Umbilical Vein Grafts Research Articles

A two-dimensional incremental study of the static mechanical properties of vascular grafts

We have used a two-dimensional incremental model to examine the static mechanical properties of canine iliac artery and, with a view to compliancematching, the properties of several vascular grafts: expanded PTFE grafts, human umbilical cord vein grafts (HUV) and helically-wound prototype polyurethane grafts with wrap angles of 30°, 45°, and 60°. Whole vessels were tested in the isotonic mode under physiological conditions using a video analysis system. Using the incremental analysis, circumferential and longitudinal moduli and the two Poisson ratios were derived at operating points of 80, 100, 120, 140, and 160 mm Hg pressure and 30 g end-load (or in vivo end-load for the arterial samples). The model can be manipulated to produced excellent predictions of results from the more common compliance testing. While the PTFE and HUV samples were much stiffer than the natural vessels, a polyurethane graft with a wrap angle of approximately 45° is a good match for canine iliac artery.

Chemically fixed human umbilical cord vein grafts as arterial substitutes: potential and limits.

In spite of reported successes, synthetic fabric grafts and microporous and plain synthetic conduits have proven unsuitable for aorto-coronary bypasses and showed weaknesses below the knee. Readily available and uniform diameter vascular substitutes with biological and mechanical properties comparable to human vessels would be of paramount interest. Following reported successes with chemically fixed human umbilical veins (HUV), we have attempted to develop smaller diameter blood conduits and have improved the currently prevalent techniques of fixation, preparation and storage to generate more convenient surgical products. In vitro assessment of the processed HUV demonstrated that the HUV can be easily processed to make an arterial substitute that can be preserved either in a liquid medium or as a dry product. However, the in vivo implantations in dogs led to disappointing results for liquid-preserved or albuminated veins. Critical-point dried grafts gave better results, unfortunately they do not heal and they can only degrade after implantation.

Pathologic features of surgically excised human umbilical vein grafts

Pathologic features of surgically excised human umbilical vein grafts

Below-knee Reconstructions with the Human Umbilical Veins - Three-year Results

Arterial reconstructions in high flow, low resistance locations (aorta, iliac and common femoral arteries) usually have good long-term results. The late failure rate of below-knee arterial grafts is significantly higher because of their considerable length, the limited outflow bed and the small diameters (low flow, high resistance). In addition, there is the biomechanical stress with genuflexion. Apart from the operative technique and patient-specific vascular morphology, the long-term success of crural reconstructions depends largely on the type of arterial substitute. Based on a retrospective study, we have examined the influence of the bypass material in infragenicular reconstructions with distal popliteal, and with crural, insertion. The three-year patency (life-table method) in reconstructions with distal popliteal insertion was 83% for autologous vein grafts and 72% for umbilical vein grafts. In reconstructions with crural insertion patency was 62% for autologous veins, 50% for umbilical veins and 26% for PTFE grafts. Graft-specific early and late morphologic changes influencing the long-term performance have been analyzed by follow-up angiograms, and in some cases by macroscopic and histologic examination.

The fate of human umbilical vein grafts as an infrarenal aortic substitute in monkeys.

The literature contains conflicting reports about the potential value of the processed human umbilical vein graft as an arterial substitute. With a view to a better understanding of the ultimate fate of this device, a series of long-term implantation was undertaken with a nonhuman primate model. Dardik Biografts were implanted as an infrarenal aortic substitute in 13 monkeys. Nine were put to death following complications after post-operative periods ranging from 3 months to 3 years, while four animals remain alive. No calcification or lipid infiltration was found, presumably because the animals were healthy. The patency rate was poor because of complications associated with thrombotic deposits and thinning of the graft wall after implantation, which led to stenosis and fibrous hyperplasia along the anastomoses. The external polyester mesh was found to encourage external tissue proliferation, which could not prevent the graft from dilating since it contained neither elastin nor smooth muscle cells. Because the places where the graft had been damaged before or during processing were the sites of thrombotic accumulation and initial collagen degeneration, it is essential to use only defect-free material. As a consequence the long-term durability of this graft continues to be questioned.

The fate of human umbilical vein grafts as an infrarenal aortic substitute in monkeys

The literature contains conflicting reports about the potential value of the processed human umbilical vein graft as an arterial substitute. With a view to a better understanding of the ultimate fate of this device, a series of long-term implantation was undertaken with a nonhuman primate model. Dardik Biografts were implanted as an infrarenal aortic substitute in 13 monkeys. Nine were put to death following complications after post-operative periods ranging from 3 months to 3 years, while four animals remain alive. No calcification or lipid infiltration was found, presumably because the animals were healthy. The patency rate was poor because of complications associated with thrombotic deposits and thinning of the graft wall after implantation, which led to stenosis and fibrous hyperplasia along the anastomoses. The external polyester mesh was found to encourage external tissue proliferation, which could not prevent the graft from dilating since it contained neither elastin nor smooth muscle cells. Because the places where the graft had been damaged before or during processing were the sites of thrombotic accumulation and initial collagen degeneration, it is essential to use only defect-free material. As a consequence the long-term durability of this graft continues to be questioned.

Aneurysm formation in human umbilical vein grafts used as arterial substitutes.

A series of 257 human umbilical vein grafts for femoropopliteal bypass in 203 patients, inserted between 1978 and 1984, is presented. The 6-year cumulative patency rate is 74% for above-knee and 44% for below-knee cases. Late complications, such as formation of aneurysms in the human umbilical vein graft, occurred in nine grafts, 21/2 to 6 years after implantation. This corresponds to 3.5% of the total number of 257 human umbilical vein grafts. Three of the grafts developed a second aneurysm at a later time, making a total of 12 aneurysms. The aneurysms were evident as a painful, pulsating mass. All patients were operated on, primarily by resection and interposition grafting. All aneurysms were saccular and false. Macroscopic and microscopic examination revealed that all aneurysms except four originated from a gap in the umbilical vein wall and the Dacron mesh. The adjacent graft wall had a completely normal architecture without biodegradation. The cause of the origin of the gap in the wall remains obscure. Four aneurysms were anastomotic and were located at the site of the suture line, placed at the factory, joining the two components of a composite human umbilical vein graft; these anastomotic aneurysms were caused by breaking of the Prolene suture.

Aneurysm formation in human umbilical vein grafts used as arterial substitutes

A series of 257 human umbilical vein grafts for femoropopliteal bypass in 203 patients, inserted between 1978 and 1984, is presented. The 6-year cumulative patency rate is 74% for above-knee and 44% for below-knee cases. Late complications, such as formation of aneurysms in the human umbilical vein graft, occurred in nine grafts, 212 to 6 years after implantation. This corresponds to 3.5% of the total number of 257 human umbilical vein grafts. Three of the grafts developed a second aneurysm at a later time, making a total of 12 aneurysms. The aneurysms were evident as a painful, pulsating mass. All patients were operated on, primarily by resection and interposition grafting. All aneurysms were saccular and false. Macroscopic and microscopic examination revealed that all aneurysms except four originated from a gap in the umbilical vein wall and the Dacron mesh. The adjacent graft wall had a completely normal architecture without biodegradation. The cause of the origin of the gap in the wall remains obscure. Four aneurysms were anastomotic and were located at the site of the suture line, placed at the factory, joining the two components of a composite human umbilical vein graft; these anastomotic aneurysms were caused by breaking of the Prolene suture.

Bacterial adherence to vascular grafts after in vitro bacteremia

All currently used arterial prosthetics have a greater susceptibility to infection following bacteremia than does autogenous tissue. This experiment compares quantitative bacterial adherence to various prosthetic materials after bacteremia carried out in a tightly controlled and quantitative fashion. Ten centimeters long, 4 mm i.d. Dacron, umbilical vein (HUV), and polytetrafluoroethylene (PTFE) grafts, as well as PTFE grafts with a running suture line at the midportion were tested. Each graft was interposed into a pulsatile perfusion system modified from a Waters MOX 100 TM renal transplant pump. Indium-111-labeled Staphylococcus aureus were added to heparinized canine blood to give a mean concentration of 4.7 × 10 6 bacteria/cc. This infected blood was recirculated through each graft for 30 min at a rate of 125 cc/m, 100 Torr (sys), 60 beats/min. The gamma counts/graft were used to calculate the number of bacteria/cm 2 of graft surface. After nine experiments, a mean of 9.63 × 10 5 bacteria/cm 2 were adherent to the Dacron, 1.04 × 10 5 bacteria/cm 2 to the HUV, and 2.15 × 10 4 bacteria/cm 2 to the PTFE. These differences were all significant at the 0.05 level. The addition of a suture line increased bacterial adherence to the PTFE graft by 50%. These results suggest that PTFE is the vascular graft material of choice when a prosthetic graft must be implanted despite a high risk of subsequent clinical bacteremia. Our in vitro, pulsatile perfusion model gave accurate and reproducible results, and appears well suited for further studies of bacterial, or platelet adherence to grafts, as well as the biomechanics of vascular conduits.

Popliteal and Tibial Artery Bypasses for Limb Salvage

This is a report on personal experiences with 549 cases of popliteal and tibial artery revascularization. There were 204 cases of femoral-popliteal artery by pass procedures utilizing vein grafts. In 193 cases, this procedure was done with autogenous greater saphenous vein grafts. The remainder of the cases consisted of arm veins, bank veins and superficial femoral veins. There were 149 femoral- tibial or popliteal-tibial artery bypasses utilizing vein grafts or composite grafts. In 83 cases, tibial artery bypasses were done with autogenous greater saphenous vein grafts. In 30 cases, popliteal-tibial artery bypasses were done with autoge nous greater saphenous vein grafts. In 25 cases, femoral-popliteal-tibial artery sequential bypasses were done with autogenous greater saphenous vein grafts. The remainder were arm veins and composite grafts with arm vein, leg vein and graft materials. In 178 cases, femoral-popliteal or tibial artery bypasses were done with PTFE grafts. Of these cases, 157 femoral-popliteal bypasses were done with PTFE. Femoral-tibial artery bypasses were done with PTFE in 21 cases. In 18 cases, femoral-popliteal artery bypasses were done with biografts, utilizing human umbilical vein grafts. The sexual ratio in the total number of cases was 62% male to 38% female. The total number of cases was further divided into different groups. The cumulative patency rate of femoral-popliteal artery bypass, utilizing PTFE graft with distal anastomosis at above-knee level, was 90% at the third year. The femoral-popliteal artery bypass with autogenous greater saphenous vein graft had a patency rate of 84% at the fifth year. The patency rate of femoral-tibial artery bypass with autogenous greater saphenous vein graft was 68% at the fifth year. The femoral-popliteal-tibial artery sequen tial bypass, with autogenous greater saphenous vein graft, had a third-year patency rate of 80%. The popliteal-distal-tibial artery bypass, with autogenous greater saphenous vein graft, had a patency rate of 70% at the third year. These patients had been faced with major limb loss due to extremely poor distal run- off, and had been offered major amputation at one time. The patency rate of femoral-popliteal artery bypass, utilizing PTFE, combining both above and be low-knee level of distal anastomosis, was 85% at the third year. However, the femoral-tibial artery bypass utilizing PTFE graft had an extremely poor pat ency rate. At the third year, the patency rate was around 20%. The five year patency rate of femoral-popliteal artery bypass with PTFE graft was 75%, if the distal anastomosis was made at the above-knee level. The same graft, at the below-knee level, was 60%. The patency rate in five years was extremely poor for femoral-tibial artery bypass with PTFE graft. The five-year patency rate of femoral-popliteal-tibial artery sequential bypass, with autogenous greater saphenous vein graft, was 70%. The popliteal-distal tibial artery bypass graft, with autogenous greater saphenous vein graft, had a patency rate of 65% at the fifth year. The femoral-popliteal artery bypass with autogenous greater saphe nous vein graft had a patency rate of 70% at the eighth year. The femoral-tibial artery bypass with autogenous greater saphenous vein graft had a patency rate of 60% at the eighth year.

In vivo evaluation of the acute thrombogenicity of the modified human umbilical vein and autologous artery

With the aim to evaluate acute thrombogenicity, segments of human umbilical vein grafts (Dardik Biograft, Meadox Medicals, Inc., Oakland, N.J.), nonheparinized, heparin-alcohol-treated, or covalently heparinized, were implanted into the carotid arteries of sheep. Autologous carotid arteries were used as control grafts. Flow was restricted to 25 ml/min. Accumulation of autologous 32P-labeled platelets was registered at both anastomotic and midgraft regions for 240 minutes. At the end of the perfusion period, grafts were removed, opened longitudinally, and the thrombus-free surface (TFS) and thrombus weight determined. The ex vivo determinations showed good correlation with results obtained with in vivo registration. In vivo accumulation of platelets was significantly larger in nonheparinized human umbilical vein grafts compared with heparin-alcohol treated grafts. Covalently heparinized grafts showed a tendency toward lower radioactive values, but visual examination after perfusion revealed areas of “intimal” damage with thrombotic deposits, probably caused by heparinization procedure. Autologous arteries showed the largest TFS and the smallest thrombi. Platelet accumulation in autologous arteries decreased almost to reference values after an initial rapid increase. In conclusion, heparin-alcohol treatment of human umbilical vein grafts reduces acute thrombogenicity. Although covalent heparin bonding seems to act in the same way, the fragility of the graft appears to preclude use of this method. Autologous arteries exhibit excellent antithrombotic characteristics.

Dardik Biograftの臨床的, 実験的研究

Dardik Biograftの臨床的, 実験的研究

Hemodynamics of an anastomotic arteriovenous fistula

Various vascular surgical techniques have been employed to increase both graft patency and limb survival when the prognosis for limb salvage in arteriosclerotic patients is especially poor due to a diseased outflow tract. Ibrahim et al described the creation of an anastomotic arteriovenous fistula in distal tibial bypasses as the reconstructive procedure of choice in severely ischemic extremities unsalvageable by more conventional methods. This study presents the hemodynamics of an anastomotic arteriovenous fistula under such circumstances. Four adult mongrel dogs were anesthesized, and a femoral artery and vein were exposed from the groin to the knee. The femoral artery was ligated in midthigh, and the ligated segment was than bypassed using an umbilical vein graft. The distal anastomosis included an arteriovenous fistula. Flow was measured electromagnetically, and pressure was measured with intravascular catheters attached to strain gauges. The creation of an anastomotic arteriovenous fistula rapidly leads to a reversal of flow in the distal artery, distal arterial hypotension, and distal venous hypertension. Its clinical use in contraindicated as a result of our experimental observations.

Human umbilical vein for vascular access in chronic hemodialysis.

Since 1979 we have used human umbilical vein graft as the ultimate vascular access for hemodialysis in patients with chronic renal failure. In 24 patients 33 graft fistulas were performed. Several complications were encountered. Among these infection was the most serious, occurring in seven grafts. All these grafts were removed and never used for hemodialysis. Thrombosis occurred 25 times, and five grafts were lost because of this, whereas 20 grafts had successful thrombectomy and continued to function. Aneurysm formation occurred four times, two grafts were lost. Stenosis was seen in three cases, one graft was lost. In the material 26 grafts were used for hemodialysis and a median function time of 8.5 months was obtained. At the end of the observation period 10 grafts were open, eight were used for hemodialysis, two were not used because of successful transplantation. The umbilical vein graft is an acceptable alternative as vascular access where conventional methods of fistula formation have been exhausted.

In vitro evaluation of a biologic graft surface. Effect of treatment with conventional and low molecular weight (LMW) heparin

Human umbilical vein grafts were treated with either conventional or LMW heparin, followed by exposure to alcohol. The grafts were investigated for their ability to adsorb and inactivate thrombin, and comparison was made with non-heparinized and saline-alcohol treated grafts and grafts supplied with a covalently bonded layer of conventional heparin. In addition, the effect of protamine exposure to heparin-alcohol and LMW heparin-alcohol treated grafts as well as native human umbilical veins (HUV) was studied. Native HUV and heparin treated graft surfaces adsorbed and inactivated thrombin, whereas non-heparinized and saline-alcohol treated grafts inactivated surface-bound thrombin to only a small degree. Surface-bound LMW heparin exhibited a significantly lower ability to inactivate thrombin as compared with conventional heparin, but LMW heparin-alcohol surfaces were better than non-heparinized ones. Protamine treatment of “heparinized” surfaces impaired the thrombin inhibiting ability of the heparin-alcohol surface, whereas this property was totally abolished for the LMW heparin-alcohol surface. The findings indicate that LMW heparin, despite its weaker thrombin inhibiting capacity, may be an alternative to conventional heparin, for “heparinizing” the human umbilical vein graft. Protamine exposure may be potentially harmful for a heparin treated surface, although protamine concentrations used in the present in vitro study may not be reached in vivo. The native HIV was not at all affected by protamine exposure regarding its ability to inactivate thrombin.

Biogenic grafts in arterial surgery--long-term results (I. The homologous vein--II. The modified heterologous bovine carotid artery--III. The human umbilical vein).

This report summarizes the authors' experience with homologous vein grafts, modified heterologous bovine carotid artery grafts and human umbilical vein grafts in reconstructive vascular surgery. The homologous saphenous vein, taken from living donors, was implanted in 21 patients. The high percentage of early and late complications (28% and 38%, respectively), the difficult availability and the development of modern materials appear to suggest that these grafts, at least the type used in this study, should no longer be employed. The experience with 102 femoro-popliteal and femoro-tibial bypasses in 140 revascularization operations carried out with modified heterologous bovine carotid artery grafts (Solcograft) is presented. The cumulative patency rate was 43% after 5 years for the above-knee and 33% for the below-knee femoro-popliteal bypasses. The high early and late complication rates (37% and 35%) lead us to believe that this graft should also no longer be employed. The human umbilical cord vein (Meadox-Dardik-Biograft) was used in performing 68 femoro-popliteal and 15 femoro-crural bypasses in 60 limbs of 57 patients. The patency rates calculated according to the standard life table method was 36% for the above-knee (after 5 years) and 32% for the below-knee femoro-popliteal bypass (after 4 years) and 31% (after 3 years) for the femoro-tibial bypass, respectively. On the understanding that other materials should be preferred in the individual case, this material still seems to be recommendable as a graft of second or third choice.

Vascular Grafting: Clinical Applications and Techniques

This is an up-to-date discussion of graft development and techniques. Editor Creighton B. Wright has assembled a chronicle of the development of the first grafts, the present standards, and the future of grafting procedures. Many of the contributors are the original investigators. The forte of this book is the section on small vessel grafting. Statistics from the major reported series are compared clearly in the text and in graphs. Comparisons of materials, techniques, locations, and risk factors are made. The development of, indications for use of, and applicable surgical techniques involved in a variety of grafts are discussed (autogenous saphenous veins; in situ saphenous vein bypasses; fresh and preserved homologous veins; modified bovine arterial grafts; umbilical vein grafts; externally supported, noncrimped, external-velour Dacron prostheses; and polytef). The future lies in improving small vessel grafts—endothelial seeding, carbon grafts, negatively charged glutaraldehyde-tanned grafts, etc. There is an excellent discussion of thrombosis. As

Thromboxane production in umbilical vein grafts

Umbilical vein grafts were placed in the carotid arteries of sheep and removed after 10 or 90 days for determination of in vitro production of 6-keto-PGF 1α and thromboxane B 2 (TxB 2) in the anastomoses and in the middle of the grafts. At both intervals the grafts produced much more TxB 2 than carotid arteries, but no significant difference in production of 6-keto-PGF 1α was found between grafts and carotid arteries. The strongly decreased 6-keto-PGF 1α/TxB 2 ratio indicates a low resistance to platelet adhesion and aggregation, which may be a contributory cause of the thrombogenicity of vascular grafts and may possibly be involved in the pathogenesis of neotintimal fibrous hyperplasia.

Biodegradation and aneurysm formation in umbilical vein grafts. Observations and a realistic strategy.

In a series of 756 glutaraldehyde-stabilized umbilical vein grafts implanted over a 7 1/2-year period, aneurysms were identified in seven cases. The earliest aneurysm was seen at 31 months after implantation and the remainder between 43 and 79 months after surgery. Corrective surgery was performed in five cases and succeeded in four. Although definite mechanisms have not been identified, mechanical fatigue, reversal of aldehyde crosslinks, and immunologic factors may be operative. The pathologic changes include: (1) actual dilation of both graft and mesh with or without intraluminal thrombus and, (2) maintenance of graft diameter with erosion of the umbilical vein and polyester mesh rupture leading to perigraft hematoma and false aneurysm formation. Microscopic examination and infrared spectral analysis confirmed the presence of host-contributed lipid in some specimens. Although this is a low incidence of aneurysm formation, umbilical vein grafts should be selected primarily for patients with limited life expectancy or for whom alternative materials with comparable or superior patency rates are not available or acceptable. Periodic angiography, particularly after 3 or 4 years, is recommended as a routine part of follow-up examinations. Improved graft materials and control of host environmental factors are potential means to reduce the noted degradation.

Femoropopliteal and tibioperoneal artery reconstruction using human umbilical vein.

We used 99 human umbilical vein (HUV) grafts for femoropopliteal or tibioperoneal artery reconstruction in 94 patients. Results were calculated according to the life-table method for several categories possibly influencing graft patency. For above-knee v below-knee distal anastomosis, there was no difference in patency or limb-salvage rates at 30 months. Comparison of good and poor runoff situations disclosed similar 30-month graft patency rates, but significantly better limb-salvage rates among patients with good runoff. Primary revascularization fared significantly better than secondary procedures in terms of patency and limb salvage. We found no significant differences between HUV and polytef (polytetrafluoroethylene) for above-knee anastomoses or good runoff situations. However, patency and limb salvage were better for HUV use in below-knee anastomosis and poor runoff situations. The HUV may offer advantages in long-term patency and limb salvage in selected patients.