Vascutek sealed products feature a unique patented modified mammalian gelatin impregnation with over 15 years of clinical experience worldwide. These products are 100% porosity tested by Vascutek.
The impregnation also demonstrates a number of other significant features, in addition to its primary function as a sealant. Unlike other sealants, it hydrolyses over a period of 14 days by a non-enzymatic mechanism that does not elicit a prolonged inflammatory response2,3. This degradation profile allows unimpaired tissue incorporation into the matrix of the graft 4.
Low Thrombogenicity / Heparin Bonding*
Gelatin has been shown to have a low thrombogenicity4,5. Under test conditions, sealed polyester attracts fewer platelets than non-impregnated polyester 6 and collagen sealed polyester7. It also passively absorbs heparin* (achieved with a simple soaking technique) providing short-term high local concentration at the surface of the material. This gives additional active thromboresistance during the critical post-operative period that is particularly useful in low flow situations8.
Heparin bonding to Vascutek unique gelatin has CE dossier approval15
Vascutek gelatin has been shown to be the ideal sealant for ionically bonding to the antibiotic Rifampicin*9. This technique maybe used in order to minimise the incidence of postoperative graft infection10. The simple bonding procedure is particularly useful in high-risk cases10,11, including the replacement of infected grafts12, where the rifampicin-gelatin combination will survive arterial pressure and flow13. Vascutek Rifampicin* bonded grafts have been shown to be significantly more resistant to bacteremic infection than silver/collagen coated grafts14.
Rifampicin* bonding to Vascutek unique gelatin has CE dossier approval15 and is backed by over 35 publications and 10 years experience. Publications on request.
Note: * These applications of Heparin and Rifampicin have not been approved by the FDA for use in the USA or by TPD for use in Canada
1. US Patent No: 4,747,848
2. Vohra R, et al.
Sealed Versus Unsealed Knitted Dacron® Prosthesis: A Comparison of the Acute Phase Protein Response.
Annals of Vasc Surg. (1987) I: 548-551
3. Jonas R A, et al.
Unsatisfactory Clinical Experience with a Collagen-Sealed Knitted Dacron® Extracardiac Conduit.
J Cardiac Surg. (1987), Vol 2, No 2, 257-264
4. Harasaki H. et al.
Blood-Blood Pump Surface Interaction.
Ch 9 Biocompatible Polymers, Metals and Composites, ed. M. Szycher, Technomic (1983)
5. Gloviczki P. et al.
Experimental Evaluation of Bleeding Complications, Thrombogenicity and Neointimal Characteristics of Prosthetic Patch Materials Used for Carotid Angioplasty.
Cardiovascular Surgery (1996), Vol. 4, No 6, 746-752
6. Drury J.K. et al.
Experimental and Clinical Experience with a Gelatin Impregnated Dacron® Prosthesis.
Ann. Vascular Surgery (1987), 542-547
7. Safepharm Report on Thrombogenicity (Data available on request)
8. Data on file at Vascutek Ltd.
9. Ashton T. et al
Antibiotic Loading of Vascular Grafts
16th Annual Meeting of the Society for Biomaterials, May 1990, Charleston, USA
10. Strachan C.J.L. et al.
The Clinical Use of an Antibiotic-Bonded Graft.
Eur J Vasc Surg (1991), 5, 627-632
11. Strachan C.J.L. et al.
Prosthetic Graft Infection.
Critical Ischaemia (1993), Vol 2. No 3, 5-16
12. Naylor A R et al.
Treatment of Major Aortic Graft Infection: Preliminary Experience with Total Graft Excision and In Situ Replacement with a Rifampicin Bonded Prosthesis.
Eur J Vasc Endovasc Surg. (1995), 9, 252-256
13. Braithwaite B.D. et al
Early Results of a Randomized Trial of Rifampicin-Bonded Dacron Grafts for Extra-Anataomic Vascular Reconstruction
British Journal of Surgery 1998; 85; 1378-1381
14. Goëau-Brissonnière, Olivier et al
Comparison of the Resistance to Infection of Rifampicin Bonded Gelatin-Sealed and Silver/Collagen-Coated Polyester Prostheses.
J Vasc Surg 2002; 35; 1260-1263
15. Rinsing of Gelatin Sealed Prostheses with Rifampicin and/or Heparin BSI EQ# 10020927
Vascutek woven grafts feature superior strength and consistent quality. Industry-leading custom-designed machines ensure the best possible quality in manufacture and reliability in use. Equipment designed by a former NASA engineer who was involved in a number of projects for the Space Shuttle.
Custom designed weaving machines
Vascutek manufactures Köper knitted grafts for excellent dilatation resistance.
The unique, patented knitted structure, produced by this technology results in yarns being arranged perpendicular to each other on the inner surface of the graft, more similar to a woven rather than a conventionally knitted structure.
This innovative configuration preserves all the advantages of a knitted material, such as absence of fraying, no need for cautery and soft handling, along with the added benefit of dilatation resistance3,4,5.
At standard thickness (e.g. Gelsoft™ Plus), the structure provides enhanced strength and radial stability4,6, and in the Thin Wall grafts and patches, the inherent strength has allowed a reduction in thickness of the product. This provides superb handling, particularly useful in peripheral procedures. In all cases, the balanced, stable fabric structure provides excellent suture retention6, facilitating rapid anastomosis.
Unique Köper Knitted Structure with woven configuration
The Köper Knitted structure features yarns arranged perpendicular to each other on the inner surface.
Increased Radial Stability
The Köper Knitted structure displays superior dilatation resistance to conventional knitted grafts3.
1. US Patent No: 5732572
2. European Patent No: 691829
3. Guidoin R, et al.
In Vitro and In Vivo Studies of a Polyester Arterial Prosthesis with a Warp-knitted Sharkskin Structure.
Journal of Biomedical Materials Research (1997) 35, 459-472
4. Walker D, et al.
Novel Structure for a Polyester Vascular Prosthesis with Improved Mechanical Properties.
Society for Biomaterials, March 1995
5. Goëau-Brissonnière O et al
Can Knitting Effect Dilation of Polyester Bifurcated Prosthesis? A Randomised Study with the Use of Helical Computed Tomographic Scanning.
Journal of Vascular Surgery (2000) 31,157-163
6. Data on file, Vascutek Ltd
This is a novel, patented technology whereby the surface of each fibre within a macroporous polyester matrix is totally covered by fluoropolymer molecules.
An interpenetrating polymer network ensures that the fluoropolymer is tightly bonded to each fibre.
This is a novel, patented technology1, 2, whereby the surface of each fibre within a macroporous polyester matrix is totally covered by fluoropolymer molecules. The process ensures that the fluoropolymer molecules bond with the polyester giving an interpenetrating molecular network at the interface between the two polymers.
The thinness of the covering (less than 10 nanometres) does not allow it to be seen using mainstream technology - this can however be achieved by using Secondary Ion Mass Spectroscopy (SIMS). The output from the SIMS instrument visualises the presence of fluorine atoms over the total surface, providing evidence of a completely fluoropassivated structure.
The result is a new biomaterial - the first macroporous fluoropolymer. In vitro, in vivo and ex vivo studies3,4,5 on platelet deposition confirm that the Fluoropassiv™ biomaterial exhibits significantly reduced thrombogenicity compared to polyester and ePTFE. Improved healing is evidenced in animal models by more complete pseudointimal development and vasa vasorum6,7, formation. A thin pseudointima has been noted with extensive coverage by endothelium even in the mid portion of long thoracoabdominal grafts. Fluoropassivation is used in the production of Thin Wall peripheral grafts and carotid patches.
No clinical data is available which evaluates the long-term impact of the fluoropassivated surface modification treatment.
(Claims based on animal and laboratory data available from Vascutek Ltd).
Fluoropassivated carotid patches received FDA clearance in April 1998. Available in USA from 1st April 1999.
Gloviczki's Group, Mayo Clinic, Rochester,
Minnesota USA4 (carotid patch model)
Hanson's Group, Emory University School
of Medicine, Atlanta, Goergia, USA5
(ex vivo arteriovenous shunt model)
1. U.S. Patent No. 5,356,668
2. European Patent No. 645 161
3. Ashton T. et al.
Platelet Thrombogenic Response to Polyester can be Passivated by Fluoropolymer surface Treatment.
European Society for Biomaterials, (1995)
4. Rhee R. et al.
Experimental Evaluation of Bleeding Complications, Thrombogenicity, and Neonintimal Characteristics of Prosthetic Patch Materials used for Carotid Angioplasty.
Cardiovascular Surgery, (1996). Vol.4, No.6, 746-752
5. Chinn J.A. et al.
Blood & Tissue Compatibility of Modified Polyester: Thrombosis, Inflammation and Healing.
J. Biomed. Mat.Res.(1998), Vol. 39, 130-140
6. Curti T. et al.
Biocompatibility of the New Fluoropassiv™ Vascular Prosthesis- Ultrastructure Analysis.
Giornale Italiano di Chirurgia Vascolare (1994), Vol.1, No.1-2, 27-30
7. Guidon R. et al.
The Benefits of Fluoropassivation of Polyester Arterial Prosthesis as Observed in a Canine Model.
American Society for Artificial Internal Organs, (1994), Vol 40, No. 3, M870-879
All clinical papers are available upon request.
State of the Art ePTFE Graft Manufacturing
Vascutek utilises the very latest state of the art computer controlled manufacturing and monitoring systems in its ePTFE production facility.
These systems ensure that an exacting level of consistency and quality of product is achieved.
ePTFE Graft Production
Stage 1 – PTFE Mixing
PTFE resin is mixed with an alcohol-based liquid, forming a PTFE paste.
Stage 2 – Billet Formation
PTFE paste is then crushed into a solid structure (billet) using high pressure.
The pressure is computer controlled to ensure a homogenous billet.
Stage 3 – Extrusion
The billet is then placed into the extrusion equipment.
Different extrusion heads and pins are used, depending upon which type of graft is being manufactured, for example a 6mm thin wall or a 7mm standard wall.
Stage 4 – Alcohol Evaporation
The extruded PTFE is cut into short lengths and placed in a low temperature oven to allow the alcohol to evaporate. At this stage the PTFE has internal diameter and wall thickness parameters of the final product. The high pressure used in the extrusion process aligns the PTFE molecules in a longitudinal direction.
Stage 5 – Stretching
This process enables the conversion of extruded PTFE to expanded PTFE.
The short lengths of PTFE are placed into an oven and allowed to warm. This heating process softens the extruded PTFE. The short tubes are then stretched in a longitudinal direction at a pre-determined rate. The stretching process causes the tube to fibrillate. This results in a conversion from extruded PTFE to expanded PTFE. The computer controlled rate and ratio of stretching determines the inter-nodal distance (pore size) of the graft.
Stage 6 – ePTFE Film Wrapping
This process adds mechanical strength to the final expanded PTFE graft. An ePTFE film is wrapped in a double layer onto the outer surface of the expanded PTFE tube using a laser guided system. Vascutek ePTFE film has the same porosity as the base graft, therefore the potential for tissue incorporation is possible with this ePTFE film structure.
Stage 7 – Sintering (Cooking the expanded PTFE)
The expanded PTFE is next placed into the sintering oven. This is the most critical part of the entire production process as sintering stabilises the PTFE and vastly improves the mechanical strength of the product.
Vascutek Ltd. has developed a "continuous conveyor" sintering process where the ePTFE passes through a high temperature zone that causes the molecules to coalesce. The continuous conveyor sintering oven operates at temperatures in excess of 380°C with the hot zone being tightly controlled to within 3°C. This vastly reduces product variability seen in the traditional batch oven process used by other manufacturers.
Stage 8 – Printing (Adding the guideline)
All products are then printed with a guideline.
Stage 9 – Reinforcing (Adding external support if required)
External spiral support is added to the graft (if required). The external spiral support provides kink and crush resistance and may be over the entire length of the graft, or have a central or end position.
Stage 10 – Gelatin Sealing (Process used with SEALPTFE™ and Taperflo™ product ranges)
Vascutek has developed a unique patented gelatin sealing process for its ePTFE products. This process coats the external surface of the graft with Vascutek’s proven gelatin sealant technology.
Stage 11 – Cutting, Packaging & Sterilisation
At this stage, the grafts are cut to the desired length, packaged and then sterilised using Ethylene Oxide.
ePTFE Quality Control Procedures
Quality and consistency are paramount at every stage of ePTFE production.
From raw material checks to finished goods, Vascutek’s Quality Assurance Programme guarantees production excellence.
To ensure our finished products meet their exacting design specifications, we remove multiple samples from each production batch and test these to destruction. The remainder of the batch is held in quarantine.
The testing schedule includes the following:
- Longitudinal tensile strength
- Suture retention (straight & oblique)
- Differential scanning calorimetery (DSC)
- Wall thickness measurements
- Internal diameter measurements
- Radial burst strength
- Peel strength (externally reinforced products)
- Peel strength (wrapped products)
Only after the samples have passed ALL tests, will the remainder of the batch be released for sale.
If the products fail to meet the design specification for ANY of the tests – the whole batch will be rejected and destroyed.