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

Is there a difference between aortic and brachial vein blood lipoprotein and total cholesterol levels?

OBJECTIVE

Atherosclerosis is a disease of the arteries that is not practically observed in veins. There are a lot of proposed mechanisms underlying this phenomenon. We aimed to compare the lipoprotein and total cholesterol levels in aortic and venous blood samples.

METHODS

A total of 125 patients ≥18 years of age were included in the study. After overnight fasting, we drew blood from the proximal ascending aorta and brachial vein. Serum lipid profiles were compared between these samples.

RESULTS

Out of 125 patients, 45 (36%) were females, and 80 (64%) were males. The mean age of the patients was 62 years (24-85 years). Notably, 39 (31%) patients were using statin treatment. Coronary angiography showed that 103 (82%) patients had coronary artery disease. Mean arterial total cholesterol (low-density lipoprotein), high-density lipoprotein, and triglyceride levels were significantly lower than mean venous total cholesterol, low-density lipoprotein, high-density lipoprotein, and triglyceride levels (187.3±45.3 mg/dL vs. 204.5±52.6 mg/dL, p<0.001; 116.7±41.5 mg/dL vs. 128±45 mg/dL, p<0.001; 40.8±12.9 mg/dL vs. 45.3±13.3 mg/dL, p<0.001; and 142.8±81.5 vs. 161.5±100.3 mg/dL, p<0.001, respectively).

CONCLUSION

Aortic lipoprotein and total cholesterol levels are significantly lower than venous lipoprotein and total cholesterol levels in patients presenting to the hospital for coronary angiography.

Application of virtual histological intravascular ultrasound in plaque composition assessment of saphenous vein graft diseases

OBJECTIVE

Saphenous vein grafts disease (SVGD) is a common complication after coronary artery bypass graft (CABG) and normally treated by percutaneous coronary intervention (PCI). The most common complication after SVG-PCI is slow or no-reflow. It is known that the no-reflow phenomenon occurs in up to 15% of the SVG-PCI and is associated with high risk of major adverse cardiac events (MACEs) and mortality, therefore, it is important to investigate the factors that could predict the clinical outcome of PCI for risk stratification and guiding interventions. In recent years, the spectral analysis of intravascular ultrasound (IVUS) radiofrequency data (virtual histology-IVUS [VH-IVUS]) has been used to provide quantitative assessment on both plaque compositions and morphologic characteristics.

DATA SOURCES

The PubMed, Embase, and Central databases were searched for possible relevant studies published from 1997 to 2018 using the following index keywords: "Coronary artery bypass grafting," "Saphenous venous graft disease," "Virtual histology-intravascular ultrasound," "Virtual histology-intravascular ultrasound," and "Percutaneous coronary intervention."

STUDY SELECTION

The primary references were Chinese and English articles including original studies and literature reviews, were identified and reviewed to summarize the advances in the application of VH-IVUS techniques in situ vascular and venous graft vascular lesions.

RESULTS

With different plaque components exhibiting a defined spectrum, VH-IVUS can classify atherosclerotic plaque into four types: fibrous tissue (FT), fibro fatty (FF), necrotic core (NC), and dense calcium (DC). The radiofrequency signal is mathematically transformed into a color-coded representation, including lipid, fibrous tissue, calcification, and necrotic core. Several studies have demonstrated the independent relationship between VH-IVUS-defined plaque classification or plaque composition and MACEs, but a significant association between plaque components and no-reflow after PCI in acute coronary syndrome. In recent years, VH-IVUS are applied to assess the plaque composition of SVGD, based on the similarity of pathophysiological mechanisms between coronary artery disease (CAD) and SVGD, further studies with the larger sample size, the long-term follow-up, multicenter clinical trials may be warranted to investigate the relationship between plaque composition of saphenous vein graft (SVG) by VH-IVUS and clinical outcomes in patients with SVGD undergoing PCI.

CONCLUSIONS

In degenerative SVG lesions, VH-IVUS found that plaque composition was associated with clinical features, future studies need to explore the relationship between VH-IVUS defined atherosclerotic plaque components and clinical outcomes in SVGD patients undergoing PCI, an innovative prediction tool of clinical outcomes can be created.

TGFβ, smooth muscle cells and coronary artery disease: a review

Excessive vascular smooth muscle cell (SMC) proliferation, migration and extracellular matrix (ECM) synthesis are key events in the development of intimal hyperplasia, a pathophysiological response to acute or chronic sources of vascular damage that can lead to occlusive narrowing of the vessel lumen. Atherosclerosis, the primary cause of coronary artery disease, is characterised by chronic vascular inflammation and dyslipidemia, while revascularisation surgeries such as coronary stenting and bypass grafting represent acute forms of vascular injury. Gene knockouts of transforming growth factor-beta (TGFβ), its receptors and downstream signalling proteins have demonstrated the importance of this pleiotropic cytokine during vasculogenesis and in the maintenance of vascular homeostasis. Dysregulated TGFβ signalling is a hallmark of many vascular diseases, and has been associated with the induction of pathological vascular cell phenotypes, fibrosis and ECM remodelling. Here we present an overview of TGFβ signalling in SMCs, highlighting the ways in which this multifaceted cytokine regulates SMC behaviour and phenotype in cardiovascular diseases driven by intimal hyperplasia.

Saphenous vein graft near-infrared spectroscopy imaging insights from the lipid core plaque association with clinical events near-infrared spectroscopy (ORACLE-NIRS) registry

OBJECTIVES

We sought to examine near-infrared spectroscopy (NIRS) imaging findings of aortocoronary saphenous vein grafts (SVGs).

BACKGROUND

SVGs are prone to develop atherosclerosis similar to native coronary arteries. They have received little study using NIRS.

METHODS

We examined the clinical characteristics and imaging findings from 43 patients who underwent NIRS imaging of 45 SVGs at our institution between 2009 and 2016.

RESULTS

The mean patient age was 67 ± 7 years and 98% were men, with high prevalence of diabetes mellitus (56%), hypertension (95%), and dyslipidemia (95%). Mean SVG age was 7 ± 7 years, mean SVG lipid core burden index (LCBI) was 53 ± 60 and mean maxLCBI4 mm was 194 ± 234. Twelve SVGs (27%) had lipid core plaques (2 yellow blocks on the block chemogram), with a higher prevalence in SVGs older than 5 years (46% vs. 5%, P = 0.002). Older SVG age was associated with higher LCBI (r = 0.480, P < 0.001) and higher maxLCBI4 mm (r = 0.567, P < 0.001). On univariate analysis, greater annual total cholesterol exposure was associated with higher SVG LCBI (r = 0.30, P = 0.042) and annual LDL-cholesterol and triglyceride exposure were associated with higher SVG maxLCBI4 mm (LDL-C: r = 0.41, P = 0.020; triglycerides: r = 0.36, P = 0.043). On multivariate analysis, the only independent predictor of SVG LCBI and maxLCBI4mm was SVG age. SVG percutaneous coronary intervention was performed in 63% of the patients. An embolic protection device was used in 96% of SVG PCIs. Periprocedural myocardial infarction occurred in one patient.

CONCLUSIONS

Older SVG age and greater lipid exposure are associated with higher SVG lipid burden. © 2016 Wiley Periodicals, Inc.

Pathophysiology of native coronary, vein graft, and in-stent atherosclerosis

Plaque rupture, usually of a precursor lesion known as a 'vulnerable plaque' or 'thin-cap fibroatheroma', is the leading cause of thrombosis. Less-frequent aetiologies of coronary thrombosis are erosion, observed with greatest incidence in women aged <50 years, and eruptive calcified nodules, which are occasionally identified in older individuals. Various treatments for patients with coronary artery disease, such as CABG surgery and interventional therapies, have led to accelerated atherosclerosis. These processes occur within months to years, compared with the decades that it generally takes for native disease to develop. Morphological identifiers of accelerated atherosclerosis include macrophage-derived foam cells, intraplaque haemorrhage, and thin fibrous cap. Foam-cell infiltration can be observed within 1 year of a saphenous vein graft implantation, with subsequent necrotic core formation and rupture ensuing after 7 years in over one-third of patients. Neoatherosclerosis occurs early and with greater prevalence in drug-eluting stents than in bare-metal stents and, although rare, complications of late stent thrombosis from rupture are associated with high mortality. Comparison of lesion progression in native atherosclerotic disease, atherosclerosis in saphenous vein grafts, and in-stent neoatherosclerosis provides insight into the pathogenesis of atheroma formation in natural and iatrogenic settings.

Histopathology of the longest-lived saphenous vein graft in a patient with Kawasaki disease

The patency rate of saphenous vein grafts (SVGs) for children with Kawasaki disease (KD) tends to decline during the early years after coronary artery bypass grafting (CABG). Although degenerative changes have been considered the main cause of SVG occlusion, there have been no reports on the histopathologic features of the SVG in patients with KD. We herein describe a redo off-pump total arterial revascularization in a 43-year-old man with KD, 34 years after the first CABG using SVG. The histopathologic examination of the longest-lived SVG demonstrated that graft occlusion was mainly caused by the diffuse intimal hyperplasia.

Chemokine receptor CCR5: from AIDS to atherosclerosis

There is increasing recognition of an important contribution of chemokines and their receptors in the pathology of atherosclerosis and related cardiovascular disease. The chemokine receptor CCR5 was initially known for its role as a co-receptor for HIV infection of macrophages and is the target of the recently approved CCR5 antagonist maraviroc. However, evidence is now emerging supporting a role for CCR5 and its ligands CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES) in the initiation and progression of atherosclerosis. Specifically, the CCR5 deletion polymorphism CCR5delta32, which confers resistance to HIV infection, has been associated with a reduced risk of cardiovascular disease and both CCR5 antagonism and gene deletion reduce atherosclerosis in mouse models of the disease. Antagonism of CCL5 has also been shown to reduce atherosclerotic burden in these animal models. Crucially, CCR5 and its ligands CCL3, CCL4 and CCL5 have been identified in human and mouse vasculature and have been detected in human atherosclerotic plaque. Not unexpectedly, CC chemokines have also been linked to saphenous vein graft disease, which shares similarity to native vessel atherosclerosis. Distinct roles for chemokine-receptor systems in atherogenesis have been proposed, with CCR5 likely to be critical in recruitment of monocytes to developing plaques. With an increased burden of cardiovascular disease observed in HIV-infected individuals, the potential cardiovascular-protective effects of drugs that target the CCR5 receptor warrant greater attention. The availability of clinically validated antagonists such as maraviroc currently provides an advantage for targeting of CCR5 over other chemokine receptors.

Drug-eluting versus bare-metal stent for treatment of saphenous vein grafts: a meta-analysis

BACKGROUND

Saphenous vein grafts develop an aggressive atherosclerotic process and the efficacy of drug eluting stents (DES) in treating saphenous vein graft (SVG) lesions has not been convincingly demonstrated. The aim of this study was to review and analyze the current literature for controlled studies comparing DES versus bare metal stents (BMS) for treatment of SVG stenoses.

METHODOLOGY/PRINCIPAL FINDINGS

We searched several scientific databases and conference proceedings up to March 15, 2010 for controlled studies comparing target vessel revascularization (TVR) between DES and BMS. Summary odds ratios (OR) for the primary endpoint TVR and secondary endpoints infarction, stent thrombosis and death were calculated using random-effect models. A total of 29 studies (3 randomized controlled trials RCT) involving 7549 (202 in RCT) patients were included. The need for target vessel revascularization in the DES group tended to be lower compared to BMS for the 3 RCT (OR 0.50 [0.24-1.00]; p = 0.051) and for observational studies (0.62 [0.49-0.79]; p<0.001). There was no significant difference in the risk for myocardial infarction in the RCT (OR 1.25 [0.22-6.99]; p = 0.250) but a lower risk for DES based on the observational studies 0.68 [0.49-0.95]; p = 0.023. The risk for stent thrombosis was found to be non-different in the RCT (OR 0.78 [0.03-21.73], p = 0.885) while it was in favor of DES in the observational studies (0.58 [0.38 - 0.84]; p<0.001). The mortality was not significantly different between DES and BMS in the RCT's (OR 2.22 [0.17 - 29.50]; p = 0.546) while the observation studies showed a decreased mortality in the DES group (0.69 [0.55-0.85]; p<0.001).

CONCLUSION

DES may decrease TVR rate in treatment of SVG stenoses. No differences in reinfarction rate, stent thrombosis or mortality was found between the DES and BMS groups in the RCT's while the observational data showed lower risk for myocardial infarction, stent thrombosis and death in the DES group. This may be a result of patient selection bias in the observational studies or represent a true finding that was not the detected in the RCT analysis due to limited statistical power.

Outcomes with drug-eluting versus bare-metal stents in saphenous vein graft intervention results from the STENT (strategic transcatheter evaluation of new therapies) group

OBJECTIVES

This study compares outcomes of drug-eluting stents (DES) versus bare-metal stents (BMS) in patients undergoing saphenous vein graft (SVG) intervention.

BACKGROUND

The safety and efficacy of DES in patients undergoing SVG intervention is controversial.

METHODS

The STENT (Strategic Transcatheter Evaluation of New Therapies) registry is a multicenter U.S. registry evaluating outcomes with DES. Our study population includes patients undergoing PCI of SVG lesions with DES (n = 785) or BMS (n = 343) who completed 9-month or 2-year follow-up. Outcomes were adjusted with propensity analyses.

RESULTS

The DES patients had fewer emergent procedures but had smaller vessels and longer lesions. The DES patients had less death or myocardial infarction at 9 months (hazard ratio [HR]: 0.52, 95% confidence interval [CI]: 0.33 to 0.83, p = 0.006) and less death at 2 years (HR: 0.60, 95% CI: 0.36 to 0.98, p = 0.041). Target vessel revascularization (TVR) was less with DES at 9 months (7.2% vs. 10.0%, HR: 0.36, 95% CI: 0.22 to 0.61, p < 0.001) but was no different by 2 years (18.3% vs. 16.9%, p = 0.86), although adjusted TVR rates were lower (HR: 0.60, 95% CI: 0.40 to 0.90, p = 0.014). The DES reduced TVR at 9 months in SVG lesions with diameter <3.5 mm (8.0% vs. 17.2%, p = 0.013) but not >or=3.5 mm (6.0% vs. 6.6%, p = 0.74).

CONCLUSIONS

Treatment of SVG lesions with DES vs. BMS is effective in reducing TVR at 9 months, although most of this advantage is lost at 2 years. The DES seem safe with less death or myocardial infarction, although selection bias might have affected these results. Our data suggest that DES might have short-term advantages over BMS in SVG lesions with diameter <3.5 mm.

Release of TNF-α during stent implantation into saphenous vein aortocoronary bypass grafts and its relation to plaque extrusion and restenosis

The reduction in plaque volume during stent implantation is associated with the release of particulate debris and plaque-derived soluble substances. We studied the potential release of the proinflammatory cytokine TNF-α into the coronary circulation and whether such release is related to the reduction in plaque volume and, possibly, a predictor for restenosis. In 18 male patients ( n = 24 stents) with severe stenosis in a saphenous vein aortocoronary bypass graft (SVG), we used a distal balloon occlusion-aspiration device during stent implantation. The aspirate TNF-α levels were determined before and after stent implantation and related to the angiographic and intravascular ultrasound-assessed severity of stenosis and restenosis. We found that TNF-α is, indeed, released into the aspirate of stented SVG (9 ± 1 and 28 ± 3 pg/ml before and after stent implantation, respectively, P < 0.0001) and that such release is related to the reduction in plaque volume ( r = 0.88, P < 0.0001) and associated with restenosis after 5 mo ( r = 0.71, P = 0.001). The periprocedural release of plaque-derived TNF-α possibly represents the amount and activity of the atherosclerotic process and might be a predictor for restenosis.

What is the optimal management for preventing saphenous vein graft diseases?: early results of intravascular angioscopic assessment

BACKGROUND

The predominant mechanism of early failure of saphenous vein grafts (SVG) after coronary bypass remains unclear, so angioscopy was used to identify the morphological changes.

METHODS AND RESULTS

Of the 31 SVGs assessed 15 had both yellow plaque and thrombi, whereas in the remaining 16 SVGs the intima was clear white. The serum low-density lipoprotein cholesterol level was significantly higher in the diseased SVG group. Eight patients of the normal SVG group were prescribed ticlopidine, compared with only 1 from the diseased SVG group (p=0.015).

CONCLUSIONS

This is the first direct demonstration of yellow plaque and/or thrombosis in SVGs by intravascular angioscopy. In addition to the importance of prescribing statins, it might be vital to also add ticlopidine to aspirin therapy.

Coronary microembolization

Atherosclerotic plaque rupture is the key event in the pathogenesis of acute coronary syndromes and it also occurs during coronary interventions. Atherosclerotic plaque rupture does not always result in complete thrombotic occlusion of the epicardial coronary artery with subsequent impending myocardial infarction, but may in milder forms result in the embolization of atherosclerotic and thrombotic debris into the coronary microcirculation. This review summarizes the present experimental pathophysiology of coronary microembolization in animal models of acute coronary syndromes and highlights the main consequences of coronary microembolization--reduced coronary reserve, microinfarction, inflammation and oxidative modification of contractile proteins, contractile dysfunction and perfusion-contraction mismatch.Furthermore, the review presents the available clinical evidence for coronary microembolization in patients and compares the clinical observations with observations in the experimental model.

Distal protection in cardiovascular medicine: current status

Iatrogenic and spontaneous downstream microembolization of atheromatous material is increasingly recognized as a source of cardiovascular morbidity and mortality. Devising ways of reducing this distal embolization using a variety of mechanical means--distal protection--is currently under intense and diverse investigation. This review therefore summarizes the present status of distal protection. It examines the problem of distal embolization, describes the available distal protection devices, reviews those areas of cardiovascular medicine where distal protection devices are being investigated, and discusses potential future developments.

Intense Vasoconstriction in Response to Aspirate From Stented Saphenous Vein Aortocoronary Bypass Grafts

OBJECTIVES

We sought to identify soluble vasoconstrictor substances that are released during stent implantation into saphenous vein aortocoronary bypass grafts.

BACKGROUND

Atherosclerotic saphenous vein aortocoronary bypass grafts are particularly vulnerable to plaque rupture. Protection devices prevent particulate debris from being embolized. Additional soluble vasoconstrictor substances possibly also contribute to impaired microvascular perfusion.

METHODS

Peripheral venous blood (VB) and aspirate (AS) were obtained from 14 patients with a significant stenosis in a saphenous vein graft during stent implantation under protection with a distal balloon occlusion device. In five additional patients, arterial blood (AB) was also taken distal to the stented lesion before intervention. Vasomotor substances in VB, AB, and AS plasma were identified in a bioassay of rat mesenteric arteries with intact (+E) and denuded endothelium (-E). Vasoconstriction was normalized to that induced by potassium chloride depolarization (100%).

RESULTS

Venous blood, AB, and AS plasma induced maximum vasoconstriction within six minutes. The AS plasma induced a vasoconstriction of 138 +/- 13% (-E) and 87 +/- 14% (+E); VB, of 70 +/- 14% (-E) and 23 +/- 4% (+E); and AB plasma obtained before intervention, of 49 +/- 9% (-E) and 36 +/- 8% (+E). The vasoconstrictor potency of AS plasma in endothelium-denuded vessels was related to the severity of anginal symptoms, angiographic stenosis severity, plaque volume, and plaque burden as determined by intravascular ultrasound. The AS plasma-induced vasoconstriction was largely attenuated by combined serotonin/5-hydroxytryptamine (5-HT)(2A/2C)- and 5-HT(1A/1B)-receptor blockade and eliminated by additional thromboxane A2 thromboxane-prostanoid (TP)-receptor blockade.

CONCLUSIONS

Stent implantation releases, apart from and in addition to particulate debris, soluble vasoconstrictor substances that possibly contribute to impaired microvascular perfusion.

[Morphological changes in aorto-coronary vein graft--the analysis of autopsy and biopsy material]

BACKGROUND

Patients with implanted aortic coronary grafts have different survival time, which raises the question why the efficacy of graft implants is so poor. The aim of this study was to present the results of the analysis of morphological changes in the vein grafts taken after the death of patients who died after surgery in different time intervals, as well to present the analysis of the grafts obtained after surgical reintervention.

METHODS

The total number of 656 grafts of 308 dead patients was analyzed, as well as 76 grafts from 40 patients who underwent surgical reintervention. According to the duration of the graft since surgical intervention until death, all the analyzed changes were divided into two groups: a) early changes and complications, and b) late changes and complications in aorto-coronary vein grafts.

RESULTS

After the autopsy, 518 vein grafts from the first group were evaluated histopathologically. Changes were found in the form of small or large areas with peeled endothelium in 266 grafts, with the insudation of fibrin and thrombocytes in such places, subendothelial edema, and occlusive thrombosis of the graft lumen. Significant stenosis, which occurred distally from the anastomoses, was present in 118 grafts without changes in the walls of the graft, and there was significant narrowing of the graft lumen in 134 vein grafts due to intimal hyperplasia. In the second group, 138 grafts were histopathologically analyzed after autopsy. Significant hyperplasia was present in 117 grafts with the migration of smooth muscle cells from media into intima, and in 21 grafts there were atheromatous plaques. In 120 veins analyzed before the graft implantation, the lesion or the lack of endothelium was found, as well as the penetration of fibrin and blood elements and intimal hyperplasia. In 46 veins analyzed before the graft implantation, significant intimal hyperplasia with the elevated number of smooth muscle cells was found.

CONCLUSION

The most frequent lesions in the grafts were the lesions of the endothelium, which caused thrombosis formation and lumen occlusion. Intimal hyperplasia in patients with longer survival time occurred due to the migration of smooth muscle cells from the media, or due to the formation of atherosclerotic plaques, which caused graft lumen stenosis or thrombosis.