内皮型一氧化氮合酶基因转染防治移植静脉再狭窄的实验研究

移植静脉再狭窄是影响冠状动脉旁路移植(CABG)术后远期疗效的主要因素。许多研究表明，CABG术后血管桥再狭窄的发生与一氧化氮(NO)的功能异常相关，2004年7月至9月本研究采用兔颈外静脉颈总动脉旁路移植模型，应用含人内皮型一氧化氮合成酶(eNOS)基因重组腺病毒(AdCMVeNOS)转染移植静脉的方法，探讨eNOS基因防治静脉移植血管再狭窄的作用及其机制，为移植静脉再狭窄的防治提供实验和理论依据。     

内皮素、NO与自体静脉移植再狭窄的关系

目的　探讨内皮素、 Ｎ Ｏ 同自体静脉移植后狭窄的关系。方法　对２６ 例自体静脉移植后狭窄并进行２ 次手术者以及正常对照组２６ 例,利用放射免疫测定、 Ｇｒｉｓｓ 方法检测血浆内皮素和 Ｎ Ｏ 水平,利用反转录聚合酶链反应检测狭窄血管组织内皮素和一氧化氮合酶（ Ｎ Ｏ Ｓ） 基因表达水平。结果　所有患者均存在高内皮素、低 Ｎ Ｏ 血症,存在狭窄血管组织内皮素基因高表达、 Ｎ Ｏ Ｓ 基因低表达状态。结论　内皮素、 Ｎ Ｏ 同自体静脉移植再狭窄密切相关。     

冠状动脉旁路移植术后移植静脉再狭窄的研究进展

冠状动脉旁路移植术后移植静脉再狭窄是亟待解决的问题。移植静脉过度扩张导致管壁损伤,引起多种细胞因子和生长因子分泌,促进血管平滑肌细胞增生并向内膜迁移,进而细胞外基质沉积、血管壁重构和再塑,最终导致移植静脉再狭窄。血流动力学的改变和移植静脉管壁损伤是导致再狭窄的始动因素。防治方法主要有药物治疗、放射治疗、基因治疗和血管外支架治疗等,血管外支架联合基因治疗是一种前景看好的方法。     

反义技术治疗自体移植静脉再狭窄的研究

利用自体静脉作旁路转流术是血管外科临床广泛应用的术式,为血管闭塞性疾病患者提供了有效的治疗手段.但由于移植静脉再狭窄的发生,降低了远期通畅率.因此,研究再狭窄的发生机理和防治手段,是当前面临的主要课题.     

eNOS基因转染预防静脉移植血管再狭窄

目的 应用含牛内皮型一氧化氮合成酶(eNOS)基因重组腺病毒(Ad5CMVNOSⅢ)转染静脉移植血管、观察eNOS基因预防静脉移植血管再狭窄的作用。方法 将21只杂种犬分为3组，手术对照组、Ad5CMVLac—Z(含大肠杆菌β半乳糖苷酶基因重组腺病毒)对照组和Ad5CMVNOSⅢ干预组。在犬颈静脉、颈动脉旁路血管移植术中分别应用Ad5CMVNOSⅢ病毒液或Ad5CMVLac—Z病毒液常温浸泡法感染静脉移植血管30分钟，术后28天病理切片观测移植血管新内膜增生状况。结果 与正常犬颈外静脉相比，手术对照组、Ad5CMVLac—Z对照组和Ad5CMVNOSⅢ干预组颈外静脉移植血管内膜／中膜比较均有不同程度增加(P＜0．05)，但Ad5CMVNOSⅢ组内膜／中膜比显著低于另外2个对照组(P＜0．05)，新内膜增生明显减轻。结论 Ad5CMVNOSⅢ感染静脉旁路移植血管对预防再狭窄有一定作用。     

可溶性支架转染c-myc反义寡核苷酸预防静脉移植物再狭窄

目的 探讨可溶性支架转染c-myc反义寡核苷酸的可行性及其对静脉桥内膜增生的作用,以利在分子水平对静脉桥再狭窄进行防治.方法 新西兰大耳白兔随机分成5组,每组10只.建立兔颈外静脉颈总动脉旁路移植术模型.合成c-myc寡核苷酸,处理可溶性支架,依组别不同,在静脉移植时管腔内分别置人：（1）空白对照;（2）单纯可溶性支架;（3）反义寡核苷酸可溶性支架;（4）正义寡核苷酸可溶性支架;（5）不匹配寡核苷酸可溶性支架;静脉移植后7、28和90d取出静脉桥.行HE及弹力纤维染色,计算内膜、中膜厚度及内膜/中膜比值;利用免疫组化方法,检测各组静脉移植物内c-myc基因及PCNA的表达;采用原位杂交及激光灰度扫描,检测各组静脉桥中c-myc基因mRNA表达水平.结果 静脉移植后7、28和90d反义寡核苷酸可溶性支架组静脉桥内膜增生程度显著降低;c-myc及PCNA蛋白的表达显著低于同时间点其他各组;c-myc基因mRNA的表达显著低于同时间点其他各组.结论 可溶性支架可实现c-myc基因反义寡核苷酸的转染,可溶性支架转染c-myc基因反义寡核苷酸可显著抑制静脉桥c-myc及PCNA基因的表达,预防静脉桥再狭窄.     

联合转染P21基因和c-Fos反义核酸对自体移植静脉内膜增生的影响

目的 探讨联合转染P^21基因和c—Fos反义核酸对自体移植静脉内膜增殖的影响。方法 选择20只新西兰家兔，随机等分为实验组和对照组，均行自体颈外静脉、颈总动脉移植手术，仅实验组移植静脉段行腺病毒介导的P^21基因溶液浸泡、吻合口周围行c—Fos反义核酸凝胶涂布；术后2周取出移植血管，分别行病理学、免疫组织化学检查。结果 实验组移植血管内膜厚度、管腔狭窄度、内膜平滑肌细胞数以及增殖细胞核抗原(PCNA)阳性表达细胞数均较对照组明显减少。结论 联合转染P^21基因反义c—Fos核酸可有效地抑制移植静脉内膜的增生，是一种比较有发展前途的防治移植静脉再狭窄的基因疗法。     

自体移植静脉再狭窄的反义基因治疗现状

利用自体静脉旁路转流术是血管外科广泛应用的术式，为血管闭塞性疾病病人提供了有效的治疗手段。但由于移植静脉再狭窄的发生，降低了远期通畅率。因此，研究再狭窄的发生机理和防治手段，是当前面临的主要课题。１自体移植静脉再狭窄的形成机制自体移植血管主要来源于自...     

冠状动脉旁路移植术后移植静脉再狭窄的防治现状

冠状动脉旁路移植术(CABG)是冠状动脉粥样硬化性心脏病的常规治疗方法之一,动脉血管作为移植血管材料有其自身优势,但对大多数患者而言,自体大隐静脉仍然是最常用的移植血管材料,然而静脉移植后10年闭塞率高达50%余通畅的移植静脉也常有严重的病变,移植静脉的远期通畅率低已成为CABG疗效的瓶颈,新内膜形成和动脉粥样硬化导致移植静脉再狭窄已成为一个亟待解决的问题。目前,针对移植静脉再狭窄过程中的分子学机制和病理发展过程,研究者均采取了不同的防治方法,主要包括药物治疗、血管外支架、静脉保存液改进和基因治疗等,与其它方法相比较,基因治疗移植静脉再狭窄具有广阔的前景。我们对移植静脉再狭窄的防治和展望进行综述。     

野生型p53基因转染和低能量激光照射防治移植静脉再狭窄的实验研究

目的：探索转基因疗法和激光疗法防治移植静脉远期再狭窄的可行性及作用机制。方法：建立兔颈外静脉颈总动脉移植模型，分为（1）对照组，（2）绿色荧光蛋白（GFP）基因转染组，（3）p53基因转染组，（4）低能量激光照射组，（5）p53基因转染并低能量激光照射组。术后4周，免疫组织化学方法检测外源p53基因的表达及增殖细胞核抗原（PCNA），应用DNA片段末端标记法（TUNEL）标记凋亡细胞。HE、Masson及维多利亚兰染色后，应用计算机图像分析系统检测移植静脉内膜、中膜增生情况。结果：术后4周，与对照组相比，GFP基因转染组移植静脉血管平滑肌细胞（VSMC）增殖率、凋亡率差异无显著性，移植静脉内膜和中膜厚度无明显变化；p53基因转染组VSMC增殖率降低61％，凋亡率增加25％，移植静脉内膜和中膜厚度分别减少60％、33％，内膜厚度/中膜厚度比值(I/M)减少37％；应用低能量激光照射组VSMC增殖率降低41.5％，细胞凋亡率增加40.9％，移植静脉内膜和中膜厚度分别减少了58.5％、18.0％，I/M比值减少47.2％；转染p53基因同时应用低能量激光照射组VSMC增殖率较对照组降低61.7％，细胞凋亡率增高47.0％，移植静脉内膜和中膜厚度分别减少69.7％、44.4％，I/M比值减少44.5％。结论：转染野生型p53基因和低能量激光血管外照射可以抑制静脉VSMC增殖，促进移植静脉VSMC凋亡，使移植静脉内膜和中膜的增生减轻，具有防治移植静脉远期再狭窄的作用。     

Recovery of graft circulation following percutaneous transluminal angioplasty for stenotic venous complications in pediatric liver transplantation: assessment with Doppler ultrasound

Percutaneous transluminal angioplasty was performed for venous stenosis after living related liver transplantation in three children. Two of them had hepatic vein stenosis and one had stenosis of both the hepatic and portal veins. Progressive development of ascites and deterioration of liver function were found in all cases. Serial Doppler ultrasound studies showed that the flow velocity in the hepatic vein gradually decreased with a flattened velocity waveform, followed by a decrease in portal blood flow. After a successful hepatic vein angioplasty, the velocity in the hepatic and portal veins increased and the Doppler waveform in the hepatic vein became pulsatile in two cases. In the remaining case, a remarkable recovery of both graft perfusion and clinical findings was achieved via combined hepatic vein and portal vein angioplasty. We conclude that balloon angioplasty is an effective alternative to surgery for post-transplant vascular stenosis and that Doppler ultrasound is useful in monitoring graft circulation.     

Outcome of endovascular intervention for infrainguinal vein graft stenosis

Assisted graft patency rate following revision of a graft stenosis is far better than that following thrombectomy of an occluded graft. Graft revision by endovascular means has been proposed as a suitable alternative to more invasive surgery. This study reports our experience with endovascular treatment of vein graft stenosis. Between December 1992 and September 2000, percutaneous transluminal balloon angioplasty (PTA) was performed on 90 vein graft stenoses in 87 infrainguinal vein bypass grafts identified by routine graft duplex scan (peak systolic velocity, PSV > 300 cm/sec). All 90 stenoses treated by PTA were retrospectively analysed for stenosis-free patency rate (life-table analysis). Re-stenosis was defined by PSV exceeding 300 cm/sec at the same site of the vein graft where a stenosis was dilated.Ninety vein graft stenoses (72 primary stenoses and 18 recurrent stenoses) in 33 femoropopliteal (above knee), 30 femoropopliteal (below knee) and 24 femorotibial vein bypass grafts were treated by PTA. The timing of PTA ranged from one to 252 months (mean, 23.9 months) from the initial surgery. Cumulative stenosis-free patency rate after PTA was 55.8% at 6 months, 54.0% at one year and 45.0% at three years. Stenosis-free patency rate at six months was significantly lower for revision of recurrent stenosis (25.9%) than for primary stenosis (61.6%) (P = 0.01). The revision of duplex scan detected vein graft stenosis with endovascular intervention was associated with an acceptable stenosis-free patency rate. However, recurrent stenosis treated by PTA had a significantly inferior outcome. Direct surgical revision would be more appropriate for recurrent lesions.     

Comparison of duplex ultrasound with digital subtraction angiography in the assessment of infra-inguinal autologous vein bypass grafts

BACKGROUND: Postoperative surveillance of infra-inguinal vein grafts has arisen because of the high incidence of vein graft stenoses, which frequently progress to vein graft occlusion. The use of duplex ultrasound as the primary imaging method for graft surveillance is well established. This study aims to compare the accuracy of duplex ultrasound with the reference standard of digital subtraction angiography in the assessment of infra-inguinal vein grafts. METHODS: Sixty patients underwent routine postoperative duplex ultrasound as part of the local graft surveillance programme. Angiography was subsequently carried out on 18 grafts. Each lower limb arterial tree was divided into three segments (native arteries proximal to the graft, the graft itself and native arteries distal to the graft) resulting in a total of 42 comparisons. Degree of diameter stenosis on ultrasound was compared with angiography findings to determine concordance. Agreement was also expressed as a kappa value. RESULTS: Overall accuracy of duplex ultrasound was 88% (37/42). A kappa value of 0.80 indicates good agreement. In three of the five discordant cases, ultrasound correctly identified a stenosis, but overestimated the degree of stenosis compared with angiography. In each of the remaining two discordant cases, ultrasound identified a focal stenosis that was not apparent on angiography. In both cases, the area of duplex described abnormality responded to balloon angioplasty. CONCLUSION: Duplex ultrasound as part of the local vein graft surveillance programme is a reliable and accurate method in the detection of failing grafts and in some instances may be more sensitive.     

Recurrent stenosis of common carotid-intracranial internal carotid interposition saphenous vein bypass graft caused by intimal hyperplasia and treated with endovascular stent placement. Case report and review of the literature

Intimal hyperplasia is a well-known cause of delayed stenosis in vein bypass grafts in all types of vascular surgery. Options for treatment of stenosis in peripheral and coronary artery bypass grafts include revision surgery and the application of endovascular techniques such as balloon angioplasty and stent placement. The authors present a case of stenosis caused by intimal hyperplasia in a high-flow common carotid artery-intracranial internal carotid artery (IICA) saphenous vein interposition bypass graft that had been constructed to treat a traumatic pseudoaneurysm of the intracavernous ICA. The stenosis recurred after revision surgery and was successfully treated by endovascular stent placement in the vein graft. The literature on stent placement for vein graft stenoses is reviewed, and the authors add a report of its application to external carotid-internal carotid bypass grafts. Further study is required to define the role of endovascular techniques in the management of stenotic cerebrovascular disease.     

Central vein stenosis: a nephrologist's perspective

Central vein stenosis is commonly associated with placement of central venous catheters and devices. Central vein stenosis can jeopardize the future of arteriovenous fistula and arteriovenous graft in the ipsilateral extremity. Occurrence of central vein stenosis in association with indwelling intravascular devices including short-term, small-diameter catheters such as peripherally inserted central catheters, long-term hemodialysis catheters, as well as pacemaker wires, has been recognized for over two decades. Placement of multiple catheters, longer duration, location in subclavian vein, and placement on the left-hand side of neck seem to predispose to the development of central vein stenosis. Endothelial injury with subsequent changes in the vessel wall results in development of microthrombi, smooth muscle proliferation, and central vein stenosis. Central vein stenosis is often asymptomatic in nondialysis patients, but can result in edema of ipsilateral extremity and breast when challenged by increased flow from an arteriovenous fistula or arteriovenous graft. Bilateral central vein stenosis or superior vena cava stenosis can produce a clinical picture of superior vena cava syndrome, associated with engorgement of face and neck. Endovascular interventions are the mainstay of management of central vein stenosis. Percutaneous angioplasty and stent placement for elastic and recurring lesions can restore the functionality of the vascular access, at least temporarily. Frequent or multiple interventions are usually required. In recalcitrant cases, surgical bypass of the obstruction is an option. In resistant cases with severe symptoms, occlusion of the functioning vascular access will usually provide relief of symptoms. Further study of mechanisms of development of central vein stenosis and search for a targeted therapy is likely to lead to better ways of managing central vein stenosis. Prevention of central vein stenosis is the key to avoid access failure and other complications from central vein stenosis and relies upon avoidance of central vein stenosis placement and timely placement of arteriovenous fistula in prospective dialysis patient.     

Preimplant vein intimal thickness is not a predictor of bypass graft stenosis

PURPOSE: Preimplant vein morphology has been implicated as a risk factor for subsequent vein graft failure. It is controversial whether microscopic intimal thickening in random saphenous vein biopsy specimens is associated with an increased risk of graft failure. The purpose of this study was to determine the incidence of preexisting intimal thickening in a macroscopically normal preimplant vein, and to evaluate whether preimplant vein intimal thickness was predictive of future vein graft stenosis. METHODS: As part of an ongoing protocol, samples of preimplant veins were obtained at the time of the primary leg bypass. Routine duplex surveillance identified 14 patients who required operative revision for severe graft stenosis (n = 12) or graft occlusion (n = 2). Verhoeff's staining of specimens was performed to delineate the internal elastic lamina. Morphometric analysis of preimplant vein specimens was performed. The results were compared to a control group of 13 preimplant vein specimens selected from patients whose grafts have remained patent and stenosis-free by duplex. RESULTS: Preoperative risk factors were identical between the two groups. Mean intimal thickness in all 27 specimens was measured by two blinded observers. Almost 50% of specimens exhibited marked intimal thickening (>0.08 mm). The mean preimplant intimal thickness of the stenosis group was 0.108 mm +/- 0.155 compared to 0.100 mm +/- 0.064 for the control group (P = 0.866, NS). CONCLUSION: Although grossly normal preimplant veins often exhibit prominent microscopic intimal thickening, preimplant vein intimal thickness determined from a random saphenous vein biopsy at the time of primary leg bypass is not predictive to the subsequent development of vein graft stenosis.     

The detection of early femoro-distal vein graft stenosis by treadmill exercise testing

A prospective study of 125 femoro-distal vein bypass grafts (103 patients) was undertaken to assess the role of treadmill exercise testing in the detection and correction of early vein graft stenosis. Patients were followed at 1,3,6,12 months and then annually with routine clinical assessment, palpation of pulses and resting Doppler ankle/brachial index. In addition, the Doppler index was repeated after 5 minutes exercise on a treadmill set at 5 degrees and 3 km/hr. Follow-up has been carried out for a mean of 24 months (range 3-48 months) and during that time 30 vein grafts (28 patients) were submitted to angiography. This revealed vein graft stenosis in 15, native vessel disease in 11 and no morphologic abnormality in 4. One additional graft was suspected to have a stenosis but occluded before angiography could be carried out. At the time of detection by the treadmill test, 8 of the 15 (53%) confirmed vein graft stenoses, and 4 of 11 (36%) native vessel stenoses would not have been detected by clinical assessment or resting Doppler pressure measurements. The 15 vein graft stenoses which were corrected all remain patent, suggesting that treadmill testing is of value in the detection and prevention of early femoro-distal vein graft occlusion.     

Application of interventional radiology for stenosis of vascular anastomosis in living-donor liver transplantation

Stenosis of vascular anastomosis is a significant complication leading to graft loss after liver transplantation. For the diagnosis of portal vein stenosis, clinical signs of portal hypertension such as ascites and thrombocytopenia, stenosis and/or poststenotic dilatation on ultrasonography (US), and jet flow, rambling, or scarcity flow of the intrahepatic portal vein on Doppler US are useful. Three-dimensional computed tomography is used to confirm the indications for interventional radiography (IVR) to treat portal stenosis. For the diagnosis of hepatic vein stenosis, clinical signs such as ascites and slight jaundice, dilatation and stenosis on US, and reduced flow with a flat wave form of the intrahepatic portal vein on Doppler US are useful. The percutaneous transcaval approach is safer than the percutaneous transhepatic approach for patients with ascites. The requirement for multiple procedures could be a good indication for stent placement before patients develop liver cirrhosis. For hepatic artery stenosis, percutaneous intraluminal angioplasty and stenting are possible and good results have been reported recently. However, the long-term results must be evaluated in the future. IVR can be safely and successfully applied to the treatment of vascular complications using balloon dilatation and/or stent placement techniques before graft dysfunction becomes irreversible.     

THE VALUE OF DUPLEX SCANNING IN SURVEILLANCE OF INFRA-INGUINAL VEIN AND SYNTHETIC GRAFTS

The contribution of duplex scanning to improving early diagnosis of graft stenosis was evaluated in 195 patients after infra-inguinal bypass procedures. Over a 31 month period, 406 duplex scans were obtained on 232 limbs with 191 vein and 41 polytetrafluoroethylene (PTFE) grafts. Peak systolic velocities > 200cm/s with spectral broadening and lumen reduction on B-mode image were the criteria adopted for identification of a haemodynamically significant (> 50%) stenosis. Sixty-one stenoses were identified in 55 of the grafted limbs. Thirty-three of the 55 limbs had a subsequent angiogram. The angiogram showed graft occlusion in six limbs, graft stenosis in 18, and native artery stenosis in four. Twenty-one of the grafts had the angiogram within 1 month after the duplex had detected graft stenosis, and one (4.76%) became occluded in this interval. Seven had an angiogram more than 1 month after the duplex study, and five (71.4%) had become occluded. The angiographic study did not confirm a graft stenosis in five limbs. Three were submitted to operation and stenosis was confirmed. Seventeen graft thromboses were detected by duplex scanning. Graft thrombosis was demonstrated following a previous negative duplex scan in one of the 106 vein grafts (0.94%), and in four of 30 PTFE grafts (13.3%). Duplex scanning is effective in the detection of graft stenosis. The precise anatomical location is less accurate when in the region of an anastomosis. Early attention should be taken when duplex studies suggest critical graft stenosis because there is a high risk of occlusion. Polytetrafluoroethylene grafts tend to thrombose without a precursory focal stenosis.     

The Effect of «Non-critical» (<50%) Stenosis on Vein Graft Longitudinal Resistance and Impedance

OBJECTIVE: vein graft stenoses <50% cause minimal flow impairment, velocity elevation, or symptomatology and are therefore usually assumed to be "non-critical". The purpose of this study was to assess the effect of <50% vein graft stenosis on vein graft longitudinal impedance, as elevated impedance has been found to correlate with clinical graft failure. METHODS: eight segments of non-reversed cryopreserved vein (mean length 23+/-1 cm; mean outer diameter 4.7+/-0.2 mm) were saline-perfused in vitro utilising a variable pulsatile perfusion pump, Windkessel, and clamp resistor simulating the haemodynamic conditions of arterial bypass. Proximal (Pprox) and distal (Pdist) pressure were continuously measured by fluid-filled catheter transduction, and flow (Q) by ultrasonic transit-time flowmetry. Waveforms were digitally recorded at 200 Hz at pulse rates ranging from 60-180 b.p.m. with mean flow (Q) of 154 ml/min and mean proximal pressure (Pprox) of 100 mmHg (max/min 120/90). Graded mid-graft stenoses of <50% were created using an inflatable vascular occluder and measured by the corresponding changes in mean pressure gradient (DeltaP=Pprox-Pdist) and Q (%stenosis=1-{DeltaPbaselineQstenosis/Delta PstenosisQbaseline}1/4). Vein graft longitudinal resistance (RL) was calculated as DeltaP/Q. After Fourier transformation, vein graft longitudinal impedance (ZL) was calculated as DeltaP/Q at each harmonic, with ZL determined by integration over 0-4 Hz. Results are reported as mean+/-S.E.M. RESULTS: the desired levels of pressure and flow were established in all vein segments. Graded inflation of the occluder resulted in vein graft stenosis of 23+/-3% and 39+/-3%. This was accompanied by a mild reduction in Q (12% and 30%) and considerable increases in both RL (180% and 710%) and ZL (140% and 430%). CONCLUSIONS: "non-critical" vein graft stenosis (<50%) causes minimal change in mean flow, but substantial elevations in longitudinal resistance and impedance. The contribution of "non-critical" stenosis to vein graft failure may be under-appreciated.