Experimental chronic implants of a novel woven, thin and pliable polymeric prosthetic Heart Valve
Amir Basir, Remco Grobben, Gerard Pasterkamp, Jolanda Kluin, Paul Gründeman.
University Medical Center Utrecht, Utrecht, Netherlands.
OBJECTIVE: Biological and mechanical heart valves suffer from moderate durability and necessity of anticoagulant use, respectively. Ultra High Molecular Weight Polyethelene (UHMWPE) fibers are flexible, fatigue- and tear resistant and strong. Without coumarin anticoagulation, biocompatibility and functionality of a handmade stented UHMWPE heart valve made of thin woven fabric of UHMWPE fibers was tested.
METHODS: Eighteen adult sheep (± 70 kg) underwent pulmonary valve replacement by UHMWPE valves, 5 sheep received control bovine Edwards Perimount valves. Acetylsalicylic acid was administered daily. Follow-up (FU) UHMWPE group: 1 week (n=4), 1 month (n=5), 3 months (n=5) and 6 months (n=4). FU controls: 3 months (n=2) and 6 months (n=3). Echocardiography and histology were used to assess valve function and tissue deposition.
RESULTS: One/eighteen of UHMWPE group died (tambour stomach) and 2/5 controls died (cerebral cause). The UHMWPE sheep did not suffer from pulmonary embolization and at 6 months, the UHMWPE valves were completely intact without leaflet fraying. UHMWPE valves showed trivial regurgitation at 1 week-1 month. From 3 to 6 months leaflet flexibility was decreased due to leaflet-tissue retraction which resulted in decreased central coaptation and increased regurgitation. All valves exhibited incidentally focal commissural old, organized thrombi. Adhered tissue contained thrombocytes, fibrin, erythrocytes and (myo)fibroblasts at 1 week. Endothelialization was firstly recognized after 1 month without calcification (X-ray) at 6 month FU. At 3 and 6 months, 2 controls were competent with mild stenosis. One control showed severe stenotic thrombotic process at 4 months not-intended FU.
CONCLUSIONS: In a worst-case scenario of testing in a low-pressure condition with only antiplatelet therapy, the novel UHMWPE valve performed satisfactory without pulmonary embolization. Intact endothelialized UHMWPE valves showed acceptable function up to 3 months, with loss of central coaptation seen at 6 months owing to moderate leaflet retraction and minor decrease of flexibility related to tissue overgrowth and contraction of the tested thin woven leaflet design. A chronic high-pressure model without anticoagulation should confirm the promising biocompatibility and observed functionality of UHMWPE valves.
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