End-to-end versus end-to-side arterial anastomosis patency in microvascular surgery

The patency rates of microsurgical end-to-end and end-to-side anastomosis in the rat carotid artery were studied. Seventy end-to-end and seventy end-to-side arterial anastomoses, using 10-0 nylon interrupted sutures, were performed on 140 Sprague-Dawley rats. Findings indicated 100% patency in end-to-end as well as end-to-side immediately and 1 week post-anastomosis. This investigation suggests that there is no significant advantage between the methods studied based on vessel patency alone. The decision to perform an end-to-end vs. an end-to-side arterial anastomosis should be based upon the clinical circumstances encountered, since no significant difference in patency rates exists. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:125-128 1998     

Mechanical and histologic changes in canine vein grafts

Mechanical and histological studies were performed on dog femoral veins after their implantation as grafts to bypass the ligated femoral arteries. The vein grafts dilated rapidly after implantation with 90% of maximum dilation occurring at 4 weeks. Both the native veins and the vein grafts were highly compliant up to 35-50 mm Hg, but were virtually nondistensible at higher pressures. When implanted with end-to-side anastomoses (end of vein to side of artery), the compliance of the anastomotic region resembled that of the artery rather than that of the vein. This was due to the distensibility of the artery at arterial pressure, as compared with the almost rigid vein. Histologic examination showed that intimal hyperplasia was greater after end-to-side anastomosis than after end-to-end anastomosis (P less than 0.05) and that this increased hyperplasia was reduced by treatment with aspirin and dipyridamole (P less than 0.05). By contrast, medial thickening was increased in all grafts compared with native veins (P less than 0.05), but was not different in end-to-end, end-to-side, and aspirin/dipyridamole-treated end-to-side grafts. These data suggest that intimal hyperplasia and medial thickening are separate responses to different stimuli.     

Distal anastomotic intimal hyperplasia: biogenesis and etiology

Anastomotic intimal hyperplasia occurred exclusively at the heel and the toe plus the floor of the distal end-to-side anastomosis of canine autologous femoro-femoral bypass (n = 14) and not in the end-to-end carotid or femoral interposition graft (n = 14). The occurrence of anastomotic intimal hyperplasia in the absence of compliance mismatch in an autologous bypass suggests that the geometry of the end-to-side anastomosis is primarily responsible for intimal hyperplasia formation. It is believed that because an end-to-side distal anastomosis is not a natural occurrence it is conductive to turbulent flow. The latter causes endothelial injury which in turn allows platelet growth factor to incite subendothelial myoblasts in extracellular matrix synthesis and intimal hyperplasia formation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) identify myofibroblasts and fibrocollagenous matrix as the dominant cellular and extracellular substances in anastomotic intimal hyperplasia.     

End-to-side and end-to-end vascular anastomoses with a carbon dioxide laser

This study was designed to compare anastomoses performed with a carbon dioxide laser and conventional anastomoses performed with 7-0 polypropylene suture. In each of 80 rabbits, the divided left carotid artery was anastomosed by a continuous suture technique and the right carotid was anastomosed with a carbon dioxide laser. In each of 40 additional rabbits, both end-to-end and end-to-side laser anastomoses were performed on the same carotid artery. The laser technique involved the placement of three stay sutures (end-to-end technique) or four stay sutures (end-to-side technique) of 7-0 polypropylene and an everting laser seal at a power level of 65 mW. The 1-year overall patency rate was 98% (78/80) in laser anastomoses, 79% (63/80) in suture anastomoses, and 95% (38/40) in combined end-to-end and end-to-side laser anastomoses. Microscopic findings in laser anastomoses demonstrated degeneration of collagen and protein in the adventitia and media, but much less intimal injury than in suture anastomoses, with reendothelialization beginning earlier (within 7 days after anastomosis as compared with 2 to 4 weeks). The tissue tensile strength at 1 hour was less in laser anastomoses than in suture anastomoses, but the laser anastomoses still withstood an intraluminal pressure load of 380 mm Hg. Laser anastomosis improved the microscopic and histologic appearance of the intimal layer, allowing for rapid early reendothelialization and resulting in excellent patency rates.     

Comparison of nylon and polypropylene sutures in a microvenous thrombosis model

Thrombosis rates of femoral end-to-end microvenous anastomoses with nylon and polypropylene sutures (9–0 suture, 70 μ needle) were compared in a microvenous thrombosis model. The vessel injuries were produced during anastomosis by using a suture with a knot 1 cm from the needle. Anastomotic thrombosis rates were assessed by visual inspection and strip test at 24 hr postoperatively. Low thrombosis rates (0% and 20%, respectively) of anastomoses with both unknotted nylon and unknotted polypropylene sutures were obtained. Anastomoses with knotted nylon and polypropylene sutures resulted in 65% and 45% thrombosis rates, respectively. Statistical analyses showed that there were no significant differences between thrombosis rates, both in anastomosis performance with unknotted nylon and polypropylene sutures (P > 0.05) and with knotted nylon and polypropylene sutures (P > 0.05), while there were significant differences between the thrombosis rate using unknotted sutures and knotted sutures (P<0.01). It was concluded that vascular injury, not suture material, is the main factor leading to thrombosis in this model. © 1995 Wiley-Liss, Inc.     

End-to-end and end-to-side microvascular anastomoses: a comparative study

The decision to use an end-to-end versus end-to-side anastomosis remains a controversial issue in microvascular surgery, although it is generally accepted that certain clinical situations require skills in both techniques (eg, vessel size discrepancy or the need to preserve donor vessel distal flow). Using rats, this investigation presents a unique free flap model comparing not only arterial end-to-end and end-to-side anastomoses, but venous anastomoses as well. There were 15 animals in each anastomosis group with a greater than 80% flap survival rate in each group. This supports findings of earlier studies that suggested no difference in survival when these two anastomosis types were compared. Equally important was the assessment of dermofluorometry as an immediate postoperative perfusion monitoring device. In this model, fluorometry was not found to be useful for predicting flap viability in an early period after completion of the anastomoses.     

Computational investigations of a new prosthetic femoral-popliteal bypass graft design

OBJECTIVE: Prosthetic femoral-popliteal bypasses are performed by using an end-to-side anastomosis, and disease can develop at the distal end; this can lead to poor long-term patency rates. Disturbed flow characteristics are hypothesized as being a major factor in promoting disease development. The objective of this study was to propose a new prosthetic femoral-popliteal bypass graft configuration specifically engineered to reduce or eliminate certain disease-influencing factors that act on the host artery. METHODS: The proposed device contains a streamlined bifurcation toward its distal end that results in two end-to-end anastomoses, rather than the single end-to-side anastomosis in the traditional procedure. Comparisons are made between idealized representations of it and the traditional end-to-side anastomosis for specific femoral artery flow rates. Qualitative results in the form of velocity vector plots and wall shear stress contour plots are compared, and quantitative results examine the wall shear stress magnitudes and gradients along the bed and roof of each graft model. RESULTS: Velocity vector plots through each junction suggest that the proposed graft configuration promotes streamlined flow and helps to reduce the magnitude of flow recirculation and separation regions associated with the traditional end-to-side anastomosis. At peak velocity, the flow separation region distal to the toe is eliminated, as evidenced by the change in toe wall shear stress from -0.2 Pa in the traditional anastomosis to +0.5 Pa in the proposed device. Normal fully developed flow occurs sooner in the distal host artery, approximately 15 mm downstream from the toe, unlike 20 mm in the conventional case. The proposed design results in reductions of up to 58% in peak wall shear stress and 86% in peak wall shear stress gradient during the decelerative phase of the femoral pulse in the vicinity of the artery bed below the toe. CONCLUSIONS: In vitro tests on the proposed device suggest that the streamlined nature of blood flow through the junction does result in less disturbed hemodynamic conditions within the host artery junction. Abnormal wall shear stress magnitudes and gradients are reduced, and normal fully developed flow occurs sooner in the distal host artery. This suggests that the proposed graft may have design attributes that are relevant in the search for increased prosthetic femoral-popliteal bypass graft patency rates. A drawback of the proposed device is that significant flow recirculation and separation exist within the prosthesis itself. CLINICAL RELEVANCE: The search for a viable alternative to traditional end-to-side anastomosis for prosthetic femoral-popliteal bypass procedures is ongoing. Prosthetic femoral-popliteal bypass procedures have low long-term patency rates, and there is a need for methods that increase the life span of the procedure. Although research is progressing on a variety of different fronts, this study is significant in that it reports on in vitro tests on a potential device that may increase bypass patency. The device is simple, may be manufactured from clinically proven materials, does not require any additional training in its use, and combines attributes of end-to-side anastomoses with those of end-to-end anastomoses. In addition, the design concept behind the device, the natural bifurcation, may be relevant in other aspects of cardiovascular surgery.     

Manageable microsurgical technique for creating an opening in small vessels for end-to-side anastomosis

The end-to-side anastomosis is one of the most useful techniques in microsurgery. It creates a recipient opening for the donor, keeps the donor vessel intact, and does not interrupt distal blood flow, compared to the end-to-end anastomosis technique. The end-to-side anastomosis is consequently becoming more acceptable in reconstructive microsurgery. The author describes a manageable microsurgical technique for creating recipient vessel openings in small vessels for end-to-side anastomoses.     

Clinical experience with non-penetrating vascular clips in free-flap reconstructions.

To date, the gold standard for performing a microvascular anastomosis has been the penetrating suture with attached needle. During the last two decades, non-penetrating techniques have been introduced, including the Unilink system for end-to-end anastomoses, and the VCS clip-applier system for both end-to-end and end-to-side anastomoses. The aim of this study was to compare the results of different techniques used to create microvascular anastomoses in free-flap reconstructions. Between January 1995 and October 1999, we performed 474 microvascular anastomoses in 216 consecutive free-tissue transfers. The anastomosis techniques included manual sutures (42%), Unilink rings (34%) and VCS clips (24%). Seven combined sutured-clipped anastomoses were excluded from further analysis. The mean anastomotic time when rings were applied was significantly shorter than when using clips (P 0.0001) or sutures (P 0.0001). Venous anastomoses using clips took less time than those using sutures (P 0.05). There were 19 anastomotic failures, all of which lead to early flap failure. Ten flaps were salvaged by early reoperation; nine flaps were lost. Three more flaps were lost as a result of other causes, bringing the flap survival rate down to 94.4%. Early flap failure was caused by failure of the arterial anastomosis in eight cases; all of them were sutured (these represented 5% of all arterial anastomoses with sutures). None of the clipped arterial anastomoses failed. Early flap failure was caused by failure of the venous anastomosis in 11 patients. Three of these anastomoses were sutured (representing 6% of all venous anastomoses with sutures), seven were anastomosed with rings (representing 5% of all venous anastomoses with rings) and one was clipped (representing 2% of all venous anastomoses with clips). Both the VCS clip-applier system and the Unilink system are easy to handle and allow fast microvascular anastomoses without intraluminal penetration. The patency rate of clipped vessels is at least as good as the patency rates of vessels anastomosed using sutures or rings.     

端-侧吻合主动脉重建技术在婴儿主动脉缩窄合并心内畸形一期矫治术中的应用

目的比较婴儿主动脉缩窄(CoA)合并心内畸形一期矫治手术中采用端-侧吻合技术与扩大的端-端吻合技术的临床效果。方法 2008年1月至2011年7月广州市妇女儿童医疗中心共63例婴儿CoA合并心内畸形行一期矫治手术,按主动脉重建时的技术方法不同将63例患者分为两组,端-端吻合组:24例,男17例,女7例;年龄(4.6±2.9)个月,应用扩大的端-端吻合技术行手术治疗;端-侧吻合组:39例,男24例,女15例;年龄(3.4±2.6)个月,应用端-侧吻合技术行手术治疗。比较两组患者术后早期上、下肢动脉收缩压压差和围术期相关并发症发生情况。结果端-侧吻合组新生儿比率(23.1%vs.4.2%;χ2=3.979,P=0.045)、术前24 h内酸中毒比率(15.4%vs.0%;χ2=4.080,P=0.048)均高于端-端吻合组。术后端-端吻合组无死亡,端-侧吻合组死亡1例(2.6%)。端-侧吻合组术中停循环时间明显短于端-端吻合组[(18.6±2.7)min vs.(23.4±3.7)min,F=14.617,P=0.000]。端-端吻合组入心脏监护室(CICU)时上、下肢动脉收缩压压差<5 mm Hg、5～15 mm Hg、>15 mm Hg患者分别占20.8%、45.8%和33.3%,端-侧吻合组分别占97.4%、2.6%和0%,两组间差异有统计学意义(χ2=40.380,P=0.000)。术后24 h端-端吻合组上、下肢动脉收缩压压差<5 mm Hg、5～15 mm Hg、>15 mm Hg患者分别占45.8%、41.7%和12.5%,而端-侧吻合组占100%、0%和0%,两组间差异有统计学意义(χ2=26.620,P=0.000)。随访62例,随访时间2～36个月,所有患者均无血管瘤形成,无需再次手术处理的主动脉再狭窄。结论在婴儿CoA合并心内畸形的一期矫治手术中,与扩大的端-端吻合技术相比较,应用端-侧吻合技术可以安全、有效地显著降低术后早期出现的残余梗阻。     

Comparison of 10-0 polypropylene and 10-0 nylon sutures in rat arterial anastomosis

The selection of suture materials is an important factor in further improving the results of microsurgical operations. In this study, two kinds of nonabsorbable suture materials, 10-0 polypropylene and 10-0 nylon monofilament, were compared in end-to-end anastomosis of 66 femoral arteries of adult rats. Both suture types were of identical size (70 μm needle/28 μm suture) and each artery received eight sutures. The vessels were harvested at various intervals from 2 hr to 180 days postoperatively and were evaluated by pathology, radiology, and tensile strength test. The results show that both sutures are capable of achieving excellent long-term patency (100%) of anastomosed sites. Polypropylene suture was equivalent to nylon in mechanical integrity of the anastomosis sites but was superior in handling, knotting, and biocompatibility. These physical and biological properties of polypropylene sutures may offer the benefits of diminished early and late complications at anastomosis sites and reduced operation time. Enhancement of contrast against surrounding tissue may make polypropylene a superior alternative to nylon sutures for microsurgical use. © 1993 Wiley-Liss Inc.     

Effects of needle shape on the integrity of the vascular endothelium

Summary Lesions generated by the passage of micro-needles through vessel walls are of concern because any lesion may significantly alter hemodynamics of an anastomosis. To study this problem, three different needles were tested on the exposed carotid arteries of 30 rats: the 100 taper point, the 100 cutting point, and the 75 taper point. Trauma generated by the penetration of needles was tested first as the needle and its attached suture was passed through the vessel, then the suture was left in place. One hour after penetration, the arteries were prepared for scanning electron microscopy.Differences between the 100 taper point and the 75 taper point were significant in terms of size and extent of lesions. An arc of endothelial cells surrounding the wounds showed flattening, tissue destruction and clotting. To minimize endothelial trauma, taper point needles are superior to cutting needles. The 100 cutting needle caused damage to the vessel wall in tissue cutting on needle penetration, causing a slit-like incision, and in aggregation of platelets at the puncture site.Supported in part through an American Heart Association Student Clerkship in Cerebrovascular Disease Award, 1981. Additional support received from the Bauervic Foundation, West Bloomfield, Michigan and Sheldon Hayes Stroke Fund, Detroit, Michigan and Medical Materials & Devices, Inc., Pittsburgh.     

Experimental laser-assisted end-to-side microvascular anastomosis

The authors present a new technique of end-to-side microvascular anastomosis in a rat carotid artery model, employing a milliwatt CO2 laser. Both carotid arteries were isolated and approximated in an end-to-side fashion by the placement of four 10-0 nylon stay sutures. The milliwatt CO2 laser was used to effect vessel anastomosis between the sutures, using 70-100 mW of power. Animals were killed 8 weeks postoperatively. Angiography of each anastomosis was performed in all animals. All anastomoses were then harvested, and submitted for histological analysis. Anastomotic patency was 100%, both intraoperatively and angiographically. There was no evidence of intravascular thrombus, anastomotic stenosis, or pseudoaneurysm formation. Early in the experiment, some anastomoses showed localized dilatation at the anastomotic site. The histologic changes at the anastomotic site are described. Laser-assisted microvascular anastomosis is a feasible technique, and a potential alternative to conventional suture techniques.     

改进的套袖法吻合肾动脉建立大鼠原位肾移植模型

目的 观察改进的套袖法吻合肾动脉用于大鼠肾移植的可行性.方法 选择F344大鼠和Lewis大鼠分别作为肾移植的供、受者.切取供者左侧肾脏时,先剪断输尿管,然后阻断肾动、静脉水平上下的腹主动脉和下腔静脉,靠近下腔静脉剪断左肾静脉根部,经腹主动脉注入含肝素的4℃生理盐水对供肾进行原位灌洗后,靠近腹主动脉剪断肾动脉根部,取出供肾,放入4℃生理盐水中保存.切除受者左侧肾脏时,尽可能长的保留肾动、静脉以利于吻合.供肾植入时,采用改进的套袖法:用显微镊轻轻扩张供肾动脉后,协助显微持针器将针从供肾动脉血管外向血管内穿入,并从血管断端穿出第1针;接着穿入受者肾动脉断端,从受者肾动脉腔内向腔外穿出第2针;然后再从供肾动脉腔内、靠近第1针进针点处向腔外穿出,并与第1针的另外一端打结,此时受者的肾动脉已套入供肾动脉内;将供肾动脉边缘与受者肾动脉外膜固定2针,2针呈180度对角.供、受者的肾静脉及输尿管均行端端吻合.术后5 d内.若受者死亡,则认为手术失败.结泉共行肾移植20次,整个手术耗时70～90 min,供肾热缺血时间为4～9 s,冷缺血时间为30～40 min,肾动脉吻合用时(4.6±0.6)min,肾静脉吻合用时(11.8±1.2)min,输尿管吻合用时(12.2±1.4)min.术后5 d内,受者不明原因死亡1只,存活19只,手术成功率为95%.结论 采用改进的套袖法吻合肾动脉具有便捷、易于掌握、可靠及实用等优点,大鼠肾移植的成功率较高.     

Use of fibrin sealant for reinforcing arterial anastomoses

Despite improvements in needles, sutures, and technique, hemorrhage remains a problem in cardiovascular surgery. In this study conventional vascular suture lines and suture lines reinforced with fibrin sealant are compared for blood loss and burst strength. Bilateral femoral arteries in 20 dogs were divided at 50% of their circumference and repaired with six 6-0 polypropylene sutures. Ten animals were systemically heparinized (3 mg/kg), and 10 were not on anticoagulants. The right femoral artery anastomosis was treated with fibrin sealant in all animals, and the left suture line served as the control. Three minutes after initiation of the sealing procedure, blood flow was reinstituted in both femoral arteries. After 3 minutes a significant difference in blood loss between the conventional suture technique and fibrin-reinforced anastomoses was noted in both heparinized (12.1 +/- 2.79 vs. 0.13 +/- 0.06 ml/min; p less than 0.01) and nonheparinized dogs (8.45 +/- 1.37 vs. 0.20 +/- 0.08 ml/min; p less than 0.001). After 30 minutes volume inflow and pressure catheters were inserted into snared compartments encompassing the femoral artery anastomosis. Continuous pressure recordings during volume loading with normal saline solution demonstrated increased bursting pressures of the fibrin-sealed suture lines in both the heparinized (317.5 +/- 13.18 vs. 135 +/- 23.17 mm Hg; p less than 0.001) and nonheparinized animals (474.5 +/- 26.82 vs. 311 +/- 29.31 mm Hg; p less than 0.001). Histologic examination revealed no fibrosis or foreign body reaction and complete resorption of the fibrin sealant within 3 weeks. Fibrin sealant, a powerful hemostatic agent produced from human donors not suffering from hepatitis, decreases blood loss and strengthens suture lines.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microanastomotic response to needle and suture size

This study was performed to examine the microanastomotic response to needle and suture size, comparing the 10-0 (75 mu needle/22 mu suture), the 11-0 (50 mu needle/18 mu suture), and a new modified 11-0 which has a 30 mu needle and a 14 mu suture. Each artery received five full thickness sutures of either suture. The vessels were harvested at 0, 7, 14, 21, and 28 days and checked for patency, aneurysm formation, and gross strength. Histologic slides and scanning electron micrographs (SEM) were made at 7, 21, and 28 days postoperatively. The 11-0 with the 30 mu needle gave better patency rates, less incidence of aneurysm formation, and as good or better recovery in gross strength, when compared with the 10-0 75 mu needle. Histologically and by SEM, the 11-0 with the 30 mu needle was far superior to the other two larger sized sutures, showing less trauma and inflammation. The use of the modified 11-0 suture with the 30 mu needle is advantageous in anastomosis of vessels 1 mm or smaller.     

A hemodynamic study of the effects of arterial anastomoses with interrupted simple versus horizontal mattress sutures on rat epigastric flap perfusion

The effects of interrupted simple versus horizontal mattress sutures and of the internal diameter of the arterial pedicle at the level of the anastomosis on rat epigastric flap perfusion were investigated. In the first group, a microclip was applied to the femoral artery for 30 minutes. In the second group, the artery was cut, and a classic 7- to 8-suture microarterial end-to-end anastomosis was performed. In the third group, the artery was cut, and a microarterial end-to-end anastomosis with 3 horizontal mattress sutures at 120-degree intervals was performed. Perfusion was measured using a laser Doppler flowmeter (Periflux 2B, Perimed, Sweden) at 3 zones of the flap at 30 and 60 minutes and at 21 days after the procedure. Internal vascular diameters were measured histopathologically. Perfusion was better in the control group than in the experimental groups. However, the internal vascular diameters were greater with the classic method than with the new method, and the perfusion did not differ statistically in the anastomosis groups. In conclusion, even when significant narrowing develops at the anastomosis, flap viability is not affected.     

Anterior cerebral artery reconstruction

Anterior cerebral artery end-to-end, end-to-side, and side-to-side anastomoses and grafting procedures including bypass and interposition using segments of the posterior cerebral artery harvested from the same specimen were performed. The reconstruction procedures were accomplished experimentally with the A1 and A2 segments of the anterior cerebral artery, the recurrent artery of Heubner (RAH), and the orbitofrontal and frontopolar arteries in end-to-end or end-to-side anastomosis to the A1 segment. Side-to-side anastomoses between both A2 or A3 segments were completed without difficulty. We utilized the anatomical and experimental reconstruction data in the performance of three surgical procedures for aneurysms in this area. An A1 to A2 end-to-end anastomosis, an A2 to A2 end-to-side anastomosis, and an end-to-end anastomosis of the RAh were performed with no technical difficulties or complications. This study shows the feasibility of these microvascular reconstruction procedures in the anterobasal part of the interhemisphere, where cerebral aneurysms frequently develop.     

Comparison of continuous and interrupted suture techniques in microvascular anastomosis.

We evaluated the efficacy of the continuous suture technique (CST) in arteries and veins with varying external diameters (ED). In study 1 a direct end-to-end anastomosis was performed in 5 groups of animals (n = 15 in each group): group 1, rabbit carotid artery (ED, 1.8-2.0 mm); group 2, rabbit femoral artery (ED, 1.4-1.6 mm); group 3, rat femoral artery (ED, 0.7-0.9 mm); group 4, rabbit femoral vein (ED, 2.0-2.2 mm); and group 5, rat femoral vein (ED, 1.0-1.2 mm). In study 2 a graft from the femoral vein was interposed into the carotid artery, with a ratio of the diameter of graft to artery of 1.3:1 in the rats (group 6, n = 12) and 1:1 in the rabbits (group 7, n = 12). In each animal the vessel on one side was repaired using CST and the opposite vessel using the interrupted suture technique. Vessel samples were harvested 1, 2, and 4 weeks after anastomosis. The CST significantly reduced anastomosis time by up to 47% in arteries and 41% in veins. Bleeding time and blood loss were also significantly reduced with CST. Similar results were found in study 2. The total thrombosis rate was 8%, but no significant patency difference was noted between the CST and the interrupted suture technique in any vessel category. We conclude that the CST is a reliable and time-saving procedure in microvascular anastomosis of arteries with diameters greater than 0.7 mm and of veins with diameters greater than 1.0 mm.     

Thrombotic effect of purposeful back-wall stitch for end-to-side microarterial anastomosis in rats

The accidental placement of a back-wall stitch is a mistake easily made by microsurgeons during an end-to-side (ETS) anastomosis, which is technically more difficult compared with an end-to-end (ETE) anastomosis. The thrombogenic effects of a back-wall stitch may aggravate the already existing turbulence and therefore thrombus-prone ETS anastomosis. We investigated this dangerous combination by applying a purposeful back-wall stitch model (PBWS) in an ETS microarterial anastomosis model in various configurations the rat carotid and femoral arteries. We performed femoral and carotid artery bypass grafts via two ETS anastomosis. Carotid (n=28) and femoral (n=28) artery groups were equally divided into four different subgroups according to PBWS placement: Control (no PBWS) and 30-degree, 60-degree, and 90-degree subgroups with PBWS located at 30, 60, and 90 degrees, respectively. We found that there were no significant patency differences with respect to vessel type, PBWS placement, or time of assessment. The results of our current study and previous studies demonstrate that a PBWS in the ETS anastomosis does not have a major effect on thrombus formation. We think that an inadvertent back-wall stitch in the ETS anastomosis may not be a significant cause of thrombosis alone but in combination with retained thrombogenic material into lumen can contribute to thrombus.