The early days of vascular and heart valve prostheses: a historical review.

This surgical heritage article provides a historical overview of the most important early advances of vascular- and valvular surgery, that lead to the development of currently used vascular- and valvular prostheses and materials. The first writings describing techniques in vascular surgery mainly focussed on hemorrhage control and date from around 1600 B.C. The strategy of vessel ligation was first mentioned in Western literature around 200 B.C. In the 18th century, techniques of ligation were expanded towards attempts of vessel restoration. The first artificial vascular prosthesis was made in 1894. From this time on, vascular prostheses were used in animal experiments and around 1900 for the first time in humans. More than 60 years later, in 1952, the first mechanical heart valve prosthesis was implanted. Four years later, the first successful biological heart valve implantation followed. In 2000, a transcatheter heart valve was successfully implanted in a human for the first time. Over time, procedures and techniques became more efficient and effective. This led to new developments, such as the manufacturing of a tissue engineered blood vessel in 1986. Nowadays, dozens of different valve prostheses have been devised, both mechanical and biological. Still, no ideal model of vascular and heart valve prosthesis exists.

A Novel Cardiovascular Prosthesis Made from Woven Ultrahigh-Molecular-Weight Polyethylene Fibers, Proof of Concept in a Sheep Model.

BACKGROUND: A patch made of woven ultrahigh-molecular-weight polyethylene (UHMWPE) fibers is thin, strong, and flexible and may be attractive for use in cardiovascular prostheses. This study assessed the hemocompatibility of this patch in a sheep model. METHODS: The UHMWPE patches were sutured in the right carotid artery and jugular vein in 12 adult sheep, and in the same animal, expanded polytetrafluoroethylene (ePTFE) patches were sutured as control patches in the left carotid artery and jugular vein. Follow-up (FU) was 4 hrs, 1 week, and 6 weeks (n = 4 for all time points). Patency of the vessels was assessed with qualitative observational short-axis echography, and thrombus formation and tissue deposition were assessed with histology. RESULTS: All vessels were fully patent at the end of the study. Thrombus formation was comparable for the UHMWPE and the ePTFE patches. Tissue deposition was not significantly different on the UHMWPE patches, except for patches in the jugular vein at 1 week of FU where it was significantly thicker. CONCLUSIONS: These results suggest the noninferiority of the UHMWPE patch compared with the clinically used ePTFE patch; therefore, this novel cardiovascular prosthesis might be attractive for use as a cardiovascular patch.

Flexible mechanoprosthesis made from woven ultra-high-molecular-weight polyethylene fibres: proof of concept in a chronic sheep model.

OBJECTIVES: Ultra-high-molecular-weight polyethylene (UHMWPE) fibres are flexible, have high tensile strength, and platelet and bacterial adhesion is low. Therefore, UHMWPE may overcome limitations of current mechanical valves and bioprostheses. In this study, the biocompatibility and functionality of prototype handmade stented valves from woven UHMWPE (U-valve) was assessed in a chronic sheep model with acetylsalicylic acid monotherapy. METHODS: Native pulmonary valves of 23 sheep were replaced by U-valves (n = 18) or Perimount bovine bioprostheses (reference group, n = 5). Sheep received 80 mg of acetylsalicylic acid daily. Follow-up was conducted at 1 week (n = 4), 1 month (n = 5), 3 months (n = 5) and 6 months (n = 4) in the U-valve group and at 3 months (n = 2) and 6 months (n = 3) in the reference group. Epicardial echocardiography and histology were used to assess valve function and tissue deposition, respectively. RESULTS: Seventeen U-valve sheep (94%) and 3 reference sheep (60%) survived the perioperative period. One reference valve sheep was sacrificed after 4 months because of congestive heart failure. At explantation, all U-valves were intact without leaflet tearing. Up to 3 months, U-valves were flexible and free of stenosis. Regurgitation was mostly mild though gradually increasing; histology showed minimal connective tissue near the leaflet base and sparse calcification. At 6 months, connective tissue was diffusely observed on the leaflets with retraction and consecutive regurgitation and leaflet thickening. CONCLUSIONS: Valves made from UHMWPE fibres demonstrated early feasibility in the pulmonary valve position with reasonably good haemodynamics and intact valve materials up to 6 months. Gradual leaflet thickening and retraction were observed after 3 months due to connective tissue overgrowth.

Adherence of Staphylococcus aureus to Dyneema Purity® Patches and to Clinically Used Cardiovascular Prostheses.

Various materials that are used for vascular and heart valve prostheses carry drawbacks: some require anticoagulant drugs or have moderate durability; others are not suitable for endovascular treatment. These prostheses are associated with bacterial infections. A material potentially suitable for prostheses is Dyneema Purity®, made of ultra-high-molecular-weight polyethylene. Dyneema Purity® fibers are very thin, flexible, resistant to fatigue and abrasion, and have high strength. S. aureus adherence to Dyneema Purity® was tested and compared with currently used cardiovascular prostheses. We compared adhesion of S. aureus to Dyneema Purity® (1 membrane-based and 1 yarn-composed patch) with 5 clinically used yarn-composed polyester and membrane-based expanded polytetrafluoroethylene patches. Patches were contaminated with S. aureus bacteria and bacterial adherence was quantified. S. aureus adherence was also visualized in flow conditions. Overall, bacterial adherence was higher on yarn-composed prosthesis materials, with a rough surface, than on the membrane-based materials, with a smooth surface. Adherence to Dyneema Purity® materials was non-inferior to the currently used materials. Therefore, patches of Dyneema Purity® might be attractive for use in cardiovascular applications such as catheter-based heart valves and endovascular prostheses by their good mechanical properties combined with their noninferiority regarding bacterial adhesion.

In Vitro Hemocompatibility Testing of Dyneema Purity Fibers in Blood Contact.

OBJECTIVE: Heart valve and vascular prosthesis implantation is a common procedure for patients with heart valve stenosis or regurgitation and dilated or obstructive vascular disease. Drawbacks of conventional valve prostheses are the requirement for anticoagulant drugs, moderate durability, and suboptimal resistance to fatigue and tear. Dyneema Purity fibers are made from ultra-high-molecular-weight polyethylene filaments and are very thin, flexible, and fatigue and abrasion resistant and have high strength. Therefore, prostheses made from Dyneema Purity fibers might be attractive for use in the minimally invasive treatment of valvular- and vascular diseases. The aim of this study was to test the hemocompatibility of Dyneema Purity fibers in contact with blood. METHODS: Real-time platelet adhesion in human blood of 3 volunteers was quantified after 5 minutes of perfusion on single filaments (Ø 15 µm) of Dyneema Purity and polyester fibers. Plasma thrombin generation was measured by fluoroscopy for patches of Dyneema Purity fibers and for 5 commonly used polyester and expanded polytetrafluoroethylene cardiovascular prostheses. RESULTS: Platelet adhesion per 1 mm was 6 ± 1.4 on Dyneema Purity filaments and 15 ± 3.4 on polyester filaments (P = 0.02). Total formed thrombin and the time to peak of its maximum were noninferior for patches of Dyneema Purity fibers compared with the reference materials. CONCLUSIONS: Dyneema Purity fibers are noninferior in adhesion and coagulation activation compared with commonly used cardiovascular prostheses.