Value of static venous pressure for predicting arteriovenous graft thrombosis

BACKGROUND: Static venous pressure elevation has been shown to have both high sensitivity and high specificity for hemodialysis arteriovenous (AV) graft venous anastomosis stenosis. However, it is not known how well static venous pressure elevation predicts subsequent AV graft thrombosis. METHODS: Monthly static venous pressure measurements were made during two consecutive dialysis sessions in all patients with a functioning upper extremity AV graft in two hemodialysis units during a 16-month period. Static venous pressure was normalized to systolic blood pressure and corrected for the height difference between the AV graft and the dialysis machine pressure transducer to yield the static venous pressure ratio (SVPR). RESULTS: Fifty-four patients (38%) had a thrombotic event during the study period and thus were labeled as clotters. Among the clotters, SVPR just prior to thrombosis was 0.51 +/- 0.16 (mean +/- SD), and mean time to thrombosis following an elevated SVPR (> or =0.4) was 118 +/- 106 days. Receiver operating characteristic (ROC) curves were generated using the sensitivities and specificities of a range of SVPR values for access thrombosis within one, two, three and four months. The areas under the curve (AUCs) for the ROC curves ranged from 0.557 to 0.638, reflecting the absence of SVPR values with both high sensitivity and high specificity for access thrombosis. An increase in SVPR over time was not a better predictor of access thrombosis than absolute SVPR. CONCLUSION: Static venous pressure measurement is not an optimal screening test for identifying AV grafts at risk for thrombosis.     

Aggressive venous neointimal hyperplasia in a pig model of arteriovenous graft stenosis

BACKGROUND: Vascular access dysfunction is the most important cause of morbidity and hospitalization in the hemodialysis population in the United States at a cost of well over one billion dollars per annum. Venous neointimal hyperplasia characterized by stenosis and subsequent thrombosis, is the major cause of polytetrafluoroethylene (PTFE) dialysis graft failure. Despite the magnitude of the problem, there are currently no effective therapies for the prevention or treatment of venous neointimal hyperplasia in PTFE dialysis grafts. We believe that this is partly due to the lack of a validated large animal model of arteriovenous stenosis that could be used to test out novel interventions. METHODS: Seven-centimeter PTFE loop grafts were placed between the femoral artery and vein of domestic pigs. The grafts were removed at 2, 4, 7, 14 and 28 days after surgery and subjected to a detailed histological and immunohistochemical examination. RESULTS: Significant neointimal hyperplasia and venous stenosis developed by 28 days at the graft-vein anastomosis. There was minimal neointimal hyperplasia at the graft-artery anastomosis. Venous neointimal hyperplasia (VNH) was characterized by (a) the presence of smooth muscle cells/myofibroblasts; (b) angiogenesis within both the neointima and adventitia; and (c) the presence of an active macrophage cell layer lining the PTFE graft material. These results are very similar to the human lesion previously described by us in dialysis patients. CONCLUSIONS: We have developed and validated a pig model of venous neointimal hyperplasia that is very similar to the human lesion. We believe that this is an ideal model in which to test out novel interventions for the prevention and treatment of clinical hemodialysis vascular access dysfunction.     

Temporary arteriovenous fistula for venous reconstruction using synthetic graft: a clinical and experimental investigation

This report discusses venous reconstructive surgery combined with a temporary distal arteriovenous fistula creation for ilio-femoral vein obstruction. One patient who had long standing, high degree edema of the left lower extremity due to postphlebitic syndrome and four patients who had acute occlusion of the iliac vein were treated by means of extra-anatomical femoro-femoral vein bypass grafting combined with temporary distal femoro-saphenous arteriovenous (a-v) fistula creation. An expanded polytetrafluoroethylene (EPTFE) graft was selected for this procedure instead of a cross-over saphenous vein. The surgically created a-v fistula was effective in keeping the implanted grafts patent for a long time in three out of the five patients. In animal experiments, the bilateral iliac veins of mongrel dogs were replaced with several kinds of synthetic graft. Femoro-femoral a-v fistulae were made only on the left side. In 26 animals, 84.6% of the synthetic grafts on the a-v fistula side were patent, whereas only 11.5% of the grafts on the control side were patent. This investigation clearly demonstrates that the increased blood flow velocity through the created distal a-v fistula preserved the patency of synthetic vein grafts.     

Accuracy of physical examination in the detection of arteriovenous graft stenosis

Physical examination has recently been demonstrated to detect vascular access stenosis in patients with arteriovenous fistulae. However, its accuracy in the identification of stenoses when compared with the gold standard (angiography) in patients with arteriovenous grafts has not been studied in a systematic fashion. We conducted a prospective study to examine the accuracy of physical examination in the detection of stenotic lesions when compared with angiography. Forty-three consecutive cases referred for an arteriovenous graft dysfunction were included in this analysis. Preprocedure physical examination was performed. The findings of the examination and diagnosis were recorded and secured in a sealed envelope. Angiography from the feeding artery to the right atrium was performed. The images were reviewed by an independent interventionalist with expertise in endovascular dialysis access procedures and the diagnosis was rendered. The reviewer was blinded to the physical examination. Cohen's Kappa was used as a measurement of the level of agreement beyond chance between the diagnosis made by physical examination and angiography. There was a strong agreement between the physical examination and the angiography in the diagnosis of vein-graft anastomotic stenosis (kappa = 0.52). The sensitivity and specificity for this lesion was 57% and 89%, respectively. There was a moderate agreement beyond chance regarding the diagnosis of intragraft (kappa = 0.43) and inflow stenoses (kappa = 0.40). The sensitivity and specificity for the intragraft and inflow stenosis was 100%, 73% and 33%, 73%; respectively. The findings of this study demonstrate that physical examination can assist in the detection and localization of stenoses in arteriovenous grafts.     

Bovine graft arteriovenous fistula for hemodialysis

Repeated failure of conventional methods for hemodialysis has prompted the use of bovine arterial grafts as conduits in arteriovenous fistulas. Complications encountered in the use of the graft have been infrequent and have been attributed to technical difficulties that arose in four of the first five patients operated on. After revision of the operative technic no additional complications have been seen in the remaining twenty patients. These results are encouraging and the procedure warrants further investigation. The use of the modified bovine carotid artery graft in the construction of subcutaneous arteriovenous fistulas for chronic hemodialysis may be the procedure of choice.     

Utility of static pressure ratio recording during angioplasty of arteriovenous graft stenosis

Intra-access static pressure ratio (SPR) (intra-access pressure/mean arterial pressure) can be measured during angioplasty (PTA) to assess the functional importance of an arteriovenous graft (AVG) stenosis. We used SPR in 70 patients with AVGs who underwent 98 angioplasty procedures. SPR was measured during angioplasty by placing a catheter tip at mid-access. Inflow stenosis (IF) = stenosis proximal to the tip of the catheter. Outflow stenosis (OF) = stenosis distal to the tip of the catheter up to the superior vena cava-atrial junction. Post PTA, access flow (Qa) was assessed within 2 weeks. Complete data sets for both SPR and Qa were available in 83 procedures. Using a normal SPR ratio of 0.3-0.4 at mid-graft, three patterns of SPR were noted. In 63 of 83 (76%) cases SPR was elevated prior to PTA (0.71 +/- 0.13 SD). PTA reduced SPR toward normal range (0.44 +/- 0.12) in 53 cases (84%). In the remaining 10 (16%), SPR decreased to a low value (0.22 +/- 0.03) and normalized (0.40 +/- .0.11) only after PTA of a coexisting inflow stenosis. In 12 of 83 (14%) procedures, the initial SPR was low (0.18 +/- 0.04) and increased toward normal (0.3 +/- 0.08) following IF stenosis PTA in seven (58%) cases. For the remaining five (42%) cases SPR increased to a high value (0.70 +/- 0.21) and decreased toward normal range (0.33 +/- 0.07) only after OF stenosis angioplasty. In 8 of 83 (10%) procedures, initial SPR was normal (0.33 +/- 0.02). Angiography revealed coexisting IF and OF stenoses. SPR remained within the normal range after PTA of these lesions (0.33 +/- 0.02). Qa increased significantly in 74 of 83 (89%) procedures (before = 572 +/- 201, after = 1109 +/- 368 ml/min; p < 0.001). SPR measurements can assist in hemodynamic assessment of an AVG during angioplasty procedure.     

PTFE graft arteriovenous fistulae for hemodialysis access

The use of expanded PTFE graft arteriovenous fistulae for hemodialysis access is becoming increasingly popular. Its low infection rate, low thrombogenicity, low body reactivity, and longevity make it an ideal vascular substitute. From May 1976 to June 2, 1978 we have placed 102 grafts in 89 patients, many of whom represent management problems of other access means. Major complications are pseudointimal proliferation at the venous anastomosis, pseudoaneurysm formation, and thrombosis, usually associated with low blood volume. These problems are, however, readily rectifiable. Other types of grafts, according to the literature, have not been successful for hemodialysis access.     

Bovine graft as arteriovenous fistula for hemodialysis

We used the bovine carotid artery (BCA) as arteriovenous shunt for hemodialysis in 11 patients since December 1975. We discuss our results. For implantations we used two methods: straight and loop grafts. The BCA have many advantages as: good access for punction, anticoagulation not permanently necessary, volume of shunt more than 250 ml/min; the disadvantages are: increased tendence to infection and thrombosis. Thrombosis in BCA can be easier removed than in other grafts. Reduction of the complications incidence is possible with an accurate technique. We think that the BCA is very useful when Cimino-Brescia fistula has failed or is unavailable; we prefer BCA to a saphenous arteriovenous graft in these situations.     

血液透析患者中心静脉留置导管失功与处理

回顾性分析212例采用Seldinger技术中心静脉置管行维持性血液透析(HD)患者导管失功状况。212例中发生导管失功61例,发生率为28.77%,其中导管通路功能障碍28例,导管相关性感染33例。经对症处理,45例恢复正常HD,16例拔管。导管内血栓形成和导管相关性感染是失功主要原因,护理人员在HD过程中应熟练掌握操作技术,严格无菌操作,加强健康教育,及时发现异常及时处理,尽可能降低导管失功发生率。     

血液透析带涤纶环中心静脉留置导管功能不良原因分析

目的 分析血液透析(HD)患者带涤纶环中心静脉留置导管(cvc)功能不良的原因.方法 对本院99例带涤纶环CVC的患者进行了前瞻性研究.导管插入后记录实验室和临床变量,临床过程跟踪6个月,根据6个月内出现导管功能不良分为:导管功能不良组、功能正常组.结果 导管功能不良组患者超敏C-反应蛋白(hs-CRP)显著高于功能正常组;而初始血流量(BF)、血白蛋白(Alb)显著低于功能正常组.结论 微炎症状态、初始BF、低蛋白血症与HD带涤纶环CVC导管功能不良有关.     

Clinical application of mid-thigh arteriovenous graft

Objective To evaluate the clinical outcomes of hemodialysis patients after superficial femoral artery-superficial femoral vein arteriovenous graft (AVG). Methods Hemodialysis patients with mid-thigh superficial femoral artery-superficial femoral vein AVG from August 2015 to March 2018 in department of vascular surgery, Longhua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine were enrolled. Their clinical outcomes and complications after operation were analyzed retrospectively. Patency rates were measured by Kaplan-Meier survival curve. Results A total of 18 cases were enrolled. The success rate of the operation was 100% without complication. Follow-up time was (22.00±11.77) months with 100% follow-up rate. The 6 months-, 12 months-, 24 months-primary patency rates were 83.3%±8.8%, 48.5%±12.1%, 24.2%±13.5%, respectively; secondly patency rates were 100.0%, 100.0%, 87.5%±11.7%. There were 1 case of seroma, 1 case of puncture site infection, 11 cases of stenosis and 5 cases thrombosis during follow-up, while no heart failure, ischemia or pseudoaneurysm. Conclusion Mid-thigh AVG has low infection rate and high patency rate, so it can be as the first choice for the lower extremity AVG in hemodialysis patients.     

Dual function of the distal arteriovenous fistula for maintenance of arterial and venous prosthetic graft patency in the lower extremity

Venous hypertension, severe swelling, and tissue necrosis occurred in a limb previously subjected to distal arterial bypass plus adjunctive arteriovenous fistula. Occlusion of the popliteal vein had not been recognized during the early treatment period. Subsequent to identification of this mechanism, limb salvage was achieved with an interposition graft of the popliteal vein using externally supported PTFE. The prereconstruction venous pressure gradient of 29 cm H2O was virtually abolished immediately after reestablishing venous outflow. The distal arteriovenous fistula, initially established to maintain prosthetic arterial graft patency, now serves, in this case, a dual function by additionally maintaining prosthetic venous graft patency. An intact deep venous system is critical for achieving successful arterial reconstruction and to avoid the complications associated with an occluded outflow tract in the face of augmented inflow.     

Transcranial approach for venous embolization of dural arteriovenous fistulas

OBJECT: This study was undertaken to investigate the healing process and to delineate factors important for the survival of free fascial grafts used for dural repair. METHODS: A dural defect was created in guinea pigs and then reconstructed using either a free fascial graft or an expanded polytetrafluoroethylene (ePTFE) sheet. The fascial graft was covered directly by subcutaneous tissue (Group I) or by a silicone sheet to prevent tissue ingrowth from the subcutaneous tissue (Group II). The ePTFE sheet was covered with a silicone sheet (Group III). One or 2 weeks postoperatively, the strength of the dural repair was evaluated by determining the pressure at which cerebrospinal fluid (CSF) leaked through the wound margins. The dural repair was also histologically examined. In addition, using a rat model, specimens obtained from similar reconstruction sites were immunohistochemically stained with antibodies against basic fibroblast growth factor (bFGF), epidermal growth factor, or transforming growth factor-beta. The pressures at which CSF leaked after 1 and 2 weeks, respectively, were 50 +/- 14 mm Hg and 126 +/- 20 mm Hg in Group I, 70 +/- 16 mm Hg and 101 +/- 38 mm Hg in Group II, and 0 mm Hg and 8 +/- 8 mm Hg in Group III. Failure of repairs made in Group III occurred at significantly lower pressures when compared with Groups I and II. In Groups I and II, a thick fibrous tissue formed around the fascial graft. This tissue tightly adhered to adjacent dura mater. The fibrous tissue displayed a positive reaction for the presence of bFGF. In Group III, only a thin fibrous membrane surrounded the ePTFE sheet. CONCLUSIONS: Fascial grafts tolerated extraordinary intracranial pressures at 1 week postoperatively. Free fascial grafts can heal with durable fibrous tissue without the presence of a blood supply from an overlying vascularized flap.     

Reconstruction of the venous outflow using a vein graft in dural arteriovenous malformation associated with sinus occlusion

In some cases of dural arteriovenous malformations (dural AVMs) of the transverse-sigmoid sinuses, the presence of an occlusion or hypoplasia on the sinus contralateral to the affected side may significantly contribute to the development of intracranial hypertension. For these cases, closure of AV shunts or removal of the affected sinus may not be sufficient to improve intracranial hypertension. We encountered 2 cases of intracranial hypertension caused by dural AVMs at the transverse-sigmoid sinuses associated with disturbance of venous outflow contralateral to the lesion. Reconstruction of venous outflow using a saphenous vein graft was performed between the transverse sinus and the subclavian or external jugular vein after the dural AVMs were partially occluded by catheter embolization. Intracranial hypertension was relieved in both cases. In one case dural AVM was obstructed by both embolization and radical surgery after the bypass was confirmed unobstructed several weeks later. The bypass remained patent at the follow-up 4 months later. In the other case, patency of the bypass lasted only for approximately 1 month. In both cases clinical improvements were not remarkable. It is considered that the presence of AV shunt in the case of dural AVM may facilitate the patency of a graft placed between the venous systems. Reconstruction of the venous outflow may deserve further trial for the treatment of intracranial hypertension associated with some types of dural AVM.     

球囊扩张联合覆膜支架植入治疗人造血管动静脉内瘘狭窄

目的 探讨球囊扩张联合覆膜支架植入治疗人造血管动静脉内瘘(AVG)狭窄的临床疗效.方法 前瞻性选取15例经皮腔内血管成型术(PTA)疗效欠佳的AVG狭窄患者,且具备以下特点:狭窄长度不超过7 cm,狭窄程度大于50％;PTA后3个月内狭窄复发2次或以上;扩张后残余狭窄＞30％或狭窄部位立即弹性回缩.所有患者在数字减影血管造影(DSA)下行球囊扩张后植入不同内径的聚四氟乙烯覆膜支架.结果 男3例,女12例,平均年龄(66±12)岁.支架植入前内瘘平均使用时间为(19.5±15.0)个月.共植入支架16枚,技术成功率100％,植入部位为静脉吻合口9例(9/15);静脉流出道6例(6/15),其中头静脉3例,肱静脉2例,腋静脉1例.首次开通率3个月为40％,6个月为19％,12个月为13％.再次开通率3个月为93％,6个月为88％,12个月为87％.术后平均随访时间为(14.9±5.3)个月,再窄狭率为87％(13/15).术后PTA 36例次,支架内狭窄36％ (13/36);支架远端狭窄8％ (3/36);支架近端狭窄22％(8/36);与支架无关的狭窄33％ (12/36).AVG中位生存时间为25个月.结论 球囊扩张联合覆膜支架植入治疗AVG狭窄技术成功率高,并发症少,首次开通率不高,但再次开通率令人满意.     

Femoro-popliteal venous graft entrapment

The authors report a case of femoropopliteal venous bypass graft entrapped between the inner femoral condylar epiphysis and the medial head of the gastrocnemius muscle, the graft being inadvertently placed medially to this tendinous structure. What makes the case exceptional is that the indication for the venous bypass graft was a femoropopliteal thrombosis, secondary to an initially overlooked popliteal artery entrapment syndrome. In the discussion, the authors made an extensive review of the literature on this rare abnormal relationship between the popliteal artery and the medial head of the gastrocnemius (embryology, anatomical variations, clinical features, diagnostic measures and treatment).     

人工血管移植动静脉瘘术后超声检测价值

目的 探讨彩色多普勒超声对人工血管移植动静脉瘘及其并发症的检测价值.方法 对18例人工血管移植动静脉瘘术后4～6周的患者,应用彩色多普勒超声测量动脉侧吻合口和移植人工血管动脉端内径、峰值流速和血流量,同时对上肢出现不适症状患者进行超声检测.结果 术后4～6周彩色多普勒超声显示吻合口和移植人工血管血流充盈良好,动脉侧吻合口内径、峰值流速和血流量分别为(3.61±0.68)mm、(298.56±93.42)cm/s、(583.62±216.77) ml/min;人工血管动脉端内径、峰值流速和血流量分别为(4.47±0.61)mm、(219.37±68.42)cm/s、(325.23±117.12)ml/min.7例患者手术侧上肢出现不适症状,超声检查发现1例血清肿;3例移植血管血栓;1例假性动脉瘤;2例单纯性皮下组织水肿.结论 超声对人工血管移植动静脉瘘术后人工血管及其并发症的检测有重要的临床应用价值.