Different venous end-to-side microanastomotic techniques: comparative study in a new rat model

End-to-side venous anastomosis is sometimes necessary when there is the lack of a suitable vein, when there is a size discrepancy in the veins to be repaired, or when the anastomosis of multiple veins is required. The effects of elliptical vs. slit venotomy on vessel patency have not been investigated in a flap model. A new, simple, reliable, and reproducible model is described in which the femoral vein of the groin flap is anastomosed to the side of the deep dorsal penile vein. Elliptical hole and slit venotomies were tested in 26 Sprague-Dawley rats, and the anastomoses were 100% patent. The type of venotomy was not found to affect patency. Either technique is equally valid in end-to-side venous anastomosis, and the model itself is convenient for training.     

Microvenous thrombosis rates following anastomosis with vein grafting and a knotted suture

An experimental microvenous thrombosis model was developed combining vein grafting in femoral vein defects with exaggerated vessel injuries using a knotted suture in the vessel repair. The rat femoral vein grafts were separately subjected to injuries caused by an anastomosis performed with a suture knotted with eight half-hitches at the distal anastomosis (upstream), the proximal anastomosis (downstream), and both anastomotic sites. These groups were compared to vein grafting done with a standard suture. Vessel patency was assessed at 20 min and 24 hr, and the thrombus component was histologically analyzed at 24 hr after the procedures. One hundred percent of control vein grafts were patent at 24 hr. All experimental groups had significantly decreased patency at 24 hr (P<0.001). Among the experimental groups, knotted suture anastomoses at both anastomoses produced significantly lower patency (13.3%, P<0.05) than knotted suture anastomoses at distal anastomoses. Histological analyses of thrombosed grafts showed that a large amount of thrombocyte deposition and inflammatory cells were noted at both anastomotic sites in the vein grafts with a knotted suture at the distal anastomosis and in the grafts with a knotted suture at both anastomoses. Thrombocyte deposition and inflammatory cells were seen only at the site of proximal anastomosis when using a knotted suture at the proximal anastomosis site alone. This study demonstrated that quantified microvenous thrombosis can be produced by exaggerating vessel injuries with a knotted suture in a vein graft model. This thrombosis model can be used to study the effects of antithrombogenic agents. © 1995 Wiley-Liss, Inc.     

Evaluation of Role of Arterialization of Venous Flaps in Abdomen in Rats

Introduction  Reconstruction forms the primary tenet in plastic surgery. Venous flaps are a known option but the survival is limited. Arterialization of venous flap can enhance its survival. While various techniques of arterialization of venous flaps are described, there are very few studies comparing them. Material and methods  The current study was conducted among 34 rats weighing 160 to 200 grams. The rats were divided into four groups. Group I—islanded epigastric flap was raised with superficial caudal epigastric vessels as pedicle. Group II—arterialized flow through venous flap was raised with superficial caudal epigastric vein (SCEV) as afferent and lateral thoracic vein as drainage vein. Side-to-side anastomosis was done between femoral artery and vein, lateral to the origin of superficial caudal epigastric artery. Group III—after raising the flap, as in group II, femoral vein was ligated proximal to superficial caudal epigastric vessels. Group IV—an arterialized flow through venous flap was raised with superficial caudal epigastric vein as afferent and lateral thoracic vein as drainage vein. End-to-side anastomosis was done between femoral artery and superficial caudal epigastric vein. Animals that died before completion of the study were excluded. The color changes of flaps were noted. Flap survival was expressed as a percentage of the total flap surface area. The patency of anastomosis was seen on postoperative day 5. Results  There was no total flap failure. On statical analysis, the flap survival area on day 5 between Group I and Group IV was not significant ( p value 0.431). The survival area in Group I (78.85 ± 10.54%) was comparable to Group IV (65.71 ± 20.70%). Group II and III had poor results as compared with Group I. In four rats, thrombosis of arteriovenous anastomosis was noted with flap survival area of 30 to 33%. Conclusion  It was noted that epigastric venous flaps with end-to-side anastomosis between femoral artery and superficial caudal epigastric vein (group IV) have survival area comparable to islanded flaps.     

Long-term histologic results of vein grafting with the telescoping anastomotic technique.

We studied the long-term histologic results of a new method for autogenous vein grafting to examine whether stenosis at the anastomosis is maintained over time. Nineteen rat inferior epigastric veins were grafted into the femoral artery using a telescoping sleeve technique at both the proximal and the distal anastomoses. Specimens were studied macroscopically and histologically three months later. Stenosis at the anastomosis was located near the tip of the inserted vessel. The smallest inner diameters of the proximal and distal anastomoses were about 80% of the corresponding femoral artery diameter; no statistically significant difference was found between the two anastomoses. The grafts had a thickened wall due to intimal hypertrophy and fibrosis of the media. The inner diameter of the graft was, however, about twice that of the femoral artery, and these graft changes did not create any apparent constriction within the graft.     

Non-suture external cuff techniques for microvascular anastomosis

Microvascular anastomosis can be achieved by eversion of the upstream vessel end over an external cuff and insertion of this into the downstream vessel. This technique, first described in 1900, was initially tested in 13 rat femoral vein anastomoses using small polythene cuffs. Two anastomoses failed and 11 were patent at 7 days. After control studies, in 16 rat epigastric flaps the femoral vein in the vascular pedicle was divided and anastomosed using an external cuff. Thirteen flaps survived. The principles underlying this method appear sound, and form the basis for microvascular anastomotic devices currently being developed.     

Effect of torsion on microvenous anastomotic patency in a rat model and early thrombolytic phenomenon

Torsion at the microanastomosis site is a basic fault and should be avoided. In this study, we investigate the effects of different degrees of microvenous torsion on patency and its physical changes on anastomoses in a rat model. One hundred anastomoses were performed at different degrees of torsion, using femoral veins of Sprague-Dawley rats. Anastomoses were performed at 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees of torsion randomly. Patency tests immediately, 1 h, and 1 week after the anastomoses were checked, using the refill test. Measurements of external diameter were recorded at three points: one at the anastomosis site, and the others 2 mm proximal and distal to the anastomotic site. Finally, histopathologic and scanning electron microscopy studies were performed. Subsequently, because of the peculiar phenomenon of early recannulation of the thrombosed vessels, 20 vessels were also explored on the first and the third days postoperatively. The data demonstrate that torsion at 180 degrees, compared with 0 degrees, 45 degrees, and 90 degrees, impaired patency significantly (P < 0.005). In the subsequent study of 20 veins that were thrombosed on the first day, all became patent on the third day and remained so. In conclusion, rotation of a microvenous anastomosis begins to affect the patency rate at 90 degrees of torsion, and at 180 degrees has a patency rate of only 25%. However, all become patent again from the third day onwards. Thrombosis of rat femoral veins without chronic obstruction results in rapid lysis of thrombus and transient proliferative changes.     

Rat epigastric flow-through flap as a modulated arteriovenous fistula: model for the radial artery flow-through flap in distal arterial bypass

The authors describe a rat flap model that is useful for flow studies. It is an epigastric flow-through flap that mimics the clinical use of a radial artery flow-through (RAFT) flap that has been used as an adjunct to a distal lower extremity arterial bypass graft to improve patency when there is potential high outflow resistance. The hypotheses were that this RAFT flap serves two purposes: 1) it allows additional blood flow through the skin flap and drainage via the vena comitans to increase the blood flow through the bypass graft and help to maintain bypass graft patency; and 2) it acts as a modulating arteriovenous fistula in which the additional flow through the vena comitans of the flow-through flap fluctuates with distal arterial outflow resistance. The rat epigastric flow-through flap model was designed to test these hypotheses. High outflow resistance was induced by sequentially ligating the outflow vessels of the rat femoral artery. Using this model, an increase in blood flow to the skin via the epigastric artery of the flow-through flap was demonstrated as outflow obstruction increased. Then, the patency rates of the flow-through flap bypass were compared to an interpositional arterial graft. The flow-through flap maintained patency while the arterial interposition bypass thrombosed, with near total outflow obstruction induced by serial ligation of the outflow vessels (75 percent patent anastomoses at 1 week for flow-through flap vs. 0 percent for the arterial graft). This flow study demonstrates the inherent ability of the flow-through flap to divert blood flow through the skin capillaries when there is high arterial outflow resistance. The authors believe that a flow-through flap such as the RAFT flap can be an important adjunct to the traditional distal arterial bypass in a subset of patients with high outflow resistance in the recipient artery.     

An animal model for the assessment of microvascular patency

A tubed superficial epigastric flap (TSEF), based on a single vascular pedicle, was designed in a rat. Forty TSEFs were created in three control groups: in 20 TSEFs both the femoral artery and vein were ligated proximal to the take-off of the superficial epigastric vessels, in 10 TSEFs the femoral artery and in the other 10 the femoral vein were ligated and transected at the same location. All TSEFs in the control groups sloughed, reflecting the dependence on the axial vasculature. A further 232 TSEFs were made with a survival rate of 84.5% (196/232). Delayed arterial or venous ligation was then performed up to 42 days after the initial surgery. The patency of the axial vein was crucial for survival for only the first postoperative week. The axial arterial patency was needed for survival of the TSEF for 6 weeks. The creation of this TSEF fulfills the need for a simple model that is as readily constructed as other models, is reproducible, has a high success rate and most importantly, reflects the patency of its nutrient vessels for a prolonged period of time.     

Microvascular anastomoses: a comparison of the end-to-end and the telescoped techniques in rats

The end-to-end anastomotic technique and the telescoped anastomotic technique were compared in a paired experimental study of 200 primarily patent anastomoses in the femoral arteries and veins of rats. It was found that the arterial telescoped anastomosis was faster and simpler to perform and had a significantly lower frequency of late thrombotic deposition (13%) than the arterial end-to-end anastomosis (41%), although the patency rates at 1 week were equal (88%). Aneurysms at the site of the anastomosis were not observed in the arterial telescoped anastomoses, while initial stages of probable aneurysms were observed in 24% of the arterial end-to-end anastomoses. The venous telescoped anastomoses were also less time-consuming and simpler to construct. Although equal patency rates at 1 week were obtained (84%-88%), the venous telescoped anastomoses displayed a significantly more pronounced incidence of thrombotic deposition at the site of the anastomosis.     

The use of long synthetic microvascular grafts to vascularise free flaps in rabbits

A 5 cm length of 2 mm internal diameter (i.d.) synthetic, expanded polytetrafluoroethylene (PTFE, or Gore-Tex) vascular graft was used to connect 25 rabbit inferior epigastric flaps to the contralateral femoral vessels. In 15 animals an expanded PTFE graft connected the opposite femoral artery to the flap while the ipsilateral venous drainage remained intact. In the remaining 10 animals an expanded PTFE graft was used to replace the venous drainage of the flap and connected to the opposite femoral vein while the ipsilateral femoral artery supplied the flap. Flap survival and graft patency were evaluated over 3 weeks. Ten of 15 flaps with intra-arterial grafts survived at 3 weeks (67%). Only 27% (4/15) of their supplying grafts remained patent for 3 weeks, although 67% (10/15) were patent at 10 days. All 10 flaps, where expanded PTFE grafts replaced venous outflow, failed within 36 hours. At exploration these grafts were thrombosed or collapsed. In conclusion, currently available 2 mm (i.d.) expanded PTFE vascular graft cannot maintain patency in a low blood flow circulation supplying an isolated free flap.     

New microvenous anastomosis model for microsurgical training: external jugular vein

In microsurgical training, the femoral vein is used frequently for a microvenous anastomosis model. But the femoral vein in the rat does not completely simulate the human vein because of its thin wall, fragility, and tendency to collapse. These anatomic characteristics cause some difficulty in carrying out anastomoses in microsurgery training particularly for beginners. The authors propose the external jugular vein of the rat for microsurgical training in microvenous anastomoses. In 10 Wistar rats, the anatomy of the external jugular vein was studied by dissection and histology. Anatomic dissections demonstrate that the external jugular vein has an average diameter of 1.9 mm (range: 1.6 to 2.1 mm) without tendency to collapse. The vein is easily dissected without any accompanying anatomic structure for an average segment of 45 mm, allowing effortless approximator clamp placement. Comparison of its cross section with that of the femoral vein and other previously described models by light microscopy and scanning electron microscopy reveals a larger diameter and much thicker vessel wall with a prominent tunica media and adventitia. Based on the anatomic findings in 20 rats, the external jugular vein was anastomosed with end-to-end standard microsurgical technique using 8-0 (n = 10) and 10-0 (n = 10) nylon sutures. Results indicate a 100 percent patency rate immediately after the anastomosis for the two subgroups and 100 percent and 90 percent patency rates 1 week after the procedure for the 10-0 and 8-0 nylon suture groups, respectively. This model presents some advantages: the vein is easily dissected with the naked eye without using the operating microscope because it is the largest vein among the superficially located veins in the rat, and has a thick vessel wall without tendency to collapse. The operative area allows for training inbilateral microsurgical anastomoses using a single skin incision and is safe from autocannibalization. The model simulates clinical microvenous anastomosis better because of its similarities to human large diameter flap veins.     

Long-term result of arterial grafts interposed for arterial defects using the telescoping anastomotic technique: histological and angiographic study.

The arterial grafting model for arterial defects provides an ideal environment for the microvascular telescoping anastomosis because tension of the repaired vessel is maintained low and deformities of the inserted vessel end is minimal due to the thick arterial wall. The left femoral artery was grafted in 46 rats into the defect created in the right femoral artery using the telescoping anastomotic technique at both the proximal and distal anastomoses. The grafts were seen histologically and angiographically 3 to 4 months postoperatively in order to fairly evaluate the telescoping anastomosis in terms of long-term patency, stenosis, and changes in the outer and inner walls at the anastomosis. All arterial grafts were patent 3 to 4 months postoperatively and there were no aneurysms at the anastomoses. Enlargement of the graft diameter was minimal. The rate of stenosis at the anastomosis was smaller than that 1-day postoperatively. Even though the thick arterial wall was initially inserted and the intimal hyperplasia was still present at the anastomosis 3 to 4 months postoperatively, the long-term stenosis was relatively mild due to the atrophy in the overlapped walls.     

New method for autogenous vein grafting with the telescoping anastomotic technique.

An experimental study was performed to examine whether a microsurgical telescoping anastomotic technique could be applied twice in one vessel, for use in autogenous vein grafting. The rat inferior epigastric vein was grafted into a defect created in the femoral artery. The original telescoping method of Lauritzen was used, with two additional suture placements, to allow anastomosis at both proximal and distal sites. By placing the four sutures symmetrically and carefully timing the removal of the proximal and distal clamps, we achieved a patency rate of 77.3%. This is a new method for autogenous vein grafting that may serve as a prototype for an easier and possibly faster vein grafting technique. Our results appear to indicate that complete coaptation of the severed vessel ends is not necessarily required for patency in microvascular repair.     

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.     

Assessment of the patency of microvascular venous anastomosis

There is an absence of data on the timing of occlusion of vessels after anastomosis, and on the possible subsequent reopening (recanalization) of these vessels. This lack of information may be an important factor in the wide discrepancies found among reported patency rates for laboratory microvascular repair. In this study, a total of 300 standard microsurgical anastomoses were performed on rat femoral veins. The patency of each anastomosis was assessed at regular intervals within a 2-week study period. These results showed that the majority of venous occlusions occurred within 1 day after repair. Recanalization of the occluded vein was first seen at day 3 postoperatively. Recanalization was observed over a 2-week postoperative period with increasing frequency. The authors conclude that the optimal time to assess the technical outcome of experimental venous patency is 1 to 2 days after the repair.     

Lymphatic vessel-to-isolated-vein anastomosis for secondary lymphedema in a canine model

To design a more rational and effective surgical method of performing lymphatic-venous anastomosis to treat secondary lymphedema of the lower extremities, the following experiments were conducted on three groups of dogs: group A underwent an end-to-side lymphatic node-to-vein anastomosis at the inferior vena cava; group B underwent a burying lymphatic vessel-to-vein anastomosis at the femoral vein; and group C underwent a burying lymphatic vessel-to-isolated-vein anastomosis at the femoral vein. In group C, the femoral venous segment was isolated by distal ligation and proximal valvuloplasty and the patency of the anastomosis was investigated by infusing yellow Microfils through the distal lymphatic vessel. The patency of the anastomosis was nil in group A by 10 days after the anastomosis, 40% in group B by 180 days; and 71.4% in group C by 180 days, respectively. Thus, we clinically applied the technique of lymphatic vessel-to-isolated-saphenous-vein anastomosis in a patient with secondary lymphedema of the bilateral lower extremities. A satisfactory reduction in the size of the limbs was achieved and there has been no further recurrence of cellulitis in the 42 months since her surgery. This study shows that lymphatic vessel-to-vein anastomosis is an effective technique for the surgical management of secondary lymphedema, so long as the anastomosis is completely protected from any contact with blood.     

Platelet aggregation inhibition in human umbilical vein grafts and negatively charged bovine heterografts.

Glutaraldehye-tanned human umbilical vein grafts (4 mm) and negatively charged bovine heterografts (4 mm) were placed as bypasses in the femoral arteries of 20 dogs randomized into 10 treated with aspirin and dipyridamole and 10 were not treated. Autogenous vein grafts were placed as controls. Platelet aggregation inhibition by aspirin and dipyridamole significantly improved the patency of human umbilical vein grafts from 10% to 60%. It had no effect on patencies of autogenous veins (100%) or on negatively charged bovine heterografts (0% patency). Inherent graft properties continue to play an important and sometimes overriding role in long-term graft patency in small vessel bypasses. Neointimal fibrous hyperplasia at both proximal and distal anastomoses again was shown to be intimately associated with late graft occlusions.     

Remote distal arteriovenous fistula to improve infrapopliteal bypass patency

The results of the use of prosthetic materials for femorocrural bypass surgery have been less than optimal. The creation of a distal anastomotic arteriovenous fistula to augment blood flow and velocity through the graft is well known. However, it may create turbulence at the anastomosis and steal blood flow away from the distal artery. A canine model was developed to evaluate the effect of fistula size on graft/arterial hemodynamics. In 16 patients we have constructed a distal arteriovenous fistula, which is remote from the distal anastomosis, and we studied the effect of such fistulas on bypass patency and distal arterial hemodynamics. Patients selected for this procedure had multiple previously failed reconstructions and limb-threatening ischemia and did not have usable autogenous vein. Femorotibial bypass graft reconstructions were performed with polytetrafluoroethylene followed by the creation of a side-to-side arteriovenous fistula 5 to 15 cm below the distal anastomosis in the same artery and accompanying veins. We have achieved a 1-year patency of 67% with a 75% limb salvage rate. We also serially measured blood flow and velocity within the bypass, the arteriovenous fistula, and the distal outflow vessel using duplex scanning after surgery. Mean estimated blood flow through the bypass during the immediate postoperative period was 264 ml/min, the arteriovenous fistula was 157 ml/min, and the distal artery was 19 ml/min. Unlike an arteriovenous fistula created at the distal anastomosis, a remote distal arteriovenous fistula not only increases graft blood flow but also augments native arterial blood flow between the distal anastomosis and fistula and thus may improve distal limb perfusion.     

Further Evaluation of the Circular Sequential Vein Graft Technique of Coronary Artery Bypass

Our study reports a series of circular sequential vein grafts in 21 patients with highly symptomatic triple-vessel coronary artery disease. Four or more distal anastomoses were done in each patient. Thirteen of the patients were restudied, and the results revealed a 97% patency rate for distal anastomoses (58 out of 60) at 4 to 13 months after operation. One patient died 2 months after operation. Postmortem examination revealed a desmoplastic, fibrotic reaction at the proximal anastomosis of the circular graft, with 3 of 4 distal anastomoses patent. Twenty of the 21 patients in this series are now alive with asymptomatic cardiac status 14 to 22 months after operation.The finding by Grondin and associates [1] of increased patency rate with this technique for distal anastomoses is confirmed. The circular sequential vein graft represents a particularly advantageous technique for patients in whom 4 to 6 distal anastomoses are needed for complete revascularization and in whom one or more vessels have limited runoff. The obvious disadvantage of this technique is that all distal anastomoses depend on a single proximal anastomosis.     

Femoropopliteal in situ saphenous vein bypass: Technical aspects and factors determining patency

The results and the factors influencing long-term patency rates in two technical variations of femoropopliteal «in situ» saphenous vein bypass procedures were evaluated retrospectively. Technique I (n=33) consisted of a limited approach to the saphenous vein, destruction of the valves with a Cartier stripper and no tributary ligation. Technique II (n=55) included complete exposure of the saphenous vein valvular destruction using Hall’s stripper and ligation of all tributaries. Early thrombosis was observed in 21% and 3.6% of cases in techniques I and II, respectively. The frequency of local complications was identical in both techniques (18%). Overall actuarial primary patency at 4 years was 70%. Secondary patency (including patency following reoperations for graft failure) was 88 % overall, 78.5% in technique I and 95% in technique II (p<0.05). The site of the distal anastomosis significantly influenced the four year cumulative patency rate (upper popliteal ?100%, lower popliteal ?93.6%, tibioperoneal vessels ?70.5%, p<0,05), whereas the number of patent leg vessels, the clinical stage of disease and the site of the proximal anastomosis (common femoral or superficial fernoral artery) did not. Results obtained with the in situ saphenous vein bypass using technique II were better than with technique I. Close follow-up and preventive reoperations clearly enhanced patency rates. The site of distal anastomosis significantly affected long-term results.