A Review of Arterial Grafts Used for Microvascular Arterial Reconstruction

Arterial grafts are sometimes used in microvascular reconstruction and their clinical benefit over standard venous grafts is unknown. To determine arterial graft utilization in clinical microvascular arterial reconstruction, a review of the literature was done. PubMed search resulted with 4,352 finds, and after screening for relevance, 11 articles reporting on 55 arterial grafts were analyzed. All reports were retrospective studies, case reports, and case series, with no randomized controlled trials. Two retrospective series reported better patency of arterial versus venous grafts in upper-limb revascularization for chronic occlusion, but the findings were highly biased. Better patency of arterial grafts did not lead to higher rate of clinical improvement. Antiplatelet and lipid-lowering agents seem to be underused in venous graft recipients and use of no-touch venous grafting has not been reported. Based on the available data, routine use of arterial grafts cannot be recommended. Studies that show better patency of arterial grafts in hand revascularization for chronic vascular insufficiency are retrospective and biased, so a randomized controlled trial is needed.     

PTFE血管加自体静脉段减轻动脉内膜增生的实验研究

目的:探讨PTFE人造血管加自体静脉段吻合对动脉内膜增生的缓和作用。方法:12只健康杂种犬的24条犬腿随机分成对照组及实验组。对照组股动脉阻断后,以PTFE人造血管直接行旁路转流术,实验组以自体颈外静脉段间置于PTFE与远端股动脉之间,术后第八周动脉造影后,收集标本行病理组织学观察及计算机图象分析测算增生内膜、中膜的厚度,增生内膜的截面面积、血管腔截面面积及两者的比值和静脉“动脉化”后中膜的厚度,同时,行间置静脉扫描电镜观察。结果:血管造影示两组通畅率分别为16.7％和66.7％(P<0.05);内膜厚度分别是483.5μm±67.3μm和147.1μm±38.6μm(P<0.1);中膜厚度组间差异不明显;增生内膜面积分别是5217±1123(pixel)和3117±890(pixel),分别占血管腔截面的80.9％±17.2％和47.7±13.7％(P<0.01);间置静脉呈动脉化表现。结论:间置自体静脉段能明显减轻PTFE管旁路手术后的动脉内膜增生,有效地提高血管手术后的通畅率。     

Why Patencies of Femoropopliteal Bypass Grafts with Distal End-to-End Anastomosis are Comparable with End-to-Side Anastomosis

Objective: Despite the theoretical favourable hemodynamic advantage of end-to-end anastomosis (ETE), femoropopliteal bypasses with distal ETE and end-to-side anastomosis (ETS) have comparable clinical patencies. We therefore studied the effects of different in vivo anastomotic configurations on hemodynamics in geometrically realistic ETE and ETS in vitro flow models to explain this phenomenon.Methods: Four ETE and two ETS models (30° and 60°) were constructed from in vivo computed tomography angiography data. With flow visualization physiological flow conditions were studied.Results: In ETS, a flow separation and recirculation zone was apparent at anastomotic edges with a shifting stagnation point between them during systole. Secondary flow patterns developed with flow deceleration and reversal. Slight out of axis geometry of all ETE resulted in flow separation and recirculation areas comparable to ETS. Vortical flow patterns were more stable in wider and longer bevelled ETE.Conclusion: Primary flow disturbances in ETE are comparable to ETS and are related to the typical sites where myointimal hyperplasia develops. In ETS, reduction of anastomosis angle will diminish flow disturbances. To reduce flow disturbances in ETE, the creation of a bulbous spatulation with resulting axial displacement of graft in relation to recipient artery should be prevented.     

Small Intestinal Submucosa as a Small-Diameter Arterial Graft in the Dog

Autogenous saphenous vein, human umbilical vein, modified bovine collagen, Dacron, and PTFE have been used as small-diameter arterial grafts with moderate success. We tested autogenous small intestine submucosa as a small-diameter arterial graft in both a carotid and femoral artery (mean ID 4.3 mm) of 18 dogs (total of 36 grafts). All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by Doppler ultrasound techniques and angiography. Two grafts ruptured and 5 grafts occluded by 21 days after surgery. One graft became occluded at 14 weeks. Fifteen dogs were sacrificed at periodic intervals until 48 weeks after surgery. Patent grafts had no evidence of infection, propagating thrombus, or intimal hyperplasia. Graft aneurysmal dilation occurred in 4 grafts (11%). The grafts were composed of a dense organized collagenous connective tissue with no evidence of endothelial cell growth on the smooth luminal surface. Three dogs are alive at 76 to 82 weeks after surgery. Overall, graft patency was 75%. Graft patency after cessation of anticoagulation therapy was 92.3% (12 of 13 grafts). We conclude that autogenous small intestinal submucosa can be used as a small-diameter arterial graft in the dog and is worthy of further investigation.     

A Canine Model of Intimal Hyperplasia (IH) in Autogenous Vein Grafting: A Preliminary Report

High failure rates (10–40% at 1 year and 2–6% per year thereafter) of autologous vein grafts in peripheral bypass surgery due to progressive intimal hyperplasia (IH) have prompted researchers to search for an animal model that develops IH in a relatively short period of time. This study summarizes our experiences in promoting IH in a canine model. Eight to ten centimeters of both jugular veins were exposed in 40 adult mongrel conditioned dogs. After division into 4–5-cm lengths, the segment of jugular vein most proximal was ballooned at 800–900 mm Hg with a modified 8F Fogarty catheter to induce intimal and medial layer injury. The distal segment was left nonballooned. Segments of these autologous vein grafts, 1.5 cm in length, both ballooned and nonballooned, were then anastomosed, end to end, into the carotid and femoral circulations. Six weeks postoperatively the grafts were perfusion-fixed, harvested, and histologically processed, and the amount of the lumen in midgraft sections occupied by IH was determined by image analysis. In all dogs, the degree of IH was significantly greater in the balloon catheterized vs noncatheterized graft segments. IH was more severe in the femoral than in the carotid arteries. The grafts that developed the most severe intimal hyperplasia were femoral grafts that had been balloon catheterized. We conclude that these protocols are effective in inducing IH in a canine model in short postoperative limes.     

牛心包生物瓣远期损坏的原因分析

对１１４例，１１９个植入人体内１年以上损坏的瓣膜作了损坏原因的病理学分析。基本病损：９０．７６％为破损、３４．４５％钙化、５．０４％过度纤维覆盖。结果表明，胶原纤维变性是导致瓣叶破损和钙化的基础。瓣叶的应力集中处可加速胶原纤维变性。早期损坏以破损为主，而后期常是破损和钙化等多种病损因素的复合结果     

桡动脉在全动脉化冠脉搭桥术中的临床应用

目的探讨桡动脉在全动脉化冠脉搭桥术中的临床应用效果。方法22例患者采用乳内动脉和桡动脉行全动脉化冠脉搭桥手术，“不接触血管技术”游离桡动脉，与冠状动脉对角支、钝缘支、前降支、右冠状动脉等单独或序贯吻合，共搭桥31支。术后应用钙通道阻滞剂防止桡动脉痉挛。结果22例手术均顺利完成，痊愈出院，无围术期心肌梗塞，术后心肌缺血改善，无手部缺血并发症。随访2月～3年，无心绞痛复发，手部功能正常。结论桡动脉作为血管桥材料在全动脉化冠脉搭桥术中应用效果良好。     

转染人血红素加氧酶-1基因抑制移植静脉血管内膜增生

目的　应用含人血红素加氧酶 - 1基因 (human Heme Oxygenase- 1,h HO- 1)的重组腺病毒 (Adeno- XTMh HO- 1,Ad- h HO- 1)转染静脉移植血管 ,观察 h HO- 1基因预防静脉移植血管内膜增生的作用。　方法　将 2 1只日本大耳白兔分为 3组 ,对照组 ,Ad- null组和 Ad- h HO- 1组 ,每组各 7只。在兔颈外静脉移植于颈总动脉的血管移植术前分别应用肝素生理盐水、Ad- null和 Ad- h HO- 1病毒液常温浸泡静脉移植血管 30 min。术后 2 8d病理切片观察移植血管内膜增生的情况 ,计算机图象分析仪计算新生内膜厚度、中膜厚度及二者比值 ;采用免疫组织化学染色方法 (S- P法 )观察术后 14 d、2 8d移植血管壁 h HO- 1蛋白表达情况。　结果　Ad- h HO- 1组内膜厚度、内膜厚度与中膜厚度比均显著低于Ad- null组和对照组 (P<0 .0 1) ,中膜厚度差别无统计学意义 (P>0 .0 5 )。 Ad- h HO- 1组静脉血管壁细胞 h HO- 1免疫组化染色阳性。　结论　 Ad- h HO- 1转染兔静脉旁路移植血管能够抑制内膜增生。     

New Regenerative Vascular Grafts for Hemodialysis Access: Evaluation of a Preclinical Animal Model

The purpose of this study was to evaluate a suitable animal model for the in vivo evaluation of patency and vascular tissue regeneration in small intestinal submucosa (SIS) vascular grafts for hemodialysis access. First, a 4-mm U-shaped SIS vascular graft was implanted between the internal carotid artery (CA) and the external jugular vein (JV) in five sheep and six swine. The U-shape grafts remained functional for 53 ± 4 days in sheep and 32 ± 2 days in swine. The sheep model presented exaggerated inflammation, so the swine model was selected for the in vivo study. Based on these initial results, a 4-mm C-shape SIS vascular graft with SIS circumferential reinforcement was developed to mechanically improve the vascular graft and manage complications identified during surgery in both sheep and swine. The C-shape vascular graft was implanted in a swine model (n = 3) between the CA and JV. GORE-TEX® vascular grafts were used as controls in the contralateral side of the neck. C-shape grafts remained patent for 47 ± 4 days, whereas the GORE-TEX® grafts were patent for 30 ± 15 days. The C-shape vascular graft was easier to handle during surgery, and its circumferential reinforcement improved in vivo patency, avoiding kinks in the graft after implantation. Histological results showed neovascularization and some regeneration with the alignment of endothelial cells in the vascular wall of the grafts. The model developed may be helpful in other research involving in vivo studies of vascular grafts for hemodialysis access.     

Simulated Nasoalveolar Palatal Defects: A Canine Model to Study Bone Grafts

A simple, surgical technique to create a simulated nasoalveolar palatal defect in the canine is described. The procedure has been performed in 60 canines, and we have not experienced closure of the created clefts. The surgically created clefts had to fulfill five criteria: (1) bilateral maxillary alveolar clefts had to exist in each research animal; (2) each cleft had to have a 1-cm bony width; (3) a demonstrable oronasal communication had to be present; (4) each cleft had to be lined by healthy epithelialized mucosa; (5) there had to be functional teeth adjacent to each side of every cleft.     

Long-Term Follow-up of 6–8 mm Brachioaxillary Polytetrafluorethylene Grafts for Hemodialysis

Abstract: Eight millimeter expanded polytetrafluoroeth-ylene (e-PTFE) grafts, tapered to 6 mm at the arterial site, are used by our group in the upper arm in order to avoid midgraft stenosis observed with other graft sizes. Long-term results (1–12 years) on 157 6–8 mm brachioaxillary e-PTFE grafts (Gore-Tex) are analyzed. Early failure was found in 4 grafts (2.5%). The rate of late complications was 0.37 episodes per graft-year. Steal syndrome, found in 4 cases (2.5%), was successfully treated in 3 cases by graft banding. Neither midgraft nor arterial anastomotic stenosis was observed in the 63 grafts requiring surgical thrombectomy or fistulography. The primary patency rates were 73%, 53%, and 41% at 1, 3, and 5 years, respectively. The secondary patency rates were 91%, 80%, and 72% at 1, 3, and 5 years, respectively. Comparison between both curves by the log rank test was significant (p < 0.001) expressing the efficiency of rescue surgery. We conclude that a 6–8 mm graft can be successfully used for dialysis in the brachioaxillary position     

地塞米松区域动脉灌注治疗重症急性胰腺炎的实验研究

目的探讨持续区域动脉灌注(CRAI)地塞米松对重症急性胰腺炎(SAP)家兔血清炎性因子的影响及治疗效果。方法采用胰腺被膜下注射5%牛磺胆酸钠制备SAP家兔模型。采用随机数字表法将24只家兔随机分为假手术组、SAP组、静脉灌注地塞米松组及CRAI地塞米松组(每组6只)。造模成功后0.5、3、6、9及12h检测各组血清肿瘤坏死因子(TNF)-α、白介素(IL)-6、IL-10及淀粉酶(AMY)水平,并观察家兔胰腺病理变化和生存情况。结果与假手术组相比,SAP组家兔血清IL-6水平在造模成功后3h明显升高,在6h达到高峰,9h开始下降(均P<0.05);IL-10水平在6h时开始显著升高,且9h及12h时均持续升高(均P<0.001);TNF-α水平在0.5h已经显著升高,6h达到高峰,9h开始下降(均P<0.05);AMY在9h开始升高,至12h时仍持续升高(均P<0.05)。与SAP组相比,CRAI地塞米松组血清IL-6及IL-10水平在6、9及12h时均明显降低(P<0.001),静脉灌注地塞米松组3h以后的各时段血清IL-6水平降低,但仅在6h时差异具有统计学意义(P<0.05);CRAI地塞米松组TNF-α水平在3h就已经开始明显降低(P<0.001),此后各时段均明显持续降低(P<0.001),而静脉灌注地塞米松组血清TNF-α水平仅在6h显著降低(P<0.05);CRAI地塞米松组和静脉灌注地塞米松组血清AMY在12h时均显著降低(P<0.05)。与静脉灌注地塞米松组相比,CRAI地塞米松组血清IL-6和IL-10水平在6h(P<0.05)及12h(P<0.001)时明显降低;TNF-α水平在3、6、9及12h均明显降低(P<0.001);AMY变化差异无统计学意义(P>0.05)。CRAI地塞米松组胰腺组织损害明显改善,3d时动物死亡明显减少。结论 CRAI地塞米松能够减轻SAP家兔的全身炎症反应和胰腺局部的炎症反应,改善动物生存情况。     

Arterial Tissue Regeneration for Pediatric Applications: Inspiration From Up‐to‐Date Tissue‐Engineered Vascular Bypass Grafts

The need for a valid replacement for autologous tissues in vascular surgery has led to the development of tissue‐engineered vascular grafts (TEVGs). Currently, only three kinds of TEVG have been used in clinical trials: synthetic scaffold‐based TEVGs, self‐assembled grafts, and decellularized exogenous tissues. This review presents the current options in the construction of TEVG and the changes that have occurred in the design following the clinical experience while focusing on the potential for pediatric applications. The emerging trend in the field, which is also pertinent for pediatric applications, is a shift from the development of vascular analogues to implants composed of scaffolds with autologous cellular components. Designs of such implants are currently being fine‐tuned so that a natural, functional tissue can gradually take over the role of scaffolds to stimulate the host's regenerative capacity and maintain the physiological homeostasis.     

采用颈总动脉节段性阻断法建立犬动脉内膜增生模型

建立一种较易获得、具有稳定性和重复性且接近于临床实际的动脉内膜增生动物模型。方法:16只健康杂种犬随机分成4组,在游离出右侧颈总动脉后,以微型动脉夹在距环状软骨各2.00cm的近、远端分别阻断颈总动脉0、15、30和60分钟,术后4周取标本进行切片观察及计算机图象分析。结果:于阻断15分钟组,阻断段动脉内膜未见明显增生;阻断30分钟和60分钟者阻断段动脉有新内膜形成,且后者增生程度较前者明显,前者的新生内膜中细胞成份较多,而后者则以细胞间质为主。结论:间歇性节段性动脉阻断法可成功地建立动脉内膜增生的动物模型,其操作方法简单,模型稳定,重复性好,且接近于临床实际,值得推广。     

Ambulatory surgery for PTFE grafts for dialysis

All prosthetic vascular accesses for hemodialysis performed in an ambulatory surgical setting between January 1992 and December 1996 were reviewed retrospectively. During this period, 400 out of the 450 vascular accesses with PTFE grafts (88.9%) were performed as outpatient cases. All operations were under local aesthesia without premedication. There were no postoperative deaths. Early complications were as follows: mild postoperative bleeding (readily controlled by local pressure): three (0.75%); surgical site infection: three (0.75%); early thrombosis (successfully treated with rescue surgery within the first 48 h, also in an ambulatory setting): four (1%). Four patients needed hospital admission (1%), one due to threatening arrhythmia, another because of anaphylactic reaction to cephazoline and two because of severe metabolic disorders. There was no increase in morbidity when the patients travelled long distances from the hospital to their homes immediately after the operation. These results show that prosthetic vascular accesses can be constructed and repaired in patients under local aesthesia and in an ambulatory surgical setting without an increase in morbidity. Delays due to waiting lists can be avoided, less resources are required, and complications associated with the prolonged use of central vein catheters for temporary hemodialysis can be reduced.     

An Impedance Matching of Femoral-Popliteal Arterial Grafts: A Theoretical Study

Abstract: We have proposed a mathematical method to investigate the matching conditions for an arterial graft in the femoral-popliteal region from a mechanical standpoint. Pulsatory blood flow, arterial wall motions, and conservation law are expressed by linear dynamical equations based on strict mechanical and constitutional considerations. To express the physiological blood flow in an actual arterial system, the tethering effects from the surrounding tissue and wall tensions were incorporated. The physiological parameters of arterial wall and tethering were utilized from reported experimental data. By complex analysis, mathematical expressions for the local impedance and reflection coefficient were obtained. They include not only blood properties such as viscosity and density, but also arterial properties including elastic modulus, radius, Poisson ratio, wall thickness, wall tension, frequency, and tethering effects from surrounding tissue. A matching condition was defined for minimizing the local impedance and reflection coefficient. The biophysical background was to reduce any mechanical mismatches, thus minimizing the disturbance of the flow velocity profile and shear stress distribution within the artery. Impedance matching in turn diminishes the negative factors for graft substitution represented by intimal hyperplasia and thrombosis. The calculated impedance and reflection coefficient inversed parabolically to functions of the resistance of the host artery, and there was one host arterial resistance that minimized the impedance and reflection coefficient. The present analysis revealed that for matching host artery with an elevated resistance, the dynamic elastic modulus of the wall of the graft that minimizes the impedance and reflection coefficient was increased. This indicates that for a host artery with a high resistance, an impedance matched stiff wall graft is preferable. For a large radius and a compliant host artery on the other hand, a large compliant graft should be linked. The present theoretical matching conditions will prevent anastomotic hyperplasia and thrombosis in graft substitution.     

Evaluation of Neointimal Hyperplasia on Tranilast-Coated Synthetic Vascular Grafts: An Experimental Study

Tranilast is an antiallergic drug that interferes with proliferation and migration of vascular smooth muscle cell induced by platelet-derived growth factor (PDGF) and transforming growth factor-β1 (TGF-β1). We investigated the local effect of tranilast on neointimal hyperplasia using tranilast-coated prosthetic grafts. The inner sides of the thin-walled polytetrafluoroethylene (PTFE) grafts were coated with chitosan and tranilast containing chitosan solution. Wistar albino rats (32) were used in the study. Patches (1 × 2 mm) for vascular grafts were prepared. Three groups were tested: group 1 (n = 12; tranilast coated), group 2 (n = 10; adhesive-only film-layer–coated), and group 3 (n = 10; normal ePTFE patch grafts sutured to the carotid arteries of the rats). Recipient sites of the carotid arteries were excised 4 weeks after surgery. All sections were examined histologically for graft patency, thrombus formation, and neointimal thickness. Expression of PDGF, fibroblast growth factor, and TGF-β1 on cross-sections of the neointima were evaluated by immunohistochemistry. No significant differences were found regarding mean neointimal thicknesses. PDGF and TGF-β-1 expressions were significantly lower in group 1. Although a decrease in local effect of tranilast was observed for growth factor expressions at a drug concentration of 0.05 mg/cm², a significant reduction in neointimal hyperplasia was not achieved. The coating concentration of 0.05 mg/cm² may have been too low to produce an antiproliferative effect. Given our promising results, further studies are recommended and planned using different drug concentrations and time intervals.     

Augmentation Rhinoplasty with a Combination of Triple Cartilage Grafts for Secondary Rhinoplasty in a Middle-Aged Population

Because of physiologic changes with advancing age as well as previously traumatized and then healed tissues, secondary rhinoplasty for a middle-aged patient is a challenging procedure. Depending on both factors, changes in the midvault can cause a functional airway disorder, and the nose also may need a complete correction for cosmetic purposes. To achieve aesthetic and functional outcomes, augmentation rhinoplasty using a combination of triple cartilage grafts, namely, spreader, columellar, and dorsal onlays, was performed for 12 patients. Sufficient nasal airways with satisfactory appearance were achieved for 11 of 12 patients. Only one patient had improved but still insufficient nasal function with a good aesthetic result. Augmentation rhinoplasty using a combination of triple cartilage grafts for middle-aged patients could be considered an effective procedure for improving the patient’s nasal airway and appearance.     

Arterial injury repair in nonhuman primates-the role of PDGF receptor-beta

BACKGROUND: This study documents the time course of the response to injury of the saphenous artery in baboons and the role of the platelet-derived growth factor-beta. Fundamental differences with the well-characterized rat arterial injury model have been found. MATERIALS AND METHODS: Thirty-eight baboons received a unilateral balloon injury to the saphenous artery and were treated with a chimeric blocking antibody to PDGFR-beta or vehicle control for 7, 14, or 28 days. The arteries were evaluated morphologically and for cell proliferation. RESULTS: Both medial and intimal smooth muscle cell proliferation were elevated 7 days after injury and were back close to baseline at 14 days. Unlike the rat, blockade of PDGFR-beta inhibited medial proliferation over 80% at 7 and 14 days, while intimal proliferation was only inhibited at 14 days (>95%). Also, unlike the rat, the baboon arterial media, as well as the intima, increased in size by 14 days after injury. Blockade of PDGFR-beta completely inhibited both intimal and medial growth at 14 days, but there was less of an effect on intimal growth at 28 days. CONCLUSION: Blockade of PDGFR-beta may be a clinical approach to inhibit intimal hyperplasia in humans, but this study raises concerns about the long-term efficacy of this treatment.