Hemodynamic effects of varied graft diameters in the venous system

Both in vivo and mathematical models of venous hypertension were used to evaluate the hemodynamic effects of 4, 6, 8, and 10 mm diameter cross-femoral venous bypass grafts (CFBs). Eighteen grafts (length 138 +/- 3.4 mm) were tested in paired sequential fashion (four grafts, 4 and 8 mm; five grafts, 6 and 10 mm) in nine greyhounds (femoral vein diameter, 7.7 +/- 0.09 mm). Bilateral hindlimb venous pressures and flows were measured before and after unilateral iliofemoral venous ligation, 30 minutes after CFB insertion, and for 5 minutes after venous flow augmentation induced by stimulated muscle contraction. CFBs of all sizes were equally effective at relieving the occlusive venous hypertension at rest. Muscle contraction elevated venous pressure in all ligated hindlimbs (p less than 0.0001); however, the pressure returned to baseline by 3 minutes in dogs with 6, 8, and 10 mm grafts but remained elevated (p less than 0.05) with the 4 mm grafts even after 5 minutes. Peak graft flow (first 90 seconds after contraction) was significantly greater through the 8 mm grafts than through the 4 mm grafts (p less than 0.01), although no difference was noted in flow rates between 6 and 10 mm grafts. The pressure gradient across the graft as predicted by the mathematic model for 6 to 10 mm conduits was less than 5 mm Hg for flows up to 1000 ml/min, although the pressure gradient of the 4 mm graft exceeded 5 mm Hg at 200 ml/min and approached 30 mm Hg at 1000 ml/min. Therefore, data from both canine and mathematical models agreed that, at rates approximating human resting flow (1000 ml/min), no adverse short-term hemodynamic consequences result from CFB conduits of 6 to 10 mm diameter.     

Cross-Femoral Venous By-Pass (Palma’s Procedure) to Relieve Venous Hypertension Due to Retroperitoneal Leiomyosarcoma: A Case Report

Retroperitoneal leiomyosarcoma arising in, or involving, the inferior vena cava or the iliac vein are infrequent tumours. They are usually treated by “en-block” surgery. Venous reconstruction is usually not needed, since collateral circulation can adequately offset the main vessel flow. However, in rare cases, collateral circulation may be insufficient. The authors report a case of leiomyosarcoma infiltrating the left iliac vein. One week after radical resection surgery, the patient developed left leg compartmental syndrome due to venous hypertension.

The patient was successfully treated by thrombectomy of the left femoral vein and cross-femoral venous bypass (Palma’s Procedure) by means of an 8 mm diameter polytetrafluoroethylene (PTFE) prosthesis. To improve the flow inside the graft, an arterio-venous fistula (AVF) was performed. The choice of a prosthetic conduit, its diameter, and the AVF are discussed.     

Preoperative saphenous venography in arterial reconstructive surgery of the lower extremity.

Preoperative saphenous venography was performed in 100 extremities in 60 patients to evaluate the saphenous vein for use as an arterial bypass graft. In 18 of the patients (30%), venography demonstrated vein abnormality, disease, or small size, which significantly influenced the management of the patient or the conduct of the operation. Good correlation was observed between venographically determined saphenous vein anatomy and diameter and those observed at operation in 52 patients. The average diameter of the saphenous veins on preoperative venograms was 3.4 mm (range, 1.0 to 6.0 mm). These veins dilated to an average diameter 73 +/- 5% greater than that observed venographically, so that the average diameter of harvested, dilated saphenous veins was 5.5 mm (range, 3.0 to 10.0 mm). All veins measuring 2.0 mm or more on the venograms dilated to 4.0 mm or more at operation and were suitable for femoropopliteal or small vessel bypass grafts. Four saphenous veins measuring 1.0 mm or more on the venograms dilated to 3.0 mm or more at operation and were suitable for small vessel bypasses. Thus preoperative saphenous venography can be of value in lower extremity arterial reconstructions. The procedure allows detection of anomalies and disease processes that would prevent the use of one or both saphenous veins as arterial bypass grafts and identifies the best available venous segment thereby obviating unnecessary incisions and minimizing operating time.     

Cryopreserved Vein Transplantation

There have been numerous attempts to develop prosthetic conduits or utilize allograft saphenous veins for arterial bypass. This article summarizes our experimental and clinical experience with cryopreserved allograft saphenous veins. During these studies, particular attention was paid to vein donor postmortem ischemia time, vein procurement technique, and tissue storage methods. Experimental cryopreserved autograft studies demonstrated that cryopreservation of the veins does not alter subsequent graft patency, the arterialization process, blood flow, or platelet deposition in vein grafts. Endothelium-derived relaxing and contractile factors are produced by the endothelium of explanted cryopreserved autografts, and smooth muscle contractions and relaxations can be induced. In experimental cryopreserved allografts, the endothelium appears to be removed by an immune response during the first 10 days after transplantation, fibrin deposition is minimal, and re-endothelialization occurs over 6-9 months. Early clinical results using cryopreserved allograft saphenous veins are encouraging with 1-year patency rates of 79% for peripheral grafts and 86% for coronary bypass grafts.     

Failure of cryopreserved saphenous vein allografts following coronary artery bypass surgery.

Internal mammary arteries and saphenous vein grafts are the most satisfactory conduits for coronary artery bypass. However, at times these conduits are not available, due to previous use or poor quality. This paper reports our experience with 6 patients who underwent coronary artery bypass operations using 10 cryopreserved saphenous veins and internal mammary arteries. Postoperative graft patency was assessed with ultra fast computed tomography or cardiac catheterization. At operation, venous graft patency was 100% (10/10), at 1-8 weeks was 60% (6/10), and at 6-30 months was 0% (0/9). Alternately, all seven internal mammary artery grafts were patent at 2 to 18 months following surgery. One patient died 6 months following operation. Poor graft patency may be related to destruction of the cellular components or fibrosis resulting from the cryopreservation process or from immunologic factors. Because of poor patency compared to autologous conduits, we conclude the use of cryopreserved saphenous veins for coronary artery bypass should be severely restricted.     

Factors influencing the development of vein-graft stenosis and their significance for clinical management.

OBJECTIVES: To assess the influence of clinical and graft factors on the development of stenotic lesions. In addition the implications of any significant correlation for duplex surveillance schedules or surgical bypass techniques was examined. PATIENTS AND METHODS: In a prospective three centre study, preoperative and peroperative data on 300 infrainguinal autologous vein grafts was analysed. All grafts were monitored by a strict duplex surveillance program and all received an angiogram in the first postoperative year. A revision was only performed if there was evidence of a stenosis of 70% diameter reduction or greater on the angiogram. RESULTS: The minimum graft diameter was the only factor correlated significantly with the development of a significant graft stenosis (PSV-ratio > or = 2.5) during follow-up (p = 0.002). Factors that correlated with the development of event-causing graft stenosis, associated with revision or occlusion, were minimal graft diameter (p = 0.001), the use of a venovenous anastomosis (p = 0.005) and length of the graft (p = 0.025). Multivariate regression analysis revealed that the minimal graft diameter was the only independent factor that significantly correlated with an event-causing graft stenosis (p = 0.009). The stenosis-free rates for grafts with a minimal diameter < 3.5 mm, between 3.5-4.5 and > or = 4.5 mm were 40%, 58% and 75%, respectively (p = < 0.05). Composite vein and arm-vein grafts with minimal diameters > or = 3.5 mm were compared with grafts which consisted of a single uninterrupted greater saphenous vein with a minimal diameter of < 3.5 mm. One-year secondary patency rates in these categories were of 94% and 76%, respectively (p = 0.03). CONCLUSIONS: A minimal graft diameter < 3.5 mm was the only factor that significantly correlated with the development of a graft-stenosis. However, veins with larger diameters may still develop stenotic lesions. Composite vein and arm-vein grafts should be used rather than uninterrupted small caliber saphenous veins.     

The contribution of valves to saphenous vein graft resistance

Saphenous vein resistance influences graft flow rates and may affect graft patency in lower limb revascularization. To quantitate specifically the contribution of saphenous vein valves to this resistance, 10 human saphenous veins (mean length 68 cm, diameter 0.42 mm, and 5.2 valves per vein) were perfused with water under carefully controlled pressure gradients designed to simulate different peripheral resistances in the outflow bed. The Reynolds number was maintained at 350 to 600, within the physiologic range for in vivo grafts. Veins were perfused under both venous (10 mm Hg) and arterial (100 mm Hg) mean pressures to determine the effects of distension on the overall resistance of the conduit. The valves were bisected according to Leather's techniques and flow was measured in both directions, antegrade (simulating "reversed" grafts) and retrograde (simulating "in situ" grafts). Data (mean +/- standard error) were normalized to the baseline flow for each vein with intact valves and expressed as a percentage change. Data were analyzed by means of Student's t test (p less than 0.05). Baseline antegrade flow with intact valves averaged 71.0 +/- 3.0 ml/min at pressure gradients (delta P) of 10 mm Hg and 95.0 +/- 2.6 ml/min for delta P = 20 mm Hg. After valve incision, antegrade flow (reversed) increased an average of 29% at both pressure gradients. Retrograde flow (in situ) through the bisected valves was only 19% greater than baseline antegrade flow and was significantly less than antegrade flow through bisected valves. The difference is explained by theoretic considerations of stenosis area and orifice shape. The increases in flow did not correlate with vein length or diameter, nor did flow change with different distension pressures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cryopreserved saphenous vein homografts for femoral-distal vascular reconstruction

Cryopreserved saphenous vein homografts may serve as an alternative for femoral distal bypass conduits when suitable endogenous vein is not available. In a preliminary study, 6 patients underwent femoral distal bypass for limb salvage with cryopreserved saphenous vein with patency in 2 patients at 18 and 20 months, respectively. One graft, occluded at 14 months, was salvaged with thrombolytic therapy and percutaneous angioplasty, and is patent 7 months post intervention. Occlusion occurred in 3 grafts at 1 day, 7 days and 4 months, respectively. Reasons for reduced patency of cryopreserved grafts are related to destruction of the cellular components and fibrosis as a result of the cryopreservation and poor distal run-off present in these patients. Due to lower patency as compared to autogenous vein grafts, cryopreserved veins should be reserved for limb salvage when no autogenous vein is available for revascularization.     

Correction of Superior Vena Cava Syndrome with Superficial Femoral Vein Juguloatrial Bypass

Several techniques for bypass of the superior vena cava have been described, including spiraled saphenous vein graft, femoral vein graft, and polytetrafluoroethylene graft as conduits. We present two cases of superior vena cava obstruction treated with juguloatrial bypass using harvested superficial femoral vein. We feel that the superficial femoral vein, with its diameter similar to that of the internal jugular vein, provides several advantages compared to other conduits in a juguloatrial bypass.     

Replacement of in situ saphenous venous aneurysms with arterial autografts

BACKGROUND: Aneurysm formation in arterialized autologous saphenous veins is an unusual complication of in situ femoral popliteal bypass procedures. METHODS: In a personal series of 207 in situ saphenous femoral popliteal bypass operations, three nonanastomatic venous aneurysms occurred. All three venous aneurysms occurred in male patients who had no adequate autologous vein available as an interposition graft. The use of eversion endarterectomized superficial femoral artery is reported as a substitute interposition graft with long-term results. RESULTS: In the 3 male patients in this series, nonanastomatic aneurysms developed in their in situ saphenous femoral popliteal bypass grafts. The venous aneurysms developed between 5 and 8 years after the original surgical procedure. No adequate vein was available as a replacement for the excised venous aneurysm. Prosthetic conduit was not used owing to the remote possibility of a subclinical infection. A segment of eversion thromboendarectomized superficial femoral artery removed from the same leg was used as a replacement interposition graft in each patient. The in situ venous graft with the autologous interposition thromboendarterectomized superficial femoral artery remained patent until each patient's death 4 to 7 years after the venous aneurysm replacement. CONCLUSIONS: A short segment of endarectomized superficial femoral artery has been found to be a novel solution for the treatment of isolated saphenous vein graft aneurysms when no suitable vein is available. These patients should be maintained on lifelong aspirin therapy owing to the thrombogenic potential of endarectomized artery.     

Patency of saphenous vein coronary artery bypass grafts from the vascular prosthesis of the ascending aorta.

BACKGROUND: Patients who have Stanford type A aortic dissection with impaired coronary arteries or who have aneurysms from the ascending aorta to the aortic arch with coronary artery disease need coronary artery bypass grafting (CABG) with tube graft replacement of the ascending aorta simultaneously. When vein grafts are used for CABG in these patients, the proximal anastomoses of vein grafts are attached to the prosthetic tube graft of the ascending aorta. However, the validity of proximal anastomoses of vein grafts to the prosthetic tube graft of the ascending aorta has not been confirmed. PATIENTS AND METHODS: We retrospectively analyzed patients who underwent venous coronary bypass grafting with prosthetic graft replacement of the ascending aorta. Between January 1984 and October 2002, 35 patients underwent CABG using saphenous vein grafts at the time of tube graft replacement of the ascending aorta, and the proximal anastomoses of the vein grafts were attached to the tube graft of the ascending aorta. Thirty-three venous bypass grafts were analyzed in 24 survivors. RESULTS: The postoperative catheterization showed only one early vein graft occlusion of 16 vein grafts anastomosed distally to the left anterior descending artery (LAD). All 14 venous grafts anastomosed to the right coronary artery (RCA) and 3 to the left circumflex artery (LCX) were patent. Therefore, the postoperative patency rate at discharge was 97.0% (32/33). Spiral computed tomography performed for long term follow-up revealed occlusion of two vein grafts (3.5 years and 9.7 years) anastomosed to the LAD. CONCLUSIONS: The patency rate of vein grafts anastomosed from prosthetic grafts of the ascending aorta to the native coronary arteries was similar to that of conventional CABG using saphenous vein grafts.     

Non-greater saphenous vein grafting for infrageniculate bypass

Infrainguinal bypass grafting with greater saphenous vein has proven to be a highly effective procedure with primary 5-year patency and limb salvage rates exceeding 80 per cent. However, because of prior usage or intrinsic venous disease the greater saphenous vein is often not available as a conduit. Numerous studies have shown that patency rates for prosthetic bypass grafting to the infrageniculate vessels are clearly inferior to that reported for greater saphenous vein bypass. In this report we summarize our experience with the use of alternate autogenous vein grafting to the infrageniculate vessels. The records of all patients undergoing autogenous bypass grafting to the infrageniculate vessels using a conduit other than the greater saphenous vein between 1992 and 1999 were reviewed. Graft survival curves were plotted using the Kaplan-Meier method and results are reported using the Society for Vascular Surgery/International Society for Cardiovascular Surgery guidelines. Forty-eight patients underwent a total of 51 infrageniculate bypass procedures using non-greater saphenous autogenous conduits. Thirty-nine patients had reconstructions performed with single segments of arm vein, two had their operations performed with lesser saphenous vein, and ten had grafts created with two segments of non-greater saphenous autogenous vein. Twenty-one grafts were performed to the infrageniculate popliteal artery and 30 were performed to the tibial vessels. Primary and primary assisted patency rates at 30 months were 49 and 75 per cent. Limb salvage was 87 per cent. Infrainguinal bypass grafting using non-greater saphenous autogenous conduits can yield quite satisfactory intermediate limb salvage and patency rates. However, close graft surveillance and prompt intervention are required to avoid graft failure.     

Optimal prosthetic graft design for small diameter vascular grafts

Autogenous vein and arterial grafts, such as great saphenous veins and internal mammary and radial arteries, remain the gold standard conduits for vascular reconstruction. Expanded polytetrafluoroethylene (PTFE) grafts, which exhibit little inflammatory and thrombogenic reactivity, are the most commonly used material of choice for small diameter vascular grafts when autogenous grafts are not available. Several modifications of the basic graft have been attempted to enhance graft healing of expanded PTFE grafts, and little but definite experimental and clinical improvement has been achieved so far. The technique of vascular tissue engineering, in combination with stem cell research, may hold the key for the creation of a practical and successful small diameter prosthetic graft.     

Preoperative noninvasive assessment of arm veins to be used as bypass grafts in the lower extremities

Preoperative noninvasive imaging of the veins of the upper extremities has been included in the protocol to select an autogenous vein for a distal bypass in the lower extremity. Arm veins are sought as bypass grafts when the saphenous vein is absent or not usable. Duplex ultrasound provided images of the cephalic and basilic veins in 10 patients in whom visual inspection failed to reveal usable grafts. All arm veins implanted were at least 2 mm (range 2 to 6 mm) in internal diameter determined by ultrasound and were, on the average, 2 mm larger when unroofed. This noninvasive technique has decreased the number of fruitless surgical explorations to obtain a suitable arm vein and has increased the use of arm veins by revealing veins previously not anticipated by physical examination, which virtually eliminated the use of nonautogenous conduits in our practice.     

The Advantages of the Great Saphenous Vein as a Femoropopliteal Graft: A Report on Its Clinical Use

As a majority of vascular surgeons prefer the autologous saphenous vein as a bypass graft below the inguinal ligament, the need of alternative graft materials or reconstructive techniques is confined to patients with unavailable or unsuitable saphenous veins. The aim of this investigation was to ascertain how often these alternative procedures are necessary. From 1973 to June 1979, the great saphenous vein was used as a femoropopliteal graft without regard to fixed limitations in the diameter and the quality of the vein. During this period, vascular reconstruction was required in 148 limbs due to symptomatic atherosclerotic occlusion of the superficial femoral artery. In 144 of these cases, the ipsilateral (138) or the contralateral (6) great saphenous vein was used for a femoropopliteal bypass reconstruction. Thus, the vein could not be utilized in only 4 of 148 cases (2.7%).

As graft patency rate was not subject to the size and quality of the vein and as cumulative patency rates in the 144 grafts were most satisfactory (97.9, 92.0 and 81.9% at 1 month, 1 year and 5 years, respectively), although all these veins were used regardless of their calibre and quality, we conclude that the great saphenous vein can be used more liberally as a graft for femoropopliteal occlusion In approximately only 3% of patients requiring operation, alternative reconstructive techniques, such as ‘non-vein’ bypass grafts and thrombendarterectomy are needed.     

Distal venous patch improves results in PFTE bypasses to tibial arteries

In recent years, the management of limb-threatening ischemia has involved the use of distal bypasses to vessels beyond the popliteal trifurcation. Excellent patency rates and limb salvage data are achieved through the use of autologous long saphenous vein. However, an increasing number of patients in need of tibial bypass do not have adequate saphenous vein due to previous procedures, thrombophlebitis, or inadequate vein. In such cases alternative conduits have been proposed including lesser saphenous vein, arm vein, composite veins, composite vein with polytetrafluoroethylene (PTFE), and PTFE with or without a distal arteriovenous fistula. Unfortunately these alternative conduits have not resulted in equivalent results when used for distal bypass to tibial arteries. Several authors have reported upon the use of venous tissue at the distal anastomosis in the form of cuffs, collars, and boots to improve the results of prosthetic grafts in this challenging patient population. These techniques have been proposed as an option for revascularization in patients without adequate saphenous vein in an attempt to obtain limb salvage. The purpose of this review is to examine some of those techniques and focus on distal vein patch configuration with its perceived advantages and drawbacks.     

Distal Venous Patch improves results in PFTE bypasses to Tibial arteries

In recent years, the management of limb-threatening ischemia has involved the use of distal bypasses to vessels beyond the popliteal trifurcation. Excellent patency rates and limb salvage data are achieved through the use of autologous long saphenous vein. However, an increasing number of patients in need of tibial bypass do not have adequate saphenous vein due to previous procedures, thrombophlebitis, or inadequate vein. In such cases alternative conduits have been proposed including lesser saphenous vein, arm vein, composite veins, composite vein with poly-tetrafluoroethylene (PTFE), and PTFE with or without a distal arteriovenous fistula. Unfortunately these alternative conduits have not resulted in equivalent results when used for distal bypass to tibial arteries. Several authors have reported upon the use of venous tissue at the distal anastomosis in the form of cuffs, collars, and boots to improve the results of prosthetic grafts in this challenging patient population. These techniques have been proposed as an option for revascu-larization in patients without adequate saphenous vein in an attempt to obtain limb salvage. The purpose of this review is to examine some of those techniques and focus on distal vein patch configuration with its perceived advantages and drawbacks.     

Femoral venous trauma: techniques for surgical management and early results

During a 4 year period (1979 through 1983), 181 major arterial (69 percent) and 81 venous (31 percent) injuries were treated surgically. Of the venous injuries, 24 (30 percent) involved the femoral veins (9 common femoral, 15 superficial femoral). Management of these femoral venous injuries included lateral venorrhaphy in 10 cases (42 percent), venous patch angioplasty in 5 cases (21 percent), end-to-end anastomosis in 4 cases (17 percent), interposition autogenous saphenous vein grafts in 3 patients (12 percent), and ligation in 2 cases (8 percent). One case that included common femoral venous ligation and one that included a failed interposition saphenous vein graft in the superficial femoral vein subsequently were managed with in situ saphenous vein bypass. For one interposition saphenous vein graft repair of the common femoral vein we utilized the spiral vein graft technique. Excluding one early death from associated injuries and one superficial femoral venous injury managed by ligation without postoperative complications, 17 of 23 (74 percent) femoral venous repairs were judged patent postoperatively (13 confirmed by venography and 4 by noninvasive testing). The adjuvant use of intermittent pneumatic calf compression and low molecular weight dextran appears to have been beneficial in maintaining patency of the femoral venous repairs. Early clinical follow-up demonstrated the presence of edema in 6 of 8 cases (75 percent) initially treated by ligation or complicated by postoperative occlusion. Early postoperative edema, present in 4 of 17 (24 percent) patients with patent venous repairs, had resolved by the time of discharge. We recommend routine repair of femoral venous injuries. When significant edema or ischemia develop following obligatory venous ligation or postoperative occlusion of a venous repair, revision or venous bypass should be considered.     

Autogenous reversed vein bypass for lower extremity ischemia in patients with absent or inadequate greater saphenous vein

This report has presented the results of 329 reversed vein bypasses performed for lower extremity ischemia over a 6 3/4 year period. One hundred eighty-nine bypasses were formed from intact ipsilateral greater saphenous veins of adequate size and length. One hundred forty bypasses were formed in patients in whom the ipsilateral greater saphenous vein was absent or of inadequate size or length to complete the bypass. The grafts in these patients were accomplished using a variety of techniques including distal graft origin, use of arm veins and lesser saphenous veins, and use of vein splicing. The patency rates of these grafts were equivalent to those achieved using adequate intact ipsilateral greater saphenous vein. In view of these results, we conclude that the absence of a greater saphenous vein does not preclude successful autogenous lower extremity vein bypass and that prosthetic bypass is rarely justified.     

Technical Considerations for Use of the Gastroepiploic Artery for Coronary Artery Surgery

Disappointing long-term results with saphenous vein graft (SVG) for coronary bypass and excellent long-term results with internal mammary artery (IMA) to coronary bypass have prompted a search and research for other alternative coronary bypass conduits. Experience with the radial artery was disappointing due to early failure of those grafts. Likewise, conduits of artificial materials and homograft veins have not produced acceptable long-term results.