Vein Bypass Grafts Research Articles

Killing Two Birds with One Stone: Subclavian Vein Bypass Graft for Relief of Venous Obstruction and Haemodialysis Access

Subclavian and brachio-cephalic vein stenosis or occlusion occurs, most commonly, as an iatrogenic complication of the placement of central venous catheter. This occurrence can cause ipsilateral arm swelling in a newly-created arteriovenous fistula (AVF). Critical central vein stenoses are often successfully managed by endovascular approach; occasionally, complete occlusion with symptomatic severe arm swelling and pain that does not respond to angioplasty requires ligation of the dialysis access. We report successful surgical management of an end-stage-renal-failure (ESRF) patient with symptomatic subclavian vein occlusion refractory to angioplasty in an ipsilateral arm with an existing functional brachio-basilic transposition arteriovenous fistula by performing a basilic to internal jugular vein (IJV) bypass graft, relieving both the arm swelling and salvaging the existing vascular access for future haemodialysis.

Spontaneous Rupture of Autogenous Saphenous Vein Graft in Bypass Surgery for Peripheral Arterial Disease Possibly Associated With Collagen Disease

We encountered two cases of spontaneous rupture of a saphenous vein bypass graft for lower-leg peripheral arterial disease possibly associated with collagen disease. Rupture occurred 5 and 14 days postoperatively. Neither case had any signs of infection, graft degeneration, or evident injury, but both were associated with collagen disease diagnosed at another hospital. We believe that an association with collagen disease might have contributed to vein wall fragility in the present cases.

Aneurysm of a 32-Year-Old Aortorenal Saphenous Vein Bypass Graft

We report the case of an incidentally discovered aneurysm of a previous saphenous vein bypass graft performed 32 years earlier for a renal artery aneurysm. The patient is a 52-year-old man who initially suffered from symptoms of hypertension and left-sided back pain. Saphenous vein bypass grafting was performed with aneurysm resection. Thirty-two years after surgery, the patient underwent a magnetic resonance imaging scan for back pain, hip pain, and anemia, discovering a 1.8-cm focal aneurysm at the site of the previous bypass. The patient underwent a repeat aortorenal bypass with an 8-mm flanged Dacron graft with excision of the existing aneurysmal saphenous vein graft.

Mechanical properties of cellulose: chitosan blends for potential use as a coronary artery bypass graft

The development of intimal hyperplasia is the major cause of failure of both autologous saphenous vein and synthetic coronary artery bypass grafts. This is partially due to graft-host vessel compliance mismatch. Cellulose and chitosan (CELL:CHIT) are both biocompatible, nontoxic, and naturally occurring biopolymers that have been used extensively for biomedical applications. Elastic properties of membranes made of CELL:CHIT blends with different ratios between each polymer were determined using uniaxial tests and the ratio that yielded the less stiff membrane was chosen to prepare a small diameter hollow tube. The presence of chitosan had a favorable impact on the elasticity of the membranes, where the CELL:CHIT 5:5 ratio showed the lowest Young’s modulus. Small diameter tubular constructs were fabricated using this optimal CELL:CHIT ratio and the compliance was determined on samples with different wall thickness and internal diameter. The compliance of the hollow tube with inner diameter of 4 mm and wall thickness of 1.2 mm was found to be 5.91%/mmHg × 10−2, which is higher than those of Dacron, expanded polytetrafluorethylene, and saphenous vein, but very close to that of human coronary artery. Burst strength tests revealed that the tubes can withstand at least 300 mmHg. Finally, the tubes showed satisfactory cell attachment property when myofibroblast cells adhered and proliferated on the lumen of the samples.

A simple method for eliminating strain on aortocoronary saphenous vein bypass grafts: The suspension of the right atrial appendage and plication of the right atrium

Strain on saphenous vein grafts may compromise the blood flow in the bypass graft. This may result in early postoperative ischemic complications as well as a decrease in early and late graft patency rates. In this article, we present two simple techniques to eliminate the excessive strain on the saphenous grafts when the patient is weaned off the cardiopulmonary bypass.

Managing coronary artery vein bypass graft stump pseudoaneurysm: a novel approach

We present a case of a pseudoaneurysm of the saphenous vein graft stump, which was managed with percutaneous thrombin injection. Aneurysms of a saphenous vein coronary bypass graft are rare and aneurysms of a bypass graft stump are even rarer. To our knowledge this is the first reported case of a pseudoaneurysm of a graft stump with the use of thrombin to treat a saphenous vein graft pseudoaneurysm.

Intimal hyperplasia: slow but deadly

Intimal hyperplasia is the leading cause of long-term failure in coronary artery bypass vein grafting, coronary artery stenting, angioplasty, arteriovenous fistula for dialysis, and allograft transplantation. Intimal hyperplasia is a product of vascular smooth muscle cell proliferation, migration through the internal elastic lamina, and deposition of extracellular matrix proteins driven by growth factors in the vasculature. This vascular pathology results in a progressive diminution of the vessel lumen and serves as a site for thrombosis and atherosclerotic lesions. A key cell type in the initiation of intimal hyperplasia is the vascular endothelial cell, which appears to have down-stream effects on the vascular smooth muscle proliferation and migration. Currently, the only means available for prevention of intimal hyperplasia is through inhibition of mammalian target of rapamycin (mTOR) with the immunosuppressant rapamycin. mTOR integrates up-stream signals from growth factors such as IL-2 and senses the cellular nutrient and energy levels and redox status. This presentation will discuss the potential means of preserving the vascular endothelial cell and, thereby, reducing the development of intimal hyperplasia in our open-heart surgical patients.

Submandibular High-Flow Bypass in the Treatment of Skull Base Lesions

Cerebral bypass surgery remains an integral part of the treatment of complex skull base tumors and unclippable aneurysms. The authors retrospectively analyzed a single-surgeon experience using a high-flow submandibular-infratemporal saphenous vein graft bypass technique after carotid artery sacrifice in the resection of complex skull base tumors and carotid isolation in unclippable aneurysms. Data on indications, surgical technique, bypass patency, complications, and outcome were collected for patients treated with adjunctive submandibular high-flow bypass for skull base lesions. Eleven patients (age range, 13-77 years) were treated for various skull base lesions: 4 patients were treated for skull base tumors with resection of the internal carotid artery (ICA), 6 were treated for aneurysms not amenable to clipping, and one was treated for invasive Mucor infection. With the use of a saphenous vein graft, a high-flow bypass was created from the high cervical ICA or external carotid artery to ICA or middle cerebral artery by means of a submandibular-infratemporal route. Postoperative angiography indicated bypass patency in 10 of 11 patients. There was no operative mortality. Follow-up of up to 12 years (mean, 56 months) was achieved. Direct high-flow submandibular-infratemporal interpositional saphenous vein bypass graft is an effective and durable technique for the treatment of complex skull base lesions where ICA revascularization is indicated.

A comparison of tibial artery bypass performed with heparin-bonded expanded polytetrafluoroethylene and great saphenous vein to treat critical limb ischemia

Expanded polytetrafluoroethylene (ePTFE) bonded with heparin (HePTFE) has been reported to perform equivalent to saphenous vein graft (SVG) for below-knee bypass. This series examines outcomes for tibial artery bypass using HePTFE and SVG over a contemporaneous time period. A retrospective analysis of prospectively collected data was conducted for 112 tibial bypasses (62 HePTFE, 50 SVG) performed from November 2006 to January 2009. Demographics for age, sex, race, diabetes mellitus, and end-stage renal disease were similar. Indications for revascularization were also similar: disabling claudication, 9%; rest pain, 25%; and tissue loss, 66%. The HePTFE group included more reoperative procedures (45% vs 26%). All HePTFE bypasses were performed using an autologous vein patch at the distal anastomosis. Postoperative graft surveillance by pulse examination, ankle-brachial index, and duplex ultrasound imaging occurred at 1, 3, 6, and 12 months. Follow-up ranged from 1 to 12 months. Kaplan-Meier and Cox regression analysis evaluated results in patients with no missing variables. HePTFE and SVG bypasses demonstrated no significant differences in target tibial artery distribution: anterior tibial (15 vs 17), dorsalis pedis (4 vs 5), posterior tibial (22 vs 16), and peroneal (21 vs 12). Graft occlusion occurred in 19 patients (16.9%) during follow-up. Primary patency at 1 year was 75.4% for HePTFE and 86.0% for SVG. There was no significant difference in primary patency due to sex (male, 78%; female, 84%), race (white, 82%; African American, 77%), or diabetes mellitus (no diabetes mellitus, 84%; diabetes mellitus, 76%). End-stage renal disease resulted in decreased patency (57%), with an eightfold reduction (95% confidence interval, 1.8%-39.8%; P = .006). SVG patients had a lower risk of occlusion/death (95% confidence interval, 14.2%-94.5%; P > .05). Sixteen amputations were performed, with no significant difference based on conduit. This experience indicates a trend for single-segment quality saphenous vein to remain the conduit of choice for tibial artery bypass compared with HePTFE. Factors relevant to decreased 1-year patency for the entire cohort were end-stage renal disease and nonhealing ulceration as the indication for revascularization. Although relatively short-term, these results do support HePTFE as a viable alternative conduit for patients with absent or poor quality saphenous vein who need a tibial bypass.

Pathology of Drug-Eluting Versus Bare-Metal Stents in Saphenous Vein Bypass Graft Lesions

The purpose of this study was to assess the pathological responses of atherosclerotic saphenous vein bypass grafts (SVBGs) to drug-eluting stents (DES) versus bare-metal stents (BMS). Repeat bypass surgery is typically associated with a high rate of morbidity and mortality. Percutaneous coronary interventions have emerged as the preferred treatment; however, only limited data are available on SVBGs pathological responses to DES and BMS. Formalin-fixed SVBG of >2 years duration (n = 31) were collected to histologically characterize advanced atherosclerotic lesions in native SVBG. In a separate group, SVBGs treated with DES (n = 9) and BMS (n = 9) for >30 days duration were assessed for morphological and morphometric changes. Necrotic core lesions were identified in 25% of SVBG sections, and plaque rupture with luminal thrombosis was observed in 6.3% of histological sections (32% [10 of 31] vein grafts examined). Morphometry of DES demonstrated reduction in neointimal thickening versus BMS (0.13 mm [interquartile range: 0.06 to 0.16 mm] vs. 0.30 mm [interquartile range: 0.20 to 0.48 mm], p = 0.004). DES lesions also showed greater delayed healing characterized by increased peristrut fibrin deposition, higher percentage of uncovered struts, and less endothelialization compared with BMS. Stent fractures (DES 56% vs. BMS 11%, p = 0.045) and late stent thrombosis (DES 44% vs. BMS 0%, p = 0.023) were more common in DES versus BMS. Advanced SVBG atherosclerotic lesions are characterized by large hemorrhagic necrotic cores. Stenting of such lesions is associated with delayed vascular healing and late thrombosis particularly following DES implantation, which may help explain the higher rates of cardiovascular events observed in SVBG stenting as compared with native coronary arteries.

Sex-based differences in the inflammatory profile of peripheral artery disease and the association with primary patency of lower extremity vein bypass grafts

This study was conducted to determine if there are sex-based differences in the inflammatory phenotype of patients undergoing lower extremity bypass (LEB) and if they correlate with clinical outcomes. This was a retrospective analysis of a prospective cohort of 225 patients (161 men and 64 women) who underwent autogenous vein LEB between February 2004 and May 2008. Fasting baseline blood samples were obtained before LEB, and the inflammatory biomarkers high-sensitivity C-reactive protein (CRP) and fibrinogen were assessed. All patients underwent ultrasound graft surveillance. CRP levels were dichotomized at 5 mg/L and fibrinogen levels at 600 mg/dL. There were no significant differences in age, race, history of hypertension or diabetes mellitus, body mass index, or coronary artery disease between men and women. Men were more likely to be current smokers (P = .02), have a history of hypercholesterolemia (P = .02), and be taking statins (P = .02). Women were more likely to present with critical limb ischemia (P = .03) and had higher median baseline CRP levels (5.15 mg/L; interquartile range [IQR], 1.51-18.62 mg/L) than men (2.70; IQR, 1.24-6.98 mg/L; P = .02). Median follow-up was 893 days (IQR, 539-1315 days). A multivariable Cox proportional hazards model for primary vein graft patency showed a significant interaction between sex and CRP (P = .03) and fibrinogen (P = .02). After adjustment for key covariates, primary vein graft patency was significantly less in women with CRP >5 mg/L compared with women with CRP <5 mg/L (P = .02). No such difference was seen in men (P = .95). Primary graft patency was also decreased in women with fibrinogen >600 mg/dL vs women with fibrinogen <600 mg/dL (P = .002); again, this pattern was not evident in men (P = .19). Women undergoing LEB for advanced peripheral artery disease have a different inflammatory phenotype than men. Elevated baseline levels of CRP and fibrinogen are associated with inferior vein graft patency in women but not in men. These findings indicate an important interaction between sex and inflammation in the healing response of vein grafts for LEB. Women with elevated preoperative CRP and fibrinogen levels may benefit from more intensive postoperative graft surveillance protocols.

In‐Hospital and 1‐year outcomes with drug‐eluting versus bare metal stents in saphenous vein graft intervention: A report from the EVENT registry

To compare outcomes of patients receiving drug-eluting stents (DES) versus bare metal stents (BMS) during percutaneous coronary intervention (PCI) of saphenous vein bypass grafts (SVG). Long-term benefits of DES versus BMS are well established for native vessel PCI. Benefit in patients undergoing SVG intervention is less certain. We used data from a multicenter registry (evaluation of drug eluting stents and ischemic events, EVENT) to compare outcomes among patients treated with DES versus BMS 1-year following SVG interventions. Between July 2004 and December 2007, 684 patients in EVENT underwent SVG PCI (515 DES only, 169 BMS only). The primary endpoint was a composite of death, myocardial infarction (MI), and target lesion revascularization between hospital discharge and 1-year follow-up. Propensity score stratification was used to adjust for differences between groups. Baseline demographic and clinical characteristics of patients treated with DES and BMS were similar. The DES group had fewer men and a higher prevalence of prior PCI. Patients receiving DES had less angiographic thrombus, less frequent use of embolic protection devices, greater total stent length, and smaller maximum stent diameters. Unadjusted outcomes between discharge and 1-year follow-up did not differ between the groups. After risk adjustment, the primary outcome was less frequent among patients treated with DES (adjusted HR = 0.48, 95% CI = 0.27-0.84, P < 0.01) with similar relative benefits across the individual endpoints. Among patients undergoing SVG PCI in a "real world" registry analyzed using propensity score stratification, treatment with DES compared with BMS was associated with reduced MACE at 1 year following PCI.

A completely fractured zotarolimus-eluting stent in an aortocoronary saphenous vein bypass graft

Drug-eluting stents (DES) have significantly improved the rate of target vessel revascularization in comparison with bare metal stents. DES fracture was not reported in multicenter randomized clinical trials, but several case reports of DES fracture have been published, mostly with sirolimus-eluting stents. DES fracture is associated with stent restenosis and thrombosis. We report a zotarolimus-eluting stent fracture in an aortocoronary saphenous vein graft (SVG) bypass. The patient presented with chest pain and a non-ST-elevation myocardial infarction. He underwent cardiac catheterization that showed a complete fracture of a zotarolimus-eluting stent in the ostium of a sequential SVG to the diagonal and obtuse coronary arteries. His management included coronary angioplasty and retrieval of the proximal fractured segment. We discuss the potential causes for this stent fracture and suggest caution when using a DES in an ostial location of a SVG bypass, especially in a highly mobile vessel.

The Clinical Course of Reverse-flow Anterolateral Thigh Flap: Need to Prepare for Venous Congestion and Salvage Operation

The Clinical Course of Reverse-flow Anterolateral Thigh Flap: Need to Prepare for Venous Congestion and Salvage Operation

Abstract 76: Preoperative Genome-wide Differences in Inflammatory Gene Expression Predict Success Versus Failure in Lower Extremity Vein Bypass

Introduction: Vein bypass grafting is standard surgical therapy in the treatment for peripheral arterial disease (PAD), especially for those with limb threatening ischemia. However, the durability of vein grafts remains problematic with recent studies reporting disappointing 1-year primary patency rates as low as 61%. We hypothesized that an individual’s systemic inflammatory state, characterized by genome-wide inflammatory gene expression, would be predictive of ultimate clinical success or failure of these grafts. Methods: 41 patients undergoing vein bypass grafting for symptomatic PAD (85% critical limb ischemia; 25% claudication) had complete pre-operative gene expression data for analysis and one-year follow-up. There were 16 failures (39%) by one-year. Gene expression was analyzed for the entire genome using the novel Affymetrix GGH2 6.9 million feature oligonucleotide array system. Expression levels for the 35,123 gene transcripts and initial unsupervised and supervised (success/failure outcome) clustering was performed using BRB array tools. To then determine the additional predictive influence of specific genes or groups of genes, a novel objective Bayes method for dichotomous outcomes using stochastic search algorithms and probit regression models was employed. A series of increasingly predictive candidate models of gene combinations were derived. Clinical parameters including Rutherford disease severity score at presentation, vein conduit (GSV vs. composite vein), diabetes, smoking, statin use, and antiplatelet/anticoagulant use were standardized in the predictive model. Results: A random search through the space of possible models including the six clinical covariates and different combinations of gene products was executed, resulting in a list of 20 models ranked based on their posterior probabilities. The additional predictive power of the top gene products are listed in Table 1 and genes with the highest marginal posterior probabilities are listed in Table 2. This modeling approach suggests that the genes identified, independent of any relationship functionally, exhibit class prediction potential for bypass outcome. Conclusions: Using both a powerful and novel gene array system and a novel probit model selection method, we were able to identify a small number of gene clusters with predictive capability for bypass success or failure. This may both be prognostic and feasible for use in clinical practice as a point-of-care tool moving forward. Validation of these models is currently underway.

Hemodynamic conditions in a failing peripheral artery bypass graft

The mechanisms of restenosis in autogenous vein bypass grafts placed for peripheral artery disease are not completely understood. We investigated the role of hemodynamic stress in a case study of a revised bypass graft that failed due to restenosis. The morphology of the lumen was reconstructed from a custom three-dimensional ultrasound system. Scans were taken at 1, 6, and 16 months after a patch angioplasty procedure. Computational hemodynamic simulations of the patient-specific model provided the blood flow features and the hemodynamic stresses on the vessel wall at the three times studied. The vessel was initially free of any detectable lesions, but a 60% diameter-reducing stenosis developed during the 16-month study interval. As determined from the simulations, chaotic and recirculating flow occurred downstream of the stenosis due to the sudden widening of the lumen at the patch location. Curvature and a sudden increase in the lumen cross-sectional area induced these flow features that are hypothesized to be conducive to intimal hyperplasia. Favorable agreement was found between simulation results and in vivo Doppler ultrasound velocity measurements. Transitional and chaotic flow occurs at the site of the revision, inducing a complex pattern of wall shear as computed with the hemodynamic simulations. This supports the hypothesis that the hemodynamic stresses in the revised segment, produced by the coupling of vessel geometry and chaotic flow, led to the intimal hyperplasia and restenosis of the graft.

Midterm Results of Beating Heart Coronary Bypass Surgery for Non-left Internal Thoracic Artery Anastomosis According to Grafting Design and Implications of Intraoperative Flow Characteristics on Graft Patency

The aim of the present study was to investigate the midterm patency of coronary artery bypass grafting (CABG) surgery according to the grafting design and intraoperative flow characteristics. Between March 2007 and July 2008, 218 beating heart CABG patients were prospectively divided into two groups according to the non-left internal thoracic artery (LITA) bypass grafting design; Group I (n = 161, aorta-saphenous vein) and Group II (n = 57, LITA-radial artery composite grafting). Preoperative patient characteristics and the additive EuroSCORE were similar between the two groups (p = 0.82). Mean flow (mL/min) and pulsatility index were measured intraoperatively and coronary multidetector computed tomography (MDCT) was performed immediately and 1 year postoperatively. For the non-LITA bypasses, the mean flow was significantly greater in group I than in group II (27.9 ± 17.7 mL/min vs. 17.6 ± 12.6 mL/min, p < 0.001). Uni- and multivariate analysis showed the grafting design (group I) to be the only predictive factor for the favorable midterm patency of the non-LITA grafts (p < 0.001). There were no significant intergroup differences in the incidence of complications including that of stroke or death in the immediate postoperative period. A total of four patients had cerebral events: three in group I (1.87%) and one in group II (1.75%). The overall rates of freedom from graft occlusion for the non-LITA to LAD bypasses at 100, 200, and 300 days were 99, 98, and 89%, respectively, in group I, and 95, 88, and 70%, respectively, in group II (P < 0.01). Overall freedom from graft occlusion for LITA to LAD bypasses showed no significant differences between the two groups (98 vs. 93%, p = 0.053). The results suggest superior intraoperative flow characteristics of the direct aorta-saphenous vein bypass grafting design to be attributable for its favorable patency results.

Repeat Percutaneous Treatment of a Large Vein Graft Aneurysm with Covered Stents

We present a case of repeat percutaneous intervention on a coronary artery bypass vein graft using polytetrafluoroethylene (PTFE) covered stents. The original intervention was performed using a combination of PTFE covered stents and bare metal stents for a large vein graft aneurysm. Successful exclusion of the aneurysm was demonstrated on follow up angiography. The patient represented six years after the original intervention with a non ST-segment elevation myocardial infarction. Further angiography demonstrated a recurrence of the aneurysm which we presumed to be due to late malapposition and required repeat PTFE covered stent deployment.

Acute popliteal pseudoaneurysm rupture secondary to distal femoral osteochondroma in a patient with hereditary multiple exostoses

A 21-year-old man with known hereditary multiple exostoses presented with a 24-hour history of atraumatic bruising and swelling of the posterior thigh. A leaking popliteal pseudoaneurysm was diagnosed on ultrasonography and an emergency saphenous vein bypass graft procedure performed. The patient required a post-operative blood transfusion but otherwise made a full recovery. Vascular complications from osteochondromas are rare and include vessel displacement, stenosis, occlusion, arteriovenous fistulas and pseudoaneurysm formation. Pseudoaneurysms usually present as an enlarging mass behind the knee. Acute rupture of an occult popliteal pseudoaneurysm caused by a distal femoral exostosis has not been reported previously.

Isolated Superficial Femoral Artery Aneurysm: A Case Study

Introduction Isolated aneurysms of the superficial femoral artery (SFA) are rare, and their etiology is not yet fully understood. Although not as common as abdominal aortic or popliteal artery aneurysms, they pose a serious threat of rupture and/or thrombosis. Because of their atypical presentation, they can be easily misdiagnosed. Methods A 58-year-old man presented with a painful lump over his left medial thigh, first noted 6 months previously. The patient was asymptomatic in regards to claudication. The findings of magnetic resonance imaging suggested a vascular mass versus pseudoaneurysm of the SFA. The patient was referred to the vascular laboratory and underwent duplex evaluation. This revealed an 8.3–cm long SFA aneurysm with a maximum diameter of 5.9 cm with extensive mural thrombus present. Angiography confirmed a true aneurysm, with an estimated length of 5 cm and luminal diameter of 2.5 cm. Result The patient underwent open aneurysmorrhaphy with a femoral to popliteal reverse saphenous vein bypass graft. Upon direct visualization, the aneurysm was estimated to measure 8 cm length and 6 cm in diameter. The patient recovered without incident and has normal ankle brachial indices. Conclusion True isolated aneurysms in the SFA are rare, and the exact cause is not yet known. Proper diagnosis and identification are crucial to patient outcome. In our case, duplex ultrasound yielded a more accurate measurement of the true aneurysm size when compared with the angiogram. This is attributable to the angiogram measuring the flow channel of the residual lumen while not visualizing the thrombus filled sac. Endovascular stent grafts or open repair with bypass grafts (vein or prosthetic) are the accepted methods of treatment with good patient outcome. Allowed to progress untreated, these aneurysms often rupture or thrombose, which can ultimately lead to limb loss. Because of the increased incidence of aneurysmal disease elsewhere in the body, these patients should undergo additional screening.