate intimal hyperplasia and late-stage accelerated atherosclerosis. Additionally, we underscore the convergence of nanofabricated biomaterials, with a particular focus on hydrogels, external graft support devices and cell-based therapies, alongside bypass surgery to improve local delivery efficiency and therapeutic efficacy. Finally, we provide a specific discussion on the considerations, challenges and novel perspectives for the future clinical translation of nanomedicine for the treatment of vein graft disease.

Electronic vascular conduit for in situ identification of hemadostenosis and thrombosis in small animals and nonhuman primates

Patients suffering from coronary artery disease (CAD) or peripheral arterial disease (PAD) can benefit from bypass graft surgery. For this surgery, arterial vascular grafts have become promising alternatives when autologous grafts are inaccessible but suffer from numerous postimplantation challenges, particularly delayed endothelialization, intimal hyperplasia, high risk of thrombogenicity and restenosis, and difficulty in timely detection of these subtle pathological changes. We present an electronic vascular conduit that integrates flexible electronics into bionic vascular grafts for in situ, real-time and long-term monitoring for hemadostenosis and thrombosis concurrent with postoperative vascular repair. Following bypass surgery, the integrated bioelectronic sensor based on the triboelectric effect enables monitoring of the blood flow in the vascular graft and identification of lesions in real time for up to three months. In male nonhuman primate cynomolgus monkeys, the electronic vascular conduit, with an integrated wireless signal transmission module, enables wireless and real-time hemodynamic monitoring and timely identification of thrombi. This electronic vascular conduit demonstrates potential as a treatment-monitoring platform, providing a sensitive and intuitive monitoring technique during the critical period after bypass surgery in patients with CAD and PAD.

Small-diameter artery grafts engineered from pluripotent stem cells maintain 100% patency in an allogeneic rhesus macaque model

Autologous vascular grafts, the only clinically approved option for small-diameter (<6 mm) revascularizations, require invasive harvesting and have limited availability and variable quality. To address these challenges, we develop a 3-mm-diameter artery graft by using arterial endothelial cells (AECs) derived from pluripotent stem cells (PSCs). After establishing technologies for pure AEC generation and expanded polytetrafluoroethylene (ePTFE) graft coating, we engineer artery grafts by seeding the inner lumen of ePTFE vascular grafts with either major histocompatibility complex (MHC) mismatched unmodified-wild-type (MHC-WT) AECs or MHC class I/II double knockout (MHC-DKO) AECs. Their function is evaluated in a rhesus arterial interposition grafting model. MHC-WT grafts maintained 100% patency for 6 months, significantly better than naked and MHC-DKO grafts. Additionally, the endothelium of MHC-WT grafts is repopulated with host cells, supporting long-term patency. Collectively, our study demonstrates that PSC-derived MHC-WT artery grafts provide an unlimited homogenous resource for allogeneic arterial revascularization.

No-touch vein grafts in coronary artery bypass surgery: a registry-based randomized clinical trial

BACKGROUND AND AIMS

No-touch saphenous vein harvesting may enhance graft patency and improve clinical outcomes after coronary artery bypass grafting (CABG).

METHODS

In this registry-based, randomized trial, patients undergoing CABG were randomly assigned to no-touch or conventional harvesting. The primary composite outcome was the proportion of patients with occluded/stenosed >50% vein graft on coronary computed tomography angiography, or who underwent percutaneous coronary intervention to a vein graft, or died. Secondary outcomes included clinical outcomes and leg wound complications.

RESULTS

A total of 902 patients were enrolled with a mean total number of distal vein anastomoses of 2.0 (SD 0.87). The primary endpoint occurred in 90/454 (19.8%) of patients randomized to no-touch and in 107/446 (24.0%) of patients randomized to the conventional technique [difference, -4.3 percentage points; 95% confidence interval (CI) -10.1-1.6; P = .15] at a mean follow-up time of 3.5 (SD 0.1) years. The composite of death, myocardial infarction, or repeat revascularization at 4.4 (SD 1.3) years occurred in 57/454 (12.6%) and 44/446 (9.9%) in the no-touch and conventional groups, respectively (hazard ratio 1.3; 95% CI, 0.87-1.93). Leg wound complications were more common in patients assigned to no-touch harvesting at 3 months [107/433 (24.7%) vs. 59/427 (13.8%); difference, 10.9 percentage points; 95% CI 5.7-16.1]. At 2 years, 189/381 (49.6%) vs. 91/361 (25.2%) had remaining leg symptoms (difference, 24.4 percentage points; 95% CI 17.7-31.1).

CONCLUSIONS

No-touch vein graft harvesting for CABG was not superior to conventional open harvesting in reducing vein graft failure or clinical events after CABG but increased leg wound complications. The primary outcome requires cautious interpretation due to a lower-than-expected number of primary events.

A comparative study of storage solutions on the biomechanical preservation of human saphenous veins

Storage solutions have a significant impact on the physiological properties of saphenous veins (SV), yet their effects on the biomechanics remained unclear. This study investigated how different storage solutions affect the biomechanical properties of SV. The goal was to find a solution that minimally impacts SV biomechanics, providing an effective method for SV preservation. A total of 108 SV samples (54 axial, 54 circumferential) were randomly divided into four groups: Baseline (tested within 24 h after surgical removal), and three stored for 72 h-sodium lactated ringer's solution (SLR), physiological saline (PS), and Air. Uniaxial tensile experiments were performed, and differences in elastic modulus, maximum stress, and average stress-strain curves were evaluated. In the axial direction, the elastic modulus of SVs stored in SLR was significantly higher than in PS (7.21 ± 2.78 MPa vs. 3.90 ± 1.54 MPa, p = 0.009) and similar to Baseline (vs. 8.52 ± 3.43 MPa), while the PS group did not differ significantly from the Air group (3.90 ± 1.54 MPa vs. 2.50 ± 1.34 MPa, p > 0.99). The maximum stress in SLR was similar to Baseline (1.92 ± 0.82 MPa vs. 1.91 ± 0.58 MPa) and significantly higher than in PS (vs. 1.05 ± 0.56 MPa, p = 0.002). Similar trends could also be observed in the circumferential direction. PS significantly impairs the mechanical performance of SVs, while short-term storage in SLR can effectively preserve the biomechanical characteristics of SVs. SLR may be considered as an effective short-term storage solution for SV.

Non-coding RNAs to treat vascular smooth muscle cell dysfunction

Vascular smooth muscle cell (vSMC) dysfunction is a critical contributor to cardiovascular diseases, including atherosclerosis, restenosis and vein graft failure. Recent advances have unveiled a fascinating range of non-coding RNAs (ncRNAs) that play a pivotal role in regulating vSMC function. This review aims to provide an in-depth analysis of the mechanisms underlying vSMC dysfunction and the therapeutic potential of various ncRNAs in mitigating this dysfunction, either preventing or reversing it. We explore the intricate interplay of microRNAs, long-non-coding RNAs and circular RNAs, shedding light on their roles in regulating key signalling pathways associated with vSMC dysfunction. We also discuss the prospects and challenges associated with developing ncRNA-based therapies for this prevalent type of cardiovascular pathology. LINKED ARTICLES: This article is part of a themed issue Non-coding RNA Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.2/issuetoc.

o8G-miR-6513-5p/BCL2L13 Axis Regulates Mitophagy during Oxidative Stress in the Human Saphenous Vein Endothelial Cells

Venous graft decay (VGD) occurs in coronary artery bypass grafting (CABG), and ischemia-reperfusion oxidative stress injury during the operation is involved in VGD. To explore the cellular phenotypic changes during this process, a stable oxidative stress model of human saphenous vein endothelial cells (HSVECs) is constructed. Through proteomics and cell experiments, it is found that the expression of BCL2L13 is upregulated during oxidative stress of HSVECs, and BCL2L13 regulated mitophagy through receptor-mediated interaction with LC3 and plays a role in cell protection. During oxidative stress, intracellular o8G epigenetic modification occurs, and the o8G modification of miR-6513-5p causes this molecule to lose its targeted regulation of BCL2L13 and participates in the upregulation of BCL2L13. There is a regulatory pathway of o8G modification-BCL2L13-LC3-mitophagy when oxidative stress occurs in HSVECs.

Inhibition of endothelial-to-mesenchymal transition in a large animal preclinical arteriovenous fistula model leads to improved remodelling and reduced stenosis

AIMS

Vein grafts are used for many indications, including bypass graft surgery and arteriovenous fistula (AVF) formation. However, patency following vein grafting or AVF formation is suboptimal for various reasons, including thrombosis, neointimal hyperplasia, and adverse remodelling. Recently, endothelial-to-mesenchymal transition (EndMT) was found to contribute to neointimal hyperplasia in mouse vein grafts. We aimed to evaluate the clinical potential of inhibiting EndMT and developed the first dedicated preclinical model to study the efficacy of local EndMT inhibition immediately prior to AVF creation.

METHODS AND RESULTS

We first undertook pilot studies to optimize the creation of a femoral AVF in pigs and verify that EndMT contributes to neointimal formation. We then developed a method to achieve local in vivo SMAD3 knockdown by dwelling a lentiviral construct containing SMAD3 shRNA in the femoral vein prior to AVF creation. Next, in Phase 1, six pigs were randomized to SMAD3 knockdown or control lentivirus to evaluate the effectiveness of SMAD3 knockdown and EndMT inhibition 8 days after AVF creation. In Phase 2, 16 pigs were randomized to SMAD3 knockdown or control lentivirus and were evaluated to assess longer-term effects on AVF diameter, patency, and related measures at 30 days after AVF creation. In Phase 1, compared with controls, SMAD3 knockdown achieved a 75% reduction in the proportion of CD31+ endothelial cells co-expressing SMAD3 (P < 0.001) and also a significant reduction in the extent of EndMT (P < 0.05). In Phase 2, compared with controls, SMAD3 knockdown was associated with an increase in the minimum diameter of the venous limb of the AVF (1.56 ± 1.66 vs. 4.26 ± 1.71 mm, P < 0.01) and a reduced degree of stenosis (P < 0.01). Consistent with this, neointimal thickness was reduced in the SMAD3 knockdown group (0.88 ± 0.51 vs. 0.45 ± 0.19 mm, P < 0.05). Furthermore, endothelial integrity (the proportion of luminal cells expressing endothelial markers) was improved in the SMAD3 knockdown group (P < 0.05).

CONCLUSION

EndMT inhibition in a preclinical AVF model by local SMAD3 knockdown using gene therapy led to reduced neointimal hyperplasia, increased endothelialization, and a reduction in the degree of AVF stenosis. This provides important proof of concept to pursue this approach as a clinical strategy to improve the patency of AVFs and other vein grafts.

Preoperative methionine restriction induces perivascular adipose tissue browning and improves vein graft remodeling in male mice

Short-term preoperative methionine restriction (MetR) is a promising translatable strategy to mitigate surgical injury response. However, its application to improve post-interventional vascular remodeling remains underexplored. Here we find that MetR protects from arterial intimal hyperplasia in a focal stenosis model and pathologic vascular remodeling following vein graft surgery in male mice. RNA sequencing reveals that MetR enhances browning in arterial (thoracic aorta) perivascular adipose tissue (PVAT) and induces it in venous (caval vein) PVAT. Specifically, Ppara is highly upregulated in PVAT-adipocytes upon MetR. Furthermore, MetR dampens the postoperative pro-inflammatory response to surgery in PVAT-macrophages in vivo and in vitro. This study shows that the detrimental effects of dysfunctional PVAT on vascular remodeling can be reversed by MetR, and identifies pathways involved in MetR-induced browning of PVAT. Furthermore, we demonstrate the potential of short-term preoperative MetR as a simple intervention to ameliorate vascular remodeling after vascular surgery.

Relationship between uric acid to albumin ratio and saphenous vein graft disease in patients with coronary artery bypass graft

OBJECTIVE

Saphenous vein graft disease (SVGD) remains a challenging issue for patients with coronary artery bypass grafting (CABG). It is associated with poor outcomes and atherosclerosis is the major cause of SVGD. Uric acid to albumin ratio (UAR) is a new marker which associated with cardiovascular mortality. We aim to evaluate the relationship between the SVGD and UAR.

METHODS

We retrospectively enrolled 237 patients who underwent elective coronary angiography (CAG) for stable angina or positive stress test results >1 year after CABG. The patients were divided into two groups; SVGD (+) patients and SVGD (-) patients. The SVGD was defined as presence of at least 50% stenosis in at least 1 SVG.

RESULTS

UAR were significantly higher in the SVGD (+) group ( P  < 0.001). Similarly, Hs-CRP, white blood cell count, and neutrophil count were significantly higher in SVGD (+) group ( P  = 0.03, P  = 0.027 P  = 0.01, respectively). In multivariate logistic regression analysis, time interval after CABG [OR = 1.161, 95% confidence interval (CI) 1.078-1.250; P  < 0.001] and UAR (OR = 2.691, 95% CI 1.121-6.459; P  < 0.001) were found to be independent predictors of SVGD.

CONCLUSION

Our results suggested that UAR could be a simple and available marker to predict SVGD in patients with CABG who underwent elective percutaneous coronary intervention.

Investigating the peri-saphenous vein graft fat attenuation index on computed tomography angiography: relationship with progression of venous coronary artery bypass graft disease and temporal trends

BACKGROUND

To clarify the fat attenuation index (FAI) change trend of peri-saphenous vein graft (SVG) and determine the association between FAI and graft disease progression based on CCTA images.

METHODS

Patients with venous coronary artery bypass grafts (CABGs) were consecutively enrolled in this retrospective study. In study 1, 72 patients who had undergone 1, 3, and 5 years of CCTA examinations without graft occlusion were recruited, and generalized estimation equation was used to analyze the peri-SVG FAI change trend over time. In study 2, 42 patients with graft disease progression and 84 patients as controls were propensity score-matched. Generalized linear mixed model and continuous net reclassification improvement (NRI) were used for assessing the associations with graft disease progression. Multivariable Cox regression analysis was used for assessing risk factors predicting cardiac events.

RESULTS

In study 1, both the FAI of proximal right coronary artery and SVG decreased over time. In study 2, the 1-year CTA-derived FAI of grafts and graft anastomosis were independent indicators of graft disease progression at the 3-year CCTA follow-up (graft: odds ratio [OR] = 1.106; 95% confidence interval [CI] = 1.030-1.188, P = 0.006; graft anastomosis: OR = 1.170, 95% CI = 1.091-1.254, P < 0.001). Inclusion of the graft anastomosis FAI significantly improved reclassification compared with graft FAI (continuous NRI = 0.638, 95% CI: 0.345-0.931, P < 0.001). Moreover, The graft anastomosis FAI was found to be a risk factor for cardiac events after CABG and no statistically significant difference was found in the graft FAI (graft anastomosis: HR = 1.158, 95% CI = 1.034-1.297, P = 0.011; graft: HR = 1.116, 95% CI = 0.995-1.251, P = 0.061).

CONCLUSIONS

A synchronism was found in the FAI change trend between native coronary artery and venous graft, which both decreased over time. The CCTA-derived FAI of venous grafts showed the potential of demonstrating SVG disease progression and graft anastomosis served as the optimal measured location.

The Predictive Value of Pan-Immune-Inflammation Value for Saphenous Vein Graft Disease in Post-Coronary Artery Bypass Grafting Patients

Background: Coronary artery bypass grafting (CABG) remains the gold standard treatment for patients with significant coronary artery disease (CAD) and high-risk profiles for percutaneous coronary intervention. Despite the frequent use of saphenous vein grafts (SVGs) in CABG, their patency rates are lower than those of arterial grafts. Identifying noninvasive methods to determine SVG patency is crucial. Aims: This study investigates the relationship between a novel inflammation marker, pan-immune-inflammation value (PIV), and SVG patency in post-CABG patients. Methods: The study included 507 patients who underwent coronary angiography (CAG) due to clinical indications between 2016 and 2023. Patients who had undergone CABG at least one year prior with at least one SGV used were divided into two groups based on the presence or absence of SVG stenosis (SGVS). Results: Among the 507 patients, 244 had SVGS. Patients with SVGS exhibited higher levels of diabetes mellitus and inflammatory markers such as NLR, SII, CAR, and PIV. Multivariate analysis identified PIV as an independent predictor of SVGS. ROC analysis showed that a PIV cut-off value > 315.5 predicted SVGS with 75.8% sensitivity and 68.6% specificity. Conclusions: PIV, a simple and easily measurable marker, demonstrated strong predictive value for SVGS in post-CABG patients.

Stretch-induced damage in endothelial monolayers

Endothelial cells are constantly exposed to mechanical stimuli, of which mechanical stretch has shown various beneficial or deleterious effects depending on whether loads are within physiological or pathological levels, respectively. Vascular properties change with age, and on a cell-scale, senescence elicits changes in endothelial cell mechanical properties that together can impair its response to stretch. Here, high-rate uniaxial stretch experiments were performed to quantify and compare the stretch-induced damage of monolayers consisting of young, senescent, and aged endothelial populations. The aged and senescent phenotypes were more fragile to stretch-induced damage. Prominent damage was detected by immunofluorescence and scanning electron microscopy as intercellular and intracellular void formation. Damage increased proportionally to the applied level of deformation and, for the aged and senescent phenotype, induced significant detachment of cells at lower levels of stretch compared to the young counterpart. Based on the phenotypic difference in cell-substrate adhesion of senescent cells indicating more mature focal adhesions, a discrete network model of endothelial cells being stretched was developed. The model showed that the more affine deformation of senescent cells increased their intracellular energy, thus enhancing the tendency for cellular damage and impending detachment. Next to quantifying for the first-time critical levels of endothelial stretch, the present results indicate that young cells are more resilient to deformation and that the fragility of senescent cells may be associated with their stronger adhesion to the substrate.

Administration of a new nano delivery system coated with Tirofiban to prevent early thrombosis of vein graft

OBJECTIVE

To verify the administration of a new nano delivery system coated with Tirofiban on preventing early thrombosis in vein graft.

METHODS

Forty New Zealand white rabbits were randomly divided into five groups with eight rabbits in each group. The rabbits of all groups underwent jugular vein transplantation, except group I with only neck opening and closing operation. Vein grafts of group II were preprocessed by intravenous injection of normal saline; group III were preprocessed by tirofiban alone; group IV were preprocessed by unloaded nanoparticles of PLGA-PEG; group V were preprocessed by PLGA-PEG coated with tirofiban. Coagulation and platelet function of peripheral and vein graft blood were detected at 1, 2, 4, 12 h and 1, 3, 7, 10, 14 days after operation. Patency rate of vein graft and blood flow index were measured by vascular ultrasound at third, seventh, 10th, and 14th days after operation; two rabbits in each group were randomly sacrificed at the corresponding time of detection. Pathological differences of vein grafts were observed by HE stainin.

RESULTS

The patency rate of vein grafts in group V was significantly higher than that in group II to IV. The platelet and platelet aggregation rate in group V were inhibited in vein graft blood significantly. The post-operative PT and APTT in vein graft blood in group V were increased obviously while the FBG, D-dimer and FDP were significantly inhibited. Except group I, the lumen loss rate of vein grafts in group V was significantly lower than that in other groups, and vein graft blood in group V had a significant lower expression of platelet P-selectin and GP IIb/IIIa receptor than that in other groups.

CONCLUSION

This study proves that PEG-PLGA coated with tirofiban can effectively prevent early vein graft stenosis from thrombosis by inhibition of platelet function, coagulation function.

Pre-Coronary Artery Bypass Grafting Computed Tomography-Based Fractional Flow Reserve Predicts Graft Failure: Implications for Planning Invasive Treatment of Coronary Artery Disease

OBJECTIVE

The aim of the study is to evaluate whether a pre-coronary artery bypass grafting (CABG) coronary computed tomography-based fractional flow reserve (FFR-CT) result at the site of a future anastomosis would predict the graft failure in patients undergoing CABG.

METHODS

In 43 patients who had coronary computed tomography angiography (CCTA) prior to the CABG, follow-up CCTA were acquired >12 months post-CABG procedure. The FFR-CT values were simulated on the basis of the pre-CABG CCTA. Based on follow-up CCTA, the anastomosis sites and the graft patency were determined. The graft failure was defined as either its stenosis >50% or occlusion.

RESULTS

Ninety eight (44 saphenous, 54 left or right internal mammary artery) grafts were assessed. Eighteen grafts from 16 patients were dysfunctional on follow-up CCTA. The FFR-CT values at the location of future anastomosis were higher in dysfunctional than in normal grafts (0.77 [0.71-0.81] vs 0.60 [0.56-0.66], respectively, P = 0.0007). Pre-CABG FFR-CT (hazard ratio = 1.1; 95% CI: 1.012-1.1, P = 0.0230), and bypass graft to right coronary artery (hazard ratio = 3.7; 95% CI: 1.4-9.3 vs left anterior descending artery) were independent predictors of graft dysfunction during follow-up. The optimal threshold of FFR-CT to predict graft failure was >0.68 (sensitivity 88.9% (95% CI: 65.3-98.6), specificity 63.7% (95% CI: 52.2-74.2), positive predictive value 35.6% (95% CI: 28.3%-43.5%), negative predictive value 96.2% (95% CI: 87.2%-99.0%)).

CONCLUSIONS

Pre-CABG functional FFR-CT predicts future coronary bypass graft failure. This shows utility of FFR-CT for guiding coronary revascularization and also suggests significance of physiological assessment prior to CABG.

Dynamic changes in proresolving lipid mediators and their receptors following acute vascular injury in male rats

Acute vascular injury provokes an inflammatory response, resulting in neointimal hyperplasia (NIH) and downstream pathologies. The resolution of inflammation is an active process in which specialized proresolving lipid mediators (SPM) and their receptors play a central role. We sought to examine the acute phase response of SPM and their receptors in both circulating blood and the arterial wall in a rat angioplasty model. We found that the ratio of proresolving to pro-inflammatory lipid mediators (LM) in plasma decreased sharply 1 day after vascular injury, then increased slightly by day 7, while that in arteries remained depressed. Granulocyte expression of SPM receptors ALX/FPR2 and DRV2/GPR18, and a leukotriene B4 receptor BLT1 increased postinjury, while ERV1/ChemR23 expression was reduced early and then recovered by day 7. Importantly, we show unique arterial expression patterns of SPM receptors in the acute setting, with generally low levels through day 7 that contrasted sharply with that of the pro-inflammatory CCR2 receptor. Overall, these data document acute, time-dependent changes of LM biosynthesis and SPM receptor expression in plasma, leukocytes, and artery walls following acute vascular injury. A biochemical imbalance between inflammation and resolution LM pathways appears persistent 7 days after angioplasty in this model. These findings may help guide therapeutic approaches to accelerate vascular healing and improve the outcomes of vascular interventions for patients with advanced atherosclerosis.

Glutathione S-Transferase α4 Alleviates Hyperlipidemia-Induced Vascular Neointimal Hyperplasia in Arteriovenous Grafts via Inhibiting Endoplasmic Reticulum Stress

ABSTRACT

Neointimal hyperplasia causes the failure of coronary artery bypass grafting. Our previous studies have found that endothelial dysfunction is 1 candidate for triggering neointimal hyperplasia, but which factors are involved in this process is unclear. Glutathione S-transferase α4 (GSTA4) plays an important role in metabolizing 4-hydroxynonenal (4-HNE), a highly reactive lipid peroxidation product, which causes endothelial dysfunction or death. Here, we investigated the role of GSTA4 in neointima formation after arteriovenous grafts (AVGs) with or without high-fat diet (HFD). Compared with normal diet, HFD caused endothelial dysfunction and increased neointima formation, concomitantly accompanied by downregulated expression of GSTA4 at the mRNA and protein levels. In vitro, overexpression of GSTA4 attenuated 4-HNE-induced endothelial dysfunction and knockdown of GSTA4 aggravated endothelial dysfunction. Furthermore, silencing GSTA4 expression facilitated the activation of 4-HNE-induced endoplasmic reticulum stress and inhibition of endoplasmic reticulum stress pathway alleviated 4-HNE-induced endothelial dysfunction. In addition, compared with wild-type mice, mice with knockout of endothelial-specific GSTA4 (GSTA4 endothelial cell KO) exhibited exacerbated vascular endothelial dysfunction and increased neointima formation caused by HFD. Together, these results demonstrate the critical role of GSTA4 in protecting the function of endothelial cells and in alleviating hyperlipidemia-induced vascular neointimal hyperplasia in arteriovenous grafts.

Early Injury Landscape in Vein Harvest by Single-Cell and Spatial Transcriptomics

BACKGROUND

Vein graft failure following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. Although previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on vein graft failure. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury.

METHODS

Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing and spatial transcriptomics analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-carotid vein bypass implantation in a canine model (n=4).

RESULTS

Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P<0.05) involved in the activation of endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells, namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and ECM (extracellular matrix) remodeling throughout the vein wall. Subsequent single-nuclei RNA-sequencing analysis supported these findings and further unveiled distinct EC and fibroblast subpopulations with significant upregulation (P<0.05) of markers related to endothelial injury response and cellular activation of ECs, fibroblasts, and vascular smooth muscle cells. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN, FBN1, and VEGFC, in addition to novel genes of interest, such as GLIS3 and EPHA3. These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the spatial transcriptomics and single-nuclei RNA-sequencing data sets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and fibroblasts were notably enriched in the intima and media of distended veins. Finally, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal-transitioning ECs, protomyofibroblasts, and vascular smooth muscle cells in upregulating signaling pathways associated with cellular proliferation (MDK [midkine], PDGF [platelet-derived growth factor], VEGF [vascular endothelial growth factor]), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension.

CONCLUSIONS

Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

External Support of Autologous Internal Jugular Vein Grafts with FRAME Mesh in a Porcine Carotid Artery Model

BACKGROUND

Autologous vein grafts are widely used for bypass procedures in cardiovascular surgery. However, these grafts are susceptible to failure due to vein graft disease. Our study aimed to evaluate the impact of the latest-generation FRAME external support on vein graft remodeling in a preclinical model.

METHODS

We performed autologous internal jugular vein interposition grafting in porcine carotid arteries for one month. Four grafts were supported with a FRAME mesh, while seven unsupported grafts served as controls. The conduits were examined through flowmetry, angiography, macroscopy, and microscopy.

RESULTS

The one-month patency rate of FRAME-supported grafts was 100% (4/4), whereas that of unsupported controls was 43% (3/7, Log-rank p = 0.071). On explant angiography, FRAME grafts exhibited significantly more areas with no or mild stenosis (9/12) compared to control grafts (3/21, p = 0.0009). Blood flow at explantation was higher in the FRAME grafts (145 ± 51 mL/min) than in the controls (46 ± 85 mL/min, p = 0.066). Area and thickness of neo-intimal hyperplasia (NIH) at proximal anastomoses were similar for the FRAME and the control groups: 5.79 ± 1.38 versus 6.94 ± 1.10 mm2, respectively (p = 0.558) and 480 ± 95 vs. 587 ± 52 μm2/μm, respectively (p = 0.401). However, in the midgraft portions, the NIH area and thickness were significantly lower in the FRAME group than in the control group: 3.73 ± 0.64 vs. 6.27 ± 0.64 mm2, respectively (p = 0.022) and 258 ± 49 vs. 518 ± 36 μm2/μm, respectively (p = 0.0002).

CONCLUSIONS

In our porcine model, the external mesh FRAME improved the patency of vein-to-carotid artery grafts and protected them from stenosis, particularly in the mid regions. The midgraft neo-intimal hyperplasia was two-fold thinner in the meshed grafts than in the controls.

Redefining vascular repair: revealing cellular responses on PEUU-gelatin electrospun vascular grafts for endothelialization and immune responses on in vitro models

Tissue-engineered vascular grafts (TEVGs) poised for regenerative applications are central to effective vascular repair, with their efficacy being significantly influenced by scaffold architecture and the strategic distribution of bioactive molecules either embedded within the scaffold or elicited from responsive tissues. Despite substantial advancements over recent decades, a thorough understanding of the critical cellular dynamics for clinical success remains to be fully elucidated. Graft failure, often ascribed to thrombogenesis, intimal hyperplasia, or calcification, is predominantly linked to improperly modulated inflammatory reactions. The orchestrated behavior of repopulating cells is crucial for both initial endothelialization and the subsequent differentiation of vascular wall stem cells into functional phenotypes. This necessitates the TEVG to provide an optimal milieu wherein immune cells can promote early angiogenesis and cell recruitment, all while averting persistent inflammation. In this study, we present an innovative TEVG designed to enhance cellular responses by integrating a physicochemical gradient through a multilayered structure utilizing synthetic (poly (ester urethane urea), PEUU) and natural polymers (Gelatin B), thereby modulating inflammatory reactions. The luminal surface is functionalized with a four-arm polyethylene glycol (P4A) to mitigate thrombogenesis, while the incorporation of adhesive peptides (RGD/SV) fosters the adhesion and maturation of functional endothelial cells. The resultant multilayered TEVG, with a diameter of 3.0 cm and a length of 11 cm, exhibits differential porosity along its layers and mechanical properties commensurate with those of native porcine carotid arteries. Analyses indicate high biocompatibility and low thrombogenicity while enabling luminal endothelialization and functional phenotypic behavior, thus limiting inflammation in in-vitro models. The vascular wall demonstrated low immunogenicity with an initial acute inflammatory phase, transitioning towards a pro-regenerative M2 macrophage-predominant phase. These findings underscore the potential of the designed TEVG in inducing favorable immunomodulatory and pro-regenerative environments, thus holding promise for future clinical applications in vascular tissue engineering.

Intimal hyperplasia, saphenous vein graft disease, and clinical outcomes: Insights from the CTSN VEST randomized trial

BACKGROUND

Diffuse intimal hyperplasia and graft irregularity adversely affect the long-term patency of saphenous vein grafts (SVGs) and clinical outcomes of patients undergoing coronary artery bypass grafting (CABG). The VEST trial evaluated the efficacy of external graft support in limiting the development of intimal hyperplasia (IH) at 1 year postsurgery. In the present secondary analysis, we explored the associations between graft disease and IH and clinical events. We also examined risk factors for early graft occlusion.

METHODS

VEST is a within-patient randomized, multicenter trial that enrolled 224 patients with multivessel coronary disease undergoing CABG surgery, of whom 203 were evaluated by 1 year postsurgery. Intimal hyperplasia, lumen uniformity, graft stenosis, and graft perfusion were measured by intravascular ultrasound and angiography. Major cardiac and cerebrovascular events (MACCE; including death, myocardial infarction, stroke, and revascularization) were recorded over a median follow-up of 3 years.

RESULTS

Worse lumen uniformity, greater stenosis, and worse graft perfusion were associated with higher IH values and an increased incidence of clinical events. Consistent with previous findings, we identified endoscopic vein harvesting, female sex, and transit time flow measurement of pulsatility index and flow as risk factors for SVG occlusion during the first year postsurgery.

CONCLUSIONS

In this secondary analysis of the VEST trial, we observed an association between intimal hyperplasia area and clinical measures of SVG disease at 1 year postsurgery. More severe SVG disease and larger areas of IH were associated with a higher incidence of 3-year MACCE. Ongoing follow-up to 5 years will further elucidate the impact of SVG disease on long-term clinical outcomes of CABG.

Antithrombotic strategies for preventing graft failure in coronary artery bypass graft

Coronary artery bypass graft (CABG) procedures face challenges related to graft failure, driven by factors such as acute thrombosis, neointimal hyperplasia, and atherosclerotic plaque formation. Despite extensive efforts over four decades, the optimal antithrombotic strategy to prevent graft occlusion while minimizing bleeding risks remains uncertain, relying heavily on expert opinions rather than definitive guidelines. To address this uncertainty, we conducted a review of randomized clinical trials and meta-analyses of antithrombotic therapy for patients with CABG. These studies examined various antithrombotic regimens in CABG such as single antiplatelet therapy (aspirin or P2Y12 inhibitors), dual antiplatelet therapy, and anticoagulation therapy. We evaluated outcomes including the patency of grafts, major adverse cardiovascular events, and bleeding complications and also explored future perspectives to enhance long-term outcomes for CABG patients. Early studies established aspirin as a key component of antithrombotic pharmacotherapy after CABG. Subsequent randomized controlled trials focused on adding a P2Y12 inhibitor (such as clopidogrel, ticagrelor, or prasugrel) to aspirin, yielding mixed results. This article aims to inform clinical decision-making and guide the selection of antithrombotic strategies after CABG.

Integrated single-nuclei and spatial transcriptomic analysis reveals propagation of early acute vein harvest and distension injury signaling pathways following arterial implantation

Background

Vein graft failure (VGF) following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. While previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on VGF. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury.

Methods

Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing (snRNA-seq) and spatial transcriptomics (ST) analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-cartoid vein bypass implantation in a canine model (n=4).

Results

Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P < 0.05) involved in the activation of endothelial cells (ECs), fibroblasts (FBs), and vascular smooth muscle cells (VSMCs), namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and extracellular matrix (ECM) remodeling throughout the vein wall. Subsequent snRNA-seq analysis supported these findings and further unveiled distinct EC and FB subpopulations with significant upregulation (P < 0.00001) of markers related to endothelial injury response and cellular activation of ECs, FBs, and VSMCs. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury-response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN (versican), FBN1 (fibrillin-1), and VEGFC (vascular endothelial growth factor C), in addition to novel genes of interest such as GLIS3 (GLIS family zinc finger 3) and EPHA3 (ephrin-A3). These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the ST and snRNA-seq datasets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and FBs were notably enriched in the intima and media of distended veins. Lastly, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal transitioning ECs, protomyofibroblasts, and VSMCs in upregulating signaling pathways associated with cellular proliferation (MDK, PDGF, VEGF), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension.

Conclusions

Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

The stress hyperglycemic ratio can predict the no-reflow phenomenon following saphenous vein graft intervention in patients with acute coronary syndrome

AIMS

The no-reflow phenomenon (NRP) is a common complication of saphenous vein graft (SVG) interventions. The aim of this study was to investigate the effect of the stress hyperglycemia ratio (SHR) on the development of NRP in patients with acute coronary syndrome (ACS) undergoing percutaneous SVG intervention.

METHODS

The study included 223 patients who presented at our center with ACS, had a history of coronary artery bypass graft and underwent a saphenous graft procedure. The relationship between SHR calculated at the time of presentation from glucose and HbA1c values, and the development of NRP evaluated after the procedure with angiography was determined with univariate and multivariate binary regression analysis.

RESULT

The study population was separated into two groups as those who developed and did not develop NRP. Mean age was determined to be significantly higher in the group that did not develop NRP compared to the group with NRP (p: 0.004). Angiographically, the thrombus burden was determined to be significantly higher in the group that developed NRP (p < 0.001). Patients were separated into 3 tertiles according to the SHR level (T1, T2, T3), and the rate of NRP development was determined at a significantly higher rate in the T3 group (p < 0.001).

CONCLUSIONS

This study showed that SHR, a parameter that can be easily calculated noninvasively, is an independent predictor of NRP development in ACS patients undergoing saphenous interventions. In addition, high thrombus burden and predilatation before stenting were also found to be factors that increase the likelihood of developing NRP.

Myeloid PHD2 Conditional Knockout Improves Intraplaque Angiogenesis and Vascular Remodeling in a Murine Model of Venous Bypass Grafting

BACKGROUND

Intraplaque angiogenesis occurs in response to atherosclerotic plaque hypoxia, which is driven mainly by highly metabolically active macrophages. Improving plaque oxygenation by increasing macrophage hypoxic signaling, thus stimulating intraplaque angiogenesis, could restore cellular function and neovessel maturation, and decrease plaque formation. Prolyl hydroxylases (PHDs) regulate cellular responses to hypoxia. We therefore aimed to elucidate the role of myeloid PHD2, the dominant PHD isoform, on intraplaque angiogenesis in a murine model for venous bypass grafting.

METHODS AND RESULTS

Myeloid PHD2 conditional knockout (PHD2cko) and PHD2 wild type mice on an Ldlr-/- background underwent vein graft surgery (n=11-15/group) by interpositioning donor caval veins into the carotid artery of genotype-matched mice. At postoperative day 28, vein grafts were harvested for morphometric and compositional analysis, and blood was collected for flow cytometry. Myeloid PHD2cko induced and improved intraplaque angiogenesis by improving neovessel maturation, which reduced intraplaque hemorrhage. Intima/media ratio was decreased in myeloid PHD2cko vein grafts. In addition, PHD2 deficiency prevented dissection of vein grafts and resulted in an increase in vessel wall collagen content. Moreover, the macrophage proinflammatory phenotype in the vein graft wall was attenuated in myeloid PHD2cko mice. In vitro cultured PHD2cko bone marrow-derived macrophages exhibited an increased proangiogenic phenotype compared with control.

CONCLUSIONS

Myeloid PHD2cko reduces vein graft disease and ameliorates vein graft lesion stability by improving intraplaque angiogenesis.

Therapeutic strategies based on non-ionizing radiation to prevent venous neointimal hyperplasia: the relevance for stenosed arteriovenous fistula, and the role of vascular compliance

We have reviewed the development and current status of therapies based on exposure to non-ionizing radiation (with a photon energy less than 10 eV) aimed at suppressing the venous neointimal hyperplasia, and consequentially at avoiding stenosis in arteriovenous grafts. Due to the drawbacks associated with the medical use of ionizing radiation, prominently the radiation-induced cardiovascular disease, the availability of procedures using non-ionizing radiation is becoming a noteworthy objective for the current research. Further, the focus of the review was the use of such procedures for improving the vascular access function and assuring the clinical success of arteriovenous fistulae in hemodialysis patients. Following a brief discussion of the physical principles underlying radiotherapy, the current methods based on non-ionizing radiation, either in use or under development, were described in detail. There are currently five such techniques, including photodynamic therapy (PDT), far-infrared therapy, photochemical tissue passivation (PTP), Alucent vascular scaffolding, and adventitial photocrosslinking. The last three are contingent on the mechanical stiffening achievable by the exogenous photochemical crosslinking of tissular collagen, a process that leads to the decrease of venous compliance. As there are conflicting opinions on the role of compliance mismatch between arterial and venous conduits in a graft, this aspect was also considered in our review.

Medical Therapy After CABG: the Known Knowns, the Known Unknowns, and the Unknown Unknowns

PURPOSE

Medical therapies play a central role in secondary prevention after surgical revascularization. While coronary artery bypass grafting is the most definitive treatment for ischemic heart disease, progression of atherosclerotic disease in native coronary arteries and bypass grafts result in recurrent adverse ischemic events. The aim of this review is to summarize the recent evidence regarding current therapies in secondary prevention of adverse cardiovascular outcomes after CABG and review the existing recommendations as they pertain to the CABG subpopulations.

RECENT FINDINGS

There are many pharmacologic interventions recommended for secondary prevention in patients after coronary artery bypass grafting. Most of these recommendations are based on secondary outcomes from trials which include but did not focus on surgical patients as a cohort. Even those designed with CABG in mind lack the technical and demographic scope to provide universal recommendations for all CABG patients.

CONCLUSION

Recommendations for medical therapy after surgical revascularization are chiefly based on large-scale randomized controlled trials and meta-analyses. Much of what is known about medical management after surgical revascularization results from trials comparing surgical to non-surgical approaches and important characteristics of the operative patients are omitted. These omissions create a group of patients who are relatively heterogenous making solid recommendations elusive. While advances in pharmacologic therapies are clearly adding to the armamentarium of options for secondary prevention, knowing what patients benefit most from each therapeutic option remains challenging and a personalized approach is still required.

Techniques and Technologies to Improve Vein Graft Patency in Coronary Surgery

Vein grafts are the most used conduits in coronary artery bypass grafting (CABG), even though many studies have suggested their lower patency compared to arterial alternatives. We have reviewed the techniques and technologies that have been investigated over the years with the aim of improving the quality of these conduits. We found that preoperative and postoperative optimal medical therapy and no-touch harvesting techniques have the strongest evidence for optimizing vein graft patency. On the other hand, the use of venous external support, endoscopic harvesting, vein preservation solution and anastomosis, and graft configuration need further investigation. We have also analyzed strategies to treat vein graft failure: when feasible, re-doing the CABG and native vessel primary coronary intervention (PCI) are the best options, followed by percutaneous procedures targeting the failed grafts.

Perivascular CLICK-gelatin delivery of thrombospondin-2 small interfering RNA decreases development of intimal hyperplasia after arterial injury

Bypass graft failure occurs in 20%-50% of coronary and lower extremity bypasses within the first-year due to intimal hyperplasia (IH). TSP-2 is a key regulatory protein that has been implicated in the development of IH following vessel injury. In this study, we developed a biodegradable CLICK-chemistry gelatin-based hydrogel to achieve sustained perivascular delivery of TSP-2 siRNA to rat carotid arteries following endothelial denudation injury. At 21 days, perivascular application of TSP-2 siRNA embedded hydrogels significantly downregulated TSP-2 gene expression, cellular proliferation, as well as other associated mediators of IH including MMP-9 and VEGF-R2, ultimately resulting in a significant decrease in IH. Our data illustrates the ability of perivascular CLICK-gelatin delivery of TSP-2 siRNA to mitigate IH following arterial injury.

Bilayer vascular grafts with on-demand NO and H2S release capabilities

Nitric oxide (NO) and hydrogen sulfide (H2S) gasotransmitters exhibit potential therapeutic effects in the cardiovascular system. Herein, biomimicking multilayer structures of biological blood vessels, bilayer small-diameter vascular grafts (SDVGs) with on-demand NO and H2S release capabilities, were designed and fabricated. The keratin-based H2S donor (KTC) with good biocompatibility and high stability was first synthesized and then electrospun with poly (l-lactide-co-caprolactone) (PLCL) to be used as the outer layer of grafts. The electrospun poly (ε-caprolactone) (PCL) mats were aminolyzed and further chelated with copper (II) ions to construct glutathione peroxidase (GPx)-like structural surfaces for the catalytic generation of NO, which acted as the inner layer of grafts. The on-demand release of NO and H2S selectively and synergistically promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation and migration of human umbilical artery smooth muscle cells (HUASMCs). Dual releases of NO and H2S gasotransmitters could enhance their respective production, resulting in enhanced promotion of HUVECs and inhibition of HUASMCs owing to their combined actions. In addition, the bilayer grafts were conducive to forming endothelial cell layers under flow shear stress. In rat abdominal aorta replacement models, the grafts remained patency for 6 months. These grafts were capable of facilitating rapid endothelialization and alleviating neointimal hyperplasia without obvious injury, inflammation, or thrombosis. More importantly, the grafts were expected to avoid calcification with the degradation of the grafts. Taken together, these bilayer grafts will be greatly promising candidates for SDVGs with rapid endothelialization and anti-calcification properties.

Contrast-enhanced ultrasound evaluation of plaque vulnerability and the relationship between peripheral blood leukocytes

OBJECTIVE

To evaluate plaque vulnerability by carotid contrast-enhanced ultrasound (CEUS) and to analyze the correlation between plaque vulnerability and peripheral blood leukocyte classification.

MATERIALS AND METHODS

135 patients with carotid plaque were examined by contrast-enhanced ultrasound. Plaque vulnerability was assessed by semiquantitative visual classification. Baseline clinical data and peripheral leukocyte classification were collected. Ordered logistic regression was used to analyze the correlation between plaque neovascularization grade and peripheral leukocyte classification count.

RESULTS

There were significant differences in leukocyte, monocyte, neutrophil, mean platelet volume, lymphocyte, and neutrophil counts between different neovascular plaque grades and peripheral blood (P < 0.05). Correlation analysis showed that leukocyte, monocyte, and neutrophil counts were significantly positively correlated.

CONCLUSION

The increase in plaque neovascularization is associated with an increase in circulating leukocytes, monocytes, and neutrophils. Therefore, CEUS combined with peripheral blood leukocytes may serve as an early warning of plaque vulnerability and provide a theoretical basis for clinical treatment.

Dual-Antiplatelet Therapy After Coronary Artery Bypass Grafting: A Survey of UK Cardiac Surgeons

OBJECTIVE

Antiplatelet therapy after coronary artery bypass grafting (CABG) is important in postoperative medical management. Although cardiac surgeons are well-versed in the guidelines regarding discontinuation of dual-antiplatelet therapy (DAPT; aspirin and a P2Y12 antagonist) before CABG to minimize bleeding risk, there is considerable variability in DAPT dosing after CABG. The objective of this study was to explore the current trends in DAPT after CABG in the UK to improve understanding of the existing practice.

DESIGN

This study used an online survey with 9 questions about the use of DAPT after CABG. An invitation to participate was sent to all adult cardiac surgeons currently in practice in the UK and the Republic of Ireland.

SETTING

The study was conducted in the UK and the Republic of Ireland.

PARTICIPANTS

Participants in this study were adult cardiac surgeons currently in practice in the UK and the Republic of Ireland.

INTERVENTIONS

There were no interventions in this study.

MEASUREMENTS AND MAIN RESULTS

Responses were received from across the UK (85.4% UK; 4% each from Scotland and Northern Ireland, 1.3% from Wales) and 5.3% from the Republic of Ireland. Fifty-seven percent of the respondents performed between 50 and 100 CABGs per year. Ninety-one percent of the respondents prescribe DAPT postoperatively, but the choice of which patients receive it varied. Most responding surgeons used DAPT for selective patient cohorts, such as those with acute coronary syndrome (51%), diffuse coronary artery disease (42%), perioperative myocardial infarction (36%), coronary endarterectomy (31%), or when bypassing a stented coronary artery (23%). Thirty-eight percent of the respondents began all their patients with CABGs on DAPT. The most preferred P2Y12 antagonist was clopidogrel, used by 75% of respondents and introduced on day 1 after surgical revascularization (71%). The routine duration for DAPT is 12 months, which 78% of the respondents preferred. The main reason for not starting DAPT in those surveyed was the bleeding risk associated with DAPT (72%).

CONCLUSIONS

The survey uncovered variation in the use of DAPT after CABG. However, DAPT remains the preferred strategy after CABG in the UK. The study highlighted the need to develop standardized protocols for DAPT after CABG.

Endothelial damage inhibitor preserves the integrity of venous endothelial cells from patients undergoing coronary bypass surgery

OBJECTIVES

Despite the success of coronary artery bypass graft (CABG) surgery using autologous saphenous vein grafts (SVGs), nearly 50% of patients experience vein graft disease within 10 years of surgery. One contributing factor to early vein graft disease is endothelial damage during short-term storage of SVGs in inappropriate solutions. Our aim was to evaluate the effects of a novel endothelial damage inhibitor (EDI) on SVGs from patients undergoing elective CABG surgery and on venous endothelial cells (VECs) derived from these SVGs.

METHODS

SVGs from 11 patients participating in an ongoing clinical registry (NCT02922088) were included in this study, and incubated with both full electrolyte solution (FES) or EDI for 1 h and then examined histologically. In 8 of 11 patients, VECs were isolated from untreated grafts, incubated with both FES and EDI for 2 h under hypothermic stress conditions and then analysed for activation of an inflammatory phenotype, cell damage and cytotoxicity, as well as endothelial integrity and barrier function.

RESULTS

The EDI was superior to FES in protecting the endothelium in SVGs (74 ± 8% versus 56 ± 8%, P < 0.001). Besides confirming that the EDI prevents apoptosis in SVG-derived VECs, we also showed that the EDI temporarily reduces adherens junctions in VECs while protecting focal adhesions compared to FES.

CONCLUSIONS

The EDI protects the connectivity and function of the SVG endothelium. Our data suggest that the EDI can preserve focal adhesions in VECs during short-term storage after graft harvesting. This might explain the superiority of the EDI in maintaining most of the endothelium in venous CABG surgery conduits.

Short-term Pre-operative Methionine Restriction Induces Browning of Perivascular Adipose Tissue and Improves Vein Graft Remodeling in Mice

Short-term preoperative methionine restriction (MetR) shows promise as a translatable strategy to modulate the body's response to surgical injury. Its application, however, to improve post-interventional vascular remodeling remains underexplored. Here, we find that MetR protects from arterial intimal hyperplasia in a focal stenosis model and adverse vascular remodeling after vein graft surgery. RNA sequencing reveals that MetR enhances the brown adipose tissue phenotype in arterial perivascular adipose tissue (PVAT) and induces it in venous PVAT. Specifically, PPAR-α was highly upregulated in PVAT-adipocytes. Furthermore, MetR dampens the post-operative pro-inflammatory response to surgery in PVAT-macrophages in vivo and in vitro . This study shows for the first time that the detrimental effects of dysfunctional PVAT on vascular remodeling can be reversed by MetR, and identifies pathways involved in browning of PVAT. Furthermore, we demonstrate the potential of short-term pre-operative MetR as a simple intervention to ameliorate vascular remodeling after vascular surgery.

3D Elastomeric Stent Functionalized with Antioxidative and Perivascular Tissue Regenerative Activities Ameliorated PVT Deprivation-Induced Vein Graft Failure

Clinically, arterial injuries are always accompanied with perivascular tissue damage, which may contribute to high failure rate of vein grafts due to intimal hyperplasia and acute thrombosis. In this study, a "perivascular tissue (PVT) deprivation" animal model is constructed to mimic clinical scenarios and identify the contribution of arterial PVT to the success of vein grafts. Proteomics analysis suggests that depriving PVT may exacerbate reactive oxygen species (ROS)-induced endothelial apoptosis by up-regulating inflammation response and oxidative stress. Locally administering metformin on vein grafts through 3D-printed external stent (PGS-PCL) shows antioxidative and anti-inflammatory properties to protect cells from ROS invasion, thereafter decreasing acute thrombosis. Moreover, metformin induce rapid regeneration of perivascular adipose tissue in recipient regions, which improves patency by inhibiting intimal hyperplasia. Proteomics, western blot, and in vitro blocking tests reveal that metformin resists endothelial apoptosis through AMPK/mTOR and NFκB signaling pathways. To conclude, PVT deprivation exacerbates inflammatory response and oxidative stress in vein grafts bridging arterial circulation. Metformin-loaded stent ameliorates "PVT damage" related vein graft failure, and enhances patency of through resisting endothelial apoptosis and regenerating arterial PVAT, offering a promising avenue to improve the success of vein grafts in clinic.

External stenting for saphenous vein grafts in coronary artery bypass grafting: A meta-analysis

OBJECTIVES

Autologous saphenous vein grafts (SVGs) are the most commonly used bypass conduits in coronary artery bypass grafting (CABG) with multivessel coronary artery disease. Although external support devices for SVGs have shown promising outcomes, the overall efficacy and safety remains controversial. We aimed to evaluate external stenting for SVGs in CABG versus non-stented SVGs.

METHODS

MEDLINE, EMBASE, Cochrane Library and clinicaltrails.gov were searched for randomized controlled trials (RCTs) to evaluate external-stented SVGs versus non-stented SVGs in CABG up to 31 August 2022. The risk ratio and mean difference with 95% confidence interval were analysed. The primary efficacy outcomes included intimal hyperplasia area and thickness. The secondary efficacy outcomes were graft failure (≥50% stenosis) and lumen diameter uniformity.

RESULTS

We pooled 438 patients from three RCTs. The external stented SVGs group showed significant reductions in intimal hyperplasia area (MD: -0.78, p < 0.001, I2  = 0%) and thickness (MD: -0.06, p < 0.001, I2  = 0%) compared to the non-stented SVGs group. Meanwhile, external support devices improved lumen uniformity with Fitzgibbon I classification (risk ratio (RR):1.1595, p = 0.05, I2  = 0%). SVG failure rates were not increased in the external stented SVGs group during the short follow-up period (RR: 1.14, p = 0.38, I2  = 0%). Furthermore, the incidences of mortality and major cardiac and cerebrovascular events were consistent with previous reports.

CONCLUSIONS

External support devices for SVGs significantly reduced the intimal hyperplasia area and thickness, and improved the lumen uniformity, assessed with the Fitzgibbon I classification. Meanwhile, they did not increase the overall SVG failure rate.

Exosomes from umbilical cord-derived mesenchymal stem cells combined with gelatin methacryloyl inhibit vein graft restenosis by enhancing endothelial functions

BACKGROUND

The prevalence of coronary artery disease is increasing. As a common treatment method, coronary artery bypass transplantation surgery can improve heart problems while also causing corresponding complications. Venous graft restenosis is one of the most critical and intractable complications. Stem cell-derived exosomes could have therapeutic promise and value. However, as exosomes alone are prone to inactivation and easy removal, this therapeutic method has not been widely used in clinical practice. Methacrylated gelatin (GelMA) is a polymer with a loose porous structure that maintains the biological activity of the exosome and can control its slow release in vivo. In this study, we combined human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-Exos) and GelMA to explore their effects and underlying mechanisms in inhibiting venous graft restenosis.

RESULTS

Human umbilical cord mesenchymal stem cells (hUCMSCs) were appraised using flow cytometry. hUCMSC-Exos were evaluated via transmission electron microscopy and western blotting. hUCMSC-Exos embedded in a photosensitive GelMA hydrogel (GelMA-Exos) were applied topically around venous grafts in a rat model of cervical arteriovenous transplantation, and their effects on graft reendothelialization and restenosis were evaluated through ultrasonic, histological, and immunofluorescence examinations. Additionally, we analyzed the material properties, cellular reactions, and biocompatibility of the hydrogels. We further demonstrated that the topical application of GelMA-Exos could accelerate reendothelialization after autologous vein transplantation and reduce restenosis in the rat model. Notably, GelMA-Exos caused neither damage to major organs in mice nor excessive immune rejection. The uptake of GelMA-Exos by endothelial cells stimulated cell proliferation and migration in vitro. A bioinformatic analysis of existing databases revealed that various cell proliferation and apoptosis pathways, including the mammalian target of rapamycin (mTOR)-phosphoinositide 3-kinase (PI3K)-AKT signaling pathways, might participate in the underlying regulatory mechanism.

CONCLUSIONS

Compared with the tail vein injection of hUCMSC-Exos, the local application of a mixture of hUCMSC-Exos and GelMA was more effective in promoting endothelial repair of the vein graft and inhibiting restenosis. Therefore, the proposed biomaterial-based therapeutic approach is a promising treatment for venous graft restenosis.

Neointima abating and endothelium preserving - An adventitia-localized nanoformulation to inhibit the epigenetic writer DOT1L

Open vascular reconstructions such as bypass are common treatments for cardiovascular disease. Unfortunately, neointimal hyperplasia (IH) follows, leading to treatment failure for which there is no approved therapy. Here we combined the strengths of tailoring nanoplatforms for open vascular reconstructions and targeting new epigenetic mechanisms. We produced adhesive nanoparticles (ahNP) that could be pen-brushed and immobilized on the adventitia to sustainably release pinometostat, an inhibitor drug selective to the epigenetic writer DOT1L that catalyzes histone-3 lysine-79 dimethylation (H3K79me2). This treatment not only reduced IH by 76.8% in injured arteries mimicking open reconstructions in obese Zucker rats with human-like diseases but also avoided the shortcoming of endothelial impairment in IH management. In mechanistic studies, chromatin immunoprecipitation (ChIP) sequencing revealed co-enrichment of the histone mark H3K27ac(acetyl) and its reader BRD4 at the gene of aurora kinase B (AURKB), where H3K79me2 was also enriched as indicated by ChIP-qPCR. Accordingly, DOT1L co-immunoprecipitated with H3K27ac. Furthermore, the known IH driver BRD4 governed the expression of DOT1L which controlled AURKB's protein level, revealing a BRD4- > DOT1L- > AURKB axis. Consistently, AURKB-selective inhibition reduced IH. Thus, this study presents a prototype nanoformulation suited for open vascular reconstructions, and the new insights into chromatin modulators may aid future translational advances.

Biological Materials for Tissue-Engineered Vascular Grafts: Overview of Recent Advancements

The clinical demand for tissue-engineered vascular grafts is still rising, and there are many challenges that need to be overcome, in particular, to obtain functional small-diameter grafts. The many advances made in cell culture, biomaterials, manufacturing techniques, and tissue engineering methods have led to various promising solutions for vascular graft production, with available options able to recapitulate both biological and mechanical properties of native blood vessels. Due to the rising interest in materials with bioactive potentials, materials from natural sources have also recently gained more attention for vascular tissue engineering, and new strategies have been developed to solve the disadvantages related to their use. In this review, the progress made in tissue-engineered vascular graft production is discussed. We highlight, in particular, the use of natural materials as scaffolds for vascular tissue engineering.

The Role of TGF-β Signaling in Saphenous Vein Graft Failure after Peripheral Arterial Disease Bypass Surgery

Saphenous vein bypass grafting is an effective technique used to treat peripheral arterial disease (PAD). However, restenosis is the major clinical challenge for the graft vessel among people with PAD postoperation. We hypothesize that there is a common culprit behind arterial occlusion and graft restenosis. To investigate this hypothesis, we found TGF-β, a gene specifically upregulated in PAD arteries, by bioinformatics analysis. TGF-β has a wide range of biological activities and plays an important role in vascular remodeling. We discuss the molecular pathway of TGF-β and elucidate its mechanism in vascular remodeling and intimal hyperplasia, including EMT, extracellular matrix deposition, and fibrosis, which are the important pathways contributing to stenosis. Additionally, we present a case report of a patient with graft restenosis linked to the TGF-β pathway. Finally, we discuss the potential applications of targeting the TGF-β pathway in the clinic to improve the long-term patency of vein grafts.

Early asymptomatic graft failure in coronary artery bypass grafting: a study based on computed tomography angiography analysis

BACKGROUND

Asymptomatic graft failure after coronary bypass grafting surgery (CABG) may have negative impact on the patients' short- and long-term outcomes. Cardiac computed tomography angiography (CTA) has been proved to be another choice to detect graft failure besides coronary artery angiography in several studies. We aimed to identify the rate and predictors of asymptomatic graft failure detected by CTA before discharge.

METHODS AND RESULTS

A total of 955 grafts of 346 consecutive asymptomatic patients who received CTA examination after CABGs were included in this retrospective study from July 2017 to Dec 2019. We divided 955 grafts into the patent group and occluded group by CTA results. Logistic regression model at graft-level were established to determine predictors of the early asymptomatic graft occlusion. The overall asymptomatic graft failure rate was 4.71% (45/955), and there was no difference between the arterial and venous conduits in different target territories (P > 0.05). The logistic regression at graft-level analysis showed that female (OR 3.181, CI 1.58-6.40, P = 0.001), composite grafting (OR 6.762, CI 2.26-20.28, P = 0.001), pulse index value (OR 1.180, CI 1.08-1.29, P < 0.001) and new postoperative atrial fibrillation (POAF) (OR2.348, CI 1.15-4.78, P = 0.018) were independent risk factors that affect graft failure, while early postoperative dual-antiplatelet treatment with aspirin and clopidogrel was a protective factor (OR 0.403, CI 0.19-0.84, P = 0.015).

CONCLUSIONS

Early asymptomatic graft failure is associated with both patient and surgical factors including female gender, high PI value, composite graft strategy and the new POAF. However, the early dual- antiplatelet therapy with aspirin and clopidogrel may be useful for preventing graft failure.

Importance of Flow Waveform and Flow Volume as Prognostic Indicators for the Patency of Infra-Inguinal Autologous Vein Bypass

OBJECTIVE

To investigate the association of the intra-operative flow waveform and the flow volume with graft prognosis of the infra-inguinal vein bypass.

METHODS

This was a retrospective study of intra-operative flowmetry performed for infra-inguinal autologous vein bypass between 2011 and 2020. Flow waveforms were classified as type 0 - IV according to the Kyushu University (KU) classification. The patients (n = 340) were divided into three groups based on the flow waveform predicting the graft patency: type 0/I (long patency), type II (no early occlusion but late occlusion possible), and type III/IV (early occlusion). The graft occlusion rates of popliteal artery bypass (PAB) and infrapopliteal artery bypass (IPAB) within 30 days of surgery were compared between type 0/I + II and type III/IV groups, while the midterm graft patency rates were compared between type 0/I and type II groups. Additionally, a multivariate analysis was performed to identify independent risk factors for early and late graft occlusion.

RESULTS

The early graft occlusion rates of type 0/I + II and type III/IV groups were 3.9% and 0%, respectively, (p = 1.0) for PAB, and 5.3% and 46.2%, respectively, (p < .001) for IPAB. The two year primary patency rates of type 0/I and type II groups were 91% and 75%, respectively, (p = .030) for PAB, and 58% and 63%, respectively, (p = .72) for IPAB. Independent risk factors for early occlusion were none in PAB and flow waveform (type IV) in IPAB. Independent risk factors for patency loss in PAB were flow waveform (type II), end stage renal disease, and dual antiplatelet use, and those in IPAB were older age, women, lower flow volume, and iterative bypass.

CONCLUSION

Intra-operative flowmetry is useful for predicting the graft prognosis in infra-inguinal vein bypass and this is dependent on the distal target artery.

Prevention of anastomotic stenosis for decellularized vascular grafts using rapamycin-loaded boronic acid-based hydrogels mimicking the perivascular tissue function

Abnormal proliferation of vascular smooth muscle cells (VSMCs) induces graft anastomotic stenosis, resulting in graft failure. Herein, we developed a drug-loaded tissue-adhesive hydrogel as artificial perivascular tissue to suppress VSMCs proliferation. Rapamycin (RPM), an anti-stenosis drug, is selected as the drug model. The hydrogel was composed of poly (3-acrylamidophenylboronic acid-co-acrylamide) (BAAm) and polyvinyl alcohol. Since phenylboronic acid reportedly binds to sialic acid of glycoproteins which is distributed on the tissues, the hydrogel is expected to be adherent to the vascular adventitia. Two hydrogels containing 25 or 50 mg/mL of BAAm (BAVA25 and BAVA50, respectively) were prepared. A decellularized vascular graft with a diameter of <2.5 mm was selected as a graft model. Lap-shear test indicates that both hydrogels adhered to the graft adventitia. In vitro release test indicated that 83 and 73 % of RPM in BAVA25 and BAVA50 hydrogels was released after 24 h, respectively. When VSMCs were cultured with RPM-loaded BAVA hydrogels, their proliferation was suppressed at an earlier stage in RPM-loaded BAVA25 hydrogels compared to RPM-loaded BAVA50 hydrogels. An in vivo preliminary test reveals that the graft coated with RPM-loaded BAVA25 hydrogel shows better graft patency for at least 180 d than the graft coated with RPM-loaded BAVA50 hydrogel or without hydrogel. Our results suggest that RPM-loaded BAVA25 hydrogel with tissue adhesive characteristics has potential to improve decellularized vascular graft patency.

Venous External Support in Coronary Artery Bypass Surgery: A Systematic Review and Meta-Analysis

OBJECTIVES

Neointimal hyperplasia and lumen irregularities are major contributors to vein graft failure and the use of VEST^(R) should prevent this. In this review, we aim to evaluate the angiographic outcomes of externally supported vein grafts.

METHODS

Medline, Embase and Cochrane Library were systematically reviewed for randomized clinical trials published by August 2022. The primary outcome was graft failure. Secondary outcomes included graft ectasia, intimal hyperplasia area and thickness, and graft non-uniformity. Odds ratios (OR) for dichotomous variables and mean difference (MD) for continuous variables with 95% confidence intervals (CI) were pooled using a fixed-effects model.

RESULTS

Three randomized controlled trials with a total of 437 patients were included with follow-up ranging from 1 to 2 years. The odds of graft failure were similar in the two groups (OR 1.22; 95%CI 0.88 to 1.71; I²=0%). Intimal hyperplasia area [MD -0.77 mm²; 95%CI -1.10 to -0.45; I²=0%] and thickness [MD -0.06 mm; 95%CI -0.08 to -0.04; I²=0%] were significantly lower in the VEST group. Fitzgibbon Patency Scale of II or III (representing angiographic conduit non-uniformity; OR 0.67; 95%CI 0.48 to 0.94; I²=0%) and graft ectasia (OR 0.53; 95%CI 0.32 to 0.88; I²=33%) were also significantly lower in the VEST group.

CONCLUSIONS

At short-term follow-up, VEST does not seem to reduce the incidence of graft failure, although it is associated with attenuation of intimal hyperplasia and non-uniformity. Longer angiographic follow-up is warranted to determine whether these positive effects might translate into a positive effect in graft failure and in long-term clinical outcomes.