Endothelial cell injury in cardiovascular surgery: atherosclerosis

Impact of Atherogenic Indexes in Saphenous Vein Graft Stenosis

Fundamento

Os enxertos de veias safenas (EVS) são frequentemente usados em pacientes submetidos a cirurgia de revascularização do miocárdio (CRM).

Objetivos

Avaliar as relações entre índices aterogênicos e estenose de EVS. Métodos: No total, 534 pacientes (27,7% mulheres, com idade média de 65±8,4 anos) submetidos a CRM e angiografia coronariana eletiva foram incluídos no estudo. Pacientes com pelo menos uma estenose EVS ≥50% foram alocados ao grupo estenose EVS (+) (n=259) e pacientes sem estenose foram classificados como EVS (-) (n=275). O índice aterogênico plasmático (IAP) e o coeficiente aterogênico (CA) foram calculados a partir dos parâmetros lipídicos de rotina dos pacientes. A significância foi estabelecida no nível p<0,05.

Resultados

O número de pacientes com histórico de hipertensão (HT), diabetes mellitus (DM), acidente vascular cerebral e insuficiência cardíaca (IC) se mostrou significativamente maior no grupo EVS (+) do que no grupo EVS (-). O colesterol total, triglicerídeos e colesterol LDL mostraram-se significativamente mais altos e o colesterol HDL mostrou-se menor no grupo EVS (+) do que no grupo EVS (-). IAP (p<0,001) e CA (p<0,001) apresentaram-se significativamente mais altos no grupo EVS (+) do que no grupo EVS (-). A análise ROC mostra que tanto o IAP quanto o CA mostraram-se melhores que o colesterol HDL, colesterol LDL e colesterol não HDL na predição de estenose de EVS. Na análise multivariada, histórico de DM, HT, acidente vascular cerebral, IC, número de enxertos de safena, colesterol HDL, colesterol LDL, colesterol não HDL, IAP e CA foram fatores de risco independentes para estenose de EVS.

Conclusão

O IAP e o CA foram preditores independentes de estenose de EVS. Além disso, tanto o IAP quanto o CA têm melhor desempenho na predição de estenose de EVS do que o colesterol LDL, colesterol HDL e colesterol não HDL. (Arq Bras Cardiol. 2020; 115(3):538-544)

Role of smooth muscle cells in coronary artery bypass grafting failure

Atherosclerosis is the underlying pathology of many cardiovascular diseases. The formation and rupture of atherosclerotic plaques in the coronary arteries results in angina and myocardial infarction. Venous coronary artery bypass grafts are designed to reduce the consequences of atherosclerosis in the coronary arteries by diverting blood flow around the atherosclerotic plaques. However, vein grafts suffer a high failure rate due to intimal thickening that occurs as a result of vascular cell injury and activation and can act as 'a soil' for subsequent atherosclerotic plaque formation. A clinically-proven method for the reduction of vein graft intimal thickening and subsequent major adverse clinical events is currently not available. Consequently, a greater understanding of the underlying mechanisms of intimal thickening may be beneficial for the design of future therapies for vein graft failure. Vein grafting induces inflammation and endothelial cell damage and dysfunction, that promotes vascular smooth muscle cell (VSMC) migration, and proliferation. Injury to the wall of the vein as a result of grafting leads to the production of chemoattractants, remodelling of the extracellular matrix and cell-cell contacts; which all contribute to the induction of VSMC migration and proliferation. This review focuses on the role of altered behaviour of VSMCs in the vein graft and some of the factors which critically lead to intimal thickening that pre-disposes the vein graft to further atherosclerosis and re-occurrence of symptoms in the patient.

Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery-A randomized, double-blinded, clinical trial

BACKGROUND

Experimental and volunteer studies have reported pulmonary vasoconstriction during transfusion of packed red blood cells (PRBCs) stored for prolonged periods. The primary aim of this study was to evaluate whether transfusion of PRBCs stored over 21 days (standard-issue, siPRBCs) increases pulmonary artery pressure (PAP) to a greater extent than transfusion of PRBCs stored for less then 14 days (fresh, fPRBCs) in critically ill patients following cardiac surgery. The key secondary aim was to assess whether the pulmonary vascular resistance index (PVRI) increases after transfusion of siPRBCs to a greater extent than after transfusion of fPRBCs.

METHODS

The study was performed as a single-center, double-blinded, parallel-group, randomized clinical trial. Leukoreduced PRBCs were transfused while continuously measuring hemodynamic parameters. Systemic concentrations of syndecan-1 were measured to assess glycocalyx injury. After randomizing 19 patients between January 2014 and June 2016, the study was stopped due to protracted patient recruitment.

RESULTS

Of 19 randomized patients, 11 patients were transfused and included in statistical analyses. Eight patients were excluded prior to transfusion, 6 patients received fPRBCs (10±3 storage days), whereas 5 patients received siPRBCs (33±4 storage days). The increase in PAP (7±3 vs. 2±2 mmHg, P = 0.012) was greater during transfusion of siPRBCs than during transfusion of fPRBCs. In addition, the change in PVRI (150±89 vs. -4±37 dyn·s·cm-5·m2, P = 0.018) was greater after transfusion of siPRBCs than after transfusion of fPRBCs. The increase in PAP correlated with the change of systemic syndecan-1 concentrations at the end of transfusion (R = 0.64,P = 0.034).

CONCLUSION

Although this study is underpowered and results require verification in larger clinical trials, our findings suggest that transfusion of siPRBCs increases PAP and PVRI to a greater extent than transfusion of fPRBCs in critically ill patients following cardiac surgery. Glycocalyx injury might contribute to pulmonary vasoconstriction associated with transfusion of stored blood.

Anti-Inflammatory Effects of Taraxasterol on LPS-Stimulated Human Umbilical Vein Endothelial Cells

In the present study, we used the human umbilical vein endothelial cells (HUVECs) to investigate the anti-inflammatory effects and mechanism of taraxasterol on vascular inflammation. HUVECs were pre-treated with taraxasterol 1 h before lipopolysaccharide (LPS) treatment. The concentrations of TNF-α, IL-8, PGE2, and NO were measured. The expression of VCAM-1, ICAM-1, iNOS, COX-2, NF-κB, and LXRα was detected by western blot analysis. The results showed that taraxasterol not only reduced the production of TNF-α, IL-8, PGE2, and NO induced by LPS, but also reduced the expression of iNOS and COX-2. Taraxasterol also suppressed LPS-induced NF-κB activation and VCAM-1 and ICAM-1 expression. Furthermore, taraxasterol concentration-dependently increased the expression of LXRα. The inhibition of taraxasterol on TNF-α, IL-8, PGE2, and NO production can be reversed by geranylgeranyl diphosphate (GGPP, the LXRα inhibitor). Here, we found that taraxasterol inhibited vascular inflammation through activating LXRα.

Mesenchymal Stromal Cells Protect Endothelial Cells from Cytotoxic T Lymphocyte-Induced Lysis

The integrity of the vasculature plays an important role in the success of allogeneic organ and haematopoietic stem cell transplantation. Endothelial cells (EC) have previously been shown to be the target of activated cytotoxic T lymphocytes (CTL) resulting in extensive cell lysis. Mesenchymal stromal cells (MSC) are multipotent cells which can be isolated from multiple sites, each demonstrating immunomodulatory capabilities. They are explored herein for their potential to protect EC from CTL-targeted lysis. CD8(+) T cells isolated from human PBMC were stimulated with mitotically inactive cells of a human microvascular endothelial cell line (CDC/EU.HMEC-1, further referred to as HMEC) for 7 days. Target HMEC were cultured in the presence or absence of MSC for 24 h before exposure to activated allogeneic CTL for 4 h. EC were then analysed for cytotoxic lysis by flow cytometry. Culture of HMEC with MSC in the efferent immune phase (24 h before the assay) led to a decrease in HMEC lysis. This lysis was determined to be MHC Class I restricted linked and further analysis suggested that MSC contact is important in abrogation of lysis, as protection is reduced where MSC are separated in transwell experiments. The efficacy of multiple sources of MSC was also confirmed, and the collaborative effect of MSC and the endothelium protective drug defibrotide were determined, with defibrotide enhancing the protection provided by MSC. These results support the use of MSC as an adjuvant cellular therapeutic in transplant medicine, alone or in conjunction with EC protective agents such as defibrotide.

Role of Vorapaxar After Coronary Revascularization

We aim to evaluate the potential benefit and risk of addition of vorapaxar to standard medical therapy in patients who underwent coronary revascularization with either percutaneous coronary revascularization or coronary artery bypass graft surgery. We searched PubMed, EMBASE, the Cochrane Central Register of Controlled trials, and the clinical trial registry maintained at clinicaltrials.gov for randomized control trials evaluating the safety and efficacy of vorapaxar in patients who underwent coronary revascularization procedures with either percutaneous coronary revascularization or coronary artery bypass graft surgery. Event rates were compared using a Forest plot of relative risk using a random-effects model. The 5 studies (n = 24,025) that met all criteria were included in the final analysis. After coronary revascularization procedures, addition of vorapaxar to standard medical therapy was associated with reduction in the risk of myocardial infarction (MI; risk ratio 0.83 [0.75 to 0.92]) and ischemic stroke (0.011 [0.007 to 0.016]); however, it also resulted in significant increase risk of hemorrhagic stroke (1.57 [1.01 to 2.44]) and Thrombolysis In Myocardial Infarction major and minor bleeds (1.36 [1.07 to 1.70]). There was no significant difference in the risk of cardiovascular mortality (0.90 [0.73 to 1.09]), repeat revascularization (0.78 [0.23 to 2.70]), and stent thrombosis (0.95 [0.62 to 1.45]) in the vorapaxar and control groups. In conclusion, after coronary revascularization procedures, addition of vorapaxar to standard medical therapy was associated with reduction in the risk of MI and ischemic stroke and increase in risk of hemorrhagic stroke and Thrombolysis In Myocardial Infarction major and minor bleeds.

Pulmonary Protection Strategies in Cardiac Surgery: Are We Making Any Progress?

Pulmonary dysfunction is a common complication of cardiac surgery. The mechanisms involved in the development of pulmonary dysfunction are multifactorial and can be related to the activation of inflammatory and oxidative stress pathways. Clinical manifestation varies from mild atelectasis to severe respiratory failure. Managing pulmonary dysfunction postcardiac surgery is a multistep process that starts before surgery and continues during both the operative and postoperative phases. Different pulmonary protection strategies have evolved over the years; however, the wide acceptance and clinical application of such techniques remain hindered by the poor level of evidence or the sample size of the studies. A better understanding of available modalities and/or combinations can result in the development of customised strategies for the different cohorts of patients with the potential to hence maximise patients and institutes benefits.

Optimization of metabolite extraction of human vein tissue for ultra performance liquid chromatography-mass spectrometry and nuclear magnetic resonance-based untargeted metabolic profiling

Tissue extraction optimization for untargeted metabolic profiling.

Efficient differentiation of human pluripotent stem cells to endothelial progenitors via small-molecule activation of WNT signaling

Human pluripotent stem cell (hPSC)-derived endothelial cells and their progenitors may provide the means for vascularization of tissue-engineered constructs and can serve as models to study vascular development and disease. Here, we report a method to efficiently produce endothelial cells from hPSCs via GSK3 inhibition and culture in defined media to direct hPSC differentiation to CD34⁺CD31⁺ endothelial progenitors. Exogenous vascular endothelial growth factor (VEGF) treatment was dispensable, and endothelial progenitor differentiation was β-catenin dependent. Furthermore, by clonal analysis, we showed that CD34⁺CD31⁺CD117⁺TIE-2⁺ endothelial progenitors were multipotent, capable of differentiating into calponin-expressing smooth muscle cells and CD31⁺CD144⁺vWF⁺I-CAM1⁺ endothelial cells. These endothelial cells were capable of 20 population doublings, formed tube-like structures, imported acetylated low-density lipoprotein, and maintained a dynamic barrier function. This study provides a rapid and efficient method for production of hPSC-derived endothelial progenitors and endothelial cells and identifies WNT/β-catenin signaling as a primary regulator for generating vascular cells from hPSCs.

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WNT pathway activation directs hPSC differentiation to endothelial progenitors

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hPSC-derived endothelial progenitors can differentiate to endothelial cells

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Purified hPSC-derived endothelial cells are capable of 20 population doublings

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WNT pathway activation permits defined production of endothelial cells from hPSCs

The effect of resveratrol on intimal hyperplasia and endothelial proliferation of rabbit carotid artery anastomosis

OBJECTIVES

We assessed the effect of resveratrol on intimal hyperplasia and endothelial proliferation after its use for carotid artery anastomosis in rabbits.

METHODS

Fourteen New Zealand-type male rabbits, weighing a mean of 2-3 kg were selected randomly. Their right carotid arteries were transected and anastomosed side by side using 8/0 polypropylene. The rabbits were divided into two groups with seven in each group. While the rabbits in the first group were accepted as the Control group, the rabbits in the second group were given resveratrol (1 mg/kg/day) for 14 days intravenously. At the end of the 28th day, all the carotid artery segments that were transected and anastomosed and the left carotid arteries that did not undergo surgery were removed and evaluated histologically.

RESULTS

The results of histological evaluation were as follows: lumen diameter (P <0.001) and lumen area (P <0.05) of the Resveratrol group were larger than those of the Control group, intimal thickness (P <0.05) and media thickness of the Resveratrol group (P = 0.04) were thinner than those of the Control group, and intima/media ratio of the Control group was found to be greater than that of the Resveratrol group (P = 0.002).

CONCLUSIONS

Resveratrol can prevent intimal hyperplasia and endothelial proliferation following surgical anastomosis.

Coronary artery bypass graft: why is the saphenous vein prone to intimal hyperplasia?

Proliferation and migration of smooth muscle cells and the resultant intimal hyperplasia cause coronary artery bypass graft failure. Both internal mammary artery and saphenous vein are the most commonly used bypass conduits. Although an internal mammary artery graft is immune to restenosis, a saphenous vein graft is prone to develop restenosis. We found significantly higher activity of phosphatase and tensin homolog (PTEN) in the smooth muscle cells of the internal mammary artery than in the saphenous vein. In this article, we critically review the pathophysiology of vein-graft failure with detailed discussion of the involvement of various factors, including PTEN, matrix metalloproteinases, and tissue inhibitor of metalloproteinases, in uncontrolled proliferation and migration of smooth muscle cells towards the lumen, and invasion of the graft conduit. We identified potential target sites that could be useful in preventing and (or) reversing unwanted consequences following coronary artery bypass graft using saphenous vein.

Unmet needs in the management of acute myocardial infarction: role of novel protease-activated receptor-1 antagonist vorapaxar

Platelet activation with subsequent aggregation is a complex process leading to thrombus formation, which remains a key component for atherothrombotic manifestations, in particular myocardial infarction. Therefore, antiplatelet therapies are pivotal for the treatment of these patients. Current oral antiplatelet therapies used for secondary prevention of ischemic recurrences include aspirin and adenosine diphosphate P2Y12 platelet-receptor antagonists. However, despite these therapies, patients who have experienced a myocardial infarction remain at risk for ischemic recurrences. Therefore, more aggressive secondary prevention measures have been an area of research, including identifying additional targets modulating platelet-activation and -aggregation processes. Among these, thrombin-mediated platelet activation via protease-activated receptors (PARs) has been subject to extensive clinical investigation. Several PAR-1 receptor antagonists have been developed. However, vorapaxar is the only one that has completed large-scale clinical investigation. The present manuscript will provide an overview on the role of thrombin-mediated signaling, the impact of PAR-1 blockade with vorapaxar on ischemic and bleeding outcomes, and the potential role for vorapaxar in clinical practice.

Inhibitory effects and mechanisms of luteolin on proliferation and migration of vascular smooth muscle cells

Atherosclerosis (AS) is a complicated progress, involving many types of cells. Although the exact mechanisms of progression of atherosclerosis are uncertain, the balance of vascular smooth muscle cells (VSMCs) proliferation and apoptosis appears to play a pivotal role in the pathogenesis and progression of atherosclerosis, and much discussion has been undertaken to elucidate the detailed mechanisms, relevant gene expression and transduction pathways. Drug treatment has focused on ameliorating atherosclerosis. Some researchers have indicated that inhibiting VSMCs proliferation is involved in attenuating atherosclerosis. Luteolin is a kind of flavonoids naturally occurring in many plants and possesses beneficial effects on cardiovascular diseases. Luteolin can reduce VSMCs’ proliferation and migration and this reduction is stimulated by several factors. The aim of this review is to summarize the existing inhibitory effects and mechanisms of luteolin on proliferation and migration of VSMCs, and consider whether luteolin may be a potential candidate for preventing and treating atherosclerosis.

Natural History of Saphenous Vein Grafts

Aortocoronary saphenous vein graft is an effective treatment of coronary artery disease and a means of markedly improving long-term prognosis in certain patient subgroups. However, there is a significant failure rate with these conduits. Early failure occurs within the first 1-2 months, most likely from primary thrombosis. Intermediate failure is usually caused by the development of neointimal hyperplasia. Late failure occurs after 3-5 years and results from accelerated atherosclerosis. The impact of saphenous vein graft failure on cardiovascular outcomes is significant, and it is important to implement appropriate therapeutic strategies to prevent or minimize failure rates.

Saphenous vein graft disease: review of pathophysiology, prevention, and treatment

Saphenous vein graft (SVG) disease after coronary artery bypass grafting (CABG) occurs in three phases: thrombosis, intimal hyperplasia, and atherosclerosis. Within the first month, thrombosis plays a major role. From month 1 to month 12, intimal hyperplasia occurs. Beyond 12 months, atherosclerosis becomes the primary cause for late graft failure. Endothelial damage has been shown to be the major underlying pathophysiology of SVG disease. Many factors contribute to endothelial damage from the moment the vein is harvested to when the vein is grafted into an arterial environment. To address this disease process, various therapeutic modalities, from surgical methods to medical treatment, have been evaluated. Surgically, the technical method of harvesting the vein has been shown to affect SVG patency. From a pharmacologic perspective, only two guideline class I recommended medications, aspirin and statins, have been shown to improve short- and long-term SVG patency after CABG. Despite these surgical and medical advances, SVG disease remains a significant problem with 1-year patency rates of 89% dropping to 61% after 10 years. This review discusses the pathogenesis of SVG disease, predictors of SVG failure, and current surgical and pharmacologic therapies to address SVG disease, including possible future treatment.

Vascular effects of estrogen and progestins and risk of coronary artery disease: importance of timing of estrogen treatment

The effects of estrogen and progestins on the vascular wall have drawn major medical attention, and significant controversy over various studies has been developed. Several experimental and observational studies have shown cardioprotective effects; however, prospective randomized trials showed an increase in cardiovascular events in postmenopausal women on estrogen/ medroxyprogesterone acetate treatment. The most significant parameter for cardiovascular benefit of estrogen seems to be the interval since the onset of menopause. In the early postmenopausal years, estrogen has beneficial effects on the vascular wall by inhibition of atherosclerosis progression, whereas in the late postmenopause, adverse effects like upregulation of the plaque inflammatory processes and plaque instability may develop. The effects of progestins on the cardiovascular system are not as clear and may differ according to the choice of progestins that is used. The aim of this review is to summarize the effects of estrogen and progestins on the vascular wall and their clinical implications.

Endothelin-1-induced pain and hyperalgesia: a review of pathophysiology, clinical manifestations and future therapeutic options

Pain in patients with metastatic cancer contributes to increased suffering in those already burdened by their advancing illness. The causes of this pain are unknown, but are likely to involve the action of tumour-associated mediators and their receptors. In recent years, several chemical mediators have increasingly come to the forefront in the pathophysiology of cancer pain. One such mediator, endothelin-1 (ET-1), is a peptide of 21 amino acids that was initially shown to be a potent vasoconstrictor. Extensive research has revealed that members of the ET family are indeed produced by several epithelial cancerous tumours, in which they act as autocrine and/or paracrine growth factors. Several preclinical and clinical studies of various malignancies have suggested that the ET axis may represent an interesting contributor to tumour progression. In addition, evidence is accumulating to suggest that ET-1 may contribute to pain states both in humans and in other animals. ET-1 both stimulates nociceptors and sensitises them to painful stimuli. Selective stimulation of ET receptors has been implicated as a cause of inflammatory, neuropathic and tumoural pain. ET-1-induced pain-related behaviour seems to be mediated either solely by one receptor type or via both endothelin-A receptors (ETAR) and endothelin-B receptors (ETBR). Whereas stimulation of ETAR on nociceptors always elicits a pain response, stimulation of ETBR may cause analgesia or elicit a pain response, depending on the conditions. The administration of ETAR antagonists in the receptive fields of these nociceptors has been shown to ameliorate pain-related behaviours in animals, as well as in some patients with advanced metastatic prostate cancer. The identification of tumour-associated mediators that might directly or indirectly cause pain in patients with metastatic disease, such as ET-1, should lead to improved, targeted analgesia for patients with advanced cancer. In this review, we will describe the current status of the role of ET-1 in different types of painful syndromes, with special emphasis on its role in the pathophysiology of cancer pain. Finally, potential new treatment options that are based on the role of the ET axis in the pathophysiology of cancer are elaborated.

Clinical Follow-Up of Paclitaxel-Eluting (TAXUS?) Stents for the Treatment of Saphenous Vein Graft Disease

BACKGROUND

Randomized trials in selected patient populations have demonstrated dramatic reductions in the incidence of in-stent restenosis (ISR) following implantation of paclitaxel-eluting (PE) coronary stents compared with bare metal stents in native coronary disease. The clinical outcome following implantation of PE stents for saphenous vein graft (SVG) stenosis is largely unknown.

AIM

To assess the safety and efficacy of PE coronary stents for the treatment of SVG stenosis in an unselected population.

METHODS

All patients who received PE stents for the treatment of SVG disease from May 1, 2003, to May 1, 2005, were entered into a prospectively collected database. Fifty-five patients were identified with 69 lesions. In-hospital and late major adverse cardiac events (MACE) including death, myocardial infarction (MI), and target lesion revascularization (TLR) were recorded as well as the rate of target vessel revascularization (TVR).

RESULTS

Mean follow-up was 13 months with 54 of the 55 patients contacted. The number of stents implanted was 1.12 +/- 0.37 per lesion and 1.38 +/- 0.59 per patient. Clinically significant procedural MACE was 0%. The late MACE rate was 9% with a 2% clinically driven TLR, a 4% coronary artery bypass graft (CABG), and a 4% TVR rate. There were four deaths, two cardiac and two noncardiac.

CONCLUSION

PE stents appear safe and effective in the treatment of SVG disease at a mean follow-up time of 13 months. Randomized studies are needed to further delineate the optimal management of this high-risk group.

Diabetes and distal access location are associated with higher wall shear rate in feeding artery of PTFE grafts

BACKGROUND

Surgical creation of permanent vascular access for haemodialysis leads to considerable haemodynamic changes. They could be implicated in the pathogenesis of access complications, which limit access survival, especially in diabetics. Physiologically, the relation between arterial diameter and blood velocity is maintained by wall shear stress (WSS), which is directly related to both blood viscosity and wall shear rate (WSR = blood velocity/internal diameter). Because of methodological difficulties, WSR is used as a measure of WSS. Extremely high values of WSS might induce hypercoagulable states, which might contribute to access thrombosis. We performed a study, which was aimed to (i) describe WSR values in feeding arteries of various polytetrafluoroethylene access types and (ii) prove that diabetic patients have higher WSR than non-diabetics.

METHODS

A linear-array 11 MHz probe of SONOS 5500 (Phillips, USA) was used to obtain blood velocity and internal diameter in the feeding arteries of radial or brachial polytetrafluoroethylene grafts. WSR was calculated as 4 x blood velocity/internal diameter. We compared observed values of WSR according to feeding artery (radial vs brachial artery) and according to diabetic status using unpaired t-test.

RESULTS

We included 106 patients (58 non-diabetic and 48 diabetic) in the study. WSR was significantly higher in radial arteries compared with brachial arteries independent of diabetes status. Diabetic subjects had significantly higher WSR in both radial and brachial arteries.

CONCLUSIONS

Diabetes mellitus and distal vascular access creation are associated with higher WSR in the feeding artery. This could be of relevance in the pathogenesis of access complications, e.g. thrombosis, and thus lower patency rates in diabetic patients.

Present status of outcome prediction of invasive coronary treatment by using genetic markers

A growing number of studies suggest that the outcome after invasive coronary treatment may be in part genetically determined. Here, we review the present status of outcome prediction of invasive coronary treatments by using genetic markers. Although some studies found an association between one or another genetic marker with one or another clinical endpoint, many other studies found no such relations; to date, none of the genetic markers that have been investigated in association studies are used in routine clinical practice to prospectively assess the prognosis following invasive coronary treatment or to decide upon therapeutic strategies. Many associations between genetic markers and certain clinical endpoints were initially reported in small studies but could not be confirmed in larger ones. Some of these discrepancies may be explained by publication bias. Some genetic variants may have true effects on clinical endpoints, which, albeit biologically interesting, do not bear much clinical relevance. On the other hand, many-if not most-studies that have been published to date are more or less grossly underpowered and very rarely report on the results of an a priori power analysis. Thus, there is still a need for further high-quality studies designed to investigate the specific contribution of genetic factors to the outcome after invasive coronary interventions.

Effect of cardiopulmonary bypass on pulmonary clearance of adrenomedullin in humans

BACKGROUND

Adrenomedullin is a potent vasodilatory peptide and its plasma concentration increases after cardiopulmonary bypass. We analyzed the contribution of the lung to the disposition of adrenomedullin before and after cardiopulmonary bypass in humans.

METHODS

Thirty-five patients undergoing cardiac surgery with cardiopulmonary bypass were studied. Bloods were sampled from the pulmonary artery and left atrium at the following times: prior to systemic heparinization, during pulmonary reperfusion and after cardiopulmonary bypass. Plasma concentrations of total and mature adrenomedullin were measured using an immunoradiometric assay kit specific for human adrenomedullin. Intermediate adrenomedullin was calculated as the difference between total adrenomedullin and mature adrenomedullin.

RESULTS

Before cardiopulmonary bypass, mature and intermediate adrenomedullin concentrations were reduced by the pulmonary circulation by approximately 30% and 20%, respectively. However, these effects were not observed during pulmonary reperfusion. Mature, but not intermediate, adrenomedullin was reduced after cardiopulmonary bypass. Furthermore, pulmonary clearance quantity of mature adrenomedullin was significantly enhanced after cardiopulmonary bypass.

CONCLUSION

These results indicate that cardiopulmonary bypass temporally impairs the pulmonary clearance of mature and intermediate adrenomedullin, but clearance of mature, not intermediate adrenomedullin is enhanced after cardiopulmonary bypass.

Initial experience with a new right ventricular support device for beating heart surgery

OBJECTIVE

Device supported beating heart surgery has been advocated to extend patient selection criteria for off-pump surgery. This article reports the initial experimental and clinical results with a novel paracardial right ventricular support device.

METHODS

Preclinical experiments were performed in two pigs. Ten elective patients with triple vessel disease were subjected to beating heart coronary artery bypass grafting surgery during right ventricular support by the paracardial device. Measurements included intraoperative hemodynamics during cardiac tilting, perioperative left ventricular ejection fraction (LVEF), hemolysis parameters, mortality and major morbidity events.

RESULTS

A mean of 3.2 +/- 0.2 distal anastomoses per patient were performed. Mean arterial pressure and central venous oxygen saturation remained stable during cardiac tilting. Perioperative LVEF did not vary significantly. Sixty-day mortality and postoperative infarction rate were 0%. Functional Canadian Cardiovascular Society class at 6 days after surgery was 1.2 +/- 0.1 vs. 3.3 +/- 0.2 pre-operatively.

CONCLUSION

In this initial clinical experience, application of the novel paracardial right ventricular support device proved to be safe and efficient.

Endothelium and valvular diseases of the heart

It has become increasingly evident that the endothelium plays a critical role in the pathogenesis of valvular heart disease. The endothelium helps regulate vascular tone, inflammation, thrombosis, and vascular remodeling. Dysfunction of the endothelial cells has been linked to many vascular disorders including atherosclerosis. Common valvular diseases such as senile degenerative valve disease, myxomatous (or floppy) valves, rheumatic valves, and infective endocarditis valves show changes in the synthetic, morphologic, and metabolic functions of the valvular endothelial cells. These diseases are active processes related to endothelial cell dysfunction. Endothelial cell dysfunction is caused by mechanical forces, bacterial infection, autoantibodies, and circulating modulators of endothelial cell function. This study reviews the role of endothelial cell dysfunction in the more common valvular diseases. Continued research on endothelial cell dysfunction is crucial to our understanding of valvular heart diseases and may elucidate novel treatment and prevention strategies.

[Surgical revascularization of the myocardium]

It has been 45 years ago when Longmire (1958.) used internal thoracic artery (ITA) for the first time in coronary artery bypass surgery (CABG). In this review, we are presenting novel surgical approaches in CABG surgery. We have also been summarized the best of knowledge, up to date, regarding histology, pharmacology and pathophysiology of conduits (VSM, ITA and alternative venous and arterial grafts) which have been used in CABG surgery, as well as factors influence on its short and long-term patency.

CD44v10 interaction with Rho-kinase (ROK) activates inositol 1,4,5-triphosphate (IP3) receptor-mediated Ca2+ signaling during hyaluronan (HA)-induced endothelial cell migration

Aortic endothelial cells (GM7372A) express a major cell adhesion molecule, CD44v10, which binds the extracellular matrix component, hyaluronan (HA), at its external domain and interacts with various signaling molecules at its cytoplasmic domain. In this study, we have determined that CD44v10 and Rho-Kinase (ROK) are physically associated as a complex in vivo. Using a recombinant fragment of ROK (in particular, the pleckstrin homology [PH] domain) and in vitro binding assays, we have detected a specific binding interaction between the PH domain of ROK and the cytoplasmic domain of CD44. Scatchard plot analysis indicates that there is a single high-affinity CD44 binding site in the PH domain of ROK with an apparent dissociation constant (Kd) of 1.76 nM, which is comparable to CD44 binding (Kd approximately 1.56 nM) to intact ROK. These findings suggest that the PH domain is the primary ROK binding region for CD44. Furthermore, HA binding to GM7372A cells promotes RhoA-mediated ROK activity, which, in turn, increases phosphorylation of three different inositol 1, 4, 5-trisphosphate receptors (IP(3)Rs) [in particular, subtype 1 (IP(3)R1), and to a lesser extent subtype 2 (IP(3)R2) and subtype 3 (IP(3)R3)] all known as IP(3)-gated Ca(2+) channels. The phosphorylated IP(3)R1 (but not IP(3)R2 or IP(3)R3) is enhanced in its binding to IP(3) which subsequently stimulates IP(3)-mediated Ca(2+) flux. Transfection of the endothelial cells with ROK's PH cDNA significantly reduces ROK association with CD44v10, and effectively inhibits ROK-mediated phosphorylation of IP(3)Rs and IP(3)R-mediated Ca(2+) flux in vitro. The PH domain of ROK also functions as a dominant-negative mutant in vivo to block HA-dependent, CD44v10-specific intracellular Ca(2+) mobilization and endothelial cell migration. Taken together, we believe that CD44v10 interaction with ROK plays a pivotal role in IP(3)R-mediated Ca(2+) signaling during HA-mediated endothelial cell migration.

Accelerated atherosclerosis in saphenous vein bypass grafts: a spectrum of diffuse plaque instability

Our understanding of plaque instability may be extended to vein graft atherosclerosis, which appears to represent the end of a continuum of plaque instability. Compared with plaque in native coronary arteries, vein graft atheroma is more diffuse and vulnerable to rupture, and the consequences of plaque rupture in vein grafts seem to be associated with almost certain thrombotic occlusion within 7 to 12 years after surgery.

The kallikrein-kinin system in humans

1. Kinin peptides are implicated in many physiological and pathological processes, including the regulation of blood pressure and sodium homeostasis, inflammation and the cardioprotective effects of preconditioning. In humans, the plasma and tissue kallikrein-kinin systems (KKS) generate bradykinin and kallidin peptides, respectively. 2. We established methodology for the measurement of bradykinin and kallidin peptides and their metabolites in order to study the function of the plasma and tissue KKS in humans. 3. Bradykinin peptides were more abundant than kallidin peptides in blood and cardiac atrial tissue, whereas kallidin peptides were predominant in urine. The levels of kinin peptides in tissue were higher than in blood, confirming the primary tissue localization of the KKS. 4. Angiotensin-converting enzyme inhibition increased blood levels of bradykinin and kallidin peptides. 5. Blood levels of kallidin peptides were suppressed in patients with severe cardiac failure, indicating that the activity of the tissue KKS is suppressed in this condition. 6. Bradykinin peptide levels were increased in the urine of patients with interstitial cystitis, suggesting a role for these peptides in the pathogenesis and/or symptomatology of this condition. 7. Cardiopulmonary bypass, a model of activation of the contact system, activated both the plasma and tissue KKS. 8. Measurement of individual bradykinin and kallidin peptides and their metabolites gives important information about the operation of the plasma and tissue KKS and their role in physiology and disease states.

Changes in coronary vessel resistance during postischemic reperfusion and effectiveness of nitroglycerin

OBJECTIVE

Microvascular incompetence after ischemia and reperfusion may compromise the normal postischemic coronary perfusion and additionally jeopardize the recovery of the myocytes. We investigated whether such a form of acute endothelial dysfunction occurs in the routine operative setting despite the use of protective measures. For this purpose, we measured pressure-flow relations in the coronary vasculature during heart operations before and after ischemia and after reperfusion and their reaction to the nitric oxide donor nitroglycerin.

METHODS

Forty-eight patients with a low risk profile scheduled for routine coronary artery bypass surgery were included. During normothermic extracorporeal circulation, the fibrillating heart was completely excluded from bypass by clamping of the ascending aorta and snaring of the caval veins. It was relieved of blood by opening the right atrium and venting the left atrium and ventricle to avoid distention. The coronary vessels were perfused under controlled flow, and the perfusion pressures were monitored. This protocol was performed in 24 patients before and immediately after ischemia and after a reperfusion period.

RESULTS

Compared with the preischemic control, vascular resistance was decreased by 17% (P <.003) immediately after ischemia but increased again by 46% (P <.0001) during an average of 25 minutes of reperfusion and, even more important, by 23% (P <.028) in comparison with the preischemic values. In two groups of 12 patients, nitroglycerin was added to the perfusate either in a dosage of 3 microg. kg. min(-1) or as a bolus injection of 2 mg. Low-dose nitroglycerin did not reduce the elevated postreperfusion resistances significantly, but bolus injection did (P <.0002). Coronary vessel resistance increased during reperfusion in particular in patients with a history of hypertension.

CONCLUSION

Coronary vasoconstriction during postischemic reperfusion is regularly present in the routine operative setting in cardiac surgery, despite myocardial protection measures. The amount of vasoconstriction varies considerably and is particularly increased in patients with hypertension. The nitric oxide donor nitroglycerin can normalize the elevated resistances, but only in high dosages. This demonstrates a preserved ability of vascular smooth muscle to relax. The phenomenon had no sequelae in our low-risk patients having elective operations. However, it may gain significance in the case of severe left heart hypertrophy and in patients at risk with both a postoperative low-output syndrome and reduced mean arterial pressures during reperfusion.

Suitability of venous and arterial conduits used for coronary artery bypass grafting in conjunction with coronary disease risk factors

BACKGROUND/STUDY OBJECTIVES: We studied patients undergoing coronary artery bypass grafting. Risk factors for coronary disease were studied in conjunction with the histopathologic findings of the grafts prior to implantation. Our aim was to correlate the histologic condition of the grafts and evaluate the morphological changes in conjunction with existing risk factors.

DESIGN/PATIENTS

In 10 candidates for surgical revascularization (nine males, mean age 60.8 years), the risk factor profile was studied (smoking, dyslipidaemia, hypertension, diabetes, family history) and the Body Mass Index was calculated. Of a total of 14 grafts, 10 were saphenous vein grafts and four left internal thoracic artery grafts. Histologic samples were studied under optical and electron microscopy. We studied the intima morphology and thickness, the width of the intercellular spaces, the texture of the subendothelial layer, the endothelial status, and the condition of the basal lamina. Histopathological changes were correlated with risk factors.

RESULTS

Histopathological changes were observed in the wall structure of all grafts. The most important changes were found in the venous grafts, notably: intima thickening, existence of foam cells in the intima, widening of the intercellular spaces, subendothelial oedema, degeneration and detachment of endothelial cells, and wide multilayered basal lamina. The co-existence of two or more risk factors seems to exarcerbate morphological changes.

CONCLUSION

Morphological changes are present principally in the walls of venous but also arterial conduits, even prior to implantation. These changes may be attributable to preparation techniques and preservation conditions of the grafts, but they could additionally be induced by coexisting risk factors. It is conceivable that these alterations could perhaps precipitate and accelerate atherosclerotic changes, inducing lumen narrowing or even occlusion of the graft postoperatively.

A complex role for the progesterone receptor in the response to vascular injury

Clinical studies of hormone replacement therapy to prevent cardiovascular diseases have heightened interest in the cardiovascular effects of progestins. However, the role of the progesterone receptor (PR) in vascular biology has not been studied in vivo. We studied ovariectomized female PR knockout (PRKO) mice and their wild-type (WT) littermates using the mouse carotid artery injury model. Placebo-treated PRKO mice showed significantly greater vascular medial hypertrophy and vascular smooth muscle cell (VSMC) proliferation in response to vascular injury than did WT mice. Progesterone had no significant effect in the PRKO mice, but worsened the response to injury in WT mice. VSMCs cultured from PRKO mouse aortae were markedly hyperproliferative, and their growth was not affected by progesterone. In contrast to the in vivo findings, progesterone inhibited proliferation of WT-derived VSMCs. Furthermore, reintroduction of PR into PRKO-derived VSMCs using adenoviral methods restored progesterone-mediated inhibition of proliferation to these cells. This effect was reversed by the PR antagonist, RU 486. Thus, the effects of PR and progesterone differ markedly between cultured VSMCs and intact blood vessels. These data demonstrate a direct role for the PR in regulating the response to vascular injury and VSMC proliferation.

Lazaroid reduces production of IL-8 and IL-1 receptor antagonist in ischemic spinal cord injury

BACKGROUND

21-aminosteroids (lazaroids) have demonstrated the protective effect against cerebral ischemic injury through the inhibition of lipid peroxidation. We examined whether lazaroids affected the production of proinflammatory and antiinflammatory cytokines in ischemic spinal cord injury model.

MATERIALS

Anesthetized New Zealand white rabbits underwent a 20-minute infrarenal aortic cross-clamping (AXC) with pretreatment of either an intravenous 3 mg/kg lazaroid U74389G (group L; n = 10) or the same volume saline (group P; n = 10). Sham operation group (group S; n = 6) underwent only exposure of the aorta. Plasma concentrations of interleukin (IL)-8, -1beta, -1 receptor antagonist (IL-1ra) and tumor necrosis factor (TNF)-alpha were measured at four time points. Functional assessment with Tarlov score at 24 and 48 hours after pretreatment, pathologic assessment of the spinal cord, and measurements of cytokine levels in the spinal cord were performed.

RESULTS

The maximum elevation of plasma IL-8 and -1ra levels occurred at 1 hour after declamping in four measurement points. Plasma IL-8 and -1ra levels in group L were significantly lower than those in group P (*p < 0.05). Plasma TNFalpha peaked at 5 minutes after declamping, but decreased afterwards. Plasma TNFalpha levels were not different among three groups. Spinal IL-8 levels in group L (0.98 +/- 0.34 ng/g tissue) were lower than those in group P (7.26 +/- 2.26 ng/g tissue)(*p < 0.05). Spinal IL-1ra and TNFalpha were not significantly different. Tarlov score and pathologic assessment were better in group L.

CONCLUSIONS

Lazaroid U-74389G reduced the production of systemic IL-8 and -1ra and spinal IL-8 when AXC caused spinal cord injury. These results indicate that lazaroids may attenuate ischemic endothelial cell injury or activation of leukocytes.

Lipid uptake across the wall of an expanded polytetrafluoroethylene vascular graft

Previous studies have shown that vascular grafts were prone to inducing an atherosclerosis-like phenomenon, thus possibly jeopardizing their performance. Furthermore, lipid retention, observed in most synthetic arterial prostheses explanted from humans, appears to have an important role in the progression of this atherosclerotic process, therefore hindering the healing process and neo-intima formation of these synthetic conduits. The current study examined lipid concentration profiles across prosthesis membranes exposed to lipid dispersion under various transmural pressures, flow rates, and durations of exposure. It was demonstrated that the lipids rapidly permeated the prosthesis membrane, as lipid advection increased to a maximum, then steadily decreased until the membrane became completely impermeable to the fluid. The concentration of lipids within the grafts was monitored using FT-IR microspectroscopy, then correlated as a function of time in order to evaluate the mass transfer coefficients and lipid saturation concentration. Lipid sorption, as a function of time, was described by a mechanism taking into account two first-order kinetic models. The lipids were first rapidly adsorbed onto the Teflon(R), potentially influenced by the strong affinity of these lipids for the highly hydrophobic polytetrafluoroethylene polymer. This affinity then enhanced the germination of the lipid deposits that filled in the prosthesis wall. For lipid retention as a function of the transmural pressure and flow rate, no clear tendency was established.

Involvement of tyrosine kinase in the hypoxia/reoxygenation-induced gap junctional intercellular communication abnormality in cultured human umbilical vein endothelial cells

Vascular endothelial cells (EC), communicating with one another across gap junctions, are usually made dysfunctional by hypoxia and reoxygenation (H/R); however, very limited information exists regarding the effects of H/R on the endothelial gap junctions. We investigated whether H/R interferes with endothelial gap junctional intercellular communication (GJIC). After human umbilical vein EC had grown to confluence, they were exposed to hypoxia (pO2 < 0.1%) for 12-16 h and then returned to normal atmospheric conditions for reoxygenation. At 0-, 2-, 4-, 6-h reoxygenation, GJIC was detected by means of a fluorescence recovery after a photobleaching technique. The results demonstrated that a GJIC reduction (about 20% less than that under normoxia) was induced after 2 h of reoxygenation; after 4 h of reoxygenation, it began to recover (to about 10% less than that under normoxia); and after 6 h of reoxygenation, GJIC was restored to the normal level. Calphostin C (1 x 10(-7) mol/l), a specific protein kinase C inhibitor, partially inhibited the reduction in GJIC (resulting in a level about 10% less than that under normoxia), whereas the tyrosine kinase inhibitor genistein (10 micromol/L) completely blocked the reduction in GJIC. Vanadate (1.5 mmol/l), a tyrosine phosphatase inhibitor, amplified the inhibitory effect of H/R on GJIC (to about 40% less than that under normoxia). Immunofluorescence and immunoprecipitation showed that 2-h reoxygenation significantly stimulated tyrosine protein phosphorylation, and this phosphorylation event was obviously enhanced by vanadate. The results of Western blotting showed that the gap junctional protein connexin 43 (Cx43) was phosphorylated by H/R; moreover, immunoprecipitation demonstrated that 2-h reoxygenation induced a prominent increase of tyrosine phosphorylation of Cx43 compared with that under normoxia. These data indicate that H/R induces a transient endothelial GJIC dysfunction through the activation of tyrosine kinase and phosphorylation of tyrosine residues of Cx43.

Endothelium removal induces iNOS in rat aorta in organ culture, leading to tissue damage

After endothelial damage in vivo, there is an induction of nitric oxide synthase (NOS) in the underlying smooth muscle cells. We hypothesized that intrinsic factors could induce NOS independently of blood elements. This was tested using an in vitro organ culture technique. Rat aortas with endothelium removed before 24-h organ culture (ERB) failed to constrict to phenylephrine after culture, whereas with endothelium removal after culture there was a normal constrictor response. Constrictor activity in ERB aortas was restored by the concomitant treatment with either the protein synthesis inhibitor cycloheximide (1 microM) or the NOS inhibitor L-N5-(1-iminoethyl)ornithine hydrochloride (L-NIO, 100 microM). The ERB aortas also had an elevated NOS activity and induced NOS (iNOS) immunoreactivity. The constrictor response to phenylephrine in ERB aortas was only partially restored by acute application of L-NIO subsequent to the 24-h organ culture, which suggests that other effects during culture contributed to the diminished tissue response. When ERB aortas were treated with reduced glutathione (GSH, 3 mM for 24 h), acute application of L-NIO then fully restored the constrictor effect. This suggests that peroxynitrite produced during culture may in part be responsible for loss of constrictor effects, and this was substantiated by the presence of nitrated tyrosine residues in aortic proteins and also widespread DNA damage, which was prevented by both L-NIO and GSH. Thus some of the immediate (24-h) effects of endothelium removal involve intrinsic mechanisms resulting in iNOS synthesis, which leads to both nitric oxide and peroxynitrite generation, with resultant tissue damage and loss of contractile function.

Lipid uptake in expanded polytetrafluoroethylene vascular grafts

PURPOSE

The mechanisms of vascular prosthesis failure are reported to be associated, in part, with an atherosclerotic degenerative process that is related to an abnormal lipid infiltration. The lipid uptake in expanded polytetrafluoroethylene (ePTFE) vascular grafts was reproduced in vitro, and the effect of time on the permeability of these prostheses was studied.

METHODS

Water permeability tests were carried out under dynamic flow conditions at various hydrostatic pressures. Lipid uptake was simulated by circulating a phosphatidylcholine suspension inside an expanded Teflon prosthesis under pulsatile or continuous transmural pressure ranging between 80 mm Hg and 180 mm Hg, at a flow rate of 500 mL/min and 2000 mL/min, for a duration ranging from 2 hours to 1 month.

RESULTS

Water permeability tests indicated that under hydrostatic pressures of 180 mm Hg and 300 mm Hg, water percolated through the prosthesis wall after an exposure of 720 minutes and 75 minutes, respectively. After exposing the prostheses to the lipid dispersion under the various flow conditions, the fluid convection through the wall occurred. Preferential convection pathways with a constant periodicity were observed across the length of each prosthesis and were, therefore, associated with regularly spaced perforations depicted in the structure of the devices. Phospholipids gradually agglomerated within the prosthesis wall, allowing a restrictive molecular mobility. Infrared spectroscopy results indicated that the lipid uptake depended on the transmural pressure and time of exposure.

CONCLUSION

The occurrence of the membrane permeability may be associated with the dilatation and plastic deformation of the prosthesis. Lipid uptake occurs in ePTFE grafts after an aggressive kinetic process.

Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention

Aortocoronary saphenous vein graft disease, with its increasing clinical sequelae, presents an important and unresolved dilemma in cardiological practice. During the 1st month after bypass surgery, vein graft attrition results from thrombotic occlusion, while later the dominant process is atherosclerotic obstruction occurring on a foundation of neointimal hyperplasia. Although the risk factors predisposing to vein graft atherosclerosis are broadly similar to those recognized for native coronary disease, the pathogenic effects of these risk factors are amplified by inherent deficiencies of the vein as a conduit when transposed into the coronary arterial circulation. A multifaceted strategy aimed at prevention of vein graft disease is emerging, elements of which include: continued improvements in surgical technique; more effective antiplatelet drugs; increasingly intensive risk factor modification, in particular early and aggressive lipid-lowering drug therapy; and a number of evolving therapies, such as gene transfer and nitric oxide donor administration, which target vein graft disease at an early and fundamental level. At present, a key measure is to circumvent the problem of vein graft disease by preferential selection of arterial conduits, in particular the internal mammary arteries, for coronary bypass surgery whenever possible.