In vitro laser recanalization of chronically occluded prosthetic grafts.

Polytetrafluoroethylene (PTFE) and Dacron grafts were implanted in canine femoral and carotid arteries using PTFE and Prolene suture, respectively. Arteries containing occluded grafts were explanted and laser recanalization was attempted in vitro. Laser recanalization was successful in 78% of PTFE grafts compared to 30% of Dacron grafts. Recanalization was complete (residual stenosis less than 5%) in opened PTFE grafts, whereas residual stenosis averaged 60% in recanalized Dacron grafts. PTFE graft/PTFE suture anastomotic tensile strength was unchanged after recanalization, while Dacron graft/Prolene suture anastomotic tensile strength decreased significantly. In addition, anastomotic bursting pressure was significantly higher for lased PTFE grafts with PTFE sutures (300 mg Hg) compared to lased Dacron grafts with Prolene sutures (70 mm Hg). Chronically occluded PTFE grafts with PTFE suture can be safely and effectively opened by laser recanalization. In contrast, attempted laser recanalization of Dacron grafts sutured with Prolene suture is seldom successful, significantly weakens the graft artery anastomosis, and should be avoided.     

Reduced anastomotic bleeding using new sutures with a needle-suture diameter ratio of one

Reduction of blood loss from a vascular anastomosis, especially when one is using a polytetrafluoroethylene (PTFE) graft, is of great interest; even when a technically perfect anastomosis has been performed, there can still be significant and often bothersome bleeding from the needle holes. Currently, sutures have a needle-to-suture ratio of 2:1 or 3:1. Two new sutures, one made of PTFE and the other of polypropylene, were designed to have a needle-to-suture diameter ratio of 1:1. Theoretically, this allows the suture to completely fill the graft needle hole and control bleeding. These sutures were evaluated in a heparin-treated canine in vivo model to measure graft needle-hole bleeding. The materials were also tested by an independent laboratory to compare the basic physical characteristics. Twenty centimeters of 6 mm PTFE graft was interposed in an end-to-end fashion to the infrarenal canine aorta. The graft was then transected at its midpoint and a series of end-to-end, graft-to-graft anastomoses were performed with alternate experimental and control sutures. The experimental PTFE suture bled a mean of 12.46 ml per anastomosis. The experimental polypropylene bled 4.32 ml per anastomosis, while a control suture of polypropelene with a needle-to-suture ratio of 1.94 (5-0 prolene with a C-1 needle), produced a mean blood loss of 33.35 ml per anastomosis. These data are based on a total of 82 anastomoses. The results were analyzed with a two-tailed paired t test. As the data indicate, both experimental sutures allowed significantly less bleeding than the controls (p = .05). The testing of physical properties of the suture included diameter, tensile strength, needle pull-off strength, and elongation percent and were performed by an independent laboratory. These findings are included along with subjective evaluations of the sutures' handling qualities. We believe that sutures produced with needle-to-suture ratios of 1:1 greatly reduce graft needle-hole bleeding and will be a useful addition to the vascular surgeon's armamentarium.     

Suture technique and para-anastomotic compliance

We previously described a para-anastomotic hypercompliant zone (PHZ), located 3 to 4 mm from end-to-end continuous anastomoses in canine femoral arteries, in which arterial compliance first increases approximately 50% above adjacent reference values before falling to a minimum at the anastomosis. To determine if PHZ is affected by suture technique, 16 interrupted and 21 continuous end-to-end anastomoses were studied. Pulsed ultrasound was used to obtain detailed longitudinal profiles of compliance and diameter vs. distance, at 1 mm intervals within a 2 cm region centered at the anastomoses. Both compliance and diameter at the anastomosis were lower in continuous compared with interrupted anastomoses (p less than 0.003). The PHZ was present in 86% of continuous but in only 50% of interrupted anastomoses (p less than 0.03). The site of peak compliance averaged 3.8 +/- 1.2 mm from the anastomosis and was independent of suture technique. The increase in peak compliance at the PHZ, when normalized to adjacent references values, was the same in continuous and interrupted anastomoses. PHZ augments any preexisting compliance mismatch between artery and graft, which may contribute to the development of para-anastomotic subintimal hyperplasia. Interrupted anastomoses, which create a smaller compliance mismatch than do continuous and have a lower incidence of PHZ, may be preferred in certain settings.     

The direct effect of graft compliance mismatch per se on development of host arterial intimal hyperplasia at the anastomotic interface

To study thedirect andsole effect of compliance mismatch on anastomotic intimal hyperplasia of the host arterial wall and to minimize possible confounding factors, dogs with a low thrombotic potential were selected as experimental subjects. Externally supported 6 cm × 5 mm Dacron grafts with a compliance value of approximately 1/300 of the host artery were implanted into the carotid arteries with end-to-end anastomoses on one side and end-to-side anastomoses on the other. The control graft was an autogenous carotid artery segment 4 cm in length transplanted into the femoral artery. Eight cases (24 grafts) were studied for 1 year and three (nine grafts) for 6 months. All were patent throughout the study period except for two noncompliant grafts with end-to-end anastomoses; thrombosis was the documented cause of occlusion. For the patent grafts, follow-up arteriograms showed no progressive narrowing of noncompliant anastomoses. Whether compliant or noncompliant, light microscopy studies showed slight intimal thickening within 1 to 2 mm of the anastomotic line, possibly the result of the normal healing response to stitch and surgical trauma. Quantitatively, 22 measurements representing longitudinal and circumferential thickness of the neointima were taken at each of the 40 patent noncompliant and 22 patent compliant control anastomoses. There was no statistically significant difference in anastomotic neointimal thickness in compliant and noncompliant grafts or for the different implantation periods. These data suggest that graft/host artery compliance mismatch does not cause arterial intimal hyperplasia at the anastomotic interface.Presented at the Seventh Annual Meeting of the Western Vascular Society, Maui, Hawaii, January 11–15, 1992.     

A comparison of para-anastomotic compliance profiles after vascular anastomosis: nonpenetrating clips versus standard sutures

PURPOSE: Anastomotic compliance is an important predictive factor for long-term patency of small diameter vascular reconstruction. In this experimental study we compare the compliance of continuous and interrupted sutured vascular anastomoses with those using nonpenetrating clips. METHODS: Both common carotid arteries in nine goats (average weight, 57 +/- 5.7 kg) were transected, and end-to-end anastomoses were constructed with nonpenetrating clips or polypropylene sutures. The latter were applied with both interrupted and continuous techniques. Intraluminal pressure was measured with a Millar Mikro-tip transducer, and vessel wall motion was determined with duplex ultrasound equipped with an echo-locked wall-tracking system. Diametrical compliance was determined. Environmental scanning electron microscopy was performed on explanted anastomoses. RESULTS: There was a reduction in anastomotic compliance and associated proximal and distal para-anastomotic hypercompliant zones with the use of all techniques. However, compliance loss was significantly less in those anastomoses with clips and interrupted sutures when compared with continuous suture (P <.001). Furthermore, the total compliance mismatch across anastomoses with continuous sutures was significantly greater than those with clips or interrupted sutures (P <.05). The mean time for constructing clipped anastomoses was 5.7 +/- 1.4 minutes, which was significantly less than either continuous (P <.0001) or interrupted sutures (P <.0001). Furthermore, environmental scanning electron microscopy demonstrated minimal intimal damage with good intimal apposition in the clip group. CONCLUSION: Anastomoses performed with nonpenetrating clips resulted in improved para-anastomotic compliance profiles and reduced intimal damage when compared with those with polypropylene sutures. These benefits may enhance long-term graft patency by reducing the risk of anastomotic intimal hyperplasia.     

Animal model to compare the effects of suture technique on cross-sectional compliance on end-to-side anastomoses.

OBJECTIVE: An animal model has been developed to compare the effects of suture technique on the luminal dimensions and compliance of end-to-side vascular anastomoses. METHODS: Carotid and internal mammalian arteries (IMAs) were exposed in three pigs (90 kg). IMAs were sectioned distally to perform end-to-side anastomoses on carotid arteries. One anastomosis was performed with 7/0 polypropylene running suture. The other was performed with the automated suture delivery device (Perclose/Abbott Labs Inc.) that makes a 7/0 polypropylene interrupted suture. Four piezoelectric crystals were sutured on toe, heel and both lateral sides of each anastomosis to measure anastomotic axes. Anastomotic cross-sectional area (CSAA) was calculated with: CSAA = pi x mM/4 where m and M are the minor and major axes of the elliptical anastomosis. Cross-sectional anastomotic compliance (CSAC) was calculated as CSAC=Delta CSAA/Delta P where Delta P is the mean pulse pressure and Delta CSAA is the mean CSAA during cardiac cycle. RESULTS: We collected a total of 1200000 pressure-length data per animal. For running suture we had a mean systolic CSAA of 26.94+/-0.4 mm(2) and a mean CSAA in diastole of 26.30+/-0.5 mm(2) (mean Delta CSAA was 0.64 mm(2)). CSAC for running suture was 4.5 x 10(-6)m(2)/kPa. For interrupted suture we had a mean CSAA in systole of 21.98+/-0.2 mm(2) and a mean CSAA in diastole of 17.38+/-0.3 mm(2) (mean Delta CSAA was 4.6+/-0.1 mm(2)). CSAC for interrupted suture was 11 x 10(-6) m(2)/kPa. CONCLUSIONS: This model, even with some limitations, can be a reliable source of information improving the outcome of vascular anastomoses. The study demonstrates that suture technique has a substantial effect on cross-sectional anastomotic compliance of end-to-side anastomoses. Interrupted suture may maximise the anastomotic lumen and provides a considerably higher CSAC than continuous suture, that reduces flow turbulence, shear stress and intimal hyperplasia. The Heartflo anastomosis device is a reliable instrument that facilitates performance of interrupted suture anastomoses.     

Polydioxanone suture material in growing vascular anastomoses. Experimental study

We studied the growth of vascular anastomoses after use of absorbable suture material in 21 piglets. In six piglets, end-to-end anastomosis of the infrarenal aorta was performed with 5-0 continuous polypropylene suture; stenosis developed in two of these animals. In 15 piglets, continuous polydioxanone sutures were used for the anastomoses, and no stenosis developed. On the contrary, 14 of these anastomoses showed some degree of dilation at the anastomotic site. Burst testing to 300 mm Hg caused no disruption. On histologic examination, only scar tissue at media and intima with good degree of differentiation was noted. Growth of a vascular anastomosis after use of absorbable polydioxanone suture material seems to be perfectly possible without stricture formation. Because the growing process takes years instead of months in human beings, with obviously less stress at the anastomotic site, it is likely that dilatation at the level of the suture line will not occur in clinical use.     

Laser-Fused Biologic Vascular Graft Anastomoses

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n;eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance. The technique may provide a method to limit development of anastomotic stenosis by eliminating the foreign body reaction. In addition, the canine arteriovenous model used in these experiments develops aggressive intimal lesions at the venous anastomosis within weeks and may be used to evaluate the effect of anastomotic technique on the development of this lesion.     

Increased compliance near vascular anastomoses

Mismatch in mechanical properties (compliance mismatch) between host artery and prosthetic graft has been suggested as a cause of graft failure, but no mechanism linking the two has been identified. With the use of a simplified model based on isocompliant arterial grafts, pulsed ultrasound was used to generate detailed longitudinal profiles of diameter and compliance near the anastomoses. These longitudinal profiles revealed that although arterial diameter decreases monotonically to a minimal level at an anastomosis, arterial compliance first increases by approximately 50% before decreasing to 60% of the control value. This para-anastomotic hypercompliant zone (PHZ) is centered 3.6 mm from the anastomosis. PHZ also occurs in the artery adjacent to compliant or stiff grafts and is probably caused by transmitted effects of the suture line on the arterial wall. PHZ adds to any mismatch in compliance that already exists between artery and graft and can produce a compliance mismatch even between an artery and a nominally isocompliant prosthetic graft. It is hypothesized that PHZ, a region of increased cyclic stretch, promotes subintimal hyperplasia near anastomoses and may thus be a link between the mechanical properties of arteries and the failure of bypass grafts.     

End-to-end oesophageal anastomosis: an experimental study in the rat

To study the effects of suture material, calibre and tension on the end-to-end oesophageal anastomosis, the cervical oesophagus of the rat was resected for 2.5 mm, 7.5 mm and 12.5 mm respectively in three groups of 60 rats each. End-to-end anastomosis was performed with either 6/0 silk, 6/0 polypropylene or 9/0 polypropylene sutures. There was no postoperative leakage. Mortality was mainly due to hair bolus obstruction at the site of anastomosis. There was no difference in mortality and anastomotic stenosis between groups with different resection lengths. Within each group, however, mortality and anastomotic stenosis were significantly higher in the subgroup of rats with 6/0 silk suture than that in the subgroup with 6/0 polypropylene sutures, which also had significantly higher mortality and anastomotic stenosis than the subgroup with 9/0 polypropylene sutures. Histological examination of the stenosed anastomosis showed disruption of muscle layers and submucosal thickening. It is concluded that the use of fine calibre sutures of biologically inert material would be preferred for the end-to-end anastomosis of the oesophagus.     

Vein cuff interposition prevents juxta-anastomotic neointimal hyperplasia.

This study sought to minimize juxta-anastomotic neointimal hyperplasia (JNIH) following the use of polytetrafluorethylene (PTFE) conduits. PTFE anastomoses to canine carotid arteries (noncuff grafts) were compared with grafts with vein cuffs interposed proximally and distally between the graft and native artery. This technique has been suggested clinically for below-knee PTFE femoropopliteal reconstruction. Twelve dogs received aspirin for 1 week before operation, which was continued after each animal received bilateral cuff and noncuff 4-mm PTFE grafts. At sacrifice, after 3-12 weeks, graft patency was assessed and luminal diameters measured with ophthalmic calipers at three sites along the anastomoses and 1 mm proximal or distal to graft toe (A' diameter). Specimens were perfusion fixed at arterial pressure for gross and histologic study; selected arteries were additionally fixed with 4% buffered glutaraldehyde, stored at 4 C, and examined immunochemically using antimyosin antibody immunopurified for smooth muscle. Overall patency of noncuff grafts in 11 long-term surviving dogs was 4 of 11; patency of the cuff grafts was 7 of 11. Regardless of graft thrombosis, antibody positive cellular proliferation occurred mainly at noncuffed PTFE anastomoses. Luminal encroachment was predominantly due to subintimal proliferation of cells highly reactive to smooth muscle derived antibody. JNIH was most prominent 1 mm distal to the graft toe (A' distal diameter). Average A' for noncuff grafts was 1.82 mm +/- 0.97 SEM; average A' diameter for cuff grafts was 3.41 mm +/- 0.74 SEM (p less than 0.001). Vein cuff inhibition of proliferation of smooth muscle or cells derived from smooth muscle possibly relates to wider distribution of kinetic energy (less compliance mismatch) or to interposition of venous endothelium.     

Laser radiation in the treatment of prosthetic graft stenosis. A preliminary study of prosthesis damage by laser energy

Transluminal laser recanalization is potentially an important new treatment of anastomotic intimal hyperplasia. However, currently used grafts or sutures may be damaged by laser radiation at power and energy levels required for plaque removal. To investigate this problem, two commonly used grafts (Dacron and polytetrafluoroethylene [PTFE]) and two types of vascular suture (polypropylene and PTFE) were exposed to argon laser radiation in vitro. Dacron and PTFE grafts recovered from amputations were also studied to determine whether graft "healing" affected graft resistance to laser damage. Power and energy levels required to perforate atherosclerotic superficial femoral arteries were determined for comparison. PTFE grafts were significantly (1.5 to 7 times) more resistant to perforation by laser energy than atherosclerotic arteries under all conditions. In contrast, Dacron grafts perforated at power and energy levels one half to one third of that required for vaporization of atherosclerotic plaque. PTFE sutures remained intact at power and energy levels above the levels that perforated atherosclerotic arteries, whereas polypropylene sutures were destroyed by very low levels of power and energy (0.5 joules at 0.5 watts). Because of the variable levels of power and energy that damage different types of prosthetic grafts and sutures, laser angioplasty should only be investigated clinically as a therapy for anastomotic intimal hyperplasia when PTFE grafts and sutures are present.     

In Vivo Analysis of Dynamic Tensile Stresses at Arterial End-to-end Anastomoses. Influence of Suture-line and Graft on Anastomotic Biomechanics

OBJECTIVE: to determine the influence of an anastomotic suture line and a graft on dynamic tensile stresses of vascular end-to-end anastomoses in vivo. MATERIAL AND METHODS: the abdominal aorta of twelve 35-kg pigs was used as an experimental model. Simultaneous recordings of internal arterial diameter and pressure were performed on each pig at 3 successive stages: (1) The genuine artery (REF), (2) artery-artery (A-A) and (3) graft-artery (G-A) anastomosis at 1-mm increments in the immediate perianastomotic area. Thereby, RD (relative distension), CC (compliance coefficient), E(p)(dynamic pressure-strain elastic modulus) and hysteresis loop areas could be calculated for every measuring point. RESULTS: the graft was significantly stiffer than REF. A-A and G-A anastomoses were significantly less compliant than REF. Maximum E(p), minimum CC and hysteresis loop areas were found at the anastomotic line due to minimum anastomotic RD. Downstream of the G-A anastomosis, the RD, CC, E(p)and loop areas were significantly different from REF, but significantly different from A-A. CONCLUSION: an animal model for acute studies of mechanical properties of vascular end-to-end anastomoses was developed. The main determinant for anastomotic biomechanics was the suture-line itself.     

Polydioxanone and polypropylene suture material in free internal mammary artery graft anastomoses

An experimental study with six beagle dogs was conducted to evaluate a new monofilamentous absorbable suturing material--polydioxanone. Free internal mammary artery grafts, 3 cm long, were harvested via a median sternotomy and were implanted as arterial bypasses in femoral arteries (12 end-to-end anastomoses) and as arteriovenous shunts in the carotid artery-contralateral jugular vein position (12 end-to-side anastomoses). Twenty-four anastomoses were made with monofilamentous nonabsorbable suturing material, polypropylene (12 arterial, 12 shunts), to serve as control grafts. At 6 months the grafts and anastomoses were explanted and studied with light and scanning electron microscopes. Macroscopically, the polydioxanone sutures had disappeared. The major histologic finding was the foreign body reaction around the polypropylene sutures. In the electron microscopic study the endothelial line covered the anastomotic site and in the polypropylene anastomoses the suture material was bulging up from the anastomoses. No aneurysms or dilatations were seen. According to this study, polydioxanone is a suitable suturing material for small luminal arterial anastomoses and is superior to polypropylene suturing material because it causes no tissue or other late changes on the flow surfaces.     

Does vascular stapling improve compliance of vascular anastomoses?

Elastic properties of vessel walls are altered by vascular anastomoses. Such alterations may lead to neointimal hyperplasia, which is a common cause of reocclusion following vascular surgery. The severity of paraanastomotic hypercompliant zones and anastomotic compliance drop depend on suturing material and on elastic properties of the anastomotic vessel segments. This study compares paraanastomotic hypercompliance and anastomotic compliance drop when using a new vascular closure system (VCS) and a conventional, continuous suture line in the preparation of end-to-end anastomoses. Compliance of artery-artery, vein-artery, and polytetrafluoroethylene-artery anastomoses was measured in an artificial circulation system at mean pressures of 60, 90, and 120 mm Hg, comparing conventional suturing and the VCS. When using the VCS for vein-artery anastomoses, significantly less postanastomotic hypercompliance was achieved at mean pressures of 60 mm Hg (14.2 +/-3.8% above remote postanastomotic area), compared to suture (55.1 +/-14.8%, p<0.05). At 90 mm Hg, respective values were 11.0 +/-2.3% for VCS and 54.7 +/-10.1% for suture, p<0.01. At 120 mm Hg, in polytetrafluoroethylene-artery anastomoses, the anastomotic compliance drop was significantly less when using the continuous suture line (93.9 +/-1.1% below remote postanastomotic compliance), compared to VCS (97.2 +/-0.2%, p<0.05). Compared to conventional suturing, use of the VCS reduced postanastomotic hypercompliance in vein-artery anastomoses.     

Growth of the aortic anastomosis in pigs. Comparison of continuous absorbable suture with nonabsorbable suture

Growth at the anastomotic site after continuous vascular anastomosis in the pediatric patient remains a problem. Primary end-to-end anastomosis of the infrarenal aorta was performed with absorbable Maxon suture or nonabsorbable Prolene suture in 20 piglets. Ten of the Maxon suture group and nine of the Prolene suture group survived; one pig died of infection. The animals were put to death 6 months after the operation. Each abdominal aorta was removed and a roentgenogram was obtained. The aorta was then burst-tested to 300 mm Hg, measured, and examined both grossly and histologically. All anastomoses were patent and no burst failures were observed in either group. However, Prolene sutures protruded into lumen and were partially embedded in the aortic wall in all animals in the Prolene suture group. Thrombus adhered to the intraluminal Prolene suture in six of nine animals. The growth of the anastomotic area was wider in the Maxon suture group (446.4% +/- 131.8% versus 317.6% +/- 121.5%, p less than 0.05). Stenosis was more common in the Prolene suture group (7/9) than in the Maxon suture group (1/10) (p less than 0.01), but the distal segment was widely patent in both groups. Dilatation at the anastomotic site was present in eight of 10 pigs in the Maxon suture group and in two of nine in the Prolene suture group. Histologic study showed that the area of tissue reaction was more prominent in the Prolene suture group. No sutures were observed in the Maxon suture group. We therefore recommend the use of absorbable Maxon sutures for anastomoses in which the suture line must be able to grow.     

Primary anastomotic bonding in polytetrafluoroethylene grafts?

Previous studies have demonstrated that standard knitted and woven fabric grafts are forever dependent on the suture material for anastomotic tensile strength. Clinical experience with polytetrafluoroethylene (PTFE) and double velour knitted grafts have shown that there is extensive fibrous capsular bonding between the graft and the surrounding tissues. This would lead to increased anastomotic tensile strength. To test this theory, 34 mongrel dogs underwent replacement of their infrarenal aortas with grafts made of PTFE (10 dogs), of double velour knitted Dacron (DVD, 11 dogs), of single velour knitted Dacron (SVD, 5 dogs), and of woven Dacron (WD, 8 dogs). One anastomosis was constructed with 5-0 Prolene and the opposite anastomosis was constructed with 5-0 Dexon (average absorption time, 21 days). In five grafts each of PTFE and DVD, as well as in all eight WD grafts, the midgraft was divided and resutured with 5-0 Dexon. All grafts were harvested together with adjacent proximal and distal aorta between 3 and 10 months from the time of implantation. The tensile strength of each anastomosis was measured with a tensiometer. The mean graft-to-artery (absorbable suture) anastomotic tensile strength, in pounds, for PTFE (14.3) and DVD (12.6) was significantly higher than that for SVD (6.9) or WD (7.2) (p less than 0.003). Graft-to-graft anastomotic tensile strength for PTFE (mean 17.3) was significantly better than that for DVD (mean 9.0; p less than 0.03) or WD (mean 7.9; p less than 0.001). Analysis of anastomotic tensile strength as a function of time revealed continued increase in PTFE in contrast to a slow decline with time in DVD.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Anastomotic tissue response associated with expanded polytetrafluoroethylene access grafts constructed by using nonpenetrating clips.

PURPOSE: The gross, light microscopic, and scanning microscopic appearance of arterial and venous anastomoses in expanded polytetrafluoroethylene (ePTFE) access grafts constructed with nonpenetrating clips were compared with that of those constructed with polypropylene suture. We hypothesized that clip-constructed anastomoses would provide controlled approximation of native vessel intimal and medial components with the ePTFE grafts. We further hypothesized that anastomotic healing with clips would involve primarily an intimal cellular response, as compared with suture-constructed anastomoses in which cells within the media and adventitia walls participate. METHODS: Femoral artery to femoral vein arteriovenous (AV) grafts were constructed in five dogs using 4-mm internal diameter ePTFE graft material. Each animal received one AV graft with anastomoses constructed by using polypropylene sutures in one leg and one AV graft with anastomoses constructed with Vascular Closure System clips in the contralateral leg. Animals were given aspirin for the duration of the study, and grafts were explanted at 5 weeks. At the time of explantation, graft segments were grossly evaluated and then underwent light and scanning electron microscopic analysis. RESULTS: At the time of explantation, all access grafts were patent. Joining the ePTFE grafts to the native vessels with clips resulted in minimal vessel wall damage. The lumenal contours of the discontinuous approximation were smooth and without gross endothelial disruption. These observations are in contrast to the lumenal compromise and endothelial disturbance associated with the sutured anastomoses. Furthermore, hemostasis was achieved immediately in the clipped grafts, decreasing the incidence of perianastomic hematoma. Finally, cellular reconstitution occurred at the anastomotic cleft in both the sutured and the clipped junctions. The neointima exhibited an endothelial cell lining on the lumenal surface and the presence of alpha-smooth muscle cell actin positive cells within the subendothelial layer. CONCLUSION: Vascular Closure System clips are a viable alternative to suture for the approximation of ePTFE AV access grafts to native blood vessels. The use of the clips resulted in a more streamlined anastomosis, with decreased vessel wall damage, immediate hemostasis, and a trend toward shorter procedure times.     

Infrainguinal anastomotic arterial graft infections treated by selective graft preservation.

The purpose of this study was to determine whether the type of graft material and bacteria involved in an infrainguinal arterial anastomotic infection can be used as guidelines for graft preservation. Between 1972 and 1990, the authors treated 35 anastomotic infections involving a common femoral or distal artery. The graft material was Dacron in 14 patients, polytetrafluoroethylene (PTFE) in 14, and vein in 7. Of the 14 Dacron grafts, immediate graft excision was required for overwhelming infection in eight patients (bleeding in five, sepsis in three) and for an occluded graft in one patient. Three of five patients failed attempted graft preservation because of nonhealing wounds. Thus, 12 of the 14 Dacron grafts ultimately required graft excision. Of the 21 "smooth-walled" vein and PTFE grafts, 10 required immediate graft excision for occluded grafts (five PTFE, one vein) or bleeding (three PTFE, one vein). Ten of the remaining 11 (91%) patients with patent "smooth-walled" grafts, intact anastomoses, and absence of sepsis managed by graft preservation healed their wounds and maintained distal arterial perfusion. Wound cultures grew pure gram-positive cocci in 17 of 21 "smooth-walled" graft infections versus 8 of 14 Dacron graft infections. In the absence of systemic sepsis, graft preservation is the treatment of choice for gram-positive infections involving an intact anastomosis of patent PTFE and vein grafts. Regardless of the bacterial cause, the authors recommend that any infrainguinal anastomotic infection of a Dacron graft be treated by immediate excision of all infected graft material.