A novel endothelial damage inhibitor for the treatment of vascular conduits in coronary artery bypass grafting: protocol and rationale for the European, multicentre, prospective, observational DuraGraft registry

Outcomes after surgical revascularization in diabetic patients

OBJECTIVES

Patients with diabetes mellitus (DM) undergoing coronary artery bypass grafting (CABG) have been repeatedly demonstrated to have worse clinical outcomes compared to patients without DM. The objective of this study was to evaluate the impact of DM on 1-year clinical outcomes after isolated CABG.

METHODS

The European DuraGraft registry included 1130 patients (44.6%) with and 1402 (55.4%) patients without DM undergoing isolated CABG. Intra-operatively, all free venous and arterial grafts were treated with an endothelial damage inhibitor. Primary end point in this analysis was the incidence of a major adverse cardiac event (MACE), a composite of all-cause death, repeat revascularization or myocardial infarction at 1 year post-CABG. To balance between differences in baseline characteristics (n = 1072 patients in each group), propensity score matching was used. Multivariable Cox proportional hazards regression was performed to identify independent predictors of MACE.

RESULTS

Diabetic patients had a higher cardiovascular risk profile and EuroSCORE II with overall more comorbidities. Patients were comparable in regard to surgical techniques and completeness of revascularization. At 1 year, diabetics had a higher MACE rate {7.9% vs 5.5%, hazard ratio (HR) 1.43 [95% confidence interval (CI) 1.05-1.95], P = 0.02}, driven by increased rates of death [5.6% vs 3.5%, HR 1.61 (95% CI 1.10-2.36), P = 0.01] and myocardial infarction [2.8% vs 1.4%, HR 1.99 (95% CI 1.12-3.53) P = 0.02]. Following propensity matching, no statistically significant difference was found for MACE [7.1% vs 5.7%, HR 1.23 (95% CI 0.87-1.74) P = 0.23] or its components. Age, critical operative state, extracardiac arteriopathy, ejection fraction ≤50% and left main disease but not DM were identified as independent predictors for MACE.

CONCLUSIONS

In this study, 1-year outcomes in diabetics undergoing isolated CABG were comparable to patients without DM.

Radial artery graft in coronary artery bypass surgery 1 week to 1 year postoperation

Background

The actual patency rate of the radial artery (RA) grafts 1 week and 1 year after coronary artery bypass grafting (CABG) has not been extensively reported on. We used coronary computed tomography angiography (CCTA) to evaluate the patency rate of RA grafts and compared it with that of saphenous vein (SV) grafts.

Methods

In this observational cohort study, 80 patients who underwent urgent or elective CABG with RA and SV grafts at Ruijin Hospital from August 2019 to June 2021 were included. Follow-up CCTA scans were completed about 1 year postoperation in the out-patient clinic. We graded the grafts into four classes: A, excellent; B, graft diameter <50% of target coronary artery; O, occluded; and S, string sign. Both S and O were defined as graft failure.

Results

The patients' mean age was 58.48±8.06 years, and 87.5% (70/80) of the patients were male. The 1-week patency rate of the left internal mammary artery (LIMA), RA, and SV grafts were 98.7% (75/76), 76.3% (61/80), and 93.8% (75/80), respectively. At 1 year, the patency rate of the LIMA, RA, and SV grafts were 97.4% (74/76), 80.0% (64/80), and 81.3% (65/80), respectively. The RA graft patency rate was lower than was the SV graft patency rate perioperatively [relative risk (RR): 0.918; 95% confidence interval (CI): 0.852-0.990; P=0.007]. Moreover, 63.6% (7/11) of RA grafts graded S and 25.0% (2/8) of RA grafts graded O were defined as patent (graded A or B) at 1 year postoperation. Compared with SV grafts, more RA grafts improved (RA: 12/80, 15.0%; SV: 0%) and fewer RA grafts deteriorated (RV: 10/80, 12.5%; SV: 19/80, 23.8%) from 1 week to 1 year (P=0.001). The patency rate of the 2 types of grafts became similar at 1 year postoperation (RR: 0.560; 95% CI: 0.113-2.781; P>0.99).

Conclusions

RA grafts had a lower patency rate than did SV grafts 1 week after operation. However, because of the "revival" phenomena and lower attrition rate, the patency rate of the two kinds of grafts did not show any significant difference at 1 year.

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.

Effects of hypoxia versus ischaemia on vascular functions of isolated rat thoracic aorta: revisiting the in vitro vascular ischaemia/reperfusion model

Introduction

The in vitro rat vascular ischaemia and reperfusion model is used to evaluate the molecular and functional effects of potential agents against ischaemia and reperfusion injury of autologous graft veins. However, there is no consensus on whether hypoxia, rather than ischaemia, is sufficient to induce vascular dysfunction.

Aim

To compare the effects of hypoxia and ischaemia, with or without reperfusion, on the vascular functions of isolated thoracic aortic rings of rats.

Material and methods

Thoracic aortas of 12 male Sprague-Dawley rats (350-500 g, 18-24 months old) were isolated and divided into rings that were randomly allocated to control, ischaemia, hypoxia, ischaemia-reperfusion, and hypoxia-reperfusion groups. Aortic rings other than those of the control group were stored at 4°C for 24 h in saline. For ischaemia, saline was gassed with nitrogen. After 24 h, aortic rings in the ischaemia-reperfusion and hypoxia-reperfusion groups were incubated with 200 μM sodium hypochlorite for 30 min. Vascular and endothelial functions were tested in an organ bath set-up.

Results

Vascular response to potassium chloride (80 mM) decreased in all experimental groups compared to the control group (p = 0.007), but phenylephrine-induced contraction (10-5 M) increased only in the ischaemia-reperfusion group (p < 0.0001). Acetylcholine (10-11-10-5 M)-induced endothelium-dependent vasorelaxations were impaired in all groups - particularly in the ischaemia-reperfusion group (p = 0.0011). Sodium nitroprusside (10-12-10-7 M)-induced endothelium-independent vasorelaxations were similar across all groups (p = 0.1258).

Conclusions

Ischaemia followed by reperfusion should be implanted to achieve maximum endothelial and contractile dysfunction in vitro, and to replicate ischaemia and reperfusion injury of autologous graft veins.

Clinical outcomes and quality of life after contemporary isolated coronary bypass grafting: a prospective cohort study

OBJECTIVES

The objective of the European Multicenter Registry to Assess Outcomes in coronary artery bypass grafting (CABG) patients (DuraGraft Registry) was to determine clinical outcomes and quality of life (QoL) after contemporary CABG that included isolated CABG and combined CABG/valve procedures, using an endothelial damage inhibitor (DuraGraft) intraoperatively for conduit preservation. Here, we report outcomes in the patient cohort undergoing isolated CABG.

METHODS

The primary outcome was the composite of all-cause death, myocardial infarction (MI), or repeat revascularization (RR) [major adverse cardiac events (MACE)] at 1 year. Secondary outcomes included the composite of all-cause death, MI, RR, or stroke [major adverse cardiac and cerebrovascular events (MACCE)], and QoL. QoL was assessed with the EuroQol-5 Dimension questionnaire. Independent risk factors for MACE at 1 year were determined using Cox regression analysis.

RESULTS

A total of 2532 patients (mean age, 67.4±9.2 years; 82.5% male) underwent isolated CABG. The median EuroScore II was 1.4 [interquartile range (IQR), 0.9-2.3]. MACE and MACCE rates at 1 year were 6.6% and 7.8%, respectively. The rates of all-cause death, MI, RR, and stroke were 4.4, 2.0, 2.2, and 1.9%, respectively. The 30-day mortality rate was 2.3%. Age, extracardiac arteriopathy, left ventricular ejection fraction less than 50%, critical operative state, and left main disease were independent risk factors for MACE. QoL index values improved from 0.84 [IQR, 0.72-0.92] at baseline to 0.92 [IQR, 0.82-1.00] at 1 year ( P <0.0001).

CONCLUSION

Contemporary European patients undergoing isolated CABG have a low 1-year clinical event rate and an improved QoL.

Clinical event rate in patients with and without left main disease undergoing isolated CABG: results from the European DuraGraft registry

OBJECTIVES

Left main coronary artery disease (LMCAD) is considered an independent risk factor for clinical events after coronary artery bypass grafting (CABG). We have conducted a subgroup analysis of the multicentre European DuraGraft registry to investigate clinical event-rates at 1-year in patients with and without LMCAD undergoing isolated CABG in contemporary practice.

METHODS

Patients undergoing isolated CABG were selected. The primary end-point was the incidence of a major adverse cardiac event (MACE) defined as the composite of death, myocardial infarction (MI) or repeat revascularization (RR) at 1-year. The secondary end-point was major adverse cardiac and cerebrovascular events (MACCE) defined as MACE plus stroke. Propensity score matching (PSM) was performed to balance for differences in baseline characteristics.

RESULTS

LMCAD was present in 1,033 (41.2%) and absent in 1,477 (58.8%) patients. At 1-year, the MACE rate was higher for LMCAD patients (8.2% vs 5.1%, p = 0.002) driven by higher rates of death (5.4% vs 3.4%, p = 0.016), MI (3.0% vs 1.3%, p = 0.002) and numerically higher rates of RR (2.8% vs 1.8%, p = 0.13). The incidence of MACCE was 8.8% vs 6.6%, p = 0.043 with a stroke rate of 1.0% and 2.4%, p = 0.011, for LMCAD and non-LMCAD group, respectively. After PSM, the MACE rate was 8.0% vs 5.2%, p = 0.015. The incidence of death was 5.1% vs 3.7%, p = 0.10, MI 3.0% vs 1.4%, p = 0.020, and RR was 2.7% vs 1.6%, p = 0.090, for the LMCAD and non-LMCAD group, respectively. Less strokes occurred in LMCAD patients (1.0% vs 2.4%, p = 0.017). The MACCE rate was not different: 8.5% vs 6.7%, p = 0.12.

CONCLUSIONS

In this large registry, LMCAD was demonstrated to be an independent risk factor for MACE after isolated CABG. Conversely, the risk of stroke was lower in LMCAD patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02922088.

Efficacy of Intraoperative Vein Graft Storage Solutions in Preserving Endothelial Cell Integrity during Coronary Artery Bypass Surgery

(1) Introduction: Intraoperative preservation solutions for saphenous vein grafts may influence the endothelial structure and increase the risk of graft failure after coronary surgery. The aim of the study was to compare the efficacy of three solutions in maintaining the endothelial cell integrity of venous segments. (2) Methods: We tested the efficacy of physiological saline solution (PSS), heparinized autologous blood (HAB) and DuraGraft® in preserving the endothelium of vein segments by evaluating the degree of endothelial cell apoptosis. Two incubation times (2 and 4 h from harvesting) were used for each solution. The quantification of apoptotic cells was computed as the intensity nuclei/intensity area ratio. (3) Results: After 2 h of ischemia, the degree of apoptosis decreased progressively across the use of DuraGraft, HAB and PSS (p = 0.004), although only the difference between DuraGraft and PSS yielded a statistical significance (p = 0.002). After 4 h, a similar decrease in apoptosis was shown across the three media; however, statistical significance was not reached. The analysis of the elapsed time (2 or 4 h of incubation) showed that this was a relevant factor in maintaining the endothelial structural integrity independently from the storage solution (test for interaction of media and time p = 0.010). (4) Conclusion: Within 2 h of incubation, endothelial structural integrity depended on the incubating medium. DuraGraft better protected the SVG against ischemic-induced apoptosis when compared to saline solution. Prolonged ischemia was associated with extended endothelium damage and none of the studied solutions protected the vein graft.

Effect of different storage solutions on oxidative stress in human saphenous vein grafts

BACKGROUND

Ischemia-reperfusion injury of saphenous vein grafts (SVG) during coronary artery bypass grafting surgery negatively impacts endothelial integrity and functionality and is associated with vein graft failure. The aim of this study was to evaluate the level of oxidative stress in human SVG segments following ischemic storage in three intraoperative graft storage solutions: saline (S), autologous heparinized blood (HB) and DuraGraft (DG).

METHODS

3 mm tissue rings derived from surplus SVG segments from 50 patients were stored at room temperature for 30 min in DG, S or HB. Total oxidative status (TOS) and total antioxidant status (TAS) levels were determined from which the oxidative stress index (OSI: TOS/TAS ratio) was calculated. A p-value < 0.017 was considered significant implementing a Bonferroni correction.

RESULTS

TOS values were significantly lower for DG stored samples in comparison to both S and HB; there was no difference between S and HB (DG: 32.6 ± 1.8, S: 39.6 ± 2.8 and HB: 40.6 ± 2.4 µmol H₂O₂ eqv.; DG vs. S and DG vs. HB p < 0.0001, S vs. HB p = 0.047). TAS was higher for both DG and HB in comparison to S (DG: 8.9 ± 0.9, S: 6.9 ± 1.0 and HB: 8.6 ± 0.9 mmol Trolox eqv.; DG vs S p < 0.0001, DG vs. HB p = 0.263, S vs. HB p < 0.0001). OSI differed between all groups with the lowest value for DG (DG: 3.7 ± 0.2, S: 5.8 ± 0.4 and HB: 4.7 ± 0.2 µmol H₂O₂ eqv./mmol Trolox eqv.; all p < 0.0001).

CONCLUSIONS

Saphenous veins grafts stored in DuraGraft had a lower oxidative level, higher antioxidant level and a lower oxidative stress index in comparison to saphenous vein grafts stored in saline or heparinized blood. ClinicalTrials.gov Identifier NCT02922088.

A Novel Endothelial Damage Inhibitor Reduces Oxidative Stress and Improves Cellular Integrity in Radial Artery Grafts for Coronary Artery Bypass

The radial artery (RA) is a frequently used conduit in coronary artery bypass grafting (CABG). Endothelial injury incurred during graft harvesting promotes oxidative damage, which leads to graft disease and graft failure. We evaluated the protective effect of DuraGraft®, an endothelial damage inhibitor (EDI), on RA grafts. We further compared the protective effect of the EDI between RA grafts and saphenous vein grafts (SVG). Samples of RA (n = 10) and SVG (n = 13) from 23 patients undergoing CABG were flushed and preserved with either EDI or heparinized Ringer's lactate solution (RL). The effect of EDI vs. RL on endothelial damage was evaluated ex vivo and in vitro using histological analysis, immunofluorescence staining, Western blot, and scanning electron microscopy. EDI-treated RA grafts showed a significant reduction of endothelial and sub-endothelial damage. Lower level of reactive oxygen species (ROS) after EDI treatment was correlated with a reduction of hypoxic damage (eNOS and Caveolin-1) and significant increase of oxidation-reduction potential. Additionally, an increased expression of TGFβ, PDGFα/β, and HO-1 which are indicative for vascular protective function were observed after EDI exposure. EDI treatment preserves functionality and integrity of endothelial and intimal cells. Therefore, EDI may have the potential to reduce the occurrence of graft disease and failure in RA grafts in patients undergoing CABG.

Graft Preservation Solution DuraGraft® Alleviates Vascular Dysfunction Following In Vitro Ischemia/Reperfusion Injury in Rats

Vascular ischemia/reperfusion injury (IRI) in patients undergoing coronary artery bypass grafting can result in graft failure and the need for repeat revascularization procedures. DuraGraft^® has been shown to protect structure and function in saphenous vein grafts against IRI. We compared the effect of DuraGraft^® to saline solution on arterial grafts submitted to IRI. Rat thoracic aortic rings were harvested and immediately mounted in organ bath chambers (control, n = 7 rats) or underwent cold ischemic preservation either in saline (IR, n = 9 rats) or DuraGraft^® (IR+Dura, n = 9 rats). Vascular function was measured ex vivo and immunohistochemistry was performed. Impaired maximum vasorelaxation (R_max) to ACh in the IR-group compared to controls was ameliorated by DuraGraft^®, indicating an improvement in endothelial function (R_max to ACh (%): IR + Dura 73 ± 2 vs. IR 48 ± 3, p < 0.05). Additionally, decreased aortic ring sensitivity to ACh (pD₂-value: -log 50% maximum response) seen after IR in the saline group was increased by DuraGraft^® (pD₂ to ACh: IR+Dura 7.1 ± 0.1 vs. IR 6.3 ± 0.2, p < 0.05). Impaired maximum contractile response to phenylephrine and high potassium chloride concentrations in the IR group compared to controls was significantly improved by DuraGraft^®. DuraGraft^® alleviates vascular dysfunction following IRI by reducing nitro-oxidative stress and the expression of ICAM-1, without leukocytes engagement.

Author's reply (in reference to letter to editor proposed by Etem Caliskan, Catherine J. Pachuk, Louis P. Perrault, Maximilian Y Emmert and entitled: preservation solutions to improve graft patency: The devil is in the detail)

Not applicable.

Endothelial damage inhibitors for improvement of saphenous vein graft patency in coronary artery bypass grafting

The saphenous vein graft (SVG) remains the most commonly used conduit in coronary artery bypass grafting (CABG). In light of this further research must be aimed at the development of strategies to optimize SVG patency and thereby improve both short- and long-term outcomes of CABG surgery. SVG patency in large part depends on the protection of the structural and functional integrity of the vascular endothelium at the time of conduit harvesting, including optimal storage conditions to prevent endothelial damage. This review provides an overview of currently available storage and preservation solutions, including novel endothelial damage inhibitors, and their role in mitigating endothelial damage and vein graft failure.