Management and Prevention of Saphenous Vein Graft Failure: A Review

Native coronary artery or bypass graft percutaneous coronary intervention in patients after previous coronary artery bypass surgery: A large nationwide analysis from the Netherlands Heart Registration

BACKGROUND

Patients with previous coronary artery bypass surgery (CABG) who require repeat revascularization frequently undergo percutaneous coronary intervention (PCI). We sought to identify factors associated with the decision to intervene on the native vessel versus a bypass graft and investigate their outcomes in a large nationwide prospective registry.

METHODS

We identified patients who underwent PCI with a history of prior CABG from the Netherlands Heart Registration between 2017 and 2021 and stratified them by isolated native vessel PCI versus PCI including at least one venous- or arterial graft. The primary endpoint of major adverse cardiac events (MACE) was a composite of all-cause death and target vessel revascularization (TVR) at one-year post PCI. The key secondary endpoint was a composite of all-cause death, myocardial infarction (MI), and TVR at 30 days.

RESULTS

Out of 154,146 patients who underwent PCI, 12,822 (8.3%) had a prior CABG. Isolated native vessel PCI was most frequently performed (75.2%), while an acute coronary syndrome (ACS) presentation was most strongly associated with graft interventions. The primary outcome of MACE at one-year post PCI occurred more frequently in interventions including grafts compared with native vessels alone (19.7% vs. 14.3%; adjOR 1.267; 95% CI 1.101-1.457); p < 0.001) driven by TVR. There was however no difference in mortality or the key secondary endpoint between the two groups.

CONCLUSION

In this nationwide prospective registry, ACS presentation was strongly associated with bypass graft PCI. At one year after PCI, interventions including bypass grafts had a higher composite of MACE compared with isolated native vessel interventions.

New strategy of using double-network hydrogel extravascular stent for preventing venous graft restenosis after coronary artery bypass grafting

OBJECTIVE

Effective therapies for the prevention of vein graft failure, which frequently occurs in coronary artery bypass grafting (CABG) due to intimal hyperplasia (IH), are still lacking. Here, we investigated the effects of the perivenous application of double-network hydrogel on vein grafts in carotid artery bypass grafting in a rabbit model.

METHODS

Healthy New Zealand white rabbits were randomized into the following groups: no graft, graft, or graft + Double-network hydrogel external stent (DNHES). The rabbits' carotid artery was bypassed via the jugular vein. Double-network hydrogel external stent was wrapped around the jugular graft after the anastomoses were completed. Blood flow parameters and tissue histology of the vein grafts were evaluated.

RESULTS

Compared with the untreated vein grafts at 12 weeks after the surgery, the DNHES significantly improved graft flow, attenuated intimal and medial thickening, reduced the anti-proliferating cell nuclear antigen proliferation index of the vein grafts, decreased the mRNA and protein expression of Mitogen-Activated Protein Kinase (MAPK) and Transforming Growth Factor-β (TGF-β), and increased the mRNA and protein expression of endothelial Nitric Oxide Synthase (eNOS).

CONCLUSION

The perivenous application of DNHES exerts beneficial effects on vein grafts, reduces the inflammatory response in carotid artery bypass grafting in a rabbit model, and appears to be a safe and promising strategy to prevent vein graft failure.

Pathophysiology and management of saphenous vein graft disease

INTRODUCTION

The saphenous vein graft (SVG) is the most used conduit in CABG. With standardization of its use as a conduit came an understanding of its accelerated atherosclerosis, known as saphenous vein graft disease (SVGD). Given its extensive use, a review of the pathophysiology and management of SVGD is important as we optimize its use.

AREAS COVERED

For this review, an extensive literature search was completed to identify and examine the evolution of SVG in CABG, mechanisms driving SVGD, and methods developed to prevent and manage it. This includes a review of relevant major papers and trials in this space.

EXPERT OPINION

Eras of evolution in SVG usage in CABG include an experimental era, era of SVG dominance in CABG, and the current era of mixed venous and arterial grafting. As SVGD was studied, the mechanisms behind it became more understood, and prevention and management methods were developed. As advances in surgical techniques and pharmacotherapy continue to reduce occurrence and severity of SVGD, long-term patency of SV grafts continues to improve and remain excellent in optimized settings. With continued innovation and improvement in operative techniques, the SVG conduit is and will remain an important player in the field of coronary bypass.

Acute Mechanical Consequences of Vessel-Specific Coronary Bypass Combinations

PURPOSE

Premature coronary artery bypass graft (CABG) failure has been linked to geometric, mechanical, and compositional discrepancies between host and graft tissues. Acute hemodynamic disturbances and the introduction of wall stress gradients trigger a myriad of mechanobiological processes at the anastomosis that can be associated with restenosis and graft failure. Although the origins of coronary artery disease dictate the anastomotic target, an opportunity exists for graft-vessel optimization through rationale graft selection.

METHODS

Here we explored the four distinct regions of the left (L) and right (R) ITA (1 = proximal, 2 = submuscular, 3 = middle, 4 = distal), and four common target vessels in the coronary circulation including the proximal and distal left anterior descending (PLAD & DLAD), right coronary (RCA), and left circumflex (LCX) arteries. Benchtop biaxial mechanical data was used to acquire constitutive model parameters of these tissues and enable vessel-specific computational models to elucidate the mechanical consequences of 32 unique graft-target combinations.

RESULTS

Simulations revealed the maximum principal wall stresses for the PLAD, RCA, and LCX occurred when anastomosed with LITA1, and the maximum flow-induced shear stress occurred with LITA4. The DLAD, on the other hand, reached stress maximums when anastomosed to LITA4. Using a normalized objective function of simulation output variables, we found LITA2 to be the best graft choice for both LADs, RITA3 for the RCA, and LITA3 for the LCX.

CONCLUSION

Although mechanical compatibility is just one of many factors determining bypass graft outcomes, our data suggests improvements can be made to the grafting process through vessel-specific regional optimization.

Hypothenar hammer syndrome: outcomes after ulnar artery reconstruction with autologous vein graft

The most common surgical procedure for the treatment of hypothenar hammer syndrome (HHS) is resection of the pathological segment followed by arterial reconstruction using a venous bypass. Bypass thrombosis occurs in 30% of cases, with various clinical consequences, ranging from no symptoms to reappearance of the preoperative clinical symptoms. We reviewed 19 patients with HHS who underwent bypass graft, to assess clinical outcomes and graft patency, with a minimum follow-up of 12 months. Objective and subjective clinical evaluation and ultrasound exploration of the bypass were carried out. Clinical results were compared according to bypass patency. At a mean follow-up of 7 years, 47% of patients had complete resolution of symptoms; symptoms were improved in 42% of cases, and unchanged in 11%. Mean QuickDASH and CISS scores were 20.45/100 and 28/100, respectively. Bypass patency rate was 63%. Patients with patent bypass had shorter follow-up (5.7 vs 10.4 years; p = 0.037) and a better CISS score (20.3 vs 40.6; p = 0.038). There were no significant differences between groups for age (48.6 and 46.7 years; p = 0.899), bypass length (6.1 and 9.9 cm; p = 0.081) or QuickDASH score (12.1 and 34.7; p = 0.084). Arterial reconstruction gave good clinical results, with the best results in case of patent bypass. Level of evidence: IV.

The biological functions of europium-containing biomaterials: A systematic review

The biological functions of rare-earth elements (REEs) have become a focus of intense research. Recent studies have demonstrated that ion doping or alloying of some REEs can optimize the properties of traditional biomaterials. Europium (Eu), which is an REE with low toxicity and good biocompatibility, has promising applications in biomedicine. This article systematically reviews the osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties of Eu-containing biomaterials, thereby paving the way for biomedical applications of Eu. Data collection for this review was completed in October 2022, and 30 relevant articles were finally included. Most articles indicated that doping of Eu ions or Eu-compound nanoparticles in biomaterials can improve their osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties. The angiogenic, antibacterial, and potential neuritogenic effects of Eu(OH)₃ nanoparticles have also been demonstrated.

Updated Perspectives on Direct Vascular Cellular Reprogramming and Their Potential Applications in Tissue Engineered Vascular Grafts

Cardiovascular disease is a globally prevalent disease with far-reaching medical and socio-economic consequences. Although improvements in treatment pathways and revascularisation therapies have slowed disease progression, contemporary management fails to modulate the underlying atherosclerotic process and sustainably replace damaged arterial tissue. Direct cellular reprogramming is a rapidly evolving and innovative tissue regenerative approach that holds promise to restore functional vasculature and restore blood perfusion. The approach utilises cell plasticity to directly convert somatic cells to another cell fate without a pluripotent stage. In this narrative literature review, we comprehensively analyse and compare direct reprogramming protocols to generate endothelial cells, vascular smooth muscle cells and vascular progenitors. Specifically, we carefully examine the reprogramming factors, their molecular mechanisms, conversion efficacies and therapeutic benefits for each induced vascular cell. Attention is given to the application of these novel approaches with tissue engineered vascular grafts as a therapeutic and disease-modelling platform for cardiovascular diseases. We conclude with a discussion on the ethics of direct reprogramming, its current challenges, and future perspectives.

Acute Coronary Syndromes Among Patients with Prior Coronary Artery Bypass Surgery

PURPOSE OF REVIEW

Acute coronary syndromes (ACS) often occur in individuals with prior coronary artery bypass graft surgery (CABG). Our goal was to describe the prevalence, clinical characteristics, prognosis, and treatment strategies in this group of patients.

RECENT FINDINGS

Studies demonstrate that both acute and long-term major adverse cardiovascular outcomes are increased in patients with ACS and prior CABG compared to those without CABG. Much of this risk is attributed to the greater comorbid conditions present in patients with prior CABG. Data regarding optimal management of ACS in patients with prior CABG are limited, but most observational studies favor an early invasive approach for treatment. Native vessel percutaneous coronary intervention (PCI), if feasible, is generally preferred to bypass graft PCI. Patients with ACS and prior CABG represent a high-risk group of individuals, and implementing optimal preventive and treatment strategies are critically important to reduce the risk.

A Brachial Artery Pseudoaneurysm Treated with a Bifurcated Y-Shaped Artificial Vessel Graft

Brachial artery aneurysms are rare diseases that may be caused by infection or trauma. We report a case of a 71-year-old man who presented with a mass in his right antecubital fossa that increased in size slowly over time. Three years ago, the patient underwent ascending and total-arch replacement with artificial vessel graft to treat aortic root and ascending aorta aneurysm. Preoperative physical examination of right upper extremity showed a nonpulsatile mass with normal pulse of axillary, brachial, and radial arteries. The mass was removed and brachial artery reconstruction was done initially using saphenous vein graft. Two months later, the patient revisited with recurrent pseudoaneurysm, involving the bifurcation point of brachial artery. Aneurysm was totally resected and the brachial artery was reconstructed by interposition graft using a bifurcated GORE-TEX artificial vessel graft. The patient healed without complication and no recurrence was observed. Artificial vessel graft is an available option for reconstruction, and revascularization of vessel defect after excision of brachial artery aneurysm may involve bifurcation point.

Diagnostic and Management Strategies in Patients with Late Recurrent Angina after Coronary Artery Bypass Grafting

Purpose of Review

This review will outline the current evidence on the anatomical, functional, and physiological tools that may be applied in the evaluation of patients with late recurrent angina after coronary artery bypass grafting (CABG). Furthermore, we discuss management strategies and propose an algorithm to guide decision-making for this complex patient population.

Recent Findings

Patients with prior CABG often present with late recurrent angina as a result of bypass graft failure and progression of native coronary artery disease (CAD). These patients are generally older, have a higher prevalence of comorbidities, and more complex atherosclerotic lesion morphology compared to CABG-naïve patients. In addition, guideline recommendations are based on studies in which post-CABG patients have been largely excluded.

Summary

Several invasive and non-invasive diagnostic tools are currently available to assess graft patency, the hemodynamic significance of native CAD progression, left ventricular function, and myocardial viability. Such tools, in particular the latest generation coronary computed tomography angiography, are part of a systematic diagnostic work-up to guide optimal repeat revascularization strategy in patients presenting with late recurrent angina after CABG.

Basement Membrane of Tissue Engineered Extracellular Matrix Scaffolds Modulates Rapid Human Endothelial Cell Recellularization and Promote Quiescent Behavior After Monolayer Formation

Off-the-shelf small diameter vascular grafts are an attractive alternative to eliminate the shortcomings of autologous tissues for vascular grafting. Bovine saphenous vein (SV) extracellular matrix (ECM) scaffolds are potentially ideal small diameter vascular grafts, due to their inherent architecture and signaling molecules capable of driving repopulating cell behavior and regeneration. However, harnessing this potential is predicated on the ability of the scaffold generation technique to maintain the delicate structure, composition, and associated functions of native vascular ECM. Previous de-cellularization methods have been uniformly demonstrated to disrupt the delicate basement membrane components of native vascular ECM. The antigen removal (AR) tissue processing method utilizes the protein chemistry principle of differential solubility to achieve a step-wise removal of antigens with similar physiochemical properties. Briefly, the cellular components of SV are permeabilized and the actomyosin crossbridges are relaxed, followed by lipophilic antigen removal, sarcomeric disassembly, hydrophilic antigen removal, nuclease digestion, and washout. Here, we demonstrate that bovine SV ECM scaffolds generated using the novel AR approach results in the retention of native basement membrane protein structure, composition (e.g., Collagen IV and laminin), and associated cell modulatory function. Presence of basement membrane proteins in AR vascular ECM scaffolds increases the rate of endothelial cell monolayer formation by enhancing cell migration and proliferation. Following monolayer formation, basement membrane proteins promote appropriate formation of adherence junction and apicobasal polarization, increasing the secretion of nitric oxide, and driving repopulating endothelial cells toward a quiescent phenotype. We conclude that the presence of an intact native vascular basement membrane in the AR SV ECM scaffolds modulates human endothelial cell quiescent monolayer formation which is essential for vessel homeostasis.

Recanalized saphenous vein graft once occluded in postoperative acute period

A 69-year-old female with diabetes mellitus underwent off-pump coronary artery bypass grafting for old myocardial infarction and unstable angina with reduced left ventricular wall motion due to triple vessel disease. Although the saphenous vein graft was confirmed to be patent during surgery, it developed occlusion at the distal anastomotic site on postoperative first day. However, recanalization was achieved for this saphenous vein graft following the administration of direct oral anticoagulants in addition to antiplatelet therapy. Anticoagulant therapy, in addition to antiplatelet therapy, should be considered for preventing and dissolving thrombus in postoperative acute period, especially in high-risk patients for thrombotic graft occlusion.

Contemporary coronary artery bypass graft surgery and subsequent percutaneous revascularization

Patients who have undergone coronary artery bypass graft (CABG) surgery are susceptible to bypass graft failure and progression of native coronary artery disease. Although the saphenous vein graft (SVG) was traditionally the most-used conduit, arterial grafts (including the left and right internal thoracic arteries and the radial artery) have improved patency rates. However, the need for secondary revascularization remains common, and percutaneous coronary intervention (PCI) has become the most common modality of secondary revascularization after CABG surgery. Procedural characteristics and clinical outcomes differ considerably from those associated with PCI in patients without previous CABG surgery, owing to altered coronary anatomy and differences in conduit pathophysiology. In particular, SVG PCI carries an increased risk of complications, and operators are shifting their focus towards embolic protection strategies and complex native-vessel interventions, increasingly using SVGs as conduits to facilitate native-vessel PCI rather than pursuing SVG PCI. In this Review, we discuss the differences in conduit pathophysiology, changes in CABG surgery techniques, and the latest evidence in terms of PCI in patients with previous CABG surgery, with a particular emphasis on safety and long-term efficacy. We explore the subject of contemporary CABG surgery and subsequent percutaneous revascularization in this complex patient population.

Impact of target vessel choice on outcomes following percutaneous coronary intervention in patients with a prior coronary artery bypass graft

OBJECTIVES

To evaluate and compare characteristics and clinical outcomes of percutaneous coronary intervention (PCI) among target vessel types in patients with a prior coronary artery bypass graft (CABG) surgery.

BACKGROUND

Patients with a prior CABG often require repeat revascularization with PCI. Graft PCI has been associated with worse outcomes compared to native vessel PCI, yet the optimal PCI strategy in prior CABG patients remains unknown.

METHODS

We stratified prior CABG patients who underwent PCI at a tertiary-care center between 2009 and 2017 by target vessel type: native vessel, venous graft, and arterial graft. The primary outcome of major adverse cardiac events (MACE) was a composite of all-cause death, myocardial infarction, stent thrombosis, or target vessel revascularization up to 1 year post-PCI.

RESULTS

Prior CABG patients (n = 3983) represented 19.5% of all PCI interventions during the study period. PCI was most frequently performed on native vessels (n = 2928, 73.5%) followed by venous (n = 883, 22.2%) and arterial grafts (n = 172, 4.3%). Procedural success and complications were similar among the groups; however, slow- and no-reflow phenomenon was more common in venous graft PCI compared to native vessel PCI (OR 4.78; 95% CI 2.56-8.95; p < 0.001). At 1 year, there were no significant differences in MACE or in its individual components.

CONCLUSIONS

Target vessel choice did not appear to affect MACE at 1 year in a large cohort of patients with prior CABG undergoing PCI. Whether PCI of surgical grafts versus native arteries truly results in similar outcomes warrants further investigation in randomized controlled trials.

Long-Term Sustained Drug Delivery via 3D Printed Masks for the Development of a Heparin-Loaded Interlayer in Vascular Tissue Engineering Applications

Current approaches in small-diameter vascular grafts for coronary artery bypass surgeries fail to address physiological variations along the graft that contribute to thrombus formation and ultimately graft failure. We present an innovative interlayer drug delivery system that can be utilized for the sustained delivery of heparin through a graft with a high degree of temporal and spatial control. A heparin-loaded gelatin methacrylate (gelMA) interlayer sits within a biohybrid composed of decellularized bovine pericardium (dECM) and poly(propylene fumarate) (PPF), and its UV crosslinking is controlled via three-dimensional (3D) printed shadow masks. The masks can be readily designed to modulate the incident light intensity on the graft, enabling us to control the resultant gelMA crosslinking and properties. A high heparin loading efficiency was obtained in gelMA and was independent of crosslinking. We achieved sustained heparin release over the course of 2 weeks within the biohybrid material using the 3D printed mask patterns. High doses of heparin were observed to have detrimental effects on endothelial cell function. However, when exposed to heparin in a slower, more sustained manner consistent with the masks, endothelial cells behave similarly to untreated cells. Further, slower release profiles cause significantly more release of tissue factor pathway inhibitor, an anticoagulant, than a faster release profile. The heparin-loaded gelMA interlayer we have developed is a useful tool for the temporal and spatial control of heparin release that supports endothelial function and promotes an antithrombotic environment.

CCL2 loaded microparticles promote acute patency in silk-based vascular grafts implanted in rat aortae

Cardiovascular disease is the leading cause of death worldwide, often associated with coronary artery occlusion. A common intervention for arterial blockage utilizes a vascular graft to bypass the diseased artery and restore downstream blood flow; however, current clinical options exhibit high long-term failure rates. Our goal was to develop an off-the-shelf tissue-engineered vascular graft capable of delivering a biological payload based on the monocyte recruitment factor C-C motif chemokine ligand 2 (CCL2) to induce remodeling. Bi-layered silk scaffolds consisting of an inner porous and outer electrospun layer were fabricated using a custom blend of Antherea Assama and Bombyx Mori silk (lyogel). Lyogel silk scaffolds alone (LG), and lyogel silk scaffolds containing microparticles (LGMP) were tested. The microparticles (MPs) were loaded with either CCL2 (LGMP+) or water (LGMP-). Scaffolds were implanted as abdominal aortic interposition grafts in Lewis rats for 1 and 8 weeks. 1-week implants exhibited patency rates of 50% (7/14), 100% (10/10), and 100% (5/5) in the LGMP-, LGMP+, and LG groups, respectively. The significantly higher patency rate for the LGMP+ group compared to the LGMP- group (p = 0.0188) suggests that CCL2 can prevent acute occlusion. Immunostaining of the explants revealed a significantly higher density of macrophages (CD68+ cells) within the outer vs. inner layer of LGMP- and LGMP+ constructs but not in LG constructs. After 8 weeks, there were no significant differences in patency rates between groups. All patent scaffolds at 8 weeks showed signs of remodeling; however, stenosis was observed within the majority of explants. This study demonstrated the successful fabrication of a custom blended silk scaffold functionalized with cell-mimicking microparticles to facilitate controlled delivery of a biological payload improving their in vivo performance. STATEMENT OF SIGNIFICANCE: This study outlines the development of a custom blended silk-based tissue-engineered vascular graft (TEVG) for use in arterial bypass or replacement surgery. A custom mixture of silk was formulated to improve biocompatibility and cellular binding to the tubular scaffold. Many current approaches to TEVGs include cells that encourage graft cellularization and remodeling; however, our technology incorporates a microparticle based delivery platform capable of delivering bioactive molecules that can mimic the function of seeded cells. In this study, we load the TEVGs with microparticles containing a monocyte attractant and demonstrate improved performance in terms of unobstructed blood flow versus blank microparticles. The acellular nature of this technology potentially reduces risk, increases reproducibility, and results in a more cost-effective graft when compared to cell-based options.

Extracellular Matrix-Based Biomaterials for Cardiovascular Tissue Engineering

Regenerative medicine and tissue engineering strategies have made remarkable progress in remodeling, replacing, and regenerating damaged cardiovascular tissues. The design of three-dimensional (3D) scaffolds with appropriate biochemical and mechanical characteristics is critical for engineering tissue-engineered replacements. The extracellular matrix (ECM) is a dynamic scaffolding structure characterized by tissue-specific biochemical, biophysical, and mechanical properties that modulates cellular behavior and activates highly regulated signaling pathways. In light of technological advancements, biomaterial-based scaffolds have been developed that better mimic physiological ECM properties, provide signaling cues that modulate cellular behavior, and form functional tissues and organs. In this review, we summarize the in vitro, pre-clinical, and clinical research models that have been employed in the design of ECM-based biomaterials for cardiovascular regenerative medicine. We highlight the research advancements in the incorporation of ECM components into biomaterial-based scaffolds, the engineering of increasingly complex structures using biofabrication and spatial patterning techniques, the regulation of ECMs on vascular differentiation and function, and the translation of ECM-based scaffolds for vascular graft applications. Finally, we discuss the challenges, future perspectives, and directions in the design of next-generation ECM-based biomaterials for cardiovascular tissue engineering and clinical translation.

Tissue engineered bovine saphenous vein extracellular matrix scaffolds produced via antigen removal achieve high in vivo patency rates

Diseases of small diameter blood vessels encompass the largest portion of cardiovascular diseases, with over 4.2 million people undergoing autologous vascular grafting every year. However, approximately one third of patients are ineligible for autologous vascular grafting due to lack of suitable donor vasculature. Acellular extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue have potential to serve as ideal biomaterials for production of off-the-shelf vascular grafts capable of eliminating the need for autologous vessel harvest. A modified antigen removal (AR) tissue process, employing aminosulfabetaine-16 (ASB-16) was used to create off-the-shelf small diameter (< 3 mm) vascular graft from bovine saphenous vein ECM scaffolds with significantly reduced antigenic content, while retaining native vascular ECM protein structure and function. Elimination of native tissue antigen content conferred graft-specific adaptive immune avoidance, while retention of native ECM protein macromolecular structure resulted in pro-regenerative cellular infiltration, ECM turnover and innate immune self-recognition in a rabbit subpannicular model. Finally, retention of the delicate vascular basement membrane protein integrity conferred endothelial cell repopulation and 100% patency rate in a rabbit jugular interposition model, comparable only to Autograft implants. Alternatively, the lack of these important basement membrane proteins in otherwise identical scaffolds yielded a patency rate of only 20%. We conclude that acellular antigen removed bovine saphenous vein ECM scaffolds have potential to serve as ideal off-the-shelf small diameter vascular scaffolds with high in vivo patency rates due to their low antigen content, retained native tissue basement membrane integrity and preserved native ECM structure, composition and functional properties. STATEMENT OF SIGNIFICANCE: The use of autologous vessels for the treatment of small diameter vascular diseases is common practice. However, the use of autologous tissue poses significant complications due to tissue harvest and limited availability. Developing an alternative vessel for use for the treatment of small diameter vessel diseases can potentially increase the success rate of autologous vascular grafting by eliminating complications related to the use of autologous vessel and increased availability. This manuscript demonstrates the potential of non-antigenic extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue as off-the-shelf vascular grafts for the treatment of small diameter vascular diseases.

Storage solutions to improve grafts preservation and longevity in coronary artery bypass grafting surgery: hype or hope?

PURPOSE OF REVIEW

Saphenous vein grafts (SVGs) remain the most-commonly used conduits for coronary artery bypass grafting (CABG).Significant rates of vein graft failure (VGF) remain a limitation of their use as this diminishes the long-term benefits of CABG. The choice of intraoperative SVGs preservation solution is believed to have an impact on graft patency; however, the superiority of one solution over the others remains in question.

RECENT FINDINGS

In the present review, we describe the pathophysiological mechanisms underlying the different phases of VGF. We also reviewed the most recent literature comparing and evaluating the efficacy of various storage solutions. These include heparinized saline, autologous heparinized blood, buffered solutions, and crystalloid cardioplegia.

SUMMARY

It is clear that the composition of the SVGs storage solution has an impact on vessel wall structure and function. There is a lack of translational and clinical research on the topic; thus, conclusions cannot be drawn regarding the superiority of one solution over the others in terms of VGF. Future research needs to be conducted to address this gap in the literature in order to make meaningful evidence-based recommendations on intraoperative graft storage.

Thromboelastography-Platelet Mapping Allows Safe and Earlier Urgent Coronary Artery Bypass Grafting

BACKGROUND

Current STS guidelines recommend delaying CABG for several days or performing platelet function testing in stable patients who received P2Y12 inhibitors. Our program routinely uses thromboelastography-platelet mapping (TEG-PM) to expedite CABG in P2Y12 non-responders (NR). We hypothesize that P2Y12 NR had no difference in LOS to surgery and blood product transfusion compared to patients undergoing urgent inpatient CABG not treated with a P2Y12 inhibitor.

METHODS

A total of 221 patients from 2015-2019 were P2Y12 NR based on TEG-PM result of < 50% ADP inhibition. The control group was 232 consecutive patients who also had urgent inpatient CABG but were not treated pre-operatively with a P2Y12 inhibitor. Exclusion criteria were identical between groups.

RESULTS

Sixty-seven percent of inpatient CABG patients who were treated pre-operatively with a P2Y12 inhibitor were NR. The mean number of days from cardiac surgical consultation to CABG in the TEG-PM NR group was 1.6 ± 0.1 versus 2.1 ± 0.1 in the control group (p<0.01). The mean total number of blood product units transfused was 1.6 ± 0.2 in the TEG-PM NR group versus 1.6 ± 0.4 in controls (p=0.91).

CONCLUSIONS

Our results demonstrate a very high incidence of P2Y12 non-responders in patients undergoing urgent CABG at our program. These patients underwent surgery at least 3 days earlier than STS recommendations and common practice with no difference in transfusion requirement. Routine use of TEG-PM to identify P2Y12 NR can safely decrease pre-operative hospital LOS and associated cost and improve resource utilization and patient satisfaction.

A review of methodologies evaluating superficial vein properties in viv: focus on compliance and reactivity

The saphenous vein (SV) is a hindlimb superficial vein which has aroused a considerable interest because of its implication in chronic venous disease and its use in coronary artery or lower limb bypass grafts. The morphology and patency of the SV are commonly assessed for diagnosis and management, but the dynamic properties of the vein - compliance, elasticity and reactivity, less widely studied, are also fundamental issues. The subject of this review is neither to review the pathologies, nor the treatments or surgical procedures. The goal is to gather together all existing types of investigation on the superficial vein and to focus on the dynamic venous properties in vivo. The data collected indicate that plethysmography (PG) and ultrasound (US) are extensively used to evaluate SV patency, reflux and morphology. Their use to evaluate superficial vein compliance is less widespread but highly necessary. The protocols used via venous occlusion are described and the various parameters used to accurately measure compliance and distensibility versus elasticity are presented and discussed. The advantage of US diameter measurement is shown, including additional pulsatile compliance evaluation. The overview of venous reactivity greatly differs, being poorly studied in vivo, mainly by optical methods in humans or US echotracking in animals. Existing methodologies are potent but could be certainly developed and improved further for better characterization of the SV in human and for investigations of new devices, surgical techniques and pharmacological treatment in preclinical animal studies.

Natriuretic Peptide Clearance Receptor (NPR-C) Pathway as a Novel Therapeutic Target in Obesity-Related Heart Failure With Preserved Ejection Fraction (HFpEF)

Heart failure (HF) with preserved ejection fraction (HFpEF) is a major public health problem with cases projected to double over the next two decades. There are currently no US Food and Drug Administration–approved therapies for the health-related outcomes of HFpEF. However, considering the high prevalence of this heterogeneous syndrome, a directed therapy for HFpEF is one the greatest unmet needs in cardiovascular medicine. Additionally, there is currently a lack of mechanistic understanding about the pathobiology of HFpEF. The phenotyping of HFpEF patients into pathobiological homogenous groups may not only be the first step in understanding the molecular mechanism but may also enable the development of novel targeted therapies. As obesity is one of the most common comorbidities found in HFpEF patients and is associated with many cardiovascular effects, it is a viable candidate for phenotyping. Large outcome trials and registries reveal that being obese is one of the strongest independent risk factors for developing HFpEF and that this excess risk may not be explained by traditional cardiovascular risk factors. Recently, there has been increased interest in the intertissue communication between adipose tissue and the heart. Evidence suggests that the natriuretic peptide clearance receptor (NPR-C) pathway may play a role in the development and pathobiology of obesity-related HFpEF. Therefore, therapeutic manipulations of the NPR-C pathway may represent a new pharmacological strategy in the context of underlying molecular mechanisms.

Revascularisation of type 2 diabetics with coronary artery disease: Insights and therapeutic targeting of O-GlcNAcylation

AIM

Coronary artery bypass graft (CABG) using autologous saphenous vein continues to be a gold standard procedure to restore the supply of oxygen-rich blood to the heart muscles in coronary artery disease (CAD) patients with or without type 2 diabetes mellitus (T2DM). However, CAD patients with T2DM are at higher risk of graft failure. While failure rates have been reduced through improvements in procedure-related factors, much less is known about the molecular and cellular mechanisms by which T2DM initiates vein graft failure. This review gives novel insights into these cellular and molecular mechanisms and identifies potential therapeutic targets for development of new medicines to improve vein graft patency.

DATA SYNTHESIS

One important cellular process that has been implicated in the pathogenesis of T2DM is protein O-GlcNAcylation, a dynamic, reversible post-translational modification of serine and threonine residues on target proteins that is controlled by two enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Protein O-GlcNAcylation impacts a range of cellular processes, including trafficking, metabolism, inflammation and cytoskeletal organisation. Altered O-GlcNAcylation homeostasis have, therefore, been linked to a range of human pathologies with a metabolic component, including T2DM.

CONCLUSION

We propose that protein O-GlcNAcylation alters vascular smooth muscle and endothelial cell function through modification of specific protein targets which contribute to the vascular re-modelling responsible for saphenous vein graft failure in T2DM.

Maintenance of HDACs and H3K9me3 Prevents Arterial Flow-Induced Venous Endothelial Damage

The transition of flow microenvironments from veins to arteries in vein graft surgery induces “peel-off” of venous endothelial cells (vECs) and results in restenosis. Recently, arterial laminar shear stress (ALS) and oscillatory shear stress (OS) have been shown to affect the cell cycle and inflammation through epigenetic controls such as histone deacetylation by histone deacetylases (HDACs) and trimethylation on lysine 9 of histone 3 (H3K9me3) in arterial ECs. However, the roles of H3K9me3 and HDAC in vEC damage under ALS are not known. We hypothesized that the different responses of HDACs and H3K9me3 might cause vEC damage under the transition of venous flow to arterial flow. We found that arterial ECs showed high expression of H3K9me3 protein and were retained in the G0 phase of the cell cycle after being subjected to ALS. vECs became round under ALS with a decrease in the expression of H3K9me3, HDAC3, and HDAC5, and an increase in the expression of vascular cell adhesion molecule 1 (VCAM-1). Inhibition of HDACs activity by a specific inhibitor, phenylbutyrate, in arterial ECs caused similar ALS-induced inflammation and cell loss as observed in vECs. Activation of HDACs and H3K9me3 by ITSA-1, an HDAC activator, could prevent ALS-induced peel-off and reduced VCAM-1 expression in vECs. Moreover, shear stress modulates EC morphology by the regulation of focal adhesion kinase (FAK) expression. ITSA-1 or EGF could increase phosphorylated (p)-FAK expression in vECs under ALS. We found that perturbation of the activity of p-FAK and increase in p-FAK expression restored ALS-induced H3K9me3 expression in vECs. Hence, the abnormal mechanoresponses of H3K9me3 and HDAC in vECs after being subjected to ALS could be reversed by ITSA-1 or EGF treatment: this offers a strategy to prevent vein graft failure.

Monitoring the Impact of Aggressive Glycemic Intervention during Critical Care after Cardiac Surgery with a Glycemic Expert System for Nurse-Implemented Euglycemia: The MAGIC GENIE Project

A novel, multi-dimensional protocol named GENIE has been in use for intensive insulin therapy (IIT, target glucose <140 mg/dL) in the surgical intensive care unit (SICU) after open heart surgery (OHS) at VA Pittsburgh since 2005. Despite concerns over increased mortality from IIT after the publication of the NICE-SUGAR Trial, it remains in use, with ongoing monitoring under the MAGIC GENIE Project showing that GENIE performance over 12 years (2005-2016) aligns with the current consensus that IIT with target blood glucose (BG) <140 mg/dL is advisable only if it does not provoke severe hypoglycemia (SH). Two studies have been conducted to monitor glucometrics and outcomes during GENIE use in the SICU. One compares GENIE (n = 382) with a traditional IIT protocol (FORMULA, n = 289) during four years of contemporaneous use (2005-2008). The other compares GENIE's impact overall (n = 1404) with a cohort of patients who maintained euglycemia after OHS (euglycemic no-insulin [ENo-I], n = 111) extending across 12 years (2005-2016). GENIE performed significantly better than FORMULA during contemporaneous use, maintaining lower time-averaged glucose, provoking less frequent, severe, prolonged, or repetitive hypoglycemia, and achieving 50% lower one-year mortality, with no deaths from mediastinitis (0 of 8 cases vs 4 of 9 on FORMULA). Those benefits were sustained over the subsequent eight years of exclusive use in OHS patients, with an overall one-year mortality rate (4.2%) equivalent to the ENo-I cohort (4.5%). The results of the MAGIC GENIE Project show that GENIE can maintain tight glycemic control without provoking SH in patients undergoing OHS, and may be associated with a durable survival benefit. The results, however, await confirmation in a randomized control trial.

Association of hypoxia and mitochondrial damage associated molecular patterns in the pathogenesis of vein graft failure: a pilot study

Coronary artery bypass grafting (CABG) is the standard treatment modality in revascularization of the myocardium. However, the graft failure remains the major complication following CABG procedure. Involvement of mitochondrial damage-associated molecular patterns (mt-DAMPs) in the pathogenesis of vein-graft failure is largely unknown. Here, we investigated the expression of major protein-mt-DAMPs, cytochrome-C (Cyt-C), heat shock protein-60 (Hsp-60), mitochondrial transcription factor A (mtTFA), in the occluded graft and associated tissues, including distal left anterior descending (LAD), LAD adjacent to anastomosis, and left internal mammary artery (LIMA) in the microswine CABG model. The protein expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) was significantly decreased in the graft and LIMA, whereas the protein expression of hypoxia inducible factor-1 alpha (HIF-1α) and Cyt-C was decreased and that of mtTFA and Hsp60 was increased in all tissues compared to controls. There was no significant difference in the protein expression of citrate synthase, complex-1, and mitochondrial pyruvate dehydrogenase in the graft and associated tissues compared to control. Hypoxia in cultured smooth muscle cells (SMCs) significantly upregulated all mitochondrial biomarkers and mt-DAMPs compared to normoxia. The increased reactive oxygen species (ROS) content and compromised membrane integrity in the hypoxic SMCs correlated well with increased mt-DAMPs in the graft and associated tissues, suggesting a possible role of mt-DAMPs in the pathogenesis of graft failure. These findings suggest that the pathological signals elicited by mt-DAMPs could reveal targets for better therapeutic approaches and diagnostic strategies in the management of CABG graft failure.

Anticoagulation and antiplatelet therapy post coronary artery bypass surgery

BACKGROUND

Coronary artery bypass grafting (CABG) is the gold standard treatment for patients with multivessel coronary heart disease. Although its use has proven long-term survival benefits, there is a relative degree of graft failure which increases morbidity and mortality rates.

DISCUSSION

This review discusses clinical outcomes following antiplatelet and anticoagulant therapy after CABG. There is wide variation of evidence about the use of clopidogrel or ticagrelor to aspirin postoperatively in relation to improving graft patency rates or clinical outcomes over the use of aspirin alone. These dual therapies may have significant protective effects in patients undergoing off-pump CABG. Recent studies suggest that superior outcomes may be attained by combining prasugrel with aspirin. Further research is needed to evaluate this, as well as compare the effectiveness of different dual antiplatelet regimens. There is weak evidence for post-CABG anticoagulation, with warfarin and rivaroxaban providing no protection against graft failure but decreasing long-term major adverse cardiac events. Anticoagulation seems to be indicated only in post-CABG patients at high risk of future ischemic events.

CONCLUSION

The use of dual anti-platelet therapy post coronary artery bypass surgery needs further research. Potentially, selective patient groups will benefit more from the addition of thienopyridine antiplatelets or anticoagulants to aspirin after CABG.

Emerging roles of protein O-GlcNAcylation in cardiovascular diseases: Insights and novel therapeutic targets

Cardiovascular diseases (CVDs) are the leading cause of death globally. While the major focus of pharmacological and non-pharmacological interventions has been on targeting disease pathophysiology and limiting predisposing factors, our understanding of the cellular and molecular mechanisms underlying the pathogenesis of CVDs remains incomplete. One mechanism that has recently emerged is protein O-GlcNAcylation. This is a dynamic, site-specific reversible post-translational modification of serine and threonine residues on target proteins and is controlled by two enzymes: O-linked β-N-acetylglucosamine transferase (OGT) and O-linked β-N-acetylglucosaminidase (OGA). Protein O-GlcNAcylation alters the cellular functions of these target proteins which play vital roles in pathways that modulate vascular homeostasis and cardiac function. Through this review, we aim to give insights on the role of protein O-GlcNAcylation in cardiovascular diseases and identify potential therapeutic targets in this pathway for development of more effective medicines to improve patient outcomes.

Altered Vascular Extracellular Matrix in the Pathogenesis of Atherosclerosis

Cardiovascular disease continues to grow as a massive global health burden, with coronary artery disease being one of its most lethal varieties. The pathogenesis of atherosclerosis induces changes in the blood vessel and its extracellular matrix (ECM) in each vascular layer. The alteration of the ECM homeostasis has significant modulatory effects on the inflammatory response, the proliferation and migration of vascular smooth muscle cells, neointimal formation, and vascular fibrosis seen in atherosclerosis. In this literature review, the role of the ECM, the multitude of components, and alterations to these components in the pathogenesis of atherosclerosis are discussed with a focus on versatile cellular phenotypes in the structure of blood vessel. An understanding of the various effects of ECM alterations opens up a plethora of therapeutic options that would mitigate the substantial health toll of atherosclerosis on the global population.

First Results of the Single Heartstring Aortotomy for Multiple Off-Pump Vein Grafts: A Case Series

To validate the technique of the single Heartstring aortotomy for multiple off-pump venous bypass grafts (described in 2015), the results of a 38-month follow-up study of 18 patients, including high-risk patients, are presented. No early deaths or cardiac or cerebral complications occurred. During the follow-up period, 2 patients died of non-cardiac causes, and 3 developed coronary ischemia. Ischemia occurred due to late graft occlusion in 2 patients, both of whom had normal postoperative courses and correct graft flow. The presence of acute symptoms 24 months after surgery in these patients indicated that technical graft failure was unlikely. This safe technique combines the advantages of simple and reproducible revascularization, the off-pump approach, and minimal aortic manipulation.

Extracellular Matrix for Small-Diameter Vascular Grafts

To treat coronary heart disease, coronary artery bypass grafts are used to divert blood flow around blockages in the coronary arteries. Autologous grafts are the gold standard of care, but they are characterized by their lack of availability, low quality, and high failure rates. Alternatively, tissue-engineered small-diameter vascular grafts made from synthetic or natural polymers have not demonstrated adequate results to replace autologous grafts; synthetic grafts result in a loss of patency due to thrombosis and intimal hyperplasia, whereas scaffolds from natural polymers are generally unable to support the physiological conditions. Extracellular matrix (ECM) from a variety of sources, including cell-derived, 2D, and cannular tissues, has become an increasingly useful tool for this application. The current review examines the ECM-based methods that have recently been investigated in the field and comments on their viability for clinical applications.

The role of extracellular vesicles in neointima formation post vascular injury

Pathological neointimal growth can develop in patients as a result of vascular injury following percutaneous coronary intervention and coronary artery bypass grafting using autologous saphenous vein, leading to arterial or vein graft occlusion. Neointima formation driven by intimal hyperplasia occurs as a result of a complex interplay between molecular and cellular processes involving different cell types including endothelial cells, vascular smooth muscle cells and various inflammatory cells. Therefore, understanding the intercellular communication mechanisms underlying this process remains of fundamental importance in order to develop therapeutic strategies to preserve endothelial integrity and vascular health post coronary interventions. Extracellular vesicles (EVs), including microvesicles and exosomes, are membrane-bound particles secreted by cells which mediate intercellular signalling in physiological and pathophysiological states, however their role in neointima formation is not fully understood. The purification and characterization techniques currently used in the field are associated with many limitations which significantly hinder the ability to comprehensively study the role of specific EV types and make direct functional comparisons between EV subpopulations. In this review, the current knowledge focusing on EV signalling in neointima formation post vascular injury is discussed.

Preventing treatment failures in coronary artery disease: what can we learn from the biology of in-stent restenosis, vein graft failure, and internal thoracic arteries?

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and the availability of percutaneous or surgical revascularization procedures significantly improves survival. However, both strategies are daunted by complications which limit long-term effectiveness. In-stent restenosis (ISR) is a major drawback for intracoronary stenting, while graft failure is the limiting factor for coronary artery bypass graft surgery (CABG), especially using veins. Conversely, internal thoracic artery (ITA) is known to maintain long-term patency in CABG. Understanding the biology and pathophysiology of ISR and vein graft failure (VGF) and mechanisms behind ITA resistance to failure is crucial to combat these complications in CAD treatment. This review intends to provide an overview of the biological mechanisms underlying stent and VGF and of the potential therapeutic strategy to prevent these complications. Interestingly, despite being different modalities of revascularization, mechanisms of failure of stent and saphenous vein grafts are very similar from the biological standpoint.

Bleeding complications after dual antiplatelet therapy with ticagrelor versus dual antiplatelet therapy with clopidogrel-a propensity-matched comparative study of two antiplatelet regimes in off-pump coronary artery bypass grafting

Purpose

Ticagrelor combined with aspirin had shown better saphenous vein graft patency than aspirin with clopidogrel after off-pump coronary artery bypass grafting. However, the safety of this drug in regard to bleeding complications remains unknown. The aim of our study was to assess the bleeding complications of dual antiplatelet therapy with aspirin and ticagrelor compared with aspirin and clopidogrel within the first 3 months after off-pump surgery.

Methods

Three hundred eighty-two consecutive patients who were prescribed aspirin with ticagrelor (ticagrelor group) were compared with 660 patients who received aspirin and clopidogrel (clopidogrel group). After propensity matching, 144 patients in each group were compared for bleeding events and major adverse cardiac and cerebral events. Major bleeding was defined as composite outcome of re-exploration for bleeding, any fatal bleeding, intracranial bleeding, and any bleeding requiring hospitalization.

Results

Patients in the ticagrelor group had more incidence of re-exploration for bleeding (p = 0.042), pericardial effusion requiring drainage (p = 0.007), readmissions (p < 0.01), gastrointestinal bleeding (p = 0.01), and major bleeding (5.8% vs. 2.1%, p < 0.01, OR 2.8 (1.43-5.58)). After propensity analysis, gastrointestinal bleed (p = 0.024), major bleeding (7.6% vs.1.4%, p < 0.001, OR 5.8 (1.28-26.97)), length of ICU stay (p = 0.039), and readmissions (p = 0.003, OR 11.83 (1.51-92.86)) were more in the ticagrelor group. Major adverse cardiac and cerebral events were similar between the groups.

Conclusion

Dual antiplatelet therapy with aspirin and ticagrelor increased gastrointestinal bleeding events, major bleeding events, and readmission rates compared with aspirin and clopidogrel after off-pump coronary artery bypass grafting.

Drug-eluting Vein Graft with Acetylsalicylic Acid-Ticagrelor-Unfractionated Heparin Complex Inhibits Early Graft Thrombosis

Background

Bypass graft surgery remains to be an important treatment option for left main and multivessel coronary artery disease. Approximately 2% of saphenous vein grafts are lost immediately after the coronary artery bypass graft operations and 12% in the first month due to thrombosis.

Aims

To administer one anticoagulant and two antiplatelet agents in a way that locally affects the vein graft before the bypass operation and to thereby analyse their effects on early graft thrombosis.

Study Design

Animal experimentation.

Methods

Since ticagrelor was used locally for the first time in this study, its efficacy in combination with other drugs (acetylsalicylic acid, acetylsalicylic acid and ticagrelor, and acetylsalicylic acid + ticagrelor + unfractionated heparin) was examined on rats including control (untreated) and sham (pluronic gel) group (n=14 for each group). Before the tunica adventitia layer of the femoral veins was bypassed to the femoral artery, it was coated with the drug-eluting pluronic F-127 gel. The presence or absence of thrombus in the vein graft samples was recorded under light microscopy. In vein graft preparations where thrombus was detected, the thrombus area (μm2) was calculated using the Axiovision software. Immunohistochemical staining was performed with the anti-rat von Willebrand factor polyclonal antibody kit.

Results

The number of preparations containing thrombus was significantly lower in the acetylsalicylic acid + ticagrelor + unfractionated heparin group than in the acetylsalicylic acid, control, and sham groups, according to the comparisons made on the 1st and 3rd days (p=0.001 and 0.02, respectively). von Willebrand factor staining was significantly lower in the acetylsalicylic acid + ticagrelor + unfractionated heparin group than in the other groups on the 3rd day (p=0.005).

Conclusion

Locally effective acetylsalicylic acid-ticagrelor-unfractionated heparin complex has been shown to significantly reduce thrombus formation in vein grafts in this experimental model. Local administration of these drugs, which are routinely administered orally just before stent implantations, on the vein graft before the bypass is performed can prevent the loss of vein grafts due to thrombus, thereby reducing the mortality and morbidity of these patients.

Application of tissue-engineered interventions for coronary artery bypass grafts

Coronary artery bypass graft is one of the extensively conducted procedures to release occlusion in the coronary vessel. Various biological grafts are used for this purpose, superiorly, saphenous vein graft, if unavailable, other vessels in the body, with likewise characteristics are exploited for the purpose. The choice of graft is yet under discovery that could impeccably meet all the requirements. Variation in perioperative and postoperative results have given uneven clinical inferences of these conduits. Alternatively, tissue-engineering is also being applied in this area for clinical improvements. This review underlines some of the commonly used grafts for coronary artery bypass graft and advancements in tissue engineering for this purpose.

Postoperative complications associated with coronary artery bypass graft surgery and their therapeutic interventions

Coronary artery disease is one of the commonest surgery demanding cardiovascular diseases. Coronary artery bypass graft surgery is practiced all over the world for the treatment of coronary artery disease. Systemic trauma during the surgery is associated with a wide range of complications, some of which are fatal. Preoperative risk factors such as age, previous illness and obesity are common predictors of these adverse events. Advances in therapeutic medicine have allowed timely treatment of these adverse events and co-morbidities. This review summarizes some of the most occurring complications associated with coronary artery bypass graft and corresponding treatment options.

Thrombogenic and Inflammatory Reactions to Biomaterials in Medical Devices

Blood-contacting medical devices of different biomaterials are often used to treat various cardiovascular diseases. Thrombus formation is a common cause of failure of cardiovascular devices. Currently, there are no clinically available biomaterials that can totally inhibit thrombosis under the more challenging environments (e.g., low flow in the venous system). Although some biomaterials reduce protein adsorption or cell adhesion, the issue of biomaterial associated with thrombosis and inflammation still exists. To better understand how to develop more thrombosis-resistant medical devices, it is essential to understand the biology and mechano-transduction of thrombus nucleation and progression. In this review, we will compare the mechanisms of thrombus development and progression in the arterial and venous systems. We will address various aspects of thrombosis, starting with biology of thrombosis, mathematical modeling to integrate the mechanism of thrombosis, and thrombus formation on medical devices. Prevention of these problems requires a multifaceted approach that involves more effective and safer thrombolytic agents but more importantly the development of novel thrombosis-resistant biomaterials mimicking the biological characteristics of the endothelium and extracellular matrix tissues that also ameliorate the development and the progression of chronic inflammation as part of the processes associated with the detrimental generation of late thrombosis and neo-atherosclerosis. Until such developments occur, engineers and clinicians must work together to develop devices that require minimal anticoagulants and thrombolytics to mitigate thrombosis and inflammation without causing serious bleeding side effects.

Upregulation of miR‑423 improves autologous vein graft restenosis via targeting ADAMTS‑7

Coronary artery bypass graft (CABG) is one of the primary methods of treating coronary heart disease (CHD); however, vein graft restenosis is a major limiting factor of the effectiveness of CABG. Emerging evidence has indicated that miR‑423 is associated with vascular diseases. Additionally, upregulation of a disintegrin and metalloproteinase with thrombospondin motifs‑7 (ADAMTS‑7) contributes to neointima formation by promoting the proliferation and migration of vascular smooth muscle cells and inhibiting the proliferation and migration of endothelial cells. The aim of the present study was to examine the effects of miR‑423 target, ADAMTS‑7, on regulating vein graft disease and identify novel biomarkers for use in therapy of vein graft failure (VGF). Aberrant expression of miR‑423 in plasma of patients with CHD prior to and following CABG confirms that miR‑423 may be a suitable target for preventing VGF. Furthermore, a dual‑luciferase reporter gene assay indicated that miR‑423 directly interacted with ADAMTS‑7 and suppressed its expression. Ectopic expression of miR‑423 suppressed ADAMTS‑7, resulting in decreased proliferation and migration rates of human umbilical vein smooth muscle cells by targeting ADAMTS‑7, but resulted in increased proliferation and migration of human umbilical vein endothelial cells in vitro. Overexpression of miR‑423 also enhanced re‑endothelialization and decreased neointimal formation in a rat vein graft model. In conclusion, the results of the present study demonstrated that the miR‑423/ADAMTS‑7 axis may possess potential clinical value for the prevention and treatment of restenosis in patients with CHD following CABG.

Outcomes of primary percutaneous cardiac intervention for ST elevation myocardial infarction with a saphenous vein graft culprit

BACKGROUND

Patients treated with primary percutaneous coronary intervention (pPCI) for ST elevation myocardial infarction (STEMI) who have a history of coronary artery bypass grafting (CABG) are at high risk of adverse cardiovascular outcomes. Data on the risk of a saphenous vein graft (SVG)-infarct-related artery (IRA) compared to other culprit vessels are sparse.

METHODS

The study was based on a prospectively collected registry of 2,405 consecutive patients with STEMI attending a tertiary medical center in 2001-2017. Patients with an SVG-IRA (n = 172) were compared with patients with native vessel disease (n = 2,333) for mortality and major adverse cardiac events (MACE), which included death, myocardial infarction (MI), target vessel revascularization (TVR), and coronary artery bypass surgery (CABG) at 1 month and 3 years.

RESULTS

The SVG-IRA group was significantly older than the native vessel group (p = .05), with no between-group differences in rates of male patients (76 vs. 82%, p = .59), diabetes (24.2 vs. 26.2%, p = .73), and renal failure (18.8 vs. 9.2%, p = .25). Mortality was higher in the SVG-IRA group at 1 month (13.9 vs. 2.5%, p < .01) and 3 years (23.9 vs. 7.4%, p < .01). At 3 years, SVG-IRA was associated with the highest rates of MACE (55.6%), compared with native vessel disease. After correction for confounders, SVG-IRA remained an independent risk factor for MACE both at 1 month (HR-2.08, 95%CI 1.72-3.11, p < .01) and 3 years (HR-2.01, 95%CI 1.28-3.09, p < .01).

CONCLUSION

Among patients treated with pPCI for STEMI, outcomes are worse when the culprit is an SVG.

The placental growth factor attenuates intimal hyperplasia in vein grafts by improving endothelial dysfunction

Saphenous vein grafts (SVG) patency is limited by intimal hyperplasia (IH) caused by endothelial dysfunction. This study aimed to explore the effect of placental growth factor (PlGF) on the endothelial function of SVG. In rat models of external jugular vein-carotid artery graft treated with PlGF or saline hydrogel, PlGF inhibited vein graft IH (day 28: 12.0 ± 1.9 vs. 61.7 ± 13.1 μm, P < 0.001), promoted microvessel proliferation (day 14: 33.3% 3+ vs. 50.0% 2+, P = 0.03), and increased nitric oxide (NO) production (P < 0.05 on days 1/3/5) and NO synthase (NOS) expression by immunohistochemistry. In human umbilical vein endothelial cells (HUVECs) cultured under hypoxia and treated or not with PlGF, PlGF restored the survival (50 ng/ml PlGF, 48 h: 91.7 ± 0.6% vs. 84.9 ± 0.5%, P < 0.01), migration (by Matrigel assay), and tube formation ability (junctions, tubules, and tubule total length; all P < 0.01) of HUVECs after hypoxia. PlGF increased NO production through increased eNOS expression (P < 0.05), without changes in iNOS expression. The mRNA expression of eNOS decreased after the addition of the PI3K inhibitor LY294002 (P < 0.05). PlGF promoted the protein expression of eNOS by up-regulating AKT, and the AKT and eNOS protein levels were decreased after adding LY294002 (all P < 0.05). In conclusion, PlGF is a candidate for the inhibition of IH in SVG after coronary artery bypass graft. The effects of PlGF are mediated by the upregulation of the eNOS mRNA and protein through the PI3K/AKT signaling pathway. PlGF promotes the secretion of NO by endothelial cells and thereby reduces the occurrence and development of IH.

Care of the Post-CABG Patient

An estimated 400,000 coronary artery bypass graft operations are performed annually in the United States. Saphenous vein grafts are the most commonly used conduits; however, graft failure is common. In contrast, left internal mammary artery grafts have more favorable long-term patency rates. Guidelines recommend aggressive secondary prevention. In the 2 decades following surgery, 16% of patients require repeat revascularization, and percutaneous coronary intervention accounts for 98% of procedures performed. Post-coronary artery bypass graft patients presenting with symptoms of acute coronary syndrome or progressive heart failure should undergo early coronary angiography given the high likelihood that such a presentation represents graft failure. Percutaneous coronary intervention in degenerated saphenous vein grafts is associated with embolization that may cause the "no-reflow phenomenon," which can be avoided with the use of embolic protection devices. Hybrid revascularization procedures are a promising emerging strategy to avoid the placement of vein grafts.

The long-term patency of a gastroepiploic artery bypass graft deployed in a semiskeletonized fashion: predictors of patency

OBJECTIVES

Whether or not using the gastroepiploic artery (GEA) is associated with improved outcomes of coronary artery bypass grafting (CABG) remains unclear. Previous research has shown that the short-term function of the GEA was strongly associated with the degree of native vessel stenosis. We assessed the association between long-term GEA patency and the degree of stenosis of the coronary artery.

METHODS

We retrospectively examined 517 patients who underwent CABG with an in situ semiskeletonized GEA from January 2000 to January 2015. In this cohort, 282 (54.5%) patients underwent distant radiological evaluations for >1 year post-surgery (range 1-18 years after surgery). Quantitative coronary angiography was used to measure the degree of stenosis of the native coronary artery. Preoperative angiographic parameters include the minimal lumen diameter (MLD) and the percentage of target vessel stenosis. A multivariable stepwise Cox proportional hazards regression analysis was used to identify predictors of angiographic occlusion.

RESULTS

The cumulative patency rate of the GEA was 79.3% at 10 years. A multivariable analysis showed that an MLD (hazard ratio 4.43, 95% confidence interval 3.25-6.82; P < 0.001) was an independent risk factor of GEA occlusion. A time-dependent receiver operating characteristic (ROC) curve analysis identified that an MLD >1 mm was set as the cut-off value for graft occlusion. Patients with an MLD <1 mm had a 10-year patency rate of 89.8%.

CONCLUSIONS

The long-term patency of the semiskeletonized GEA was acceptable. The target vessel MLD obtained using quantitative coronary angiography was a strong predictor of patency. Good long-term patency can be expected for an MLD <1 mm.

Adherence to lifestyle changes after coronary artery bypass graft: Outcome of preoperative peer education

OBJECTIVE

This study was done to investigate the effect of preoperative peer education on patients' adherence to medication and lifestyle changes after Coronary Artery Bypass Graft (CABG).

METHODS

In this randomized clinical trial, the peers of CABG patients conducted preoperative educational sessions at the ward in groups of 4-5 (n = 36) while the control group (n = 34) received routine education by a nurse. Adherence of both groups to medication and recommendations for lifestyle modification including physical activity, smoking, and diet was measured one and two months after discharge.

RESULTS

A multivariate analysis of co-variance showed the significant effect of peer education on adherence (F = 32.586, p < 0.001; η² = 0.671). Univariate ANCOVA revealed a significant difference in adherence to diet between the two groups (F = 62.316, p = 0 0.0001; η² = 0.482). Based on the repeated measures ANOVA, peer education significantly improved the CABG patients' adherence to diet (F = 55.373, p = 0.0001) and their total adherence (F = 9.911, p = 0.002) compared to the control group.

CONCLUSION

Preoperative peer education had a significant effect on improving CABG patients' adherence to lifestyle changes after hospital discharge.

PRACTICE IMPLICATION

Peer education can be used as an effective method to improve the CABG patients ' adherence to lifestyle changes.