| Background:Two categories of artificial heart valve prosthesis(AHVP) are used presently,including mechanical valve prosthesis(MVP) and bioprosthesis heart valve(BHP) in clinic. All MVP require permanent anticoagulation with warfarin to prevent catastrophic thromboembolism,but all BHP frequently deteriorate within few years. These defects bring disadvantaged influences to clinical efficiency of valve replacement. Unfortunately,a few groups continued reconstructive techniques in artificial valve prosthesis,but a AHVP still does not resolve aforementioned deficiency.A few studies have proceeded about synthetic leaflet heart valve (SLHV) . Expanded polytetrafluoroethylene has been investigated because of its outstanding performance about anticoagulation and anticalcinosis.Applied Performance and Biocompatibiliry of Ultrafine-Micropores-Expanded-Teflon(UMET):1. Applied Performance:(1) Wide adaptive temperature range from 260C to -263 .(2) Altitudinal chemical stability. Concentrated,sulphuric and organic solvent etc.can not pall on it hardly.(3) Excellent insulating characteristic.(4) Unglutinous surface of ultrafine-micropores-teflon.2. BiocompatibilityBecause of their low surface free energy(SFE),all kinds of expanded polytetrafluoroethylene belong to hydrophodic synthetic material in order to protein and blood platelet can not ease to be adhered,appendiculate fibrin and fibroblast reduced too. Expanded polytetrafluoroethylene has good capability about antithrombogenicity and anticalcific. But some studies invivo about plain expanded polytetrafluoroethylene have shown that calcification and thrombosis still occured. UMET has less micropores(<1um) in its surface,protein,blood platelet fibrin and fibroblast Blood adhered are less too. Plasma and concomitant blood platelet can not soak into the interior of UMET because of its ultrafine micropores. The water uptake of UMET is low. UMET has better capability about antithrombogenicity and anticalcific than simple expanded polytetraluoroethylene. Objective:1. To manufacture the facture of UMETVP.2. To assess the hydrodyamics of the UMETVP in vitro and to estimate the feasibility of using UMET to tailor UMETVP,according as aforementioned tests,to make some suggestions on the amelioration of UMETVP.Material and Mathod:1. Manufacture of UMETVP(1) The ring of UMETVP is a flexibility bracket tailored with stretch stainless steel wire,ployester felt and dacron.(2) UMETVP is a kind of four-leaflet SLHV,including two large leaflet and two small leaflet. Choose UMET patch (the thickness of UMET patch is O.lmm) qua the material of the leaflet of UMETVP (6 cases). The length of joint of the large leaflet and the ring is equal to one seventh of perimeter of the ring,similarly the inverse proportion of native anthropic mitral valve. The length of joint of the small leaflet and the ring is equal to one fourteenth of perimeter of the ring. Each large leaflet and four chordae tendineaes become one flesh.(3) Sew up the UMET leaflet with the flexibility bracket to compose the AHVP.2. Test in Vitro (1) GroupingExperimentation group has six UMETVPs. Control group has six 27# Baxter two-leaflet mechanical valve prostheses. The internal diameter of allvalve prostheses are equal to 24mm.(2) Temperature of Environment in TestThe temperature of environment in test is 20 C.(3) Characteristics of Fluid in TestThe fluid used in test was distilled water. 20C, density:998kg/m3specific gravity:1.00 viscosity:ImPa-s(2) Test about the LeakageMeasure the leakage of each valve prosthesis under the pressure range from 10 mmHg to 250 mmHg,including 10 mmHg,30 mmHg,50 mmHg,70 mmHg,90 mmHg,110 mmHg,130 mmHg,150 mmHg,170 mmHg,190 mmHg,210 mmHg,230 mmHg and 250 mmHg. Each measure under every pressure continued ten miniutes.(3)Test about the Systolic Pressure Gradient with Steady FlowUse extracorporeal circulation machine to come into being steady flow.Use color doppler ultrasonography to m... |
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