Textile heart valve prosthesis: from fabric design criteria to early in-vivo performances.

BACKGROUND AND AIM OF THE STUDY: Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients at high risk for open-chest surgery. Biological valve tissue is, however, a fragile material when folded for small-diameter catheter insertion purposes. Textile polyester is a less fragile material, and could be an alternative replacement for the valve leaflets. The dynamic performances obtained in vitro with a valve prosthesis made from textile have proven in previous studies to be satisfactory. However, as textile is a porous material the interaction processes between the fabric leaflet surfaces and living tissues remain unknown. The study aim was to discuss the fabric design criteria which are best suited to clinical application. METHODS: An appropriate design provided strength, limited porosity and low bulk to the fabric, which was particularly suited for small-diameter catheter insertion purposes. The in-vivo behavior of a non-coated polyester textile valve prototype was then studied in the mitral position in a sheep model. RESULTS: The results showed that limited tissue ingrowth occurred, and Ca deposits tended to stiffen the fabric leaflets after a two-month implantation period, which was not compatible with the survival of the animal. CONCLUSION: The initial results obtained with this non-coated polyester textile valve confirmed that this revolutionary fabric is worthy of further investigation.

Ischemic preconditioning specifically restores complexes I and II activities of the mitochondrial respiratory chain in ischemic skeletal muscle.

OBJECTIVE: Defective mitochondrial function has been reported in patients presenting with peripheral arterial disease, suggesting it might be an important underlying mechanism responsible for increased morbidity and mortality. We therefore determined the effects of prolonged ischemia on energetic skeletal muscle and investigated whether ischemic preconditioning might improve impaired electron transport chain and oxidative phosphorylation in ischemic skeletal muscle. METHODS: Thirty rats were divided in three groups: the control group (sham, n = 9) underwent 5 hours of general anesthesia without any ischemia, the ischemia-reperfusion (IR) group (n = 11) underwent 5 hours ischemia induced by a rubber band tourniquet applied on the left root of the hind limb, and in the third group, preconditioning (PC group, n = 10) was performed just before IR and consisted of three cycles of 10 minutes of ischemia, followed by 10 minutes reperfusion. Maximal oxidative capacities (V(max)) of the gastrocnemius muscle and complexes I, II, and IV of the mitochondrial respiratory chain were determined using glutamate-malate (V(max)), succinate (V(s)), and N, N, N,'N'-tetramethyl-p-phenylenediamine dihydrochloride ascorbate as substrates. RESULTS: Physiologic characteristics were similar in the three groups. Ischemia reduced V(max) by 43% (4.5 +/- 0.4 vs 7.9 +/- 0.5 micromol O(2)/(min x g dry weight), P < .01) and V(s) by 55% (2.9 +/- 0.3 vs 6.3 +/- 0.4 micromol O(2)/min/g dry weight; P < .01) in the IR and sham groups, respectively, and impairments of mitochondrial complexes I and II activities were evident. Of interest was that preconditioning prevented ischemia-induced mitochondrial dysfunction. Both V(max) and V(s) were significantly higher in the PC rats than in IR rats (+32% and +41%, respectively; P < .05), and were not different from sham values. CONCLUSIONS: Ischemic preconditioning counteracted ischemia-induced impairments of mitochondrial complexes I and II. These data support that ischemic preconditioning might be an interesting approach to reduce muscular injuries in the setting of ischemic vascular diseases.