Vascular grafts

Autogenous vein is the conduit of choice in the surgical creation of bypasses of small-to-medium-caliber vessels in patients with peripheral occlusive arterial disease and will remain so for the near future. The success rate of bypasses using conduits of diameters greater than 6 mm has been excellent, whereas the majority of bypasses using smaller conduits fail within 5 years. In addition, due to a steep increase in rates of diabetes and decreasing cardiovascular mortality rates, increasing challenges are presented by this population. These facts have motivated much of the research in the cardiovascular arena over the past four decades, with improved techniques and new materials. Strategies to improve outcomes include the use of alternative materials including autologous, nonautologous and prosthetic grafts, utilizing different methods for their harvesting and preservation; tissue engineering, using either polymer- or biological-based scaffolds for cell seeding; endovascular methodologies; and gene therapy. This report presents an overview of the several options currently available in the management of patients with peripheral arterial occlusive disease, as well as the ongoing research directed towards the creation of an artificial engineered vessel, discussing experimental work in which endothelial cells have been seeded on different scaffolds and finally the potential application of gene therapy in the field of vascular reconstruction.     

Course of peripheral occlusive arterial disease in diabetes. Vascular laboratory assessment

To determine comparative rates of development and progression of peripheral occlusive arterial disease, 110 healthy nondiabetic control subjects, 112 patients with peripheral occlusive arterial disease (POAD), 240 patients with diabetes mellitus (DM), and 100 patients with diabetes mellitus and peripheral occlusive arterial disease (DM + POAD) were studied over 4 yr with noninvasive techniques. The presence of peripheral occlusive arterial disease was determined by postexercise ankle-brachial index (ABI) values; progression of peripheral occlusive arterial disease was determined by the rate of change in postexercise ABI. Patients who underwent peripheral arterial reconstructive surgery or amputation were also classified as having progression of their peripheral occlusive arterial disease. On this basis, follow-up revealed that peripheral occlusive arterial disease developed and therefore progressed in 1 (1%) of the control group and 22 (9%) of the DM. Peripheral occlusive arterial disease progressed in 31 (28%) of the POAD and 26 (26%) of the DM + POAD. The presence of peripheral occlusive arterial disease predisposes to progression of disease, and peripheral occlusive arterial disease is more likely to develop in diabetic patients who do not have peripheral occlusive arterial disease than in nondiabetic control subjects. However, the presence of diabetes mellitus in patients with peripheral occlusive arterial disease does not seem to increase the risk of progression.     

Peripheral arterial occlusive disease and its care in hemodialysis patients

The prevalence of peripheral arterial occlusive disease (PAOD) in hemodialysis patients is several times higher than among the general population, and is the main reason for amputations in this group. Patients with peripheral arterial occlusive disease face higher hospitalization and mortality rates associated with cardiovascular disease than non-PAOD patients. The ankle brachial index (ABI) is a widely used PAOD screening tool that may under-estimate PAOD prevalence in the hemodialysis population in the presence of extensive vascular calcification. Studies have demonstrated oxygen saturation in the upper and lower limbs and the "Edinburgh Claudication Questionnaire" as simple screening methods that, in combination with ABI, can increase screening test effectiveness. Early PAOD detection, risk factor modification, medical treatment, and exercise rehabilitation therapy can improve walking function and reduce mortality in PAOD patients.     

不同材料周围动脉支架置入治疗动脉硬化闭塞症的研究与进展

背景：外周动脉支架治疗周围动脉硬化闭塞临床疗效好,但是目前没有一种完美的外周动脉支架,掌握各种支架的特点并灵活应用是取得良好疗效的关键。目的：综述不同材料周围动脉支架置入治疗动脉硬化闭塞症的研究进展。方法：应用计算机检索1968-01/2011-11PubMed数据库相关文章,检索词为＂stent＂,并限定文章语言种类为English。共检索到文献107篇,最终纳入符合标准的文献40篇。结果与结论：周围动脉支架置入治疗动脉硬化闭塞安全有效。支架材料主要有不锈钢支架、镍钛合金支架、钴基合金支架、钽金属支架、镁合金支架、高分子材料支架及多种材料复合支架。置入后支架内再狭窄是其主要并发症,支架断裂等并发症时有报道。支架置入后抗凝治疗已得到广泛认可。掌握各种支架的特点及适应证能提高支架的通畅率和减少支架置入后并发症。发展新型支架提高通畅率已成为将来研究方向。     

Gene therapy to prevent occlusion of venous bypass grafts

Revascularization with vein grafts is standard surgical therapy for occlusive arterial diseases. Autologous saphenous vein grafts are important conduits for repairing blocked coronary arteries and are used in the majority of vein graft procedures. Up to 50% of saphenous vein grafts will be occluded during the first decade after surgery. Vein graft occlusion occurs as a result of neointimal hyperplasia, which takes place in response to hemodynamic changes and vessel wall injury, and is characterized by the migration and proliferation of vascular smooth muscle cells. Intimal hyperplasia is further complicated by the concomitant development of atherosclerosis and thrombosis. In the absence of effective pharmacological interventions for the treatment and prevention of occlusive vein graft disease, gene therapy has emerged as a potential therapeutic alternative. Gene therapy could improve vein graft patency by reducing early thrombosis, neointimal hyperplasia and atherosclerosis. In this review we will summarize the emerging applications of gene therapy as a therapeutic tool in occlusive vein graft disease.     

Mutation in factor II and factor V gene in patients with peripheral arterial occlusive disease

Mutations in factor-V- and factor-II-genes are correlated with an increased risk for venous thrombosis according to the literature. The significance of the mutations in factor- II- and factor-V-genes for the development of the peripheral arterial occlusive disease is not known. Therefore, we investigated the presence of these mutations in 152 patients with documented peripheral arterial occlusive disease and 318 controls without peripheral arterial occlusive disease with polymerase chain reaction (PCR). There was no association between factor-II-mutation and peripheral arterial occlusive disease. The factor-V-mutation, however, was increased in patients with peripheral arterial occlusive disease double fold (12 positive cases in 318 controls, 12 positive cases in 152 patients with peripheral arterial occlusive disease). The significance level was reached (p = 0.05) in statistical analysis but the result did not fall below the significance level as necessary to reach statistical significance (odds ratio 2.19). Nevertheless, from these data we have to discuss a biological relevance of factor-V-mutation in the pathogenesis of peripheral arterial occlusive disease.     

MRI in Lower Extremity Peripheral Arterial Disease: Recent Advancements

Evaluation of peripheral arterial disease by cardiovascular magnetic resonance imaging continues to develop. Of the clinical diagnostics tests currently available, magnetic resonance angiography is well established as one of the preferred techniques for determining areas of arterial occlusive disease affecting the lower extremities. Despite this, there have been new developments in non-gadolinium based contrast-enhanced studies as well as testing done at higher field strength scanners. In the research arena, magnetic resonance spectroscopy, calf muscle perfusion imaging and atherosclerotic plaque evaluation all have made significant advancements over the last year. These techniques are gaining traction as surrogate endpoints in clinical trials of novel therapeutics aimed at alleviating symptoms in patients with peripheral arterial disease.     

血管内支架置入治疗周围血管疾病的应用研究

目的：探讨血管内支架置入治疗周围血管疾病的应用价值。材料与方法：16例周围血管狭窄或闭塞的患者及2例外伤性周围血管损伤的患者。15例为髂动脉或股动脉动脉硬化所致的血管狭窄或闭塞，1例为左锁骨下动脉开口处动脉硬化所致的血管狭窄，1例为右肱动脉上段外伤性动脉瘤，1例为外伤性右锁骨下动－静脉瘘。16例周围血管狭窄或闭塞的患者，采用经皮穿刺溶栓治疗，球囊导管血管内成形（PTA）及血管内支架置入进行治疗，2例外伤性血管损伤的患者，采用经皮穿刺带膜血管内支架置入进行治疗。结果：18例患者经溶栓治疗，血管内成形（PTA）及血管内支架置入术治疗后，闭塞血管重新开通，损伤血管修复，血液动力学恢复正常。未发生并发症。结论：血管内支架置入治疗周围血管疾病具有较高的临床应用价值。     

Evaluating peripheral arterial occlusive disease.

The clinical history and physical examination remain the most important factors in determining the presence, anatomic location, and physiologic extent of arterial occlusive disease and the need for operation. The physician should refrain from ordering arteriography to confirm the diagnosis of arterial disease unless operation is warranted. If peripheral arterial occlusive disease is diagnosed clinically, its anatomic and physiologic extent can be determined qualitatively and quantitatively by Doppler ultrasonic studies. These studies are also useful in following the natural history of or the influence of therapy on the course of arterial occlusive disease. Ultrasonic studies coupled with careful clinical assessment and with arteriographic evaluation prior to planned operation provide an optimal armamentarium for the diagnosis and management of peripheral arterial occlusive disease.     

Cardiac pumping capability in patients with peripheral vascular disease

INTRODUCTION: Peripheral vascular disease (PVD) is a condition characterized by atherosclerotic occlusive disease of the lower extremities, low functional capacity and low exercise tolerance. Less empirical data are available concerning the cardiovascular response to maximum exercise tests in patients with PVD. The purpose of this study was to examine cardiovascular variables in patients with peripheral vascular disease. METHODS: Fifty patients (67 +/- 9 years) completed an incremental exercise test (2 min stages, 3.2 km h(-1), with increases of 2% every 2 min) to maximum claudication pain. Maximal oxygen consumption (VO2) was assessed on a breath-by-breath basis by online expiratory gas analysis (CardiO2, Medical Graphics Co.). Blood pressure was recorded at peak exercise. Following a 30-min rest period, patients exercised at the highest level attained during the first test and cardiac output (QT) was measured using the exponential non-invasive rebreathing method. Cardiac power output peak (CPOpeak) in Watts (W), was then computed. RESULTS: Mean +/- SD values were; 13.85 +/- 4.14 ml kg min(-1); maximal walk time 357 +/- 227 s; peak mean arterial pressure 127 +/- 15 mmHg; 9.8 +/- 2.39 (l min(-1)); CPO 2.86 +/- 0.87 W. CONCLUSION: Patients with peripheral vascular disease demonstrate attenuated levels of cardiovascular capacity. This group of patients should be given exercise therapy in order to improve cardiovascular status and ambulatory function.     

The latest review of therapeutic angiogenesis using angiogenic growth factors to peripheral arterial diseases

Therapeutic angiogenesis using angiogenic growth factors is expected to be a new treatment of patients with severe ischemic diseases. Indeed, human gene therapy for peripheral arterial disease(PAD) using VEGF gene demonstrated the beneficial effects. In contrast, we have reported the potent angiogenic activity of hepatocyte growth factor (HGF) in animal study and we planned gene therapy for ASO and Buerger disease using HGF gene (TREAT-HGF). In a prospective, open-labeled clinical trial, we investigated the safety and biological efficiency of this gene therapy in patients with peripheral arterial disease(PAD) who had failed conventional therapy.     

Preservation of arm veins for arterial reconstruction.

The results of surgery for lower extremity salvage have improved steadily over the past decade. One of the principles accounting for this advance is the preferential use of autogenous veins for peripheral bypass surgery. Nonautogenous and prosthetic grafts to the infrageniculate (below knee) level have patency rates significantly lower than autogenous bypasses. Currently, the technical limits of bypass surgery often depend upon the availability of adequate venous conduits. The saphenous vein has been the conduit of choice for distal arterial bypasses. However, some patients lack saphenous veins as a result of previous vein harvesting for coronary or other arterial surgery, phlebitis, variations in venous anatomy, previous vein stripping, or other conditions. In these patients, arm veins (cephalic and basilic) have been used successfully for limb salvage. There are several requirements for the successful use of arm veins. These include a detailed knowledge of the anatomy of the cephalic and basilic veins, education of patients and health care professionals, nursing protocols to preserve arm veins, and the training of surgical nurses in the demanding technical maneuvers for arm vein implantation. This paper will address these subjects.     

Therapeutic angiogenesis for ischemic diseases

The clinical consequences of peripheral arterial disease include pain on walking, pain at rest and loss of tissue integrity in the distal ischemic limbs. Although development of beneficial drugs and intervention devices do contribute to the treatment of this disease, critical limb ischemia is estimated to develop in 500 to 1,000 individuals per million per year. As angiogenic growth factors can stimulate the development of collateral arteries, a concept called "therapeutic angiogenesis" is now evaluated in the clinical fields. Recent progress in molecular biology has led to the development of gene therapy as a new strategy to treat a variety of cardiovascular diseases using angiogenic growth factors such as vascular endothelial growth factor (VEGF). Therapeutic angiogenesis using angiogenic growth factors is expected to be a new treatment for patients with severe ischemic heart or peripheral arterial disease.     

Hyperhomocysteinaemia in patients with peripheral arterial occlusive disease.

In the Western world, cardiovascular disease is still the most common cause of death. Over the past decade it has become clear that apart from common risk factors, high concentrations of total homocysteine are relavant to the process of atherosclerosis, especially in the development of premature vascular disease. Hyperhomocysteinaemia (HHC) can be found in 25-32% of the patients with premature peripheral arterial occlusive disease (PAD). Retrospective and prospective studies, evaluating the clinical course of patients with PAD, showed significant associations between high concentrations of total homocysteine and the severity of atherosclerosis and with a more rapid disease progression and mortality rates. HHC can be treated with vitamin B6 and folic acid. Although there may be indications that there is a protective effect of treatment, prospective randomized clinical trials are urgently needed to unravel the role of HHC and its treatment in patients with premature PAD.     

Advances in endovascular treatment of femoropopliteal arterial occlusive disease

Over the past decade, accumulated experience and considerable advances in percutaneous endovascular techniques have enabled their use with increasing frequency for the management of peripheral arterial occlusive disease. However, despite the established role of endoluminal approaches in many other arterial territories, their application for the treatment of femoropopliteal occlusive disease is still debatable due to unique unfavorable anatomical, functional, and flow characteristics of this area. Conventional balloon angioplasty in the femoral and popliteal arteries is frequently associated with suboptimal results and high restenosis rates. To overcome these limitations, emerging approaches have been introduced or are currently under investigation. These include angioplasty modifications, newer concepts in stent design, adjunctive pharmacotherapy, debulking devices, and the application of gamma radiation and freezing in an attempt to reduce intimal hyperplastic response and consequently to expand the application of minimal invasive techniques in the hostile femoropopliteal environment. This review article will present the current status and future trends of endovascular therapy of femoropopliteal artery occlusive disease.     

The femoral artery: source for a worst case scenario? Possible fatal outcome succeeding the new DRG-system?

Stenoses and occlusions of the femoral artery mainly cause claudication. Their course is often silent and patients notice it by chance or in a medical checkup. Mayor amputations are rare in isolated femoral appearance of PAOD (peripheral arterial occlusive disease). Although conservative treatment is very effective in these patients, there are still a lot of operations performed, mainly bypasses, interventional dilatations or stenting. The examples of some typical courses out of more than 64,000 vascular disease patients treated in the Hochrheinklinik during the last 24 years point out a new possibility taking a wrong way in treatment decisions. The structure of the new German DRGs stimulates to carry out interventions and operations as there is a great enhancement in earnings. These may result not only in a rise of costs but in a higher risk for patients, too.     

Color flow Doppler ultrasonography: comparison with peripheral arteriography for the investigation of peripheral vascular disease.

Using arteriography as the gold standard, Color flow Doppler ultrasonography was evaluated with regard to its ability to detect peripheral vascular occlusive disease and hemodynamically significant stenosis in patients having peripheral arteriography. One hundred legs in 51 patients were compared at seven arterial segments for disease. Color flow Doppler ultrasonography correctly detected 84 occluded segments, and demonstrated a sensitivity and specificity for patency vs occlusive disease of 95% and 99%, respectively. One hundred and thirty hemodynamically significant lesions (occlusions plus significant stenosis) were correctly identified with color flow Doppler ultrasonography, with a sensitivity and specificity of 92% and 97%, respectively. Color flow Doppler ultrasonography is a safe, inexpensive, and noninvasive method of accurately documenting significant peripheral arterial disease and offers a new first-line investigation for patients presenting with symptoms of peripheral arterial insufficiency.