A histological and histochemical examination of autogenous vein grafts

Extracellular signal-regulated kinase inhibition prevents venous adaptive remodeling via regulation of Eph-B4

OBJECTIVES

Vein graft adaptation (VGA) is a process that vein as a vascular graft conduits in arterial reconstructive surgery; VGA can lead to postoperative vein graft stenosis (VGS) and complications after coronary artery bypass graft and other peripheral artery bypass surgeries. VGA is characterized by vein graft loss the venous features without exhibiting arterial features; furthermore, the activation of ERK inhibited the maintenance of venous properties of the vein graft. We hypothesized that ERK inhibition can affect vein VGS through regulating the expression of EphB4.

METHODS

Rat vein transplantation model was established using wild-type and EphB4^+/- Sprague-Dawley rats. Hematoxylin-eosin, Masson, Verhoeff, actin staining, and immunohistochemistry were applied to observe the structure of the vein grafts. Vascular smooth muscle cells (VSMCs) were isolated from the vein and vein grafts. Western blotting was used to determine the expression of p-ERK1/2 and EphB4, and immunofluorescence was applied to detect the expression and location of EphB4. Cell wound scratch assay and CCK8 assay were used to determine the migration and proliferation of VSMCs. Real-time polymerase chain reaction was used to determine the mRNA expression of EphB4.

RESULTS

Western blotting in vein sample and vein graft sample detected p-ERK1/2 and ERK1/2 expression in both EphB4^+/+ and EphB4^+/- rats. The expression of p-ERK was increased in vein graft compared to vein. Immunofluorescence in VSMCs form EphB4^+/+ and EphB4^+/- rats detected EphB4 expression in both cells, and the expression of EphB4 was increased in VSMCs form EphB4^+/+ rats. SCH772984 reduces the proliferation and migration of VSMCs. Inhibition of ERK suppressed the increase of vein graft wall thickness, and the expression of collagen fibers, elastic fibers, and α-actin was decreased. Vein graft from EphB4^+/- rats reduces the expression of EphB4, and SCH772984 suppressed the decrease of EphB4 in vivo. Vein graft from EphB4^+/- rats increased the expression of EphB4, and SCH772984 suppressed the increase of EphB4 in vivo.

CONCLUSIONS

The inhibition of ERK1/2 suppressed the process of VGS by decreasing the proliferation of VSMCs. The ERK-inhibitor SCH772984 suppressed the level of VGS by extending the time of EphB4 expression during the process of VGA, thus maintaining the venousization of vein graft. The mechanism may be that the inhibitor SCH772984 suppresses the level of VGS by extending the time of EphB4 expression during the process of VGA. Therefore, our research provides a new target of VGS treatment by inhibiting the expression of ERK1/2 through the process of VGA.

Canine Venous Graft Transplated into the Arterial System: Factors Related to Lipid Deposition and Patency

For clarifying the influences of nutritional changes in the venous graft on lipid deposition and patency, 12 dogs were bilaterally grafted with the autogen ous femoral veins into the femoral arteries, and the venous grafts on the left side were then wrapped with a Tetron sheet to impede the reconstruction of vasa vasorum. After feeding 4% cholesterol and 2% coconut oil to the dogs for 7 to 15 weeks, the serum cholesterol increased significantly (P<0.01) from 131.2 ± 12.8 to 222.9 ± 33.1 mg/dl, though it still remained relatively low. No statistical difference in patency was recognized between the two sides. In the left patent grafts, vascular lesions were not uniformly seen. Dilatation of the graft without intimal thickening was seen in 3 dogs, while marked intimal thickening without dilatation was noted in 5. Wide lipid deposition was ob served in 8 of 10 grafts on the right side showing a statistical difference (P<0.01). The distribution of vasa vasorum in the left grafts varied widely on microangiography. Intimal thickening and deposition of lipids were observed correlatively in the area with a poor distribution of vasa vasorum. From the above results, the disturbance of vasa vasorum may be an important underly ing condition in lipid deposition in the vascular wall. For preventing occlusion, it was recommended to exercise care so as to avoid stripping the adventitial layers in the venous graft and to place the graft through well vascularised tissues, and also to control the serum cholesterol before and during the first 3 months after the operation. Consideration and discussion of the causes of the confusing results relating lipid deposition and intimal thickening in the grafts have been done from a view of disturbance of vasa vasorum.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

Vein graft failure

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored.

Therapeutic strategies to combat neointimal hyperplasia in vascular grafts

Neointimal hyperplasia (NIH) in bypass conduits such as veins and prosthetic grafts is an important clinical entity that limits the long-term success of vascular interventions. Although the development of NIH in the conduits shares many of the same features of NIH that develops in native arteries after injury, vascular grafts are exposed to unique circumstances that predispose them to NIH, including surgical trauma related to vein handling, hemodynamic changes creating areas of low flow, and differences in biocompatibility between the conduit and the host environment. Multiple different approaches, including novel surgical techniques and targeted gene therapies, have been developed to target and prevent the causes of NIH. Recently, the PREVENT trials, the first molecular biology trials in vascular surgery aimed at preventing NIH, have failed to produce improved clinical outcomes, highlighting the incomplete knowledge of the pathways leading to NIH in vascular grafts. In this review, we aim to summarize the pathophysiologic pathways that underlie the formation of NIH in both vein and synthetic grafts and discuss current and potential mechanical and molecular approaches under investigation that may limit NIH in vascular grafts.

Sonoporation with doxorubicin enhances suppression of intimal hyperplasia in a vein graft model

BACKGROUND

The purpose of the present study is to examine whether sonoporation with doxorubicin enhances suppression of intimal hyperplasia (IH) in a vein graft model.

MATERIALS AND METHODS

After the administration of 1.5 mg/kg doxorubicin intravenously, the right external jugular vein of six rabbits was exposed at 2 W/cm2 and 1 MHz of ultrasound for 2 min (Sonoporation group). Tissue doxorubicin concentration was measured. In 48 rabbits, the right common carotid artery was ligated after performing a vein graft bypass. The animals were divided into the following four groups: the C0 group (surgical procedure only); the C0S (sonoporation without doxorubicin); the C1 (doxorubicin administration only); the C1S (sonoporation with doxorubicin). Twenty-four grafts were subjected to Elastic van Gieson staining for morphometric analysis 4 weeks after the operation; others were subjected to TdT-mediated X-dUTP nick end-labeling for detection of apoptic cells and to staining with a monoclonal antibody against the proliferating cell nuclear antigen for assessment of cell proliferation 1 week after.

RESULTS

The tissue doxorubicin concentration was significantly higher in the Sonoporation group than in the Control group. Compared with the C0 group, IH was not suppressed in the C1 group but was significantly suppressed in the C1S group. Sonoporation with doxorubicin administration suppressed IH significantly (C1 group versusC1S group: P < 0.05). Cell apoptosis was induced and cell proliferation was suppressed significantly in the C1S group.

CONCLUSIONS

Sonoporation with doxorubicin suppressed IH of the vein graft. Sonoporation may be effective in coronary or peripheral revascularization using vein grafts.

[True aneurysms of venous autografts: report of nine cases and review of the literature]

INTRODUCTION The true aneurysm formation of the autogenous saphenous vein graft (ASVG) is a very rare complication after bypass surgery [1 -5]. In 1969 Pillet [1] first described a true fusiform aneurysm formation of the ASVG which had been used as a replacement of the iwured superficial femoral artery in 26-year-old male patient. We present nine cases. CASE!. A 71-year-old man with previous history of arterial hypertension and higher serum lipid level, was admitted with an asymptomatic pulsating swelling of the medial portion on the thigh. Five years ago the bellow knee F-P bypass with ASVG due to occlusive disease has been performed. The transfemoral angiography (Figure 1) showed patent graft with fusiform true aneurysm formation at its mid portion. This aneurysm has been replaced with PTFE graft. The pathohistological examination showed an atherosclerotic origin of the aneurysm. This patient died four years after operation due to myocardial infarction with patent graft. CASE 2. A 57-year-old female with previous history of arterial hypertension and higher serum lipid level, had an elective resection and replacement of the superficial femoral artery aneurysm. For the reconstruction an ASVG was used. The saphenous vein showed postflebitic changes. Four years later she was admitted with asymptomatic pulsating mass of the mid portion of the thigh. The control transfemoral angiography showed patent graft with fusiform aneurysm formation of its mid portion. After aneurismal resection, an above knee F-P bypass with 8 mm PTFE graft was performed. A pathohistological examination showed a partially degenerated elastic membrane with fragmentation and disruption, without atherosclerosis (Figure 2). During the follow up period an elective resection of the subclavian artery aneurysm as well as abdominal aortic aneurysm, were performed. CASE3. A subclavian artery aneurysm caused by TOS has been repaired with sapehnous vein graft at 40-year-old female patient with regular arterial tension and normal serum lipid level. The pathohistologycal examination showed an intimai fibroelastosis associated with intimai and medial connective tissue proliferation of the aneurysm. The atherosclerotic changes were absent. Four years later this patient has been admitted urgently with ischemia of the left hand, absent distala arterial pulses and with asymptomatic pulsating mass over the supradavicular area. The Duplex ultrasonography and angiography, showed aneurysm of the ASVG, associated with occlusion (embolism) of the brachial artery (Figure 3). This aneurysm has been replaced with 6 mm PTFE graft Transbrachial thrombembolectomy has been performed too. The pathohistological examination showed a non atherosclerotic origin of the ASVG aneurysm (Figure 4). Three years after secondary operation the PTFE graft is patent. Echocardiography of the same patient showed mitral valve prolaps, probably caused by connective tissue disorder. CASE 4. A 56-year-old female patient was admitted urgently, due to hemorrhagic shock and giant pulsating swelling over the popliteal space. The Duplex ultrasonography and transfemoral angiography showed ruptured popliteal artery aneurysm. This patient had arterial hypertension and higher lipid level. During the urgent operation using dorsal approach, an aneurysm has been replaced with ASVG. A pathohistological examination showed an atherosclerotic origin of the aneurysm. Ten days postoperatively due to bleeding from the wound, a new urgent surgical procedure was performed. Intraoperatively 1 cm long graft laceration was found, while postoperative bacteriological examination showed an infection caused by Staphylococcus Aureus. The graft has been removed, and new extraanatomic, subcutaneous bypass from the superficial femoral to anterior tibial artery using ASVG was performed. Three years later this patient was admitted urgently with giant pulsating mass and skin necrosis at the knee region, associated with hemorrhagic shock. The control angiography showed a ruptured aneurysm of the ASVG (Figures 5 and 6). The aneurysm was replaced with 6mm PTFE graft. The pathohistological examination showed an atherosclerotic origin of the aneurysm. Two year postoperatively, the new graft is patent. CASE 5. A 65-year-old man with previous history of arterial hypertension and high serum lipid level, was admitted with pulsating swelling and skin necrosis at the portion on the thigh. Nine years ago the bellow knee F-P bypass with cephalic vein due to occlusive disease has been performed. Transfemoral angiography showed patent graft associated with ruptured fusiform aneurysm at its mid portion. This aneurysm has been replaced with 6mm tubular PTFE graft. The postoperative patohistological examination showed an atherosclerotic changes at the resected aneurysm. This patient was followed two years, and graft is patent., CASE 6. A 62-year-old male patient was admitted urgently, with giant pulsating swelling over the popliteal space and hemorrhagic shock. The Duplex ultrasonography and angiography showed ruptured popliteal artery aneurysm. The patients had previous history of arterial hypertension and higher serum lipid level. The aneurysm has been replaced with ASVG. Pathohistological examination showed an atherosclerotic origin of the aneurysmal sac. Seven days postoperatively, a massive bleeding from the wound due to graft infection, occurred. New urgent operation showed complete graft abrupption at the site of proximal anastomosis, while postoperative bacteriological examination showed a presence of Staphylococcus Aureus. The graft was removed and new extraantomic, subcutaneous bypass from the superficial femoral to the anterior tibial artery with contralateral ASVG, was performed. The patient recovered very well. Five years latter this patient was admitted urgently with large painful pulsating mass in the thigh. The angiography showed and ASVG fusiform aneurysm. The aneurysm has been replaced with 6 mm PTFE graft. The pathohistological examination showed an atherosclerotic origin of the resected aneurysm (Figure 7). Two years after the operation, a new graft is patent. CASE 7. A 78-year-old man with previous history of arterial hypertension and higher serum lipid level, has been admitted with an asymptomatic pulsating swelling of the medial portion on the thigh. Seven years ago the bellow knee F-P bypass with ASVG and exclusion of the poplietal artery aneurysm was performed. The Duplex ultrasonography and angiography showed a fusiform true aneurysm formation at the mid portion of the patent graft. The aneurysm has been replaced with femoro-anterior tibial artery bypass procedure using 6 mm PTFE graft. The pathohistological examination showed an atherosclerotic origin of the aneurysm. This patient died five days after the operation due to myocardial infarction with patent graft. CASE 8. A 65-year-old male with previous history of arterial hypertension and higher serum lipid level, had an elective replacement of the popliteal artery aneurysm. For the reconstruction a PTFE graft was used. Two years postoperativelly this graft occluded due to changes on the crural arteries. From these reasons a new bypass from the superficial femoral to anterior tibial artery with saphenous vein graft, was performed. Nine years later she was admitted with painful pulsating mass of the mid portion of the thigh. The Duplex ultrasonography and transfemoral angiography showed patent graft with fusiform aneurysm formation of its mid portion. The ASVG aneurysm was replaced with 8 mm Dacron graft. A pathohistological examination showed atherosclerotic origin of the ASVG aneurysm. One year latter this graft is patent. CASE 9. A 65-year-old male with previous history of arterial hypertension and higher serum lipid level, has been admitted due to disabling claudications discomfort caused by aorto-iliac occlusive disease. Nine years earlier a right sided aorto-renal bypass with ASVG was performed due to occlusive disease and renovascular hypertension. An translumbar aortography showed occlusion of the aortic bifurcation associated with fusiform aneurysm formation of ASVG (Figures 8, 9 and 10). During the same operation an aorto-bifemoral bypass and repairing of ASVG aneurysm with Dacron grafts, were performed. A pathohistological examination showed atherosclerotic origin of the ASVG aneurysm. One year latter both grafts are patent. DISCUSSION The table 1 shows 45 true aneurysmal formation at ASVG after F-P bypass surgery in cases with occlusive diseases [1-25]. In his famous paper Szilagyi [3] reported a study of the biologic fate of ASVG in 260 patients with F-P bypass procedures, and he found 10 (3.8%) aneurysms. In 1973 De Weese [5] found 4 (1.2%) ASVG aneurysms after 350 F-P reconstructions, while in 1975 Vanttinen [6] found 1 (0.9%) such case after these procedures. In 1987 Yuanagyia [26], and in 1989 Martin [27] described cases of ASVG aneurysmal formation after subclavian artery aneurysm replacement. Yanagyia's patient had a Behcet disease. We also had one case of ASVG aneurysm after subclavian artery aneurysm repair, manifested with hand ischemia due to distal embolization. Gemperle[12]in 1986 decribed ASVG aneurysm which developed 18 years after replacement of the injured brachial artery. Carrasaquilla [28] has in 1972 described a case of ASVG aneurysm formation after replacement of the common carotid artery, while in 1998 Tekeuchi et al [29] described a case of an ASVG aneurysm after subclavian to vertebral artery bypass due to stenotic lesions of the both vertebral arteries. Four years later a giant ASVG aneurysm was found, and successfully resected. In 1990 Peer et al [30] reported two ASVG aneurysms seven and eight years after popliteal artery aneurysm replacement. In 1991 Kogel et al [31] described one such case 10 years after primary operation. In 1997 Loftus [32] described 10 new cases of the ASVG aneurysms after popliteal artery aneurysm repair. We had two such cases developed three and five years after primary operation. In three of our cases ASVG aneurysm showed an atherosclerotic origin, while in 3 non atherosclerotic. The exact mechanism of aneurysm degeneration of the ASVG in arterial position is unknown. There is likely a combination of factors including: - mechanical trauma during vein harvesting and operation [9,30]; - weakness at branching sites in the vein [2,9]; - potential weakness in the vicinity of the venous valves due to absence of the circular muscle cuff in the media of the vessel wall [5]; - infection [16]; - trauma caused by bony structures near the graft [18,30]; - arteritis [13,14,26, 27, 30]; - atherosclerosis [2,3,5-11,18,19,21,24,25]; - hemodinamic factors from the arterial pressure [23]; - transmural ischemie injury of the vein wall due to disrupting of the vasa vasorum after removing of the vein segments [28,29,33]; Brody cold this fenomen ?devascularization of the venous graft" [34]; - diffuse nature of this process in patients with multiple aneurysmal changes [20,32] (our cases 2,3,4,6 and 8); - using of the cephalic [9], or superficial femoral vein [1] (case 7); - changed veins (one of our cases). The use of in situ bypass technique for arterial reconstruction would theoretically, minimize endothelial trauma by reducing operative manipulation, preserving vasa vasorum, and eliminating the pressure induced endothelial desquamation that has been associated with mechanical destination of reversed vein graft during their harvest. However, Sassoust [15] in 1986 reported 5 cases of true aneuryms of the ASVG after in situ F-P bypass. After Sassoust's new cases of ASVG aneurysm following F-P in situ bypass surgery were reported [22-24]. CONCLUSION Early ASVG aneurysm formation occurring six months after surgery has been found to be the result of preexisting unrecognized vein wall weakness or injury at the time of harvest, while aneurysm discovered 5 or more years postoperatively, were atherosclerotic in nature. The aneurysms of the ASVG are frequent, at patients with multiple aneurysms of natural arteries. The ASVG aneurysms require active surgical treatment. Then autologous vein grafts are not ?material of choice" for replacement of aneurysmally changed ASVG after peripheral vascular reconstructions.

Early adaptive responses of the vascular wall during venous arterialization in mice

Venous arterialization occurs when a vein segment is transposed as a bypass graft into the arterial circulation, resulting in a structural and functional reorganization of the vascular wall in response to the new local biomechanical environment. Although the anatomical changes of venous arterialization have been well characterized, the molecular mechanisms of vascular remodeling remain incompletely understood. Here, we present a novel model of venous arterialization in mice wherein the external jugular vein is connected to the common carotid artery. The hemodynamic characteristics of the arterialized vein, as assessed by ultrasound and magnetic resonance imaging, resemble features of the arterial circulation. Temporal analyses of the morphological changes in the venous segment at 1, 3, and 7 days after surgery demonstrate preservation of the endothelium at all time points and formation of multiple smooth muscle layers by day 7. Expression of endothelial E-selectin and VCAM-1 was documented at early time points, concomitant with the presence of neutrophils and monocytes/macrophages in the vascular wall. In addition, endothelium-dependent permeability was decreased in the arterialized vein when compared to the contralateral control vein. Thus, this novel mouse model of venous arterialization displays anatomical and cellular features present in other species, and should help to characterize the molecular mechanisms of this adaptive response of the vascular wall to changes in its biomechanical environment.

An ultrastructural study of the intimal hyperplasia in healing microarterial anastomoses

The purpose of the study was to investigate the ultrastructure of intimal hyperplastic cells. End-to-end microarterial anastomoses were studied in a rabbit free-tissue-transfer model. There were five experimental groups, with 1, 3, 7, 14, or 28 days follow-up. At sacrifice the anastomoses were tested for patency and then examined by light and electron microscopy. At days 1 and 3 the repaired intima was covered with macrophages and extravasated erythrocytes. At day 7 spindle-shaped fibroblasts with copious rough endoplasmic reticulum were seen. Some of these cells also contained pinocytotic vesicles, filaments with focal densities, and subplasmalemmal attachment sites, the features of smooth muscle cells. At day 14, more cells contained smooth muscle features and these features were also more pronounced. These young myofibroblasts were plumper than adjacent fibroblasts. At day 28 mature myofibroblasts with a full complement of organelles were present. The results, therefore, supported the hypothesis that myofibroblasts are present in the intimal hyperplasia of healing microarterial anastomoses.

An absorbable pinned-ring device for microvascular anastomosis of vein grafts: experimental studies

In the rabbit, posterior facial vein segments were grafted to the femoral arteries using either conventional suture technique or a mechanical absorbable pinned-ring device. The purpose of this study was to compare patency rates and anastomotic times for the two different methods. The anastomoses were evaluated macroscopically and using light and scanning electron microscopy. The grafts anastomosed with the absorbable rings exhibited 100% patency, while only 83% of the sutured grafts were patent. The mean anastomotic time using the mechanical pinned-ring device was 18.1 min (range 9.8-30 min). The conventionally sutured anastomoses were completed in a mean time of 60 min (range 50-75 min). The experiment has confirmed that the absorbable pinned-ring device provides a safe and fast way to perform microvascular anastomosis.

Pathophysiology of vein graft failure: a review

Vein bypass grafting is an integral component of cardiovascular surgical practice for both arterial and venous diseases. However, many of these grafts will eventually fail due to either intrinsic or extrinsic causes. This review examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the status of research on the therapeutic control of vein graft intimal hyperplasia and accelerated atherosclerosis is assessed.

Comparison of the telescoping anastomotic technique with the end-to-end technique utilizing vein grafts for venous defects: short- and long-term results

The telescoping anastomotic technique was used for both anastomoses of vein grafts placed in the rat left epigastric vein in an effort to make the anastomosis easier and faster. Vein grafting in the right epigastric vein was completed using the conventional technique. The 20 rats with 20 left and 13 right vein grafts, which were patent at 3 weeks, were seen again 3 months postoperatively to compare the two techniques with regard to long-term stenosis and histological changes. Patency of the grafts 2 hr postoperatively was also compared between the two techniques in another 25 rats to eliminate the influence of recanalization on patency. All the vein grafts, which had been patent 3 weeks postoperatively, remained patent after 3 months and no statistically significant difference was found between the telescoping and conventional technique in the degree of stenosis. The vein grafts 2 hr postoperatively were all patent in both groups.

Vein graft factors in the outcome of femorodistal bypass

Various vein factors affect the outcome of femorodistal bypass using vein in the treatment of lower limb ischaemia. In this review, the effect of factors such as vein size, compliance and morphology are discussed.

Infrainguinal vein graft stenosis

Although knowledge of the biological processes involved in the development of intimal hyperplasia has increased markedly in recent years, the precise aetiology of infrainguinal vein graft stenosis remains undetermined. Current therapy is therefore directed at treatment of the established lesion rather than its prevention. There seems little doubt, however, that recent advances in understanding of the vascular biology of normal and pathological saphenous vein will eventually lead to specific targeted therapy that will allow the prevention of vein graft stenosis.

Autologous vein supported with a biodegradable prosthesis for arterial grafting

To evaluate the potential of a supporting, compliant, biodegradable prosthesis to function as a temporary protective scaffold for autologous vein grafts in the arterial circulation, we implanted vein grafts into the carotid arteries of rabbits, either with (composite grafts) or without (control grafts) such a supporting prosthesis, and evaluated them up to 6 weeks. The control vein grafts showed edema and severe medial disruption with infiltration of polymorphonuclear cells on day 1. Over the study, irregular fibrocyte formation resulted in the formation of a fibrotic vein wall. In contrast, the composite vein grafts showed preservation of smooth muscle cell layers and elastic laminae with a minor inflammatory response. Regular proliferation of fibroblasts, which in some areas were circularly oriented, was observed. We conclude that a supporting, compliant, biodegradable prosthesis can function as a protective scaffold for vein grafts in the arterial circulation, thus reducing damage to the vein graft wall and allowing gradual arterialization.

Long-term histologic results of vein grafting with the telescoping anastomotic technique

We studied the long-term histologic results of a new method for autogenous vein grafting to examine whether stenosis at the anastomosis is maintained over time. Nineteen rat inferior epigastric veins were grafted into the femoral artery using a telescoping sleeve technique at both the proximal and the distal anastomoses. Specimens were studied macroscopically and histologically three months later. Stenosis at the anastomosis was located near the tip of the inserted vessel. The smallest inner diameters of the proximal and distal anastomoses were about 80% of the corresponding femoral artery diameter; no statistically significant difference was found between the two anastomoses. The grafts had a thickened wall due to intimal hypertrophy and fibrosis of the media. The inner diameter of the graft was, however, about twice that of the femoral artery, and these graft changes did not create any apparent constriction within the graft.

Histological appearances of the long saphenous vein

The long saphenous vein is frequently used as a graft in both coronary artery and femoro-distal bypass surgery. The histological changes which are seen after implantation into the arterial system have been well documented in the past, but little attention has been focused on the histological appearances of the donor long saphenous vein prior to grafting. In this study, samples of the long saphenous vein in excess of that required for bypass have been examined. In none of the veins did the histological appearances conform to the described normal. All showed evidence of intimal fibrosis which contained elastic tissue and enmeshed smooth muscle cells. The longitudinal and circular muscle layers showed evidence of muscle cell hypertrophy with increase in intervening connective tissue. Elsewhere, similar histological changes have been attributed to 'arterialization'. This study shows that many of the changes are present prior to grafting and may be important in graft failure.

Experimental microvascular autogenous vein grafts for arterial defects: II. A histopathologic study of the grafts

Twelve autogenous vein grafts, of average diameter 1.5 mm, which had been used to bridge defects in the contralateral femoral artery of adult rabbits by a minimally traumatic technique, were examined over a 12-week postoperative period. Each graft remained widely patent but showed fibroelastic intimal thickening with time. Further evidence of arterialisation was the development of a prominent subintimal layer of smooth muscle. Also noted was the presence of medial fibrosis, with both calcification and ossification. This latter is suggestive of damage due to disruption of the vasa vasorum. It would appear that arterialisation of microvascular vein grafts occurs independently of surgical trauma and is therefore difficult to avoid. However, these pathologic changes were not as severe, nor was there as much luminal narrowing, as at the previously described anastomotic sites. The most important cause of these changes appears to be arterial pressure.

Atherosclerosis in vascular grafts for peripheral vascular disease. Part 1. Autogenous vein grafts

29 autogenous vein grafts, from 26 patients with peripheral arterial disease, were studied. 4 grafts of Group I (less than 3 months duration) were patent and removed for reasons other than graft failure. These showed 'arterialisation' only; 4 grafts of Group II (duration 5-18 months) showed thrombotic occlusion; 21 grafts of Group III (duration greater than 2 years) showed impaired graft patency and lipid identifiable as apolipoprotein B-containing-lipoproteins (LpB), and fibrinogen-related antigens (FRA) were seen as intramural deposits in the thickened grafts. LpB was also seen in a perifibrous distribution on the collagen of organised thrombi. Complicated lesions in some Group III grafts showed stenosis or occlusion, ulceration, calcification or aneurysm formation. These features suggest that a process indistinguishable from 'true' atherosclerosis affects vein grafts of long duration. The ways in which such changes may: contribute to graft failure; and improve our understanding of the basic processes involved in atherogenesis, are discussed.

An experience using spiral vein graft as arterial substitute

In two patients wih aneurysmal changes due to arteriosclerosis in the axillary and the subclavian artery respectively, spiral vein grafts were used in a substitute for vascular reconstruction. After resection of the aneurysm, these vein grafts resulted in an excellent adaptation to the recipient vessel. Complicated techniques were not required and the construction time was minimal. Such an approach may be used even in adjacent sites to a joint.

Use of cold cardioplegic solution for vein graft distention and preservation: a light and scanning electron microscopic study

To evaluate the effect of a cardioplegic solution on the endothelium of the saphenous vein, portions of this vein were harvested from each of 5 patients undergoing coronary artery bypass operation. Each sample was divided into five segments. One segment was distended with heparinized saline solution, one with heparinized blood, and one with heparinized cardioplegic solution (25 mEq of potassium per liter). All of the distending solutions were kept at 10 degrees C, and pressure was carefully limited to 200 mm Hg. The fourth segment of vein was distended with heparinized saline solution but no effort was made to limit distending pressure, and the fifth segment was not distended. All samples were then examined with light and scanning electron microscopy. There were no great morphological differences in the endothelium of veins distended to 200 mm Hg with saline solution, blood, or cardioplegic solution. The morphology of these samples compared favorably with the control vein endothelium although scattered areas of endothelial disruption were present in every sample. Veins distended without pressure control showed massive endothelial disruption. The particular solution used to distend the sephenous veins is not as important as limiting the distending pressure.

The normal healing process of microvascular anastomoses

The vessel wall regeneration and the inflammatory response in the rabbit femoral artery and vein the first three months after microvascular end-to-end suture anastomosis was assessed histologically. The initial damage consisted of endothelial loss and partial necrosis of media and adventitia. The luminal surface was reendothelialized and the adventitial layer restored by 20 days, but the necrotized part of the media did not regenerate. Instead, the vessel wall diameter was maintained by an intimal hyperplastic response. At the anastomotic site a characteristic slight dilatation was persistent. Consequently, the vessel wall architecture was not restored to the preoperative state after microvascular anastomosis.

Postoperative changes in autologous vein grafts

Images

Changes in saphenous veins used as aortocoronary bypass grafts

This report describes morphologic changes in saphenous veins used as aortocoronary bypass conduits, and discusses the relative contribution of various factors to these changes. The three primary changes are: (1) medial fibrous replacement, (2) adventitial fibrous proliferation, and (3) intimal fibrous proliferation. Medial fibrous replacement is caused by vein wall ischemia with loss of smooth muscle cells; adventitial fibrous proliferation is the result of organization of fibrin deposits and repair of ischemic injury; and intimal fibrous proliferation results from some stimulus, probably fibrin deposition on injured intima, which causes stimulation of smooth muscle cells to become fibroblasts or "myointimal cells". Although all grafts show some changes, the degree and severity of these three changes is variable along the length of the grafts and among separate grafts in the same patient.

Aortocoronary bypass graft in dogs: late histological changes

Late histological changes occurring in aortocoronary bypass vein grafts were studied by lignt and electron microscopy in three dogs killed one, two and three years after grafting. The changes consisted of intimal thickening due to a proliferation of modified smooth muscle cells (myointimal hyperplasia) and replacement of most of the medial smooth muscle by fibrocytes. Serial angiography in the dogs did not reveal progression of the intimal thickening after one month.

Histologic fate and endothelial changes of distended and nondistended vein grafts

Sixty-two autogenous cephalic vein segments were grafted into the femoral arteries of 31 mongrel dogs, the left side receiving non-distended (control) grafts and the right side distended (experimental) grafts. Distending media were heparinized blood and saline. Veins were distended at 600 mm Hg for 2 minutes. Specimens were taken at intervals from 15 minutes to 3 months, and were studied by gross inspection, surface observations (light scanning stereoscope to X70 scanning electron microscope to X6,000) and routine histologic techniques (light microscope to X 1000). In general, grafting of veins in the arterial system was followed by progressive degenerative changes in all layers of the vein, including endothelial cell involution, desquamation and re-endothelialization. Often a variable degree of subendothelial fibrous and/or myoepithelial proliferation occurred which might compromise even a lumen lined by healthy endothelium. Distention caused these changes to occur earlier (2-4 weeks) and to be more pronounced. Distention with saline caused more damage to the endothelium than did distention with blood. We conclude that preimplant distention of vein grafts (to overcome spasm) should be employed sparingly, as it adversely affects the endothelial covering of the flow surface, accelerates the development of degenerative changes, and may predispose the graft to early thrombotic complications.

Localization of tissue plasminogen activator in relation to morphologic changes in human saphenous veins used as coronary artery bypass autografts

Employing the histochemical fibrin slide technique, we studied the localization of fibrinolytically active sites in relation to morphologic changes in saphenous veins used as coronary artery bypass autografts. Of veins from 100 patients undergoing surgery for coronary heart disease, 63 samples revealed well-demarcated intimal fibrinolytic activity. Distinct foci of lysis were present in the media and adventitia of all vein samples corresponding to the distribution of the vasa vasorum. Graft specimens obtained by autopsy from 13 patients surviving from 30 minutes to 13 days revealed considerable intimal damage with loss of fibrinolytic activity. Medial fibrinolytic activity disappeared early concomitant with disorganization of the medial muscle fibers, followed by necrosis, atrophy and fibrous transformation of the muscular structures. Adventitial activity disappeared later. One reoperation sample obtained after 8 weeks in situ showed moderate proliferative intimal fibrosis without an apparent neo-intima and without fibrinolytic activity, and one section showed evidence of valve cusp fibrosis, while most of the media had been replaced by fibrous tissue. Numerous foci of "medial" -adventitial fibrinolytic activity indicated presence of vascular structures in the venous wall. The fibrin slide technique is a convenient tool for studying the process of revascularization.

Biologic fate of autogenous vein implants as arterial substitutes: clinical, angiographic and histopathologic observations in femoro-popliteal operations for atherosclerosis

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New surgical approaches to coronary heart disease

Coronary heart disease is now the principal cause of death in the Western world. In recent years a new surgical approach to the problem has been developed with encouraging results. The operation of aorto-coronary bypass grafting with autogenous vein relieves angina in the majority of patients. Whether or not the long term prognosis is improved is not yet known. A European multi-centre controlled trial has been organised to answer this question.