Venous prostheses: improved patency with external stents

A uniformly successful prosthesis for replacement in the venous system has not been developed. This study assesses the effect of external stents on the patency of polytetrafluoroethylene (PTFE) grafts in the infrarenal vena cava. Under general anesthesia, 21 mongrel dogs underwent midline laparotomy. The infrarenal vena cava was resected and replaced by a standard segment (8 cm X 10 mm) of stented PTFE (12 dogs) and nonstented PTFE (9 dogs). Patency was assessed by contrast venography and the results compared between the two groups. The 7-, 30-, and 90-day patency was 12/12, 10/12, and 9/12, respectively, for stented PTFE and 6/9, 2/9, and 2/9, respectively, for nonstented PTFE. The patency of externally stented PTFE at 30 and 90 days was significantly better than grafts fashioned from PTFE alone (P less than 0.05 by chi-square analysis). These data demonstrate that external stenting improves the early patency of PTFE prostheses in the infrarenal vena cava. Consideration should be given to the clinical use of externally stented PTFE when prosthetic replacement in the venous system is required.     

The effect of adjunctive arteriovenous fistula on prosthetic graft patency: a controlled study in a canine model

Bilateral 6 mm PTFE grafts were placed from the external iliac artery to the femoral artery with ligation of the intervening segment of the iliofemoral artery in 14 dogs. An arteriovenous fistula was constructed at the distal anastomosis on one randomly selected side in each animal while the contralateral graft served as a control. Graft follow-up ranged between 8 and 12 months in all animals. Serial arteriography was performed to confirm graft and fistula patency and demonstrated persistence of antegrade flow into the arterial tree distal to all patent bypasses. Femoral intraarterial pressures distal to patent grafts were identical on both sides in each animal throughout the study. Cumulative life-table patency rates showed higher patency for the arteriovenous fistula bypasses than the control grafts at all time intervals: 71% vs. 57% at 3 months, 48% vs. 25% at 6 months, and 40% vs. 22% at 12 months, respectively. This is the first controlled study that provides experimental evidence suggesting that these bypasses may produce increased patency of prosthetic arterial grafts and lends support to their use in a clinical, prospective, randomized study.     

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.     

Expanded microporous polytetrafluoroethylene (PTFE) grafts in contaminated wounds: experimental and clinical study

Autogenous vein graft is regarded as an ideal arterial substitute for its long-term patency and relative resistance to infection. A clinical instance of life-threatening hemorrhage from an infected disrupted vein graft stimulated a study in dogs, comparing vein and PTFE graft performance in wounds contaminated with S. aureus and E. coli cultured from the patient's wound. Infective disruption of vein wall occurred in three of ten animals resulting in exsanguination and death. Host artery disruption at PTFE suture line occurred in one of ten animals. Thrombosis of graft and host artery in this animal precluded hemorrhage and death. This led to favorable clinical experiences with PTFE grafts in contaminated wounds of 22 trauma patients. It is concluded that PTFE is better assurance against disruption and hemorrhage than vein graft in contaminated, potentially infected sites. PTFE may be used preferentially as a vascular substitute in trauma patients provided that all traditional surgical safeguards and principles are followed.     

Intraarterial 9-beta-methyl carbacyclin improves canine polytetrafluoroethylene graft patency

This study examined the effect of 9-beta-methyl carbacyclin, a synthetic, stable prostacyclin analog, on canine polytetrafluoroethylene (PTFE) graft patency. Twenty-five dogs had 4 mm x 7 cm PTFE grafts implanted bilaterally into the femoral arteries. A subcutaneous infusion pump was used to deliver either saline solution (control) or 9-beta-methyl carbacyclin (Ciprostine) at 100 (CARB-100) or 200 ng/kg/min (CARB-200) through a femoral artery branch just proximal to one of the femoral grafts, with the contralateral graft serving as a noninfused control. Graft-platelet deposition (with 111In-labeled platelets) was measured between the fifth and seventh days, with patency determined on the seventh day. Dogs were classified as aggregators (AGG [+]) if the preoperative epinephrine-enhanced sodium arachidonate platelet aggregation was greater than 20%. CARB-200 infusion significantly improved ipsilateral graft patency (80%) compared with noninfused grafts (50%, p less than 0.05), or grafts in control and CARB-100 dogs (43%, p less than 0.05). Anastomotic platelet deposition was decreased bilaterally in CARB-200 dogs by 45% to 59% compared with CARB-100 and control dogs (p less than 0.05). With the exception of grafts infused with CARB-200, AGG (+) dogs had significantly lower graft patency (26%) than nonaggregator AGG (-) dogs (71%, p less than 0.01). CARB-200 infusion significantly improved graft patency in AGG (+) dogs (71%), compared with control and CARB-100-infused grafts (19%, p less than 0.025). Intra-arterial 9-beta-methyl carbacyclin improved early PTFE graft patency and inhibited platelet deposition in a severe canine model, independent of baseline platelet aggregation status, which also had an important effect on graft patency.     

Thrombogenicity of a fibronectin-coated, experimental polytetrafluoroethylene graft

To determine if pretreatment of polytetrafluoroethylene (PTFE) vascular grafts with fibronectin (FN) increased platelet adherence to them and adversely affected their patency, we labeled autologous canine platelets with indium III-oxine and interposed a FN-coated, experimental, 4 mm inner diameter, 10 cm long PTFE prosthesis into one carotid artery of 10 dogs. An identical graft, lacking only the FN coating, was implanted as a control in the contralateral carotid artery. A second group of 10 dogs was similarly treated, but each animal received 2 grains of aspirin and 50 mg of dipyridamole (Persantine) daily, beginning 3 days before surgery and continuing for the duration of the experiment. By means of a quantitative, gamma-camera, platelet adherence to the grafts was studied for 5 days after implantation. Graft patency was assessed with the Doppler velocity meter and was confirmed by surgical reexploration when thrombosis was suspected. FN coating increased platelet adhesion to the grafts in animals untreated with aspirin by a factor of threefold to fivefold. In those animals receiving antiplatelet drugs, patency of FN-coated grafts at 5 days was significantly (p less than 0.05) higher (80%) than in untreated animals (27.2%). In addition, mean platelet deposition on the grafts in these animals was reduced compared with untreated controls. Thus although FN coating of PTFE grafts significantly increases their affinity for platelets, this effect can be effectively abolished by pretreatment with aspirin and dipyridamole.     

Effect of a selective thromboxane synthase inhibitor on arterial graft patency and platelet deposition in dogs

This study examined the effect of selective thromboxane synthase inhibition and nonselective cyclooxygenase inhibition on vascular graft patency and indium 111-labeled platelet deposition in 35 mongrel dogs undergoing carotid artery replacement with 4 mm X 4 cm polytetrafluoroethylene (PTFE) (one side) and Dacron (opposite side) end-to-end grafts. Aspirin-dipyridamole therapy improved one-week graft patency, from 46% in untreated dogs to 93% in treated dogs. Thromboxane synthase inhibition (U-63557A) improved graft patency in these dogs to 81%. Both drug treatments reduced platelet deposition on Dacron and PTFE grafts by 48% to 68% compared with control dogs. Dacron grafts accumulated significantly more platelets than PTFE grafts but had comparable patency rates. Low-dose aspirin therapy had no significant effect on either graft patency or platelet deposition. All treatment groups showed a 60% to 76% reduction in serum thromboxane B2, but only thromboxane synthase inhibitor treatment increased plasma 6-keto-prostaglandin F1 alpha by 100%. Selective thromboxane synthase inhibition improved small-caliber prosthetic graft patency to the same extent as did conventional cyclooxygenase inhibition in this preliminary study.     

Early failure of expanded polytetrafluoroethylene in femoral vein replacement.

Grafts of expanded 30-mu fibril length polytetrafluoroethylene (PTFE) were inserted as segmental femoral vein replacements in nine dogs. The contralateral femoral vein served as a control, receiving a graft from each dog's right external jugular vein. Graft patency was monitored for 24 weeks postoperatively with serial venograms and venous pressures of the operated limbs. All expanded PTFE grafts and one autogenous graft thrombosed within 24 to 48 hours. Significant venous hypertension in the extremities receiving the PTFE grafts persisted for six months.     

A small arterial substitute: expanded microporous polytetrafluoroethylene: patency versus porosity.

Eighty-nine grafts of expanded microporous polytetrafluoroethylene (PTFE) with a diameter of 4 mm, were placed in the carotid and femoral arteries of dogs. The animals were sacrificed at varying intervals beginning three days after operation. Four animals remain alive with patent grafts 10 months post-operatively. Twenty-four of 89 grafts were occluded, an overall patency of 73%. Fibril length (pore size) of the graft material was varied from 4 to 110 microns. Average pore size ranged from 9 to 65 microns. Wall thickness varied from 0.3 to 0.75 mm. Density ranged from 0.24 to 0.35 g/ml. Tissue ingrowth, neointimization and patency rate as compared to pore size, wall-thickness and density of expanded PTFE were observed. Pore size is the primary determinant of tissue ingrowth, neointimization and patency. Of 51 grafts with an average pore size of 22 microns or less, there were 6 occlusions, an 88% patency rate. There were 38 grafts with an average pore size of 34 microns or greater. In these 38 grafts, 18 occlusions were observed, a 53% patency rate. Patent grafts demonstrated tissue ingrowth, capillary formation an a thin neointima. Using small pore grafts, patency rates of 90% can be anticipated in the dog. Expanded microporous PTFE with its ease of handling, strength and pliability may be the vascular prosthesis of choice in man.     

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.     

Das arterioarterielle Interponat als Dialysezugang

We report on two patients who received arterio-arterial PTFE grafts as vascular access for chronic hemodialysis. In both patients prior surgery for arteriovenous fistulas using either subcutaneous veins or arteriovenous, artificial PTFE grafts had failed due to recurrent thrombosis and septic complications. The arterio-arterial grafts were each positioned as a subcutaneous loop on the thigh and anastomosed with the common femoral artery and the superficial femoral artery or the profunda femoris, respectively. Postoperatively, both patients received coumadine for anticoagulation. Nine months after surgery no complications were observed in the former patient. The latter patient experienced recurrent thrombotic occlusion of the graft and a new graft was required which was anastomosed end-by-end onto the common femoral artery. As yet, 5 months after the second operation, no further complications have been reported. In conclusion, in patients lacking suitable veins for arterio-venous anastomoses, artificial arterio-arterial grafts may provide vascular access for chronic hemodialysis.     

Histologic comparison of experimental coronary artery bypass grafts. Similarity of in situ and free internal mammary artery grafts

This study compares patency and histologic structure of in situ internal mammary artery grafts, free internal mammary artery grafts, stripped, free internal mammary artery grafts, and stripped, free superficial femoral artery grafts (a muscular artery model) in a canine model of coronary artery bypass. Twenty-four adult mongrel dogs underwent bypass of the circumflex coronary artery with one of the above grafts. Three months postoperatively, graft patency was assessed by angiogram, and postmortem specimens were studied by intraluminal injection of a dilute barium solution proximal to the graft. Proximal, mid, and distal segments of each graft were examined microscopically. In situ internal mammary artery grafts and free internal mammary artery grafts were not significantly different in regard to patency, vascular wall cellular structure, or perfusion of the vasa vasorum. The stripped, free internal mammary artery group had a higher incidence of thrombosis, intimal thickening, and medial injury than the pedicled (in situ and free internal mammary artery) grafts. This difference may be due to early vascular wall ischemia as a result of poor early perfusion of the vasa vasorum. The stripped, free superficial femoral artery grafts were all patent, but all had adventitial injury.     

Small Intestinal Submucosa as a Small-Diameter Arterial Graft in the Dog

Autogenous saphenous vein, human umbilical vein, modified bovine collagen, Dacron, and PTFE have been used as small-diameter arterial grafts with moderate success. We tested autogenous small intestine submucosa as a small-diameter arterial graft in both a carotid and femoral artery (mean ID 4.3 mm) of 18 dogs (total of 36 grafts). All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by Doppler ultrasound techniques and angiography. Two grafts ruptured and 5 grafts occluded by 21 days after surgery. One graft became occluded at 14 weeks. Fifteen dogs were sacrificed at periodic intervals until 48 weeks after surgery. Patent grafts had no evidence of infection, propagating thrombus, or intimal hyperplasia. Graft aneurysmal dilation occurred in 4 grafts (11%). The grafts were composed of a dense organized collagenous connective tissue with no evidence of endothelial cell growth on the smooth luminal surface. Three dogs are alive at 76 to 82 weeks after surgery. Overall, graft patency was 75%. Graft patency after cessation of anticoagulation therapy was 92.3% (12 of 13 grafts). We conclude that autogenous small intestinal submucosa can be used as a small-diameter arterial graft in the dog and is worthy of further investigation.     

Femoropopliteal bypass for claudication: Vein vs. PTFE

The vascular graft of choice for femoropopliteal bypass in patients with intolerable claudication is controversial. We retrospectively reviewed our experience with 239 patients suffering from claudication secondary to superficial femoral artery obstruction. Femoropopliteal reconstruction was performed with saphenous vein to the below-knee popliteal artery in 66 patients (BK-vein). Polytetrafluoroethylene (PTFE) was used in 128 patients as a bypass graft to the above-knee popliteal artery (AK-PTFE) and 45 patients had a PTFE graft to the below-knee popliteal artery (BK-PTFE). All patients were enrolled in a postoperative graft surveillance program with graft revision when appropriate. There was one perioperative death (0.4%). Primary patency at 5 years for AK-PTFE, BK-PTFE, and BK-vein was 58.0%, 55.0%, and 60.3%, respectively, and was not significantly different among the graft groups. Graft revision for failed/failing grafts resulted in 5-year secondary patency rates of 79.2% (AK-PTFE), 73.3% (BK-PTFE), and 74.4% (BK-vein). These secondary patency rates were not statistically different. Eventual conversion to a vein graft in patients initially treated with PTFE maximized patency in the femoropopliteal segment with 5-year patency rates of 84.6% and 93.0% for the AK-PTFE and BK-PTFE graft groups, respectively. Major leg amputation was necessary during the entire course of the study in eight (3.3%) patients. We conclude that long-term patency rates for femoropoliteal bypass in patients with intolerable claudication are similar for PTFE and autologous saphenous vein grafts.Presented at the Twentieth Annual Meeting of the Peripheral Vascular Surgery Society, New Orleans, La., June 10, 1995.     

Small intestinal submucosa as a small-diameter arterial graft in the dog

Autogenous saphenous vein, human umbilical vein, modified bovine collagen, Dacron, and PTFE have been used as small-diameter arterial grafts with moderate success. We tested autogenous small intestine submucosa as a small-diameter arterial graft in both a carotid and femoral artery (mean ID 4.3 mm) of 18 dogs (total of 36 grafts). All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by Doppler ultrasound techniques and angiography. Two grafts ruptured and 5 grafts occluded by 21 days after surgery. One graft became occluded at 14 weeks. Fifteen dogs were sacrificed at periodic intervals until 48 weeks after surgery. Patent grafts had no evidence of infection, propagating thrombus, or intimal hyperplasia. Graft aneurysmal dilation occurred in 4 grafts (11%). The grafts were composed of a dense organized collagenous connective tissue with no evidence of endothelial cell growth on the smooth luminal surface. Three dogs are alive at 76 to 82 weeks after surgery. Overall, graft patency was 75%. Graft patency after cessation of anticoagulation therapy was 92.3% (12 of 13 grafts). We conclude that autogenous small intestinal submucosa can be used as a small-diameter arterial graft in the dog and is worthy of further investigation.     

Impact of endothelial cell seeding on long-term patency and subendothelial proliferation in a small-caliber highly porous polytetrafluoroethylene graft

Previous reports have demonstrated that endothelial cell seeding of polytetrafluoroethylene (PTFE) grafts enhances short-term patency. This experiment was undertaken to study its impact on the long-term patency of a highly porous, experimental PTFE graft and to determine whether increasing the internodal distance of the graft material resulted in increased proliferation of the subendothelium. Ten centimeter long, 4 mm internal diameter segments of an unreinforced, experimental PTFE graft were implanted into 36 mongrel dogs as carotid interpositions. In each animal, one graft was seeded with autologous endothelial cells, enzymatically derived from the external jugular veins, whereas the contralateral graft was treated in identical fashion except that endothelial cells were not added to the preclot mixture. Nineteen animals were killed at 12 weeks; six at 22 weeks; eight at 26 weeks; and three at 52 weeks. The mean follow-up period was 20.1 weeks. The overall patency rate was 58.3% (21 of 36 grafts) for seeded grafts vs. 27.8% (10 of 36 grafts) for control grafts (p less than 0.01). The thrombus-free area was planimetrically measured at 83.4% +/- 4.5% in seeded grafts vs. 55.1% +/- 9.7% in control grafts (p less than 0.05). Scanning electron microscopy confirmed the presence of a confluent cellular monolayer in seeded grafts, whereas control grafts exhibited a variable coagulum of fibrin, platelets, and endothelial cells. The thickness of the subendothelial layer varied from 56 to 95 micron with no progressive increase in thickness between 12 and 52 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Five-year experience with PTFE grafts in vascular wounds

From 1978 through 1983, 206 patients had 236 polytetrafluoroethylene (PTFE) grafts inserted in vascular wounds. More than 85% of injuries were due to gunshot wounds, shotgun wounds, or stab wounds. Arterial grafts were inserted into vessels of the upper extremity (38.8%), lower extremity (46.1%), neck and chest (8.8%), and abdomen (6.3%). Grafts were most commonly placed in the brachial or superficial femoral arteries. Venous grafts were more commonly inserted into vessels of the extremities (96.7%), with the majority located in the superficial femoral vein. PTFE was found to be an acceptable prosthesis for interposition grafting in arterial wounds, but long-term patency was less than that seen when interposed saphenous vein grafts are used. Early and late occlusions were a significant problem with 4-mm PTFE grafts in the brachial artery, and this size is not recommended in this location. Peripheral PTFE graft infection did not occur in the absence of exposure of the graft or of osteomyelitis. Exposed grafts did not fare well and early coverage is recommended, even with extensive soft-tissue wounds around the graft. PTFE grafts inserted in proximal extremity veins are excellent temporary conduits which decrease hemorrhage in blast cavities and fasciotomy sites, but all grafts studied by venography at 7 to 14 days were either narrowed or occluded.     

Evaluation of platelet deposition and neointimal hyperplasia of heparin-coated small-caliber ePTFE grafts in a canine femoral artery bypass model

INTRODUCTION: Bypass graft failure due to acute thrombosis and intimal hyperplasia remains a major challenge in small-diameter vascular prosthetic graft reconstruction. Heparin has been shown to prevent thrombus formation and inhibit intimal antithrombotic in animal studies. In this study, we evaluated the effect of small-caliber heparin-coated expanded polytetrafluoroethylene (ePTFE) grafts on platelet deposition and intimal hyperplasia in a canine model of femoral artery bypass grafting. METHODS: Nine adult greyhound dogs underwent placement of bilateral femorofemoral artery bypass grafts with ePTFE grafts (4 mm diameter and 7 cm long). In each animal, a heparin-coated ePTFE graft was placed on one side while a noncoated graft was placed on the contralateral side which served as the control. Platelet deposition was measured by autologous (111)indium-labeling and scintillation camera imaging analysis in 24 h. The graft patency was assessed at 4 weeks following the bypass. The effect of intimal hyperplasia was assessed with histological and morphometric analysis. RESULTS: Platelet deposition on the heparin-coated grafts at 24 h was significantly reduced by 72% as compared to controls (P = 0.001). The patency rate was 44% in control grafts and 89% in heparin-coated grafts. There was a significant reduction of graft intimal hyperplasia at both proximal (0.38 +/- 0.21 mm(2)) and distal (0.19 +/- 0.06 mm(2)) anastomoses in the heparin-coated grafts as compared with proximal (1.01 +/- 0.28 mm(2)) and distal (0.42 +/- 0.01 mm(2)) anastomoses in the untreated control grafts, respectively (P < 0.05). Heparin coating significantly reduced graft neointimal hyperplasia at patent graft anastomoses by 55-72% as compared to controls. CONCLUSIONS: These data demonstrate that heparin coating of ePTFE significantly reduced early platelet deposition and inhibited anastomotic neointimal hyperplasia. Moreover, small-caliber heparin-coated ePTFE graft significantly increased graft patency in a canine femoral artery bypass model. This may represent a promising treatment strategy for improving the clinical performance of small-caliber prosthetic vascular grafts.     

Autogenous venous valve transplantation in the dog

Incompetence of femoral vein valves has been causally linked to venous insufficiency of the lower extremities. Attempts to transplant competent venous valves into the femoral region have historically been associated with a high rate of early thrombosis. Using modern vasclar surgical techniques, 10 mongrel male dogs had 20 competent valves from the external jugular veins transplanted to both femoral veins. Five dogs (Group I) received no perioperative pharmacological therapy, while 5 dogs (Group II) received low-dose aspirin (2 mg/kg) daily. The surgical technique involved gentle, no-touch dissection of the external jugular veins, systematic anticoagulation with a single bolus of heparin (5000 units), excision of a valve-containing segment of the femoral vein, and transplantation of a valve-containing segment of external jugular vein using interrupted 7-O monoflament sutures. Early patency was confirmed by venography at 2, 7, and 14 days postoperatively. Five animals were sacrificed at 43, 65, 69, 91, and 105 days. Valve competency was evaluated by retrograde flushing. Group I had 100% early and late graft patency and valve competency. Group II had two thrombosed grafts (80% patency) with irreversible valve destruction. Both graft failures were associated with wound hematomas. These results suggest that autotransplantation of competent venous valves into the femoral region can be accomplished using modern vascular surgical techniques. Adjunctive measures such as distal arteriovenous fistulae or anti-platelet therapy do not appear necessary to maintain graft patency or valve competence.     

Prosthetic replacement for the thoracic vena cava: an experimental study

The superior vena cava (SVC) and thoracic inferior vena cava (IVC) were replaced in 46 dogs with autologous vein, knitted Dacron, glutaraldehyde-fixed porcine pericardium, unsupported polytetrafluorethylene (PTFE), and externally stented PTFE. After 30 days, patency rates were determined by contrast venography and were 100%, 9%, 50%, 75%, and 100%, respectively. The patency rates of Dacron and glutaraldehyde-fixed pericardium are considered unacceptable when compared to autologous vein (p less than 0.05). Stented PTFE exhibited a patency rate equal to that of autologous vein at 30 days, minimal graft reaction, excellent incorporation by host fibroblasts, and a smooth neointima. The external spiral support added to PTFE enchanced the thromboresistance of this graft in the thoracic venous system. Long-term follow-up is required to determine if the stented PTFE prosthesis remains comparable to autologous vein as a venous conduit.