Virtual histology by intravascular ultrasound study on degenerative aortocoronary saphenous vein grafts

Early Stage of Atherosclerosis in Aortocoronary Saphenous Vein Grafts: Intravascular Ultrasound Study

Introduction

Angiographically visible plaques in patent vein grafts are usually detected years after surgery. Our aim was to examine early plaque formation in vein grafts.

Methods

Bypass angiography and intravascular ultrasonography (IVUS) examination were performed on 77 aortocoronary saphenous vein grafts (SVGs) implanted in 36 patients during the first 2 years after CABG. In each graft, a good quality 25 mm ultrasound image was analyzed. We measured: plaque area, lumen area, external elastic membrane (EEM) area, graft area and wall area. For the comparative assessment of SVGs, the index plaque area/EEM area was calculated. Data were analyzed for the following 4 time periods: I – 0-4 months (22 grafts), II – 5-8 months (23 grafts), III – 9-12 months (19 grafts) and IV – 13-16 months (13 grafts) after CABG. Student’s t and Fisher-Snedecor tests were used for the purpose of statistical analysis in this retrospective study.

Results

In period I, plaque formation (neointimal) was observed in 10 grafts (45%), with a mean plaque area of 1.59 mm., in 6 grafts (26%) in period II, with a mean plaque area of 1.03 mm. and in 15 grafts (71%) in period III, with a mean plaque area of 1.41 mm., and in all (100%) grafts in period IV, with mean plaque area of 2,3 mm.. Average index plaque area/EEM area in periods I, II, III and IV were 0.12, 0.08, 0.13 and 0.22. We have showed a significant plaque increase between periods II and IV(P=0.038).

Conclusion

IVUS showed plaque in about 40% of venous grafts during the first year after CABG. Between 13-16 months plaque was visible in all studied grafts.

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.

Relationship between plaque composition by virtual histology intravascular ultrasound and clinical outcomes after percutaneous coronary intervention in saphenous vein graft disease patients: study protocol of a prospective cohort study

Background

Plaque composition and morphologic characteristics identified by virtual histology intravascular ultrasound (VH-IVUS) can determine plaques at increased risk of clinical events following percutaneous coronary intervention (PCI) among coronary artery disease (CAD) patients. However, there have been few studies to investigate the relationship between plaque composition of saphenous vein graft (SVG) by VH-IVUS and clinical outcomes in patients with saphenous vein graft disease (SVGD) undergoing PCI. The purpose of this study is to determine whether plaque components and characteristics by VH-IVUS can predict major adverse cardiac events (MACEs) among SVGD patients undergoing PCI.

Methods/design

This is a prospective cohort study conducted in Tianjin Chest Hospital, China. Participants with SVGD referred for PCI will be invited to participate in this study, and will be followed up at 1, 6, 12, 24 and 36 months post-PCI to assess clinical outcomes.

The planned sample size is 175 subjects. We will recruit subjects with SVGD scheduled to receive PCI, aged 18–80 years, with a history of previous coronary artery bypass graft (CABG) surgery more than 1 year ago, and willing to participate in the study and sign informed consent.

The composite primary study endpoint is the incidence of MACEs after PCI for SVGD, including death from cardiac causes, non-fatal myocardial infarction, unplanned target lesion revascularization (TLR) and target vessel revascularization (TVR). The primary outcome analysis will be presented as Kaplan-Meier estimates and the primary outcome analysis will be carried out using a Cox proportional hazards regression model.

Discussion

Once the predictive values of plaque components and characteristics by VH-IVUS on subsequent clinical outcomes are determined among SVGD patients undergoing PCI, an innovative prediction tool of clinical outcomes for SVGD patients undergoing PCI will be created, which may lead to the development of new methods of risk stratification and intervention guidance.

Trial registration

The study is registered to ClinicalTrials.gov (NCT03175952).

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.

Optical Coherence Tomography of De Novo Lesions and In-Stent Restenosis in Coronary Saphenous Vein Grafts (OCTOPUS Study)

BACKGROUND

The OCTOPUS registry prospectively evaluates the procedural and long-term outcomes of saphenous vein graft (SVG) PCI. The current study assessed the morphology of de novo lesions and in-stent restenosis (ISR) in patients undergoing PCI of SVG.

METHODS AND RESULTS

Optical coherence tomography (OCT) of SVG lesions in consecutive patients presenting with stable CAD and ACS was carried out. Thirty-nine patients (32 de novo and 10 ISR lesions) were included in the registry. ISR occurred in 5 BMS and 5 DES. There were no differences in the presence of plaque rupture and thrombus between de novo lesions and ISR. Lipid-rich tissue was identified in both de novo lesions and in ISR (75% vs. 50%, P=0.071) with a higher prevalence in BMS than in DES (23% vs. 7.5%; P=0.048). Calcific de novo lesions were detected in older grafts as compared with non-calcific atheromas (159±57 vs. 90±62 months after CABG, P=0.001). Heterogeneous neointima was found only in ISR (70% vs. 0, P<0.001) and was observed with similar frequency in both BMS and DES (24% vs. 30%, P=0.657). ISR was detected earlier in DES than BMS (median, 50 months; IQR, 18-96 months vs. 27 months; IQR, 13-29 months, P<0.001).

CONCLUSIONS

OCT-based characteristics of de novo and ISR lesions in SVG were similar except for heterogeneous tissue, which was observed only in ISR. (Circ J 2016; 80: 1804-1811).

Extraluminal atherosclerosis: an under-recognised finding in human aortocoronary venous bypass grafts

BACKGROUND

Coronary artery bypass grafting (CABG) is commonly compromised by graft atherosclerosis. Histopathologic studies confirm various forms of atherosclerosis, including positively remodelled lesions in native coronary arteries but there are no histopathologic reports of extraluminal atherosclerosis in vein grafts.

METHODS

We prospectively investigated the histopathologic presence and pattern of extraluminal atherosclerosis in human old vein grafts in a two-year interval among patients undergoing redo-CABG at three university hospitals in Tehran. We separately documented clinical and angiographic findings.

RESULTS

We evaluated 100 segments from 20 human old vein grafts obtained during the redo CABG. All but four segments demonstrated some degrees of luminal narrowing. Luminal atherosclerotic plaques were detectable in 61 segments. We detected extraluminal atheroscleoris in seven segments. Mean vessel wall thickness was greater in segments containing extraluminal plaques (1.41±0.26 mm versus 0.91±0.04 mm, P=0.008). Angiographic findings had a modest correlation with presence or absence of luminal atheromatous lesions (Spearman's rho: 0.331, P=0.007). Angiographic degree of stenosis could not predict the presence of positively remodelled atherosclerotic plaques (Spearman's rho: -2.21, P=0.073).

CONCLUSION

Previous studies suggested positive remodelling in vein grafts. Out study provides histopathologic evidence on extraluminal atherosclerosis in human aortocoronary vein grafts.

Vasa vasorum quantification in human varicose great and small saphenous veins

Recent research regarding saphenous vasa vasorum (VV) has focused on two main topics: the VV during varicogenesis in chronic venous insufficiency and the VV in saphenous grafts used in reconstructive vascular surgery. Our aim has been (i) to establish a technique for the histological quantification of the VV in human varicose great and small saphenous veins and (ii) to describe the density and distribution of the vasa vasorum within varicose veins. Great (n=11) and small (n=5) saphenous veins (length, 15-40cm) were collected from 12 patients who were undergoing venous stripping due to chronic venous insufficiency (Clinical-Etiology-Anatomy-Pathophysiology class 2-3). The veins were divided into 5-cm long segments. In total, 92 tissue blocks were collected to trace the variability of the density and distribution of the vasa vasorum in the proximo-distal direction. The endothelium was detected by immunohistochemistry using the von Willebrand factor. We quantified the number of microvessel profiles per section area and the relative distance of the microvessels from the outer border of the adventitia. The VV did not exhibit a preferential orientation in the varicose veins. VV density profiles were highest in the middle third of the venous wall and lowest in the inner third of the venous wall. Both the density and distribution of VV were uniform along the veins, and no differences were observed between the great and small saphenous veins. The VV density was statistically independent of the relative distance from the adventitia. The usability of this technique for perioperative frozen sections remains to be tested.

Intravascular ultrasound appearance of scattered necrotic core as an index for deterioration of coronary flow during intervention in acute coronary syndrome

In acute coronary syndrome (ACS) patients with deterioration of coronary flow during percutaneous coronary intervention (PCI), a scattered necrotic core pattern (SNC) is observed by intravascular ultrasound virtual histology (VH-IVUS). The purpose of this study was to evaluate the impact of SNC on deterioration of coronary flow during PCI in ACS. A total of 38 ACS patients were imaged using VH-IVUS before PCI. In addition to conventional definitions of thin-cap fibroatheroma by VH-IVUS (ID-TCFA), the SNC was defined as necrotic core foci with a maximum diameter of <14 pixels on a 400 × 400 VH-IVUS image in the presence of >50% plaque burden except in the ID-TCFA frame. Patients were divided into deterioration of coronary flow group (n = 15) and normal-reflow group (n = 23). The incidence of residual thrombus and plaque rupture, the external elastic membrane, plaque and fibrous volumes, the incidence of ID-TCFA and the average number of SNC per frame was significantly greater in deterioration of coronary flow group than in normal-reflow group (all parameters P < 0.05). Multivariate analysis revealed that the average number of SNC per frame was independently associated with deterioration of coronary flow in ACS patients (odds ratio 1.18, P < 0.05). In conclusion, an increased number of SNC is associated with deterioration of coronary flow during PCI in ACS patients.

Manual aspiration prior to stenting does not reduce the incidence of filter no reflow in saphenous vein graft lesions protected by FilterWire EX/EZ

BACKGROUND

The beneficial role of manual thrombus aspiration in thrombus-containing lesions has been proven in acute myocardial infarction but data is lacking in saphenous vein graft lesions.

METHODS

From January 2004 to December 2008, 74 consecutive post-bypass patients underwent percutaneous coronary interventions to 76 saphenous vein graft lesions under the protection of FilterWire EX/EZ. Among them, the latest 25 consecutive patients with 25 lesions were treated with manual aspiration before stenting. The incidence of filter no reflow was compared between patients with and without manual aspiration pretreatment.

RESULTS

No major difference in demography, clinical, lesion, and procedure characteristics, and in-hospital outcome has been observed between the two patient groups. Most importantly, the incidence of filter no reflow has not been reduced (32.0% versus 19.6%, P = 0.26) by manual aspiration, even among thrombus-containing lesions (63.2% versus 64.7%, P = 1.00). The absence of diabetes mellitus is found to be the independent predictor for the occurrence of filter no reflow.

CONCLUSIONS

Adjunctive manual thrombus aspiration fails to reduce the filter no reflow, and probably has no additional benefit in saphenous vein graft lesions already protected by FilterWire EX/EZ.