Knitted Dacron Grafts Research Articles

Replacement of thoracic aorta using gelatin impregnated knitted Dacron graft and results of follow up

Replacement of thoracic aorta using gelatin impregnated knitted Dacron graft and results of follow up

Platelet aggregometry can accurately predict failure of externally supported knitted Dacron femoropopliteal bypass grafts

Purpose: Our purpose was to evaluate whether a method for quantification of platelet aggregability will predict failure of knitted Dacron femoropopliteal bypass grafts.Methods: A numerically derived platelet aggregation (PA) score, based on the aggregation pattern and platelet count, was determined in the 40 patients available for platelet analysis who underwent 53 femoropopliteal bypass grafts with preclotted, 6 mm, externally supported knitted Dacron grafts from 1981 to 1991 (mean follow-up 50 months). The preoperative score was found to remain stable after surgery, enabling the use of postoperative values when preoperative values were not available. The PA score was available in 19 patients (23 grafts) before surgery and 23 patients (30 grafts) after surgery. The following factors were analyzed for predicting graft failure by the Cox proportional hazards regression model: PA score, age, gender, history of smoking, coronary artery disease, hypertension, hyperlipidemia, cerebrovascular disease, diabetes, claudication versus limb salvage, site of the distal anastomosis, previous ipsilateral bypass, and state of the runoff as determined by preoperative angiography.Results: Of the studied risk factors, the value of the PA score was the most significant predictor of graft closure (p < 0.0001). An increase of 10 units was associated with an increased relative risk of 2.02. Throughout the follow-up period, 15 of 16 grafts remained patent in patients with a PA score of 15 or less, but only 2 grafts out of 17 remained patent in patients with a PA score of 30 or greater.Conclusions: These data suggest that the PA score is a potential risk factor for failure of femoropopliteal bypass with externally supported knitted Dacron grafts.

Platelet aggregometry can accurately predict failure of externally supported knitted Dacron femoropopliteal bypass grafts

Our purpose was to evaluate whether a method for quantification of platelet aggregability will predict failure of knitted Dacron femoropopliteal bypass grafts. A numerically derived platelet aggregation (PA) score, based on the aggregation pattern and platelet count, was determined in the 40 patients available for platelet analysis who underwent 53 femoropopliteal bypass grafts with preclotted, 6 mm, externally supported knitted Dacron grafts from 1981 to 1991 (mean follow-up 50 months). The preoperative score was found to remain stable after surgery, enabling the use of postoperative values when preoperative values were not available. The PA score was available in 19 patients (23 grafts) before surgery and 23 patients (30 grafts) after surgery. The following factors were analyzed for predicting graft failure by the Cox proportional hazards regression model: PA score, age, gender, history of smoking, coronary artery disease, hypertension, hyperlipidemia, cerebrovascular disease, diabetes, claudication versus limb salvage, site of the distal anastomosis, previous ipsilateral bypass, and state of the runoff as determined by preoperative angiography. Of the studied risk factors, the value of the PA score was the most significant predictor of graft closure (p < 0.0001). An increase of 10 units was associated with an increased relative risk of 2.02. Throughout the follow-up period, 15 of 16 grafts remained patent in patients with a PA score of 15 or less, but only 2 grafts out of 17 remained patent in patients with a PA score of 30 or greater. These data suggest that the PA score is a potential risk factor for failure of femoropopliteal bypass with externally supported knitted Dacron grafts.

Enhanced Patency of Venous Dacron Grafts by Endothelial Cell Sodding

The effect of microvessel endothelial cell (EC) sodding on the patency of Dacron grafts interposed in canine inferior vena cava was studied. EC were harvested enzymatically from canine omentum and isolated by density gradient centrifugation. Preclotted, knitted Dacron grafts were sodded with > 10(6) EC/cm2 surface. The results demonstrate significant improvement in patency of sodded grafts placed in the inferior vena cava as compared with control grafts (p < 0.001 in grafts with a distal arteriovenous fistula and p < 0.05 in grafts without a distal fistula). The neointima of the sodded grafts were thinner and scanning electron microscopy confirmed the presence of a confluent layer of EC. In addition, the production of prostacyclin but not thromboxane A2 was significantly enhanced in the sodded grafts as compared with controls. We conclude that microvessel EC sodding of Dacron grafts significantly improves the patency rate and inhibits neointimal thickening of the prosthesis. The mechanism is unknown but may involve a more rapid endothelialization of the graft surface with the potential of producing more prostacyclin and less thromboxane A2.

Failure of the Hemashield extension in right ventricle-to-pulmonary artery conduits

Between 1989 and 1991, 17 childien underwent 18 right ventricle-to-pulmonary artery conduit placement operations using a composite of an aortic or pulmonary valved homograft and a Hemashield extension to the ventricle. Hemashield is a collagen-coated knitted Dacron graft with excellent compliance and hemostatic properties. Diagnoses included tetralogy of Fallot with pulmonary atresia (7), truncus arteriosus (6), and complex transposition of the great arteries (4). Mean age at conduit placement was 4.9 ± 4.2 years, and all patients survived. At a mean follow-up of 14 ± 4 months, postoperative Doppler echocardiographic gradients between the ventricle and pulmonary artery ranged from less than 20 to 60 mm Hg. At cardiac catheterization 13 ± 3 months postoperatively (6 patients), the systolic pressure gradient across the conduits ranged from 14 to 90 mm Hg (mean gradient, 59 ± 29 mm Hg). Conduit obstruction, when present, was demonstrated angiographically to be in the Hemashield portion and led to early conduit replacement six times in 5 patients (33% of operations) within 10 to 18 months (mean time, 14 months) after insertion of the original conduit. Pathologic examination of the explanted conduits revealed the obstruction to be a thick neointimal peel that was impossible to separate from the Hemashield graft. Failure of the Hemashield as an extension for ventricle-to-pulmonary artery conduits secondary to accelerated neointimal formation has led us to abandon its use in clinical practice.

Development of a Hierarchically Structured Hybrid Vascular Graft Biomimicking Natural Arteries

A hierarchically structured hybrid vascular graft, resembling the layered structure of the intima and the media of a natural artery, is expected to exhibit structural stability and function similar to those of an artery. Two models of hybrid vascular grafts were constructed on knitted Dacron grafts (internal diameter, 4 mm; length, 6 cm; Golaski Laboratories, Inc., Philadelphia, PA) in vitro. The model I graft consisted of only an endothelial cell (EC) monolayer, and the model II graft was hierarchically structured with an EC monolayer and smooth muscle cell (SMC) multilayers embedded in a mixed gel of type I collagen and dermatan sulfate. Both models were implanted bilaterally in carotid arteries of 11 dogs for up to 12 weeks without anticoagulant. All grafts were patent after the implantation. There was a marked difference in the formation of the neomedia between the two models at 2 weeks: only a collagenous layer was observed beneath the EC monolayer in model I grafts, whereas the reconstructed neomedia consisting of proliferating SMCs and extracellular matrix was observed in model II grafts. In model I grafts at 2 weeks, the luminal surface with a wavelike form, along with crimps of the vascular graft, was almost endothelialized, but EC orientation was disorganized at the troughs of the crimps. Leukocyte adhesion on ECs and migration into their interstices were observed in some areas. Such events were infrequent in model II grafts at 2 weeks. Model II grafts at 12 weeks had an integrated neomedia comparable to that of a natural artery: SMCs exhibited dense accumulation and circumferential orientation.(ABSTRACT TRUNCATED AT 250 WORDS)

Differentiated Biocompatible Design of Luminal and Outer Graft Surfaces

Differentiated biocompatible design of luminal and outer graft surfaces may lead to successful healing of vascular grafts. Non-cellular adhesion characteristics are required for a luminal surface, whereas enhanced cell adhesion and migration are desired for an outer surface. We molecularly designed photocurable extracellular matrices (ECMs). Photocurable chondroitin sulfate (CS) was prepared for the luminal surface and photocurable gelatin for the outer surface. Both were partially derivatized with photodimerizable groups such as cinnamate and coumarin. These ECMs were converted to produce water insoluble gels upon ultraviolet irradiation. In vitro study showed that platelet adhesion on the photogelled CS was significantly reduced, whereas endothelial cells adhered well to the photogelled gelatin. These materials were individually coated and photogelled onto respective surfaces of knitted Dacron grafts (internal diameter 5 mm, length 5 cm). The ECM coated grafts were implanted into the abdominal aortae of dogs. During acute phase implantation for up to 1 week, minimized cell adhesion was observed on the luminal surface where the photogelled CS had provided a uniform cover, and enhanced tissue ingrowth was noted at the outer surface. However, some thrombi were formed, probably because of incomplete coating of, or cracks in, the photogelled CS. Although the molecularly designed ECMs and their in vitro performance appeared to follow our concept, further improvements in coating technique and molecular design of ECMs are needed for better in vivo performance. This may result in enhanced tissue regeneration, as well as a high patency rate.

Axillofemoral bypass with externally supported, knitted Dacron grafts: A follow-up through twelve years

Purpose: The purpose of this study was to review our experience with externally supported, knitted Dacron grafts used for axillofemoral bypass.Methods: Retrospective analysis was performed on records of 79 consecutive axillofemoral bypass graft operations performed on 77 patients from January 1978 to April 1990.Results: The mortality rate within 30 days of operation was 5% (four of 79); 36 patients died in the follow-up period; none died of graft causes. During this 12-year period (mean follow-up 42 months) three patients were unavailable for follow-up. The primary patency rate was 78% at 5 years and 73% at 7 years, with no change thereafter. Neither the graft configuration (i.e., axillounifemoral [n = 50] vs axillobifemoral [n = 29]) nor patency of the superficial femoral artery had an impact on the primary patency rate. Patients who underwent surgery for disabling claudication (n = 30 grafts) had a primary patency rate of 80% at 6 years compared with 65% at 6 years for those who required surgery for limb salvage (n = 49 grafts); the difference was not significant (p = 0.37). Actuarial survival of patients with axillofemoral grafts was 23% at 10 years compared with 72% in a concurrent population of patients with aortofemoral bypass (p < 0.001).Conclusion: These findings indicate that axillofemoral bypass grafts may be appropriate for high-risk patients with severe aortoiliac disease who require revascularization for either limb salvage or incapacitating claudication.

A clinical experience of gelatin-sealed knitted dacron graft (Gelseal Triaxial) implanted in the vascular reconstructions below the abdominal aorta

A clinical experience of gelatin-sealed knitted dacron graft (Gelseal Triaxial) implanted in the vascular reconstructions below the abdominal aorta

Use of an antibiotic-bonded graft for in situ reconstruction after prosthetic graft infections.

We have developed an infection resistant vascular prosthesis by bonding rifampin to Dacron grafts with the use of a collagen matrix release system. The purpose of this study was to determine the efficacy of this antibiotic-bonded graft in resisting infection after an in situ reconstruction of a previously infected prosthetic bypass. Eighty-three adult mongrel dogs underwent implantation of a 3 cm untreated Dacron graft into the infrarenal aorta. This initial graft was deliberately infected, at the time of operation, with 10(2) organisms of Staphylococcus aureus by direct inoculation. One week later, the dogs were reexplored, the retroperitoneum debrided, and the animals randomized to undergo an end-to-end in situ graft replacement with either one of two types of prosthetic grafts: group I (collagen, n = 36) received control collagen-impregnated knitted Dacron grafts; group II (rifampin, n = 47) received experimental collagen-rifampin-bonded Dacron grafts. Each group of animals was then subdivided to receive one of four treatment protocols: (a) no antibiotic therapy, (b) cephalosporin peritoneal irrigation solution (cefazolin 500 mg/1000 ml) during operation and two doses of cephalosporin (cefazolin, 500 mg intramuscularly) postoperatively, (c) treatment as in protocol group b plus 1 week of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily), and (d) treatment as in protocol group b plus 2 weeks of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily). All grafts were sterilely removed between 3 and 4 weeks after implantation. There were no anastomotic disruptions and all grafts were patent at the time of removal.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of an antibiotic-bonded graft for in situ reconstruction after prosthetic graft infections

We have developed an infection resistant vascular prosthesis by bonding rifampin to Dacron grafts with the use of a collagen matrix release system. The purpose of this study was to determine the efficacy of this antibiotic-bonded graft in resisting infection after an in situ reconstruction of a previously infected prosthetic bypass. Eighty-three adult mongrel dogs underwent implantation of a 3 cm untreated Dacron graft into the infrarenal aorta. This initial graft was deliberately infected, at the time of operation, with 102 organisms of Staphylococcus aureus by direct inoculation. One week later, the dogs were reexplored, the retroperitoneum debrided, and the animals randomized to undergo an end-to-end in situ graft replacement with either one of two types of prosthetic grafts: group I (collagen, n = 36) received control collagen-impregnated knitted Dacron grafts; group II (rifampin, n = 47) received experimental collagen-rifampin-bonded Dacron grafts. Each group of animals was then subdivided to receive one of four treatment protocols: (a) no antibiotic therapy, (b) cephalosporin peritoneal irrigation solution (cefazolin 500 mg/1000 ml) during operation and two doses of cephalosporin (cefazolin, 500 mg intramuscularly) postoperatively, (c) treatment as in protocol group b plus 1 week of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily), and (d) treatment as in protocol group b plus 2 weeks of cephalosporin (cefazolin, 500 mg intramuscularly, twice daily). All grafts were sterilely removed between 3 and 4 weeks after implantation. There were no anastomotic disruptions and all grafts were patent at the time of removal. Cultures were obtained from the grafts and peri-graft tissues separately. Analysis included determination of the culture positivity of tissue and graft samples combined and of the graft segments alone irrespective of the results of the surrounding tissue cultures. Results were expressed as the percentage of animals that had culture positive results at sacrifice. For group I, collagen graft animals, the rate of infection in graft segments alone was 100%, 87.5%, 100%, and 80% when the animals received supplemental antibiotic therapy according to groups a through d as described, respectively. For group II, rifampin graft animals, the corresponding values were 50%, 50%, 20%, and 20%. When overall infection rates were evaluated, samples from dogs in group I were culture positive in 100%, 87.5%, 100%, and 80% of the animals in each of the supplemental antibiotic therapy groups, respectively. In group II animals, the corresponding positivity rates for overall infection were 62.5%, 62.5%, 60%, and 20%. In all four treatment groups the reduction of positive graft cultures after in situ replacement of a previously infected aortic prosthesis with a collagen-rifampin-bonded graft was statistically significant. When overall infection rates were evaluated, this reduction was statistically significant only in the subset of animals treated with 2 weeks of supplemental antibiotics. We conclude that the collagen-rifampin-bonded graft reduces the incidence of graft colonization after in situ replacement of an infected graft. A course of supplemental antibiotics is required to sterilize the surrounding peri-graft tissues.

Prostacyclin is produced from endothelial cell-seeded grafts: An experimental study in sheep

Endothelial cell seeding might be of value in reducing the thrombogenicity of small-diameter vascular grafts. We investigated the capacity of endothelial cell-seeded grafts to produce prostacyclin and compared this with that of the unseeded graft as well as the native artery. Twelve sheep were operated on with carotid interposition of externally supported knitted dacron grafts. On one side of the neck the graft was seeded with endothelial cells, enzymatically harvested from the left jugular vein. After 3 weeks, three out of 12 seeded grafts, and one out of 12 unseeded grafts were occluded (N.S.). After excision, the grafts were mounted and perfused ex vivo for five 15-min periods. During the last period, arachidonic acid (4 micrograms/ml) was added to the perfusate. The resected carotid artery was used as a control. Prostacyclin was determined as the stable degradation product 6-keto-PGF1 alpha using radio-immunoassay, and expressed as pg mm-2 luminal surface. The native artery had a significantly higher release of prostacyclin than the seeded graft, which in turn had a significantly higher release than the unseeded graft. Histological examination showed weakly positive staining for factor VIII-related antigen on the luminal surface of seeded grafts. Scanning electron microscopy showed endothelial cells with typical endothelial tufts and was evaluated blindly from 10 areas of each graft. The extent of endothelial cell coverage was evaluated and scored from 0 to 2.5. The median score for the unseeded grafts was 0.3 and for the seeded grafts 1.5 (p = 0.008). Prostacyclin production was higher in seeded than unseeded grafts, but did not influence patency in this model.

The acute thrombogenicity of an infection-resistant rifampicin soaked dacron graft: An experimental study in sheep

Every effort to reduce synthetic graft infection is welcome and when designing antibiotic-bonded grafts it is important not to increase graft thrombogenicity. In order to study the acute thrombogenicity of rifampicin-soaked gelatin-sealed Dacron grafts compared with untreated gelatin-sealed Dacron grafts, an experimental carotid artery sheep model was used. Twenty sheep were anaesthetised and 7-cm-long 5-mm-wide externally supported gelatin-sealed knitted Dacron grafts were sutured end to end into each carotid artery after excising a portion of that vessel. Test grafts had previously been immersed for 15 min in a rifampicin solution (1 mg ml-1) while control grafts were immersed in physiological saline for 15 min. There were two groups with 10 sheep in each. In one group the blood flow through the grafts was unrestricted but in the second the flow was restricted to 25 ml min-1. Platelets from sheep labelled with 111In and sheep fibrinogen labelled with 125I were injected intravenously. The isotope activities were continuously measured proximally and distally over the grafts for 4 h. With unrestricted flow 4 out of 10 rifampicin-soaked grafts occluded compared with 2 out of 10 control grafts (N.S.). Time to occlusion, thrombus weight, platelet and fibrinogen activity did not differ. In the restricted flow group 9 out of 10 rifampicin-soaked grafts occluded compared with 6 out of 10 control grafts (N.S.). The time to occlusion did not differ. The thrombus weight in the rifampicin group was significantly higher compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental comparison of albumin-sealed and gelatin-sealed knitted Dacron conduits

Two high-porosity knitted Dacron vascular grafts sealed with aldehyde cross-linked gelatin or albumin were compared with respect to the following characteristics. Porosity control by the absorbable sealant was assessed with a water porosity meter at 120 mm Hg pressure. Ease of suturing was determined by an objective needle penetration test. Sealant resorption was assessed histologically in a subcutaneous immature rat model as well as in circulatory implants. Gross and microscopic healing characteristics were compared in circulatory implants in the thoracic aorta of sheep with use of a composite conduit in every animal, which allowed direct comparison of the two graft materials and minimized differences in healing between individual animals. Both grafts demonstrated excellent porosity control and better handling characteristics than woven Dacron. Sealant resorption was generally rapid, although residual albumin sealant was often seen adjacent to anastomoses. Residual sealant appeared to result in focally poor healing with focal loss of adhesion of surrounding tissue to graft. We conclude that details of sealant preparation and application can importantly influence the performance of presealed knitted Dacron grafts and should be carefully evaluated in the laboratory before clinical implantation is begun.

Comparative Evaluation of the Elasticity and Flexibility of Bioimpregnated Knitted Grafts

Longitudinal elasticities of whole human blood clot, whole canine blood clot, Factor XIII cross-linked fibrin, glutaraldehyde-fixed human albumin, and formaldehyde-fixed collagen, gelatin and collagen/gelatin were determined and normalized to human whole blood clot. Matrices of a knitted Dacron graft were then impregnated with albumin, collagen, and collagen/gelatin and their longitudinal elasticities were determined and normalized to a preclotted graft. Comparisons were also made for the longitudinal elasticities of a virgin graft, a manipulated control for a preclotted graft, and a manipulated control for the matrix-impregnated grafts. Flexibilities were then calculated based on the weights and elasticities of these grafts and normalized to the flexibility of the preclotted graft. Fibrin had twice and 39 times more longitudinal elasticity than human blood clot and collagen, respectively. The preclotted graft has longitudinal elastic properties similar to a virgin graft, and is 2.8, 2, and 1.4 times more elastic than the albumin, collagen and collagen/gelatin grafts, respectively. The preclotted graft was 2.5, 2, and 1.4 times more flexible than the albumin, collagen and collagen/gelatin grafts, respectively.

Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms

This study reports on animal experimentation and initial clinical trials exploring the feasibility of exclusion of an abdominal aortic aneurysm by placement of an intraluminal, stent-anchored, Dacron prosthetic graft using retrograde cannulation of the common femoral artery under local or regional anesthesia. Experiments showed that when a balloon-expandable stent was sutured to the partially overlapping ends of a tubular, knitted Dacron graft, friction seals were created which fixed the ends of the graft to the vessel wall. This excludes the aneurysm from circulation and allows normal flow through the graft lumen. Initial treatment in five patients with serious co-morbidities is described. Each patient had an individually tailored balloon diameter and diameter and length of their Dacron graft. Standard stents were used and the diameter of the stent-graft was determined by sonography, computed tomography, and arteriography. In three of them a cephalic stent was used without a distal stent. In two other patients both ends of the Dacron tubular stent were attached to stents using a one-third stent overlap. In these latter two, once the proximal neck of the aneurysm was reached, the sheath was withdrawn and the cephalic balloon inflated with a saline/contrast solution. The catheter was gently removed caudally towards the arterial entry site in the groin to keep tension on the graft, and the second balloon inflated so as to deploy the second stent. Four of the five patients had heparin reversal at the end of the procedure. We are encouraged by this early experience, but believe that further developments and more clinical trials are needed before this technique becomes widely used.

The effect of extraanatomic bypass on aortic input impedance studied in open chest dogs: Should the vascular prosthesis be compliant to unload the left ventricle?

Left ventricular hypertrophy has been reported after ascending aorta-abdominal aorta bypass, despite seemingly insignificant changes in cardiac output and mean arterial pressure. Such a bypass procedure may be used for the treatment of complex coarctation of the aorta, hypoplastic aortic arch, or thoracoabdominal aortic aneurysm. To investigate the effect of the bypass procedure on left ventricular afterload, we measured aortic input impedance in six open chest dogs by placing a knitted Dacron graft from the ascending aorta to the abdominal aorta and occluding the aortic arch. Cardiac output and mean arterial pressure remained unaltered throughout the experiment, consistent with clinical reports. Systolic pressure increased by 25% of control, and the ratio of diastolic pressure-time index to tension-time index decreased by 27%. The measured input impedance was then approximated with the three-element windkessel model, which consists of resistance, compliance, and characteristic impedance (average of impedance modulus between 5 and 15 Hz). There was no change in resistance and compliance; characteristic impedance increased to 255% of control. Connecting an air chamber to the vascular prosthesis doubled the compliance and decreased the characteristic impedance nearly to the control value without altering resistance. It also reduced the systolic pressure by 14% of the bypass protocol and increased the ratio of diastolic pressure-time index to tension-time index (by 32% of control value and 82% of bypass value). Arterial systolic pressure and pulse pressure were both linearly correlated with the characteristic impedance. Thus we conclude that although ascending aorta-abdominal aorta bypass does not affect cardiac output, mean arterial pressure, resistance, or compliance, it does increase characteristic impedance. Left ventricular systolic load is directly correlated with characteristic impedance. Increased systolic wall stress might be the cause of left ventricular hypertrophy of the previously reported cases. Because decrease in the distensibility of the proximal aorta is one of the factors causing the increase in characteristic impedance, using a compliant graft might help to unload the heart.

Prevention of graft infection by use of prostheses bonded with a rifampin/collagen release system

The objective of this study was to test the efficacy of bonding rifampin to double-velour Dacron grafts with collagen to prevent graft sepsis. Fifty 6.0 mm Dacron grafts (length 5.0 cm) impregnated with either collagen (control) or collagen plus rifampin (experimental) were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into four groups (each with an experimental and control subdivision) as a function of time between grafting and bacterial challenge. At 2, 7, 10, or 12 days after graft implantation, sequential groups were challenged with 1.2 × 108 colony forming units of Staphylococcus aureus (clinical isolate) intravenously suspended in 250 ml normal saline. Three weeks after hematogenous seeding, the grafts were sterilely harvested. One-tailed Fischer's exact test was used to compare the patency and culture-proven infection of control and antibiotic coated grafts as a function of implantation time before bactermic challenge. In the 2-day group, four of six control grafts were infected compared with zero of six experimental grafts (p < 0.030). In the 7-day group, five of six control grafts were infected with S. aureus versus zero of six in the experimental group (p < 0.008). In the 10-day group, one of six experimental grafts was infected, but the control group had only two of six graft infections. In the 12-day group two of six experimental grafts and one of five control grafts were infected. These results indicate that rifampin bonded with collagen to knitted Dacron grafts will protect the graft from bacteremic infection for 7 days after implantation in a highly challenging model. After 7 days accelerated healing of the collagen graft surface may, in itself, protect against delayed bacterial seeding.

Prevention of Vascular Graft Infection by Rifampin Bonding to a Gelatin-Sealed Dacron Graft

This study examines the efficacy of rifampin bonding to a gelatin-sealed knitted Dacron graft to prevent perioperative bacteremic vascular graft infection. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 1 mg/ml saline solution of rifampin at 37 degrees C. Nineteen dogs had thoracoabdominal aortic bypass: seven (group I) received a rifampin treated graft; six (group II) received an untreated gelatin-coated graft; and six (group III) received an uncoated Dacron graft. Two days later bacteremic challenge was produced by rapid intravenous injection of 5 x 10(5) colony forming units of methicillin resistant Staphylococcus aureus. Grafts were harvested five days after this challenge and cut into 10 fragments, each submitted to bacterial counts. Results were expressed as CFU/cm2 of graft material. In group I, no graft was infected, whereas all grafts in groups II and III were infected (p less than 0.05). Median bacterial counts from the infected fragments (median +/- SD) were similar in groups II (2.5 x 10(5) CFU/cm2) and III (4 x 10(4) CFU/cm2). Blood cultures at time of sacrifice were negative in all dogs in group I and positive in five of six dogs in groups II and III. Cultures of liver, spleen, kidney, and lung specimens were always negative in group I and positive in 22 of 24 specimens in group II and 23 of 24 specimens in group III. Soaking a gelatin-sealed Dacron graft in rifampin solution evidently prevents early bacteremic graft infection and secondary foci of infection in this model.

Healing Parameters of a New Albumin-coated Knitted Dacron Graft

Knitted dacron grafts commercially coated with human albumin were implanted end-to-side between the infrarenal aorta and the bifurcation in 9 growing pigs. Uncoated knitted dacron grafts implanted in 6 pigs served as a control. Grafts were explanted after 4, 8, and 12 weeks and evaluated for neointimal healing, peeling of the inner and outer capsule, extent of neoendothelialization, absorption of the sealant, interstitial infiltration, and perigraft inflammation. Toxicological in-vitro analysis included the evaluation of residual aldehydes and plasticizers. In contrast to the uncoated knitted prosthesis, which rapidly developed a layered neointima with complete neoendothelialization, only islands of neointima were found in albumin-coated grafts after 4 weeks. The neointima remained incomplete at 8 and 12 weeks with scanning electron microscopic evidence of sharply demarcated endothelial areas. No transprosthetic bridging was detectable even after 12 weeks and peeling of the inner and outer capsule was easily provocable. These results outline that the cellular and connective infiltration of the prosthetic wall is compromised unless degradation of the sealant is completed within four weeks: the neointimal development is delayed and graft incorporation fails, leaving the outer capsule unattached.