Serial noninvasive studies do not herald postoperative failure of femoropopliteal or femorotibial bypass grafts.

We performed a 5-year retrospective case-control study of 232 patients undergoing femoropopliteal (n = 188) or femorotibial (n = 44) bypass to determine if serial noninvasive studies herald postoperative graft failure. We correlated serial ankle/arm pressure indices (API) with graft patency. An interval drop in API of greater than or equal to 0.20 was considered hemodynamically significant, but interventional therapy was carried out only for clinically symptomatic graft failure and an API less than 0.20 above the preoperative value. The cumulative 5-year limb salvage rate was 82% and the patient survival was 63%. A significant drop in API did not correlate with cumulative 5-year graft patency. The 5-year cumulative primary graft patency rates were 60% and 62% in patients with stable and interval drops in API, respectively (Z = 0.15, p = N.S.) These results suggest that a significant drop in postoperative API does not predict patients with impending femoropopliteal or femorotibial graft failure. We believe that routine noninvasive surveillance and prophylactic intervention on detected asymptomatic lesions in leg bypass grafts may not be justified.     

Factors contributing to success and failure of femorotibial bypass grafts

Femorodistal bypass grafting is an important technique in the armamentarium of vascular surgeons, and it has been found that the cost of such procedures justifies their performance in patients who have sustained critical ischemia. Graft material remains the most important factor in causation of graft failure, with all prosthetics having disadvantages when compared to the saphenous vein. In attempts to use biological materials, both bovine heterografts and human umbilical vein grafts have been seen to form aneurysms and undergo thrombosis. Meanwhile, many variations on the theme of prosthetic grafts have been tried and found wanting when used as bypasses from the femoral artery to the distal circulation. Among configurations tried have been polytetrafluoroethylene with and without external support; Dacron^® in woven and knitted format, with or without internal and external velour; and combinations of these. As patency rates of these reconstructions have proven inferior to others using the saphenous vein, attempts have been made to extend the use of autogenous biologic material. Such attempts have included cephalic vein bypass grafts, short vein bypass grafts originating distal to the femoral artery, deep veins used as grafts, and the in situ bypass. Lately, it has been recognized that the in situ bypass, when compared to concurrent controls, shows no significant advantage to the popliteal level but is the technique of choice when distal anastomoses are at or distal to the midcalf. Compositesequential bypasses represent another technique developed to utilize the autogenous vein as a distal segment. While this has increased the rate of patency of distal bypass grafting, other aids to patency such as use of anticoagulants, antiplatelet agents, and adjunctive arteriovenous fistula have not. Dynamics of the coagulation system show an intrinsic change in patient status toward coagulation in the postoperative period, and although this factor is of some significance in causing early graft thrombosis, technical defects do not seem to play an important part. This review details some of these important causes of graft failure and places them in proper perspective.

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Resumen La derivación (bypass) por injerto femorodistal representa una técnica importante dentro del armamentario de los cirujanos vasculares; se ha demostrado que el costo del procedimiento justifica su realización en pacientes con isquemia crítica sostenida. El material del injerto sigue siendo el factor más importante como causa de falla de la operación, y se reconoce la desventaja de los injertos protésicos frente al injerto de vena safena. Tratando de ampliar la utilizacíon de materiales biológicos, se han empleado heteroinjertos de vena umbilical bovina y también de vena umbilical humana con el hallazgo de la formación de aneurismas y del desarrollo de trombosis. Entre tanto, se han ensayado numerosas variantes de injertos protésicos, los cuales se han encontrado insatisfactorios cuando son implantados a partir de la arteria femoral hasta la circulación distal. Entre estas variantes se hallan el politetrafluoroetileno con y sin soporte externo, el Dacrón^® woven y knitted, con y sin velour externo, y la combination de éstos. Puesto que las tasas de permeabilidad de las reconstrucciones realizadas con dichos materiales han demostrado ser inferiores a las que se observan con el uso de la vena safena, se hacen ahora intentos hacia la utilización de materiales biológicos autógenos. Tales intentos incluyen los injertos de vena cefálica, injertos de venas cortas distales a la arteria femoral, venas profundas utilizadas como injertos, y derivaciones con venas in situ. Ultimamente se ha demostrado que las derivaciones in situ, en comparación con controles concurrentes, no exhiben ventajas de significación hasta el nivel poplíteo, pero sí representan la técnica de escogencia cuando la anastomosis distal debe hacerse al nivel de la pantorrilla media o distal a ella. Las derivaciones secuenciales combinadas representan otra técnica que permite la utilización de una vena autógena en forma de segmento distal. En tanto que estas modalidades han logrado incrementar la tasa de permeabilidad de los injertos en regiones distales, agentes tales como los anticoagulantes o las sustancias antiplaquetarias, o las fístulas arteriovenosas adyuvantes, no han probado ser efectivos. La dinámica del sistema de coagulación exhibe una alteracíon intrínseca hacia la trombosis en el estado postoperatorio, y aunque este factor tiene alguna significación como causa de trombosis postoperatoria precoz, y como los defectos técnicos en la anastomosis no parecen ser causa importante, varios estudios sugieren que los factores causantes de falla precoz del injerto permanecen no identificados y que debe prestarse atención a prévenir la falla que puede ser el resultado de embolías o de alteraciones en los sistemas de coagulación del huésped. Esta revisión analiza en detalle algunas de estas causas de falla y trata de colocarlas en su adecuada perspectiva.

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Résumé Les pontages fémorojambiers constituent une technique essentielle dans le choix thérapeutique dont dispose le chirurgien vasculaire. Le prix de ces procédés est largement justifié chez le patient ayant atteint un stade d'ischémie critique. Le facteur le plus important dans l'échec de cette chirurgie reste le choix du matériau étant donné que toutes les prothèses synthétiques sont moins bien tolérées que la veine saphène. Utilisés dans le but de conserver un support de matériau biologique, et le greffon de boeuf et la veine ombilicale humaine sont susceptibles de provoquer thrombose ou d'anévrisme. Les variations dans la fabrication des matériaux prothétiques n'ont pas manqué mais leur utilisation dans les pontages fémorodistaux laisse à désirer. Ont été utilisés le polytétrafluoroéthylène, avec ou sans renforcement externe, Dacron^®, tricoté ou tissé, avec ou sans velours interne ou externe, ainsi que des combinaisons diverses de ces matériaux. Comme le taux de perméabilité avec ces prothèses s'avère inférieur à ceux de la veine saphène, des techniques ont été imaginées pour augmenter l'utilisation des conduits biologiques. Ainsi on a utilisé pour les pontages, la veine céphalique, les segments veineux courts anastomosés en amont de l'artère fémorale, les veines profondes, et la veine saphène interne laissée in situ. Dernièrement il a été démontré que la technique in situ ne fournissait aucun avantage réel par rapport aux autres techniques classiques pour les pontages jusqu'au niveau de l'artère poplitée, mais elle devient la méthode de choix lorsque l'anastomose distale doit se situer à mi-mollet ou au-delà. Le pontage composé, avec anastomoses séquentielles, représente une autre technique utilisant de la veine autogène comme segment distal. Alors que cette technique a amélioré la perméabilité des pontages distaux, d'autres techniques comme les agents anticoagulants, antiplaquettaires ou l'association d'une fistule artérioveineuse n'a rien changé. Les dynamiques du système de la coagulation semblent montrer un chagement intrinsèque individuel dépendant du patient dans la période postopératoire. Ce facteur joue son rôle dans la thrombose précoce des prothèses, alors que les défauts techniques ne semblent pas avoir un rôle majeur. Dans cet article on passe en revue les causes principales respectives et leur importance dans l'échec des pontages.

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Supported in part by the Seabury Foundation, the Conrad Jobst Foundation, and the Northwestern Vascular Foundation.     

Patency of femoropopliteal and femorotibial grafts after outflow revascularization (jump grafts) to bypass distal disease

Repair of failing femorodistal bypass grafts with secondary distal "jump" grafts was performed 34 times in 33 patients. Indication for operation was limb salvage for all distal jump grafts and for 85% of the initial femorodistal bypass grafts. Autogenous vein bypass grafts were used in 28 of 33 initial femorodistal grafts (85%) and in 29 of 34 secondary jump grafts (85%). Sixteen of the 33 initial grafts in jeopardy extended to the infrapopliteal level (48%) and 19 of the jump grafts terminated in foot or ankle arteries (56%). The 12 jump grafts performed in the first 2 months of the initial graft were associated with high rates (9%) of graft thrombosis and amputation. Early loss of viability of initial grafts probably resulted from technical and judgment errors or underestimation of distal disease. Progression of distal disease produced late failure after 1 year of implantation of the initial grafts. The 1-year patency rate of the initial femorodistal grafts was 63% but only 32% of these grafted limbs were viable and were not at risk of amputation. Distal jump grafts produced a 49% improvement in limb viability (to an 81% limb salvage rate) and an 11% increase in the initial graft patency rate (to 74%) at 1 year.     

Above-knee femoropopliteal bypass grafts and the consequences of graft failure.

In all, 290 femoral to above-knee popliteal artery bypasses were performed between January 1983 and September 1991. PTFE grafts were used in 113 cases (39%) and vein grafts in 177 (61%) (reversed in 146 cases and in situ in 31). Patients were followed up for a median time of 20 months. The 2-, 4- and 6-year patency rates for vein and PTFE grafts were 70%, 62% and 57%, respectively, compared with 58%, 46% and 41% (no statistical difference in survival curves, P = 0.2). The 2-, 4- and 6-year limb salvage rates were 82%, 78% and 62% compared with 75%, 64% and 58% (no statistical difference in survival curves, P = 0.6). A total of 99 grafts occluded during follow-up (45 PTFE and 54 vein grafts). Major amputation was required in 63 limbs; below-knee in 37 limbs (59%), and above-knee in 26 limbs (41%). There was no statistical difference in the amputation level with respect to the graft type. Final healing at the below-knee level was achieved in 23 of 35 (66%) failed vein grafts and in 14 of 28 (50%) failed PTFE grafts.     

A 5 year follow-up of Dacron femoropopliteal bypass grafts

Over a 5 1/2 year period, 66 Dacron femoropopliteal grafts were performed for patients with an absent or unsuitable long saphenous vein. The minimum follow-up has been 6 months and cumulative patency was 50 per cent at 5 years. Twenty-five patients had critical ischaemia (preoperative Doppler ankle pressure less than 40 mmHg) and 41 patients had severe ischaemia (pre-operative ankle pressure greater than 40 mmHg). The procedure significantly improved ankle pressures in both groups and this was maintained at follow-up. In the group of 25 patients with critical ischaemia there were three operative deaths and in 10 the graft subsequently occluded, precipitating an amputation. In the group of forty-one patients with severe ischaemia, there was one operative death and in two patients the graft occluded at 18 and 24 months. In this small series there was no significant difference in patency, whether the graft was placed to the popliteal artery above or below the knee joint, or whether the popliteal had less than three patent branches at its trifurcation.     

Salvage of in situ femoropopliteal and femorotibial saphenous vein bypass with interventional radiology

Arteriovenous fistulas and late graft stenoses are well-known potential causes of in situ saphenous vein bypass failure. Three patients are described who had one or both of these complications postoperatively (early and late). Two techniques are described that can be performed at the time of arteriography to save a functioning bypass.     

Deep leg veins as femoropopliteal bypass grafts

Conclusion Our extensive experience indicates that resection of normal superficial femoral and popliteal veins is free of significant late morbidity. Adequate evidence to the contrary has never been presented. Our 5-year patency rates using deep leg veins equal or surpass the best results ever reported with saphenous veins. Erroneous presentation of our work, as exemplified by the comments of Bergan and associates, tends to delay the acceptance of a major arterial graft source. Deep leg vein grafts represent an important advance in arterial reconstructive surgery, and we are confident that future reports by other groups will confirm the high patency rates and lack of significant late morbidity in our reports [36, 37, 43] and that of Noppeney [1].     

Factors influencing patency of femoropopliteal artery bypass grafts

An analysis of 276 femoropopliteal bypass procedures performed in 264 patients at the Columbia-Presbyterian Medical Center over the past two decades showed a direct relationship of graft patency to preoperative popliteal artery runoff. Functional results were better than patency results. Sympathectomy and anticoagulation did not improve graft patency. The risk of amputation is outweighed by the benefits of restoration of blood flow to the ischemic extremity by a bypass procedure.     

The role of graft material in femorotibial bypass grafts.

"Newer" graft substitutes are being widely used in arterial reconstructive procedures in the infrafemoral region. A retrospective study of 101 consecutive femorotibial bypass grafts compares autogenous saphenous vein (ASV), polytetrafluoroethylene (PTFE), and glutaraldehyde tanned (GA) human umbilical cord vein. Symptoms prompting arterial reconstruction was rest pain or tissue necrosis in 90%. Asv (57 bypasses) was the material of choice, but when inadequate or unavailable PTFE, (29 bypasses) or GA (15 bypasses) were used. The immediate and one year patency in ASV was 92--82%. A high incidence of failure occurred in both the PTFE and GA grafts so that patency at one year was 24 and 10% respectively. An overwhelming statistical significance occurs with respect to patency in the three groups of grafts (p = 0.0002). This extremely high incidence of failure in these graft materials has prompted us to use cephalic and basilic veins in those patients which we feel require arterial reconstruction for relief of symptoms.     

Compliance changes in in-situ femoropopliteal bypass vein grafts

Changes in wall structure, including neo-intimal proliferation and medial fibrosis, have been implicated as a cause of late occlusion in reversed femoropopliteal vein grafts. These changes can be measured indirectly as a fall in compliance. It has been suggested that long-term patency might be improved by the in situ technique because the nutrient vasa vasorum are left intact and therefore wall structure preserved. We have measured the compliance of 62 in situ vein grafts, with times after operation ranging from 2 days to 6 years, and also compared the compliance changes, in the first 3 months after operation, of 15 undisturbed in situ vein grafts with 15 fully mobilized in situ vein grafts. Compliance was derived non-invasively from the pulse wave velocity using Doppler ultrasound. There was a significant fall in compliance after operation (P less than 0.001) and no difference could be found between the undisturbed and mobilized in situ vein grafts (P greater than 0.1). Histological examination of 6 grafts suggested that the fall in compliance was due to neo-intimal proliferation which still occurred although medial fibrosis was reduced. Any potential improvement in long-term patency rates using the in situ technique must be due to other factors.     

Effect of antiplatelet and anticoagulant therapy on patency of femorotibial bypass grafts

In a retrospective study, 210 autogenous femorotibial saphenous vein grafts inserted during the 15 years from 1967 to 1982 were followed-up for a mean period of 62.3 +/- 5.7 months. Seven patients, who had had eight grafts died in hospital. The remaining 202 grafts fell into three groups: (1) Sixty grafts in patients who received 325 mg of dipyridamole and 1.0 g of acetylsalicylic acid daily, starting on the second postoperative day and continuing for six months. (2) One hundred and two grafts in patients on no antithrombotic therapy. (3) Forty grafts in patients on warfarin therapy to maintain the prothrombin time (prothrombin-proconvertin method) within the therapeutic range (0.10 to 0.20). Medication was continued for six months. This group included more high-risk patients than the other two groups. The mean ages and the incidence of risk factors did not vary significantly between the groups. The patency rates in three groups at five years were 62.5%, 44.0% and 26.0% and at ten years 48.5%, 25.0% and 21.5% for the dipyridamole and acetylsalicylic acid, no therapy and warfarin groups, respectively. The limb salvage rates were 100%, 96% and 85% in the dipyridamole and acetylsalicylic acid, no therapy and warfarin groups respectively. Thus, the best results were seen in the aspirin/dipyridamole group.     

Preferential use of ePTFE for above-knee femoropopliteal bypass grafts

We have used polytetrafluoroethylene preferentially for bypasses to the above-knee popliteal artery since 1979. Since this approach has recently been challenged, we reviewed our experience with 138 grafts in 128 patients. The majority (74%) of patients were male with a mean age of 63.2 years. Risk factors included: smoking (85%), hypertension (55%), diabetes mellitus (45%), and coronary artery disease (41%). The indications for operation were disabling claudication (18%), rest pain (42%), gangrene/tissue loss (33%), and miscellaneous (7%). Perioperative (30 day) mortality was 3% and morbidity (excluding amputation or graft failure) was 5%. Patients were followed for up to eight years with a mean follow-up of 22.1 months. Grafts which remained patent, but did not prevent major amputation, were classified as failed. Primary patency was 75% at one year and 54% at five years. Limb salvage was 88% at one year and 70% at five years. Risk factors, indication for operation and arteriographic runoff had no statistically significant impact on short- or long-term patency. However, bypass grafts to isolated popliteal segments had a significantly (p=0.025) increased perioperative failure rate compared to all other grafts. Our data support the continued use of polytetrafluoroethylene for above-knee femoropopliteal bypass except perhaps in patients who require grafting to an isolated popliteal segment where higher early failure rates were seen.