Linton patch angioplasty. An adjunct to distal bypass with polytetrafluoroethylene grafts

Aortoenteric Fistula: A Differential Diagnosis of Anemia

Aortoenteric fistulas (AEFs) are a rare and deadly cause of gastrointestinal bleeding that can be easily overlooked, leading to massive bleeding. Secondary AEFs are more common than primary AEFs. An example of a secondary cause of anemia is postoperative hemorrhage due to a surgically placed aortic graft or after endovascular aneurysm repair. This report aims to increase the awareness of AEF as a differential diagnosis when anemia is detected. The clinical report presents a case of anemia in a 79-year-old man due to a secondary AEF, which occurred in a patient who had undergone abdominal aortic aneurysm surgery 10 years before. Surgical repair is considered the gold standard for AEF treatment; however, in this case, the patient was managed with medical therapy and discharged after two months.

A novel method of vein cuff creation for below-knee femoropopliteal bypass with a prosthetic graft

Vein cuff anastomosis is beneficial in cases in which a prosthetic graft is anastomosed to a small and thickened peripheral artery. Various types of vein cuff are currently in use, although their design is insufficient when a size discrepancy exists between the two vessels and the angle of anastomosis requires adjustment. We report a case of a patient who underwent below-knee femoropopliteal bypass using a new design of vein cuff (boat-form vein cuff) that increases the ease of cuff creation and enables surgeons to adjust the anastomotic size and angle.

Comparison of Endovascular Versus Bypass Surgery in Femoropopliteal TASC II D Lesions: A Single-Center Study

BACKGROUND

In patients with severe occlusive disease (Trans-Atlantic Inter-Society Consensus II D [TASC II D]) of the femoropopliteal segment, the advantages of endovascular versus bypass revascularization still remain debated. Most reports available in literature comparing percutaneous transluminal angioplasty (PTA) ± bare metal stent (BMS) versus synthetic bypass analyze patients with heterogeneous anatomical lesions creating possible bias when results of different treatments are matched. In this study, we compared early and midterm outcomes of PTA ± BMS versus heparin-bonded expanded polytetrafluoroethylene graft (Propaten-Gore) + Linton patch in patient affected by symptomatic femoropopliteal TASC II-D lesions.

METHODS

Eighty limbs with symptomatic severe occlusive disease (TASC II D) of the femoropopliteal segment observed from January 2013 to January 2017 were included in this retrospective study. Indication to treatment was severe claudication in 17 limbs (21.2%) and critical limb ischemia (CLI) in 63 (78.8%). 36.2% of limbs presented at least 2 distal patent vessels, and 63.8% had only 1 patent vessel. Of these limbs, 40 were treated by means of PTA ± BMS (group A), and 40 were treated by means of femoropopliteal bypass with Propaten-Gore graft + Linton patch (group B). Patients were followed with a clinical assessment and duplex at 1, 6, and 12 months after procedure and then annually. A closer follow-up was performed in case of any complication. Patency, reintervention rate, and limb salvage were compared in the 2 groups.

RESULTS

The mean length of arterial occlusion was 22.1 cm (range, 8-37) in group A versus 25.2 cm (range, 9-41) in group B, P = ns. A slight difference in mean procedural time was observed (83.5 min of group A versus 114 min of group B, minutes, P = 0.02). Mean follow-up was 26.7 months (range, 3-46). Primary patency at 6, 12, and 24 months of group A versus group B was 76.9% vs. 97.5% (P = 0.007), 65.7% vs. 89.1% (P = 0.05), and 52.6% vs. 78.1% (P = 0.005), respectively. Assisted primary patency was 76.9% vs. 97.5% (P = 0.007), 68.5% vs. 91.8% (P = 0.02), and 57.8% vs. 87.5% (P = 0.001), respectively. Secondary patency was 94.8% vs. 97.5% (P = ns), 85.7% vs. 97.2% (P = ns), 73.6% vs. 93.7% (P = 0.004), respectively. Rate of reintervention at 24 months was 45% in group A vs. 20% in group B (P = 0.03). Limb salvage rate at 24 months was 90% for group A vs. 92.5% for group B (P = ns). Univariate analysis showed CLI and poor runoff to be independent risk factors for significant restenosis/occlusion of target artery and reintervention.

CONCLUSIONS

In patients with severe femoropopliteal occlusive disease (TASC II D), the surgical revascularization by means of Propaten-Gore bypass + Linton patch can be considered safe and effective. Early and midterm results of this approach seem to be superior to PTA ± BMS in terms of restenosis/occlusion and reintervention rates. Larger cohort and longer term results are mandatory to better define this advantage.

Adjuncts to Improve Patency of Infrainguinal Prosthetic Bypass Grafts

The superiority of autologous venous conduit for infrainguinal arterial bypass has been well documented, especially when the bypass extends below the knee or to the tibial arteries. Nevertheless, when adequate autologous vein is not available, prosthetic bypasses (eg, polytetrafluoroethylene [PTFE] or Dacron) are often used in limb-salvage situations. The inferior long-term patency of these infrainguinal prosthetic bypasses has been documented by a number of studies. One such study reported a prospective multicenter randomized trial with only a 12% primary patency for infrapopliteal prosthetic bypasses after 4 years. Another study reported a similar experience with infragenicular bypasses with PTFE for limb salvage even for above-knee (27%, 5 year) and below-knee (25%, 5 year) femoral-popliteal bypasses. The reported PTFE graft patency was consistently inferior to that achieved with autologous vein for limb salvage. Dacron grafts appear to have similar patency rates to PTFE. In an attempt to improve prosthetic graft patency, a number of surgical and medical adjuncts have been developed. In this review, the authors discuss these adjuncts and their impact on infrainguinal prosthetic graft patency.

Long-Term Results of Infrapopliteal Bypass Using Polytetrafluoroethylene and Taylor Vein Patch for Critical Lower Extremity Ischemia

Although distal anastomotic vein patch and cuff techniques have been advocated to improve the patency of lower extremity bypass grafts with polytetrafluoroethylene (PTFE), use of this approach in the infrapopliteal position remains unproven. The purpose of this study is to evaluate the results of infrapopliteal bypass grafting using PTFE and Taylor vein patch for critical lower extremity ischemia. All patients undergoing infrapopliteal bypass grafting with PTFE and Taylor vein patch for ischemic rest pain or tissue loss were identified from the vascular surgery registry. This report describes results for surgical morbidity and mortality, patency, limb salvage, and survival for procedures performed from 1993 through 1998. Forty-two infrapopliteal bypass grafts with PTFE and Taylor vein patch were placed for critical lower extremity ischemia during the 6-year period. Surgical indications were rest pain in 25 (60%) patients and ischemic tissue loss in 17 (40%). Distal arterial anastomosis included 17 (40%) anterior tibial, 10 (24%) peroneal, eight (19%) posterior tibial, and seven (17%) tibioperoneal arteries. Follow-up ranged from 1 to 52 months (mean 17 months). Life-table primary patency, secondary patency, limb salvage, and survival at 3 years were 25%, 31%, 44%, and 66%, respectively. Infrapopliteal bypass with PTFE and Taylor vein patch for critical lower extremity ischemia has poor long-term results that are comparable to those reported for PTFE without Taylor vein patch.

Coronary artery bypass grafting hemodynamics and anastomosis design: a biomedical engineering review

In this paper, coronary arterial bypass grafting hemodynamics and anastomosis designs are reviewed. The paper specifically addresses the biomechanical factors for enhancement of the patency of coronary artery bypass grafts (CABGs). Stenosis of distal anastomosis, caused by thrombosis and intimal hyperplasia (IH), is the major cause of failure of CABGs. Strong correlations have been established between the hemodynamics and vessel wall biomechanical factors and the initiation and development of IH and thrombus formation. Accordingly, several investigations have been conducted and numerous anastomotic geometries and devices have been designed to better regulate the blood flow fields and distribution of hemodynamic parameters and biomechanical factors at the distal anastomosis, in order to enhance the patency of CABGs. Enhancement of longevity and patency rate of CABGs can eliminate the need for re-operation and can significantly lower morbidity, and thereby reduces medical costs for patients suffering from coronary stenosis. This invited review focuses on various endeavors made thus far to design a patency-enhancing optimized anastomotic configuration for the distal junction of CABGs.

Computational estimation of fluid mechanical benefits from a fluid deflector at the distal end of artificial vascular grafts

Intimal hyperplasia at the distal anastomosis is considered to be an important determinant for arterial and arteriovenous graft failure. The connection between unhealthy hemodynamics and intimal hyperplasia motivates the use of computational fluid dynamics modeling to search for improved graft design. However, studies on the fluid mechanical impact on intimal hyperplasia at the suture line intrusion have previously been scanty. In the present work, we focus on intimal hyperplasia at the suture line and illustrate potential benefits from the introduction of a fluid deflector to shield the suture line from unhealthily high wall shear stress.

[Critical ischemia in patients over 80: waiting or evidence-based surgical treatment?]

Critical ischemia is defined by continuous pain, impending sleep, with ankle pressure less than 50mm Hg, and/or first toe pressure less than 30 mm Hg (Dormandy et Rutherford, 2000; Norgren et al., 2007). Treatment of patients aged over 80 requires specific knowledge of arteriopathy at this age and an evaluation of co-morbidity factors (diabetes mellitus, renal failure, ischemic cardiopathy). Assessment should include: the degree of ischemia, the extension of arterial disease, the co-morbidity factors, and the diffusion of the atherosclerotic disease. A transatlantic consensus conference has enabled a classification of arterial lesions determining therapeutic indications. Aorto-iliac lesions may be treated by surgery or angioplasty. Femoro-popliteal or crural lesions may be treated by surgery or angioplasty. Type C or D lesions should be treated by femoro-popliteal or crural bypass. Bypass to the ankle or foot are done on high peripheral resistances. These bypasses require a venous graft. Several authors have shown the utility of short grafts: popliteo-tibial, tibiotibial, tibiopedal artery bypass, tibioplantar artery bypass. In patients over 80, the presence of arteriopathy is an important mortality factor, which is four or five times more important than in the normal population. Twenty-five percent of patients will require amputation.

A reappraisal of saphenous vein grafting

Autologous saphenous vein grafting has been broadly used as a bypass conduit, interposition graft, and patch graft in a variety of operations in cardiac, thoracic, neurovascular, general vascular, vascular access, and urology surgeries, since they are superior to prosthetic veins. Modified saphenous vein grafts (SVG), including spiral and cylindrical grafts, and vein cuffs or patches, are employed in vascular revascularization to satisfy the large size of the receipt vessels or to obtain a better patency. A loop SVG helps flap survival in a muscle flap transfer in plastic and reconstructive surgery. For dialysis or transfusion purposes, a straight or loop arteriovenous fistula created in the forearm or the thigh with an SVG has acceptable patency. The saphenous vein has even been used as a stent cover to minimize the potential complications of standard angioplasty technique. However, the use of saphenous vein grafting is now largely diminished in treating cerebrovascular disorders, superior vena cava syndrome, and visceral revascularization due to the introduction of angioplasty and stenting techniques. The SVG remains the preferable biomaterial in coronary artery bypass, coronary osteoplasty, free flap transfer, and surgical treatment of Peyronie disease. Implications associated with saphenous vein grafting in vascular access surgery for the purpose of dialysis and chemotherapy are considerable. Vascular cuffs and patches have been developed as an important and effective means of enhancing the patency rates of the grafts by linking the synthetic material to the receipt vessel. In addition, saphenous veins can be a cell source for tissue engineering. We review the versatile roles that saphenous vein grafting has played as well as its current status in therapy.

Early Results for Below-Knee Bypasses Using Distaflo

In patients who require lower extremity revascularization, prosthetic graft is a reasonable alternative in the absence of a suitable autologous vein conduit. However, prosthetic bypass grafts have limited patency, especially for infrageniculate reconstruction. Polytetrafluoroethylene grafts were geometrically modified at the distal end to increase their patency. The authors reviewed their experience with the Distaflo graft in patients who required lower extremity below-knee popliteal and tibial bypasses when no suitable autologous vein conduit was available. Chart review was conducted of the 57 patients who underwent 60 lower extremity bypasses over a 3-year period between June 2003 and April 2006. Twenty-four revascularizations were constructed to the tibial outflow sites, whereas the remaining grafts were placed to the below-knee (28) and above-knee (8) popliteal artery, respectively. Study endpoints were primary, assisted primary, secondary patency, and limb salvage at the time of follow-up. Distaflo bypass was performed at the infrageniculate level in 86.7% of cases (28 below-knee popliteal, 24 tibial). Mean follow-up time was 12 months (range, 0.5-37.5 months). At 1 year, primary, assisted primary, and secondary patencies and limb salvage rates for below-knee popliteal bypasses were 83.5%, 89.5%, 94.7%, and 94.4%, respectively. Primary, assisted primary, and secondary patencies and limb salvage rates for tibial bypasses were 44.4%, 44.4%, 63.2%, and 74.9%, respectively. Distaflo precuffed graft is a good alternative conduit for below-knee popliteal and tibial lower extremity reconstructions in the absence of an autologous vein and appears to have promising early patency and limb salvage rates even when used for tibial bypasses.

Modified prosthetic vascular conduits

Atherosclerosis in the form of peripheral arterial disease results in significant morbidity. Surgical treatment options for peripheral arterial disease include angioplasty, endarterectomy, and bypass grafting. For bypass grafting, vein remains the conduit of choice; however, poor quality and limited availability have led to the use of prosthetic materials. Unfortunately, because of a lack of endothelium and compliance mismatch, neointimal hyperplasia develops aggressively, resulting in high failure rates. To improve graft patency, investigators have developed surgical, chemical, and biological graft modifications. This review describes common prosthetic materials, as well as approaches currently in use and under investigation to modify and improve prosthetic conduits for bypass grafting in an effort to improve graft patency rates.

Comparison of Carbon-impregnated and Standard ePTFE Prostheses in Extra-anatomical Anterior Tibial Artery Bypass: A Prospective Randomized Multicenter Study

OBJECTIVES

The aim of this study was to find out whether carbon impregnated ePTFE vascular grafts have better long-term patency or limb salvage rates than Standard ePTFE vascular grafts in crural revascularization in patients with chronic critical ischemia.

DESIGN

Prospective randomized multicenter trial. Study endpoints were 36 months follow-up, major amputation or death.

MATERIALS

We used 6mm carbon ePTFE (Carboflo) and 6mm standard ePTFE vascular grafts (both C.R. BARD Inc./IMPRA).

METHODS

From June 1995 to November 1998, 283 patients were randomly assigned either to carbon (C) (n=140) or to standard (St) ePTFE (n=143) vascular grafts at 19 centres. A standard protocol was used with lateral extra-anatomic course of the graft to the anterior tibial artery and of a distal vein patch or cuff. More than 90% of the patients had rest pain or gangrene.

RESULTS

Two hundred and sixty-five (C=130; St=135) patients could be analysed in the intention-to-treat (ITT) group. Primary patency, secondary patency and limb salvage rates after 36 months were 33, 43 and 67% in the carbon- and 30, 38 and 58% in the standard PTFE group, respectively, (log-rank test: p=0.20, 0.12 and 0.16). Additional analyses were made per protocol (PP) and as-treated (AT). The retrospective power of the study was calculated as 79 and 83%.

CONCLUSION

The ITT, PP and AT analysis, showed no statistically significant advantage of the carbon ePTFE vascular graft in terms of patency or limb salvage over the standard ePTFE vascular graft at 36 months.

Lipoplex gene transfer of inducible nitric oxide synthase inhibits the reactive intimal hyperplasia after expanded polytetrafluoroethylene bypass grafting

OBJECTIVE

Intimal hyperplasia (IH) is most commonly the cause of graft occlusion in infrainguinal bypass grafting for arterial occlusive disease. We investigated the influence of nitric oxide on the IH of the arterial vessel wall at the region of prosthetic bypass anastomoses.

METHODS

Experiments were performed in 10 Foxhound dogs. We used a technique of inducible nitric oxide synthase (iNOS) overexpression by a non-virus-mediated, liposome-based iNOS gene transfer. The plasmid pSCMV-iNOS, which drives the expression of iNOS under control of the cytomegalovirus promoter, was complexed with cationic liposomes (lipoplexes). Segments of both carotid arteries were pretreated by intramural injection of a lipoplex solution by using an infiltrator balloon catheter (Infiltrator Drug Delivery Balloon System). In each dog, iNOS was administered at one side, and a control vector (pSCMV2) was administered at the contralateral side. Carotid arteries were ligated, and bypass grafts (expanded polytetrafluoroethylene, 6-mm, ring enforced) were implanted on both sides. The proximal and distal anastomoses (end-to-side fashion; running nonabsorbable sutures) were placed in the pretreated regions. After 6 months, the prostheses were excised, and the intimal thicknesses of 50 cross sections (orcein staining) of each anastomosis were measured planimetrically.

RESULTS

The average reduction of the neointima thickness of the iNOS side in proximal anastomoses at the prosthetic wall, suture region, and arterial wall was 43%, 52%, and 81%, respectively. In distal anastomoses, the average reduction was 40%, 47%, and 52%, respectively. All differences of neointima thickness between the iNOS and control sides were statistically significant (Wilcoxon test; P < or = .05).

CONCLUSIONS

Inducible NOS expression is an efficient approach for inhibition of IH. In contrast to earlier studies, which investigated the efficacy of gene therapeutic NOS expression at 3 to 4 weeks after intervention, the novelty of our findings is that a single local lipoplex-mediated transfection of the vascular wall with iNOS-expressing plasmids leads to a reduction of IH in a prosthetic in vivo model even after 6 months. Because all components can be manufactured under Good Manufacturing Practice conditions (the quality-management system of the European pharmaceutical industry based on ISO 9000), this approach is also amenable to human therapy.

Comparison of Precuffed and Vein-Cuffed Expanded Polytetrafluoroethylene Grafts for Infragenicular Arterial Reconstructions: A Case-Matched Study

Distal vein cuff interposition is often added to prosthetic infragenicular arterial reconstruction in an attempt to improve hemodynamics and patency rates. The purpose of this study was to compare the outcome of a precuffed expanded polytetrafluroethylene (ePTFE) graft with a vein-cuffed ePTFE graft for infragenicular bypass. We reviewed the clinical outcome of 77 patients with critical limb ischemia without available autologous vein conduits who underwent arterial reconstruction of 80 limbs to below-knee popliteal or tibioperoneal vessels using either ePTFE precuffed graft (precuffed group, 38 patients 40 limbs) or ePTFE vein-cuffed graft (vein-cuffed group, 39 patient, 40 limbs). Precuffed group patients were enrolled in a prospective cohort study. Vein-cuffed group patients consisted of consecutive case-matched patients operated on during the same study period. End points were primary graft patency and limb salvage rates. There were 42 males and 35 females with a mean age of 73.4 years (range, 44-92 years). Both groups were matched to demographics, risk factors for atherosclerosis, previous ipsilateral reconstruction, and location of the distal anastomosis. Proximal anastomosis was to the common (n = 68) or superficial (n = 12) femoral arteries. Distal anastomosis was to the below-knee popliteal (n = 28), anterior tibial (n = 12), posterior tibial (n = 15) and peroneal (n = 25) arteries. Operative mortality was 1.3%. Graft patency at dismissal was 90% and 95% in the precuffed and vein-cuffed groups, respectively. The mean follow-up was 25.7 months (range, 2.4-61 months). Primary patency rates at 1 and 3 years were 70% and 57% in the precuffed group, and 78% and 54% in the vein-cuffed group (p = 0.32). Limb salvage rates at 1 and 3 years were 97% and 70% in the precuffed group, and 95% and 81% in the vein-cuffed group (p = 0.49). Overall patient survival at 1 and 3 years was 81 % and 57%, respectively. In this case-control study, results of precuffed ePTFE graft were similar to those obtained with vein-cuffed ePTFE grafts. The precuffed ePTFE graft is an adequate alternative conduit for infragenicular arterial reconstruction in patients with critical limb ischemia and no available autologous veins.

Popliteal-to-Distal Bypass for Limb Salvage

A retrospective study was carried out to examine the patency and limb salvage rates of popliteal-to-distal bypass and compare the results of diabetic to those of nondiabetic patients and elective versus emergency procedures. From January 1990 to December 2001, 71 popliteal-to-distal bypasses were performed. Indications for surgery were rest pain, tissue loss, and acute ischemia, including extensive post-traumatic tibial lesions. Survival, graft patency, and limb salvage rates were determined according to the life-table method. The log-rank test was used to compare diabetic versus nondiabetic patients, elective versus emergency procedures, and saphenous vein bypass versus PTFE bypass. Postoperative primary patency, secondary patency, and limb salvage rates at 30 days were 88.7%, 91.4%, and 87%, respectively. Postoperative mortality was 2.8%, with one case of acute myocardial ischemia and one multiorgan failure. Life-table analysis showed primary and secondary patency rates of 57% and 61%, respectively, a limb salvage rate of 64%, and survival of 77% at 5 years Log-rank testing showed no statistical difference between diabetic and nondiabetic patients, whereas a statistical difference was observed in elective versus emergency procedures (p < 0.005) and great saphenous vein versus PTFE graf (p < 0.05). These results show that popliteal-to-distal bypass is a safe and effective procedure with good long-term patency and limb salvage rates in selected cases.

Experimental comparison of four methods of end-to-side anastomosis with expanded polytetrafluoroethylene

Background

Four established techniques of distal end-to-side anastomosis (direct anastomosis, Linton patch, Taylor patch and Miller cuff) were compared to investigate the local distribution of anastomotic intimal hyperplasia. The study aimed to elucidate whether mechanical factors or flow alterations are mainly responsible for the improved patency rates reported for vein cuff interposition techniques in infrainguinal arterial reconstructions using prosthetic graft material.

Methods

Thirty-two expanded polytetrafluoroethylene (ePTFE) femoropopliteal bypass grafts were implanted in 16 sheep using the four anastomotic techniques. After 6 months the grafts were explanted and examined histologically. The local distribution of intimal hyperplasia was determined, particularly for areas of material transition and of high and low shear stress.

Results

The mean amount and distribution of intimal hyperplasia were similar for all anastomotic types. Intimal hyperplasia was greatest along all transitions between ePTFE and venous patches, and between ePTFE and recipient artery. It was lower along the transitions between venous patches and artery, and was lowest at the host artery floor.

Conclusion

Vein interposition did not reduce anastomotic intimal hyperplasia and did not change the distribution patterns of hyperplasia, which were influenced mainly by mechanical factors. The effect of vein interposition is to move areas of maximum intimal hyperplasia away from the small recipient artery up to the more capacious graft-patch anastomosis.

Improving the patency of vascular bypass grafts: the role of suture materials and surgical techniques on reducing anastomotic compliance mismatch

BACKGROUND

compliance mismatch is an important factor in the development of myointimal hyperplasia in both coronary and vascular anastomoses. This mismatch may be reduced by the use of newer suture materials and techniques. This review discusses the current techniques and materials used to date in generating anastomoses in both coronary and vascular applications and to correlate these with the degree of inherent compliance achieved.

METHODS

PubMed, ISIS, CAS and PAS database searches were performed. Other articles were cross-referenced.

RESULTS AND CONCLUSION

continuous suture is still the most used technique in both cardiac and vascular surgery for the generation of anastomoses due to the reduced time and improved haemostasis. However, continuous suture results in a greater compliance mismatch than the interrupted technique. Vein cuffs and patches improve compliance and transmission of pulsatile blood flow and offer improvement of graft patency. Alternative to sutures are biological glue, clips and laser generated solders all of which have shown promising results, but further work is required before they become applicable for routine use.

Numerical study of hemodynamics and wall mechanics in distal end-to-side anastomoses of bypass grafts

The development and progress of distal anastomotic intimal hyperplasia seems to be promoted by altered flow conditions and intramural stress distributions at the region of the artery-graft junction of vascular bypass configurations. From clinical observations, it is known that intimal hyperplasia preferentially occurs at outflow anastomoses of prosthetic bypass grafts. In order to gain a deeper insight into post-operative disease processes, and subsequently, to contribute to the development of improved vascular reconstructions with respect to long term patency rates, detailed studies are required. In context with in vivo experiments, this study was designed to analyze the flow dynamics and wall mechanics in anatomically correct bypass configurations related to two different surgical techniques and resulting geometries (conventional geometry and Miller-cuff). The influence of geometric conditions and of different compliance of synthetic graft, the host artery and the interposed venous cuff on the hemodynamic behavior and on the wall stresses are investigated. The flow studies apply the time-dependent, three-dimensional Navier-Stokes equations describing the motion of an incompressible Newtonian fluid. The vessel walls are described by a geometrically non-linear shell structure. In an iterative coupling procedure, the two problems are solved by means of the finite element method. The numerical results demonstrate non-physiological flow patterns in the anastomotic region. Strongly skewed axial velocity profiles and high secondary velocities occur downstream the artery-graft junction. On the artery floor opposite the junction, flow separation and zones of recirculation are found. The wall mechanical studies show that increased compliance mismatch leads to increased intramural stresses, and thus, may have a proliferative influence on suture line hyperplasia, as it is observed in the in vivo study.

Tibial bypass using complex autologous conduit: patency and limb salvage

Over an 8-year period, we performed 93 lower extremity bypasses using complex autologous conduits, which included (1) contralateral greater saphenous vein (GSV), (2) composite GSV, (3) superficial femoral vein, (4) lesser saphenous vein, (5) cephalic or basilic veins, and (6) composite-sequential (PTFE and vein) grafts. These grafts represented 16% of all infrainguinal bypasses during this period, and all grafts were performed to treat limb-threatening ischemia. Survival, patency, and limb salvage were examined by the life-table method. Primary graft patency was 46 and 38% at 3 and 5 years. Assisted-primary patency was 62 and 59%, and secondary graft patency rates were 68 and 64% at 3 and 5 years. Twenty-nine bypasses (31%) required revision to restore or maintain patency. The 3-year limb salvage rate was significantly better when revision was performed for graft stenosis than for graft thrombosis (90% vs. 46%, p < 0.05). Overall limb salvage rate was 73% at 5 years. The mortality rate was 5.4% and the 5-year survival was 51%. Complex autologous tibial bypasses provided acceptable long-term limb salvage in patients with severe ischemia and inadequate ipsilateral GSV. The increased operating time and complexity required did not produce prohibitive operative risks. Postoperative graft surveillance in these complex vein bypasses allowed revision in many cases before graft occlusion occurred and significantly improved long-term limb salvage.

The bridge graft: a new concept for infrapopliteal surgery

BACKGROUND

The long-term results of ePTFE grafts are particularly poor in crural reconstructions. We report on a novel surgical technique, whereby both run-off and anastomotic mismatches are concomitantly addressed.

PATIENTS AND METHODS

Short segments of vein grafts (5-15 cm in length) were used to bridge two crural artery segments. Subsequently, a femoro-distal ePTFE graft was anastomosed to the bridge graft. Venous valves were made incompetent to allow bi-directional flow. In a retrospective series of 45 patients with crural bridge grafts, 12 patients were in stage III and 33 in stage IV. In 18 patients the reconstruction was the first procedure and in the remaining 28 patients it was the first or second re-operation.

RESULTS

The primary patency rate at 1, 2, 3 and 4 years was 53, 44, 35 and 26% respectively. The secondary patency rate was 67, 53, 49 and 39% respectively. The corresponding limb salvage rate was 70, 61, 56 and 45%. In a small subgroup of patients, in which the crural bridge was the first reconstructive procedure, the primary patency was 76 at 1 year and 64 at 4 years.

CONCLUSION

convincing long-term crural bridge grafts should be considered in those patients who have more than one crural or pedal artery available for grafting and an insufficient length of saphenous vein.

Effects of a venous cuff at the venous anastomosis of polytetrafluoroethylene grafts for hemodialysis vascular access

INTRODUCTION AND METHODS

The most frequent complication of polytetrafluoroethylene (PTFE) arteriovenous grafts for hemodialysis is thrombotic occlusion due to stenosis caused by intimal hyperplasia. This complication is also known for peripheral bypass grafts. Because the use of a venous cuff at the distal anastomosis improves the patency of peripheral bypass grafts, we considered that it might also improve the patency of PTFE arteriovenous grafts. Therefore, a randomized multicenter trial was carried out to study the effect of a venous cuff at the venous anastomosis of PTFE arteriovenous grafts on the development of stenoses and the patency rates.

RESULTS

Of the 120 included patients, 59 were randomized for a venous cuff. The incidence of thrombotic occlusion was lower in the cuff group (0.68 per patient-year) than in the no-cuff group (0. 88 per patient-year; P =.0007). However, the primary and secondary patency rates were comparable. The cuff group tended to have fewer stenoses at the venous and arterial anastomoses when examined with duplex scan. Graft failure was higher in patients with an initial anastomosing vein diameter smaller than 4 mm (7 of 18 [39%]) than in those with a vein diameter of 4 mm or larger (16 of 88 [18%]; P =. 052). Local edema, skin atrophy, and obesity yielded a higher risk on graft failure (23% vs 11%).

CONCLUSION

A venous cuff at the venous anastomosis of PTFE arteriovenous grafts for hemodialysis reduced the incidence of thrombotic occlusions; stenosis at the venous anastomosis was reduced. However, this did not result in a better patency rate. Therefore, the venous cuff should not be used routinely. Initial vein diameter and local problems (edema, obesity, or skin atrophy) appear to be the most important risk factors for graft failure.

The effect of a venous anastomosis Tyrell vein collar on the primary patency of arteriovenous grafts in patients undergoing hemodialysis

PURPOSE

Vein collars and patches are used at the distal anastomoses of infrainguinal prosthetic grafts to improve graft patency. We initiated a randomized, prospective study to determine whether a Tyrell vein collar at the venous anastomosis of forearm loop arteriovenous grafts (AVGs) would improve patency.

METHODS

Patients who required new forearm AVGs were randomized to (1) a standard end-to-side graft-vein anastomosis (control group) or (2) a Tyrell vein collar between the graft and the vein (study group). End points were (1) graft thrombosis, (2) graft removal and ligation, or (3) inadequate graft function. Randomization of 75 subjects was planned. The study was terminated early for ethical reasons.

RESULTS

Seventeen patients (eight men, nine women) with a mean age of 52.8 years (range, 31-79 years) had 17 grafts placed (control group, n = 10; study group, n = 7). Comorbidities were not different between the groups (P>.05). Six (86%) of seven study grafts failed by 9 months (mean, 4.6 months). Four (66%) failed study grafts had venous outflow tract stenosis from intimal hyperplasia. This was confirmed at surgery in three and by angiography in one. The 9-month primary patency was 80% for the control group versus 17% for the study group (P =.015). Smaller outflow vein diameter in the study group (P =. 048) did not account for this inferior graft patency.

CONCLUSION

A Tyrell vein collar at the venous anastomosis of a forearm AVG resulted in premature graft failure. The use of a Tyrell vein collar may accelerate venous anastomosis intimal hyperplasia.

Vein interposition cuffs decrease the intimal hyperplastic response of polytetrafluoroethylene bypass grafts

PURPOSE

The modification of the distal anastomosis of polytetrafluoroethylene (PTFE) bypass grafts with vein interposition cuffs (VCs) has been reported to increase graft patency. However, the mechanisms that are responsible for this improved patency are unclear. Because intimal hyperplasia (IH) is a primary cause of prosthetic graft failure, we hypothesized that VCs affect the distal anastomosis by decreasing the IH response of the outflow artery.

METHODS

Twenty-three female domestic Yorkshire pigs (mean weight, 35 kg) underwent 42 femoral PTFE bypass grafting procedures. The PTFE bypass grafts were separated into the following three groups according to distal anastomotic configuration: end-to-side anastomoses (ES), VCs, and cuffs constructed with PTFE (PCs). Four femoral arteries from two pigs served as healthy controls. At sacrifice, the grafts were perfusion fixed, and the distal anastomoses harvested at 1 and 4 weeks. The specimens were hemisected and serially sectioned to identify the heel, toe, and mid-anastomotic regions. The sections were cut into 5-microm segments and analyzed for intima and media thickness and area, intima/media area ratio, and the distribution of IH in the vein cuff. The roles of transforming growth factor-beta1 and platelet-derived growth factor-BB in IH development were assessed with immunohistochemistry.

RESULTS

IH development was significantly lower at all areas of the anastomosis, with VCs compared with ES and PCs at 4 weeks (P </=.001). IH decreased in VCs from 1 to 4 weeks in all areas of the anastomosis (P </=.001). PCs showed pronounced IH at the mid-anastomosis as compared with VCs and ES (P </=.001). IH was most pronounced at the toe with ES and PCs (P </=.001). Qualitatively, VCs altered the site of IH development, sparing the recipient artery with preferential thickening of the vein cuff and formation of a pseudointima at the vein-PTFE interface. Immunohistochemistry results showed positive staining for transforming growth factor-beta1, platelet-derived growth factor-BB, and smooth muscle alpha-actin in the hyperplastic intima.

CONCLUSION

PTFE bypass grafts with VCs had less IH develop than did grafts with ES and PC anastomoses. IH regression in VCs at 4 weeks suggests compensatory vessel wall remodeling mediated by the presence of the VC. Furthermore, VCs caused a redistribution of hyperplasia to the vein-PTFE interface, delaying IH-induced outflow obstruction in the recipient artery. The marked increase in IH with PCs, despite a similar geometric configuration to VCs, suggests that the biologic properties of autogenous tissue dissipate IH development. Similarly, the flow patterns in PCs and VCs should be identical, which suggests a less important role of hemodynamic forces in VC-mediated protection.

Is a Vein Patch Worthwhile for Femoropopliteal Bypass With ePTFE Grafts?

One of the factors contributing to late graft occlusion after peripheral arterial bypass with prosthetic grafts is anastomotic intimal hyperplasia. The purpose of this study was to evaluate, experimentally and clinically, the effect of placing a vein patch over the site of distal anastomosis of a ePTFE graft in peripheral arterial bypass (DAPP). After heparinization, the infrarenal abdominal aorta in 14 beagle dogs was resected, and an ePTFE graft was interposed between the resected ends. The dogs were divided into a control group without DAPP and a DAPP group. These animals were killed 3 months after surgery. A total of 89 femoropopliteal bypasses using ePTFE grafts, 71 patients were divided into two groups for analysis; namely, a direct suture group without DAPP being the DS group (n = 62 limbs) and a DAPP group with DAPP (n = 27 limbs). The mean follow-up period was 1010 days in the DS group and 302 days in the DAPP group. All the grafts were patent in both groups of dogs. The thrombus adhering to the entire intraluminal surface of the graft defined as the mean thrombus-covering ratio, in the DAPP group was significantly less than that in the control group, although there were no significant differences in the length of proximal or distal intimal ingrowth into the ePTFE grafts between the two groups. The maximal intimal thickness did not differ significantly between the control group and the DAPP group, at 541 +/- 349 µm and 353 +/- 76 µm, respectively. The 1- and 3-year cumulative patency rates of femoropopliteal bypasses were 86% and 71%, respectively, in the DS group, whereas they were both 91% in the DAPP group. Although the numbers of subjects in this study was too limited for a final evaluation, the trend was unmistakable. The findings of this study indicate that DAPP may improve the cumulative patency of femoropopliteal bypasses with ePTFE grafts.http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p193.html</hea

Comparison of Reversed, Nonreversed Translocated, and In Situ Vein Grafts in Arterial Revascularization: Techniques, Cumulative Patency, Versatility, and Durability

http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p197.html</hea

Blood flow in distal end-to-side anastomoses with PTFE and a venous patch: results of an in vitro flow visualisation study

OBJECTIVES

non-physiological flow behaviour plays a significant role in the development of distal anastomotic intimal hyperplasia. To investigate flow patterns in four anastomotic types of femoral end-to-side distal bypass graft anastomoses, a flow visualisation study was performed.

METHODS

transparent 1:1 casted replicas of distal vascular graft anastomoses created by conventional technique, Miller-cuff, Taylor- and Linton-patch were fabricated. A pulsatile mock circulation with a high-speed video system was constructed. Flow pattern was determined at mean Reynolds numbers 100-500. Migrations of the stagnation points on the bottom of the anastomoses at mean Reynolds numbers 100, 230, and 350 were measured.

RESULTS

a vortex forms during early systole and increases to maximum systole in all anastomoses. During the diastolic phase the vortex moves in the Miller-cuff distally to the toe of the anastomosis and remains standing, while in the other anastomotic types the vortex moves proximally to the heal of the junction and breaks down. The shift of the stagnation point in the Miller-cuff was considerably smaller than in the other anastomoses.

CONCLUSION

conventional, Linton and Taylor anastomoses show similar flow patterns. The Miller-cuff with its wider cavity shows lower shift of the bottom stagnation point, but a persistent washout of the anastomotic cavity, which may contribute to its reported good clinical performance.

Patency and limb salvage for polytetrafluoroethylene bypasses with vein interposition cuffs

Polytetrafluoroethelene (PTFE) is often utilized in patients with limb-threatening ischemia requiring infrainguinal revascularization in the absence of autologous saphenous vein. To increase long-term patency of PTFE grafts, vein interposition cuffs have been recommended as adjunctive procedures. The purpose of this study was to assess the efficacy of vein interposition cuffs on the long-term patency and limb salvage of patients requiring prosthetic bypass grafts for limb-threatening ischemia. Prosthetic bypass grafts with vein interposition cuffs (PTFE/VC) were performed on 56 limbs in 55 patients (32 men, 23 women; mean age of 67 years) from October 1993 to January 1998. Grafts were prospectively evaluated every 3 months for the first 12 months and biannually thereafter with duplex ultrasonography. PTFE/VC and PTFE bypasses at the popliteal level appear to have comparable patencies. However, PTFE/VC appear to offer an improved patency and limb salvage for infrapopliteal bypasses in patients with critical limb ischemia. When infrapopliteal revascularization is required in the absence of autologous saphenous vein, we recommend the use of PTFE with vein interposition cuffs.

Polytetrafluoroethylene femorodistal grafts: can the use of a vein collar offer patients a reasonable chance of success?

The growing number of patients with critical ischemia who lack a suitable autogenous vein for grafting pose a particular problem for the vascular team. In such patients the use of a polytetrafluoroethylene graft with a distal anastomotic vein cuff or patch has been advocated as an alternative to primary amputation. The use of such adjunctive techniques is reviewed through a 3-year retrospective study of 50 patients under the care of one surgeon. Data analyzed include patient demographics, risk factors, and presenting symptoms. All patients were included in a Duplex graft surveillance program. The cumulative patency rates at 1 and 2 years were 56% and 55%, respectively, with limb salvage rates of 85% and 80%. The data support a reconstructive approach to maintain the quality of the patient's life.

Prospective randomized study of carbon-impregnated polytetrafluoroethylene grafts for below-knee popliteal and distal bypass: results at 2 years. The Association Universitaire de Recherche en Chirurgie

The purpose of this prospective randomized multicenter study is to compare patency for a new carbon-impregnated polytetrafluoroethylene (PTFE) graft and standard PTFE grafts. One hundred and sixty patients presenting severe chronic ischemia of the lower extremity were recruited at 17 centers of the French Association Universitaire de Recherche en Chirurgie. Eighty-one carbon-impregnated graft and 79 standard grafts were implanted. The procedure consisted of below-knee femoropopliteal bypass in 83 cases and femorodistal bypass in 77 cases. The minimum duration of the follow-up period was 2 years. Twenty-four patients died during the study. The actuarial primary patency rate, actuarial secondary patency rate, and limb salvage rate were 45%, 53%, and 57% respectively in the carbon-impregnated PTFE group and 35%, 36%, and 47% respectively in the standard PTFE group. The carbon-impregnated graft appeared to achieve better patency than the standard graft but the difference was not statistically significant. Since there was no difference up to 12 months, the study will be continued to determine if further follow-up confirms these findings. In this study we also assessed factors contributing to patency of below-knee prosthetic bypass grafts. Only two factors had a significant influence on patency, i.e., ankle/arm pressure difference greater than 0.25 as opposed to ankle/arm pressure difference less than 0.25 (p < 0.01) and below-knee femoropopliteal bypass as opposed to femorodistal bypass (p < 0.001).

Operative adjuncts for distal revascularization

The performance of distal arterial bypass procedures in poor outflow situations may require adjunctive techniques to maximize short- and long-term patency. The rationale and technique for the most commonly used modifications are presented along with the indications for use.

Infrapopliteal polytetrafluoroethylene and composite bypass: factors influencing patency

Between January 1, 1979, and December 31, 1988, 149 infrapopliteal polytetrafluoroethylene (PTFE) bypasses were performed in 145 patients with chronic, critical, limb-threatening ischemia. These operations represented 27.9% of 534 infrapopliteal bypasses performed during the same period. There were 92 males and 53 females. Mean age was 71.8 +/- 12.3 years. Signs and symptoms of critical ischemia were gangrene, ulceration, and isolated rest pain in 101 (69%), 23 (15.3%), and 25 (16.7%) cases, respectively. A composite (PTFE-saphenous vein) graft was used in 53 (35%) cases. In 96 prosthetic bypasses the distal anastomosis was performed using vein patch angioplasty in 65 (44%) cases and directly in 31 (21%). The in-hospital mortality rate was 3.3%. Patency, limb salvage, and patient survival rates were plotted according to the actuarial method and the curves obtained were compared using the log-rank test. Actuarial survival rates were 68% +/- 5% and 57% +/- 7% at 3 and 5 years, respectively. Primary patency and lower limb salvage rates were 41% +/- 5% and 68% +/- 6% at 3 years and 35% +/- 9% and 65% +/- 10% at 5 years, respectively. There was no statistically significant difference noted in primary patency rates at 3 years according to the type of bypass (composite or all-prosthetic: 36% vs. 44%), the type of distal anastomosis (direct or vein patch angioplasty: 43% vs. 45%), the site of distal anastomosis (upper or lower half of the leg: 38% vs. 46%), lateral or medial placement of the bypass (39% vs. 43%), or according to whether or not it was a repeat operation (40% vs. 44%). In conclusion, patency rates using infrapopliteal PTFE bypasses are low. Certain technical approaches, although they do not seem to improve patency, definitely increase the feasibility of bypass and in our opinion decrease the risk of early failure in unfavorable anatomic settings. The limb salvage rates following infrapopliteal PTFE and composite bypass are encouraging and justify the use of routine distal revascularization, even in the absence of autogenous vein graft.

Aorto-femoral bypass with polytetrafluoroethylene prostheses: preliminary results in 363 cases

From October 1977 to October 1982, 363 unilateral aorto-femoral bypasses using polytetrafluoroethylene (PTFE) prostheses were performed for predominantly unilateral aorto-iliac disease. The distal anastomosis was extended into the deep femoral artery in 57% of the patients. The postoperative mortality was 0.5%. The actuarial patency rate after 6 years was 87% in patients with claudication and 77% in those with critical ischemia. No false aneurysm developed. Thrombosis of the prosthesis was due to progression of distal disease, intimal hyperplasia and postural extrinsic compression. The latter seems to be characteristic of PTFE prostheses and can be treated by thrombectomy. In 21 cases a cross-over femoro-femoral bypass was done during the follow-up period because of contralateral progression of disease.

Should polytetrafluoroethylene grafts be used in preference to saphenous vein for femoropopliteal arterial bypass?

Some surgeons have advocated using polytetrafluoroethylene (PTFE) as the graft material of choice for femoropopliteal arterial bypass so that the saphenous vein could be preserved for future cardiovascular surgery. We have examined our results to see if this approach could be justified in our patient population. PTFE was used for 101 femoropopliteal reconstructions in 96 patients (56 male and 40 female). Thirty-eight (40%) complained of debilitating claudication and 58 (60%) had limb-threatening ischaemia. There were 83 primary PTFE femoropopliteal reconstructions and 18 repetitive procedures after failure of an earlier ipsilateral bypass. Twenty-nine of the 101 PTFE grafts were anastomosed distally to the popliteal artery above knee and the remaining 72 below knee. At 5 years, the cumulative patency for all grafts was only 11%. The 4 year cumulative patency was better for claudicants (40%) than for those with threatened limb loss (11%) but two of the 38 claudicants required amputation when their grafts failed. Patency rates were not significantly affected by the site of the distal anastomosis or by a previous failed ipsilateral femoropopliteal bypass. Worthwhile limb salvage was achieved only by frequent re-operation. Our results with PTFE are not good enough to use it in preference to an adequate saphenous vein for femoropopliteal bypass.

Nonreversed and in situ vein grafts. Clinical and experimental observations

The in situ saphenous vein (ISSV) graft has shown promise in distal bypass. Although improved patency has been attributed to preservation of vasa vasorum, there is no direct evidence to support this hypothesis. Femorodistal bypass was done in 33 patients using ISSV grafts (21) or nonreversed saphenous vein (NRSV) grafts (12) during an 18-month period. The NRSV were completely removed from the vein bed but were otherwise prepared in an identical fashion to the ISSV. Immediate complications including incomplete valvulotomy (one), intimal laceration (one), persistent AV communication (two), and extrinsic graft compression (one) were identified and corrected. Two grafts of 2.5 mm diameter occluded acutely. There were no deaths. Of 30 patients discharged with a patent graft, there was one late occlusion (ISSV) at 10 months. No difference in patency between ISSV and NRSV grafts was noted during follow-up extending to 24 months. Overall limb salvage was 94%. In a canine model, 60 vein segments were interposed in the carotid artery using in situ, reversed, and nonreversed techniques. Ultrastructural studies 1, 2, 3, and 6 months after implantation reveal no differences in in situ and nonreversed grafts. New vasa vasorum were identified in NRSV within 1 month. Both ISSV and NRSV grafts demonstrate excellent patency and maintenance of smooth muscle cell architecture. Factors including reduced size disparity at the proximal and distal anastomoses, physiologic distension under arterial pressure, careful handling, and meticulous technique appear to be more important than the theoretic advantages of preserving vasa vasorum.