Low Calcium-High Magnesium Krebs-Henseleit Solution Combined with Adenosine and Lidocaine Improved Rat Aortic Function and Structure Following Cold Preservation

Background and objectives: The main problem of vascular preservation is the maintenance of vessel graft quality and function following extended storage. Conventional preservation solutions such as histidine-tryptophan-ketoglutarate (HTK) solution, Phosphate-Buffer Solution (PBS), or sodium chloride 0.9% has been shown to be inadequate in preserving vascular physiological function after 3 days of cold storage. This study aimed to evaluate whether adenosine and lidocaine (AL) in a modified Krebs-Henseleit (KH) solution can preserve the function and histological structure of rat aortic rings after 6 days. Materials and Methods: Thirty-five aortic rings from male Wistar rats (200-300 g) were harvested and immediately immersed in one of the assigned cold preservation solutions: standard KH, modified KH (mod KH) with lower calcium (Ca2+) and higher magnesium content (Mg2+) with or without adenosine and lidocaine (mod KH-AL), and modified KH with AL, insulin, and melatonin (Mod KH-ALMI). The contraction and relaxation function of the aortic rings were examined using an isometric force transducer after 6 days of cold preservation. Hematoxylin and eosin staining were used to analyze the rings' histological structure. Results: Vascular contraction and relaxation functions were severely affected after a 6-day cold storage period in standard KH. Modifying the KH solution by reducing the Ca2+ and increasing the Mg2+ levels greatly recovered the vessel functions. The addition of AL or ALMI to the modified KH did not further recover vascular contractility. However, only the addition of AL to the modified KH increased the ACh-induced relaxation at 6 days when compared to the conventional KH, suggesting that endothelium preservation is improved. From histological analysis, it was found that the addition of AL but not ALMI further improved the endothelial lining and the structure of the elastic membrane layers of the preserved vessels after 6 days of cold preservation. Conclusions: The addition of AL to low calcium-high magnesium KH solution significantly enhanced endothelial preservation and improved endothelial-induced relaxation of preserved vessels after 6 days of cold storage.

Consensus statement-graft treatment in cardiovascular bypass graft surgery

Coronary artery bypass grafting (CABG) is and continues to be the preferred revascularization strategy in patients with multivessel disease. Graft selection has been shown to influence the outcomes following CABG. During the last almost 60 years saphenous vein grafts (SVG) together with the internal mammary artery have become the standard of care for patients undergoing CABG surgery. While there is little doubt about the benefits, the patency rates are constantly under debate. Despite its acknowledged limitations in terms of long-term patency due to intimal hyperplasia, the saphenous vein is still the most often used graft. Although reendothelialization occurs early postoperatively, the process of intimal hyperplasia remains irreversible. This is due in part to the persistence of high shear forces, the chronic localized inflammatory response, and the partial dysfunctionality of the regenerated endothelium. "No-Touch" harvesting techniques, specific storage solutions, pressure controlled graft flushing and external stenting are important and established methods aiming to overcome the process of intimal hyperplasia at different time levels. Still despite the known evidence these methods are not standard everywhere. The use of arterial grafts is another strategy to address the inferior SVG patency rates and to perform CABG with total arterial revascularization. Composite grafting, pharmacological agents as well as latest minimal invasive techniques aim in the same direction. To give guide and set standards all graft related topics for CABG are presented in this expert opinion document on graft treatment.

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.

The Role of Preservation Solutions upon Saphenous Vein Endothelial Integrity and Function: Systematic Review and UK Practice Survey

The long saphenous vein is the most used conduit in cardiac surgery, but its long-term patency is limited by vein graft disease (VGD). Endothelial dysfunction is a key driver of VGD; its aetiology is multi-factorial. However emerging evidence identifies vein conduit harvest technique and preservation fluids as causal in their onset and propagation. This study aims to comprehensively review published data on the relationship between preservation solutions, endothelial cell integrity and function, and VGD in human saphenous veins harvested for CABG. The review was registered with PROSPERO (CRD42022358828). Electronic searches of Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE databases were undertaken from inception until August 2022. Papers were evaluated in line with registered inclusion and exclusion criteria. Searches identified 13 prospective, controlled studies for inclusion in the analysis. All studies used saline as a control solution. Intervention solutions included heparinised whole blood and saline, DuraGraft, TiProtec, EuroCollins, University of Wisconsin (UoW), buffered, cardioplegic and Pyruvate solutions. Most studies demonstrated that normal saline appears to have negative effects on venous endothelium and the most effective preservation solutions identified in this review were TiProtec and DuraGraft. The most used preservation solutions in the UK are heparinised saline or autologous whole blood. There is substantial heterogeneity both in practice and reporting of trials evaluating vein graft preservation solutions, and the quality of existing evidence is low. There is an unmet need for high quality trials evaluating the potential for these interventions to improve long-term patency in venous bypass grafts.

Quercetin Relieves the Excised Great Saphenous Vein Oxidative Damage and Inflammatory Reaction

Objective

The patency and quality of transplanted great saphenous vein (GSV) can seriously influence the physical state and life quality of patients who accepted the coronary artery bypass grafting (CABG). Quercetin is known for antioxidant, antithrombotic, anti-inflammatory, and antitumor properties. In this study, we examined the protection of quercetin to the great saphenous vein from oxidative and inflammatory damage.

Methods

The GSVs were collected from 15 patients undergoing CABG and cultured. Treated the veins by H₂O₂ and detected the NO, SOD, and MDA content by the relevant kits to explore the quercetin protection against oxidative damage. Then, for another group of GSVs, sheared them and detected the inflammatory cytokines, such as IL-6, TNFα, CCL20, PCNA, and VEGF. Collect the veins for H&E staining and PCNA and VEGF immunofluorescent staining.

Results

Pretreatment by quercetin reduced the production of NO and MDA induced by H₂O₂, and increased SOD activity. Quercetin also supressed the mRNA expressions of IL-6, TNFα after mechanical damage and had no influence on CCL20 and VEGF. Consistent with the lower expression of PCNA treated by quercetin, the vein intima was thinner.

Conclusion

These results demonstrated that quercetin protects GSVs by reducing the oxidative damage and inflammatory response and also suppresses the abnormal thickening of venous endothelium by inhibiting cell proliferation. It reminded that, to some extent, quercetin has the potential to release the great saphenous vein graft damage.

Increased receptor expression supports vascular reactivity of the rabbit aorta during preservation

OBJECTIVES

The mechanistic understanding of vascular functional impairment during preservation time helps determine the optimal time frame in which explanted arteries can be used. The method of choice is to measure vascular reactivity and receptor expression. Our goal was to study the influence of preservation for 24 and 48 h on vascular reactivity and receptor expression in rabbit aorta.

METHODS

Aortic rings preserved in Krebs-Henseleit solution were evaluated fresh (t0), 24 h (t24) and 48 h (t48) after harvest for (i) vascular reactivity as sensitivity (pD2) and maximum effect in response to potassium chloride, U46619 (thromboxane-A2 agonist), phenylephrine, carbachol and isoproterenol, in an organ bath; and for (ii) expression of α1, β2 and thromboxane-prostanoid receptors, by immunofluorescence.

RESULTS

Compared to the control, after 24 h of preservation, potassium chloride-induced pD2 increased a significant 3.6%, whereas U46619-induced vasoconstriction decreased 9%. None of the agonists affected vasodilation. Intimal and medial α1 receptor expression increased 2.5-fold. After 48 h of preservation, α1 expression and vasoconstrictor responses remained similar to those after 24 h of preservation, but in vasodilation the carbachol-induced maximum effect decreased 30% whereas isoproterenol-induced pD2 increased 4% and the maximum effect increased 10%. TP and β2 expression in the intima and media increased 1.8- and 2.5-fold, respectively.

CONCLUSIONS

Up to 48 h of preservation, the adrenergic pathway and its receptors support vasoconstriction and vasodilation, despite a significant deterioration in the prostanoid pathway.

A humoral solution: Autologous blood products and tissue repair

Autologous blood-derived products (ABP) are the focus of growing scientific interest and are investigated and used for multiple medical indications. ABPs hold promise thanks to their availability, ease of preparation, and low risk of adverse allogenic reaction, hypersensitivity, and contamination. Compositional analysis of ABPs reveals a diverse mixture of cellular components, cytokines and growth factors that play roles in healing processes such as tissue proliferation and angiogenesis, modulation of the local environment through chemotaxis and regulation of inflammation and the extracellular matrix, as well as several immunomodulatory actions. Thus, the administration of ABP induces supraphysiological levels of components necessary for orchestrating reparative efforts in currently difficult-to-treat medical conditions. In this article, we review the variety of autologous blood-derived products, their composition, current clinical uses, regulatory climate, and mechanisms of action.

Cardioplegic storage solution: Is it the guardian of saphenous vein graft endothelium?

INTRODUCTION

Despite their suboptimal long-term patency, saphenous vein grafts are the most widely used conduits to achieve complete revascularization during coronary artery bypass grafting (CABG). Although vein storage critically impairs endothelial integrity, contradictory data concerning optimal storage solutions exist. The aim of this study is to explore any in vitro impact of cardioplegic solutions and temperature on vein grafts endothelial integrity during their storage.

MATERIALS AND METHODS

A single-center, prospective trial including 40 consecutive patients was conducted. Eligibility criteria included patients submitted to CABG receiving at least one vein graft. An excess segment of the graft was harvested and divided into four different parts. Each one of them was stored under different conditions; either in a conventional heparin-enriched blood solution or in a cardioplegic solution, at room temperature (20°C-22°C) and in the refrigerator (5°C). Endothelial integrity was evaluated via immunohistochemistry using an antibody against CD31.

RESULTS

Endothelial integrity (measured in a scale from 1-worst to 5-best) was significantly better after cardioplegic solution storage (2.83 ± 0.15 and 3.10 ± 0.13 in cold and room temperature, respectively) compared with storage in conventional solutions (2.23 ± 0.16 and 2.0 ± 0.15 in cold and room temperature, respectively). A significant effect of cardioplegic storage solution, as well as of cold temperature and cardioplegic solution interaction on endothelial preservation was reported, whereas storage temperature did not prove a significant factor by its own.

CONCLUSIONS

Cardioplegic storage solutions result in significantly better endothelial preservation compared with conventional heparin-enriched blood solutions. The association with superior clinical outcomes remains to be proved.

Do storage solutions protect endothelial function of arterialized vein graft in an experimental rat model?

BACKGROUND

This study aims to compare the effects of storage solutions commonly used in coronary artery bypass grafting on the vascular reactivity in vein graft interposed in arterial position in syngeneic rats.

METHODS

Twenty-seven male Lewis rats were sacrified to sample a vein graft implanted 6 weeks ago into abdominal aorta position. The vein grafts were inferior venae cavae initially pretreated with heparinized saline solution (HS) or autologous heparinized blood (AHB) or our referent solution, GALA. The endothelial functionality, the in situ Reactive Oxygen Species (ROS) levels and the histological characteristics were conducted from segments of arterialized vein graft.

RESULTS

At 6 weeks, graft thrombosis occurred respectively in 22% of AHB group, 62.5% in the HS group and 82.5% in the GALA group. In each group, significative intimal hyperplasia was observed. After 6 weeks, an endothelium-remodeling layer associated with an increase of wall thickness was observed in each group. Endothelium-dependent tone was reduced in the vein graft regardless of the group. No difference was observed concerning the ROS in vein graft between the different groups. In distal aortic sections, ROS levels were increased in HS and GALA groups.

CONCLUSIONS

Storage solutions used in this experimental model of vein graft implanted in arterial position cause graft injury and a complete disappearance of vascular reactivity. GALA solution did not reduce intimal risk hyperplasia when the vein graft was exposed to arterial flow in a rat model.

Current role of saphenous vein graft in coronary artery bypass grafting

Saphenous vein was the conduit used in the first series of coronary artery bypass grafting (CABG), and, with the exception of surgical revascularization of the left anterior descending artery, it remains the most commonly used bypass conduit. However, its durability and longevity are not ideal. Arterial grafts have better patency than saphenous vein grafts and therefore should be preferred over them. However, in certain situations, like grafting right coronary arteries with lesser degree of proximal stenosis and higher competitive flow, or in certain patient populations, like those at very high risk of wound infections and octogenarians, arterial grafting may not be the best option and saphenous vein grafting should be considered instead.

Cold-Stored Venous Allografts In Different Preserving Solutions: A Study On Changes In Vein Wall Morphology

BACKGROUND:

The saphenous vein is the most frequently used bypass conduit for vascular reconstructions, which may need to be stored for a prolonged time. The aim of this study was to compare the effect of different preservation solutions on the morphology of saphenous veins during the long-term cold storage.

DESIGN:

An in vitro study.

MATERIAL AND METHODS:

Saphenous vein samples, collected from 29 patients undergoing varicose vein surgery, were stored at +4°C in (1) 10% formalin, (2) isotonic saline with heparin and antibiotic, (3) phosphate-buffered saline, (4) 2.5% glutaraldehyde + phosphate-buffered saline, and (5) Custodiol (histidine-tryptophan-ketoglutarate). Changes in the vein wall were histologically investigated up to day 35. Possible retention of the capacity of endothelial function was evaluated by immunohistochemical detection of endothelial nitric oxide synthase.

RESULTS:

Formalin as the control medium well preserved the vein wall morphology, but endothelial nitric oxide synthase immunostaining was very weak. Phosphate-buffered saline and isotonic saline with heparin and antibiotic poorly preserved vein wall morphology. Phosphate-buffered saline endothelial nitric oxide synthase staining decreased dramatically throughout the study period. Compared to phosphate-buffered saline, stronger isotonic saline with heparin and antibiotic endothelial nitric oxide synthase staining was noted at day 35 (p < 0.001). Custodiol and glutaraldehyde better preserved vein morphology compared to ISHA and PBS at day 5 and later (p < 0.001), but compared to stronger isotonic saline with heparin and antibiotic their endothelial nitric oxide synthase staining was weaker.

CONCLUSION:

In terms of preserving the morphology of saphenous veins, phosphate-buffered saline and isotonic saline with heparin and antibiotic were the poorest, while Custodiol and glutaraldehyde were the best. Demonstrating good retention of endothelial nitric oxide synthase staining throughout the study period, isotonic saline with heparin and antibiotic seems to have the best potential to retain vein wall functionality, despite relatively poor morphological preservation.

Can we improve the results of venous grafts in CABG?

Saphenous Vein as a conduit in coronary artery bypass surgery (CABG) has a high attrition rate. Yet because of free availability and technical ease of use, it accounts for 80% of all grafts in CABG. The reasons for its failure and the ways to improve its patency have been discussed in this video article with special emphasis on post harvest storage of the vein grafts.

Vascular surgical stretch injury leads to activation of P2X7 receptors and impaired endothelial function

A viable vascular endothelial layer prevents vasomotor dysfunction, thrombosis, inflammation, and intimal hyperplasia. Injury to the endothelium occurs during harvest and “back table” preparation of human saphenous vein prior to implantation as an arterial bypass conduit. A subfailure overstretch model of rat aorta was used to show that subfailure stretch injury of vascular tissue leads to impaired endothelial-dependent relaxation. Stretch-induced impaired relaxation was mitigated by treatment with purinergic P2X7 receptor (P2X7R) inhibitors, brilliant blue FCF (FCF) and A740003, or apyrase, an enzyme that catalyzes the hydrolysis of ATP. Alternatively, treatment of rat aorta with exogenous ATP or 2’(3’)-O-(4-Benzoyl benzoyl)-ATP (BzATP) also impaired endothelial-dependent relaxation. Treatment of human saphenous vein endothelial cells (HSVEC) with exogenous ATP led to reduced nitric oxide production which was associated with increased phosphorylation of the stress activated protein kinase, p38 MAPK. ATP- stimulated p38 MAPK phosphorylation of HSVEC was inhibited by FCF and SB203580. Moreover, ATP inhibition of nitric oxide production in HSVEC was prevented by FCF, SB203580, L-arginine supplementation and arginase inhibition. Finally, L-arginine supplementation and arginase inhibition restored endothelial dependent relaxation after stretch injury of rat aorta. These results suggest that vascular stretch injury leads to ATP release, activation of P2X7R and p38 MAPK resulting in endothelial dysfunction due to arginase activation. Endothelial function can be restored in both ATP treated HSVEC and intact stretch injured rat aorta by P2X7 receptor inhibition with FCF or L-arginine supplementation, implicating straightforward therapeutic options for treatment of surgical vascular injury.

Limiting Injury During Saphenous Vein Graft Preparation For Coronary Arterial Bypass Prevents Metabolic Decompensation

Standard harvest and preparation of human saphenous vein (HSV) for autologous coronary and peripheral arterial bypass procedures is associated with injury and increased oxidative stress that negatively affect graft performance. In this study we investigated the global metabolomic profiles of HSV before (unprepared; UP) and after standard vein graft preparation (AP). AP-HSV showed impaired vasomotor function that was associated with increased oxidative stress, phospholipid hydrolysis and energy depletion that are characteristic of mechanical and chemical injury. A porcine model (PSV) was utilized to validate these metabolomic changes in HSV and to determine the efficacy of an improved preparation technique (OP) using pressure-regulated distension, a non-toxic vein marker, and graft storage in buffered PlasmaLyte solution in limiting metabolic decompensation due to graft preparation. Deficits in vasomotor function and metabolic signature observed in AP-PSV could be largely mitigated with the OP procedure. These findings suggest that simple strategies aimed at reducing injury during graft harvest and preparation represents a straightforward and viable strategy to preserve conduit function and possibly improve graft patency.