Artificial Heart Valves

摘要: 1. INTRODUCTIONThe cardiovascular system is a closed circulatory systemthat ensures blood flow through the human body. Bloodcirculates two systems; first responsible forpushing from heart to lungs capture ox-ygen, and second for distributing oxy-genated bodyorgans. This composed ofadouble pump with branched tubes that leads fromthe organs (arteries) returns it theheart (veins). The essentially muscular pumpwith four rooms, receiving incoming (atria)and pushing toward (ventricles).In order maintain unidirectional of blood, 3-Dopen-close ‘‘gateways’’ (valves) are optimally located be-tweenatriaand ventricles,andbetween theventricles andthe emerging arteries. workload valves isnothing short extraordinary. open closeonce per totaling more than 3 billion times in alifetime. These movements take place under constantpressure flowing very viscous fluid richin minerals, proteins, lipids, cells.Valves may progressively become defective criti-cally influence performance heart. defectsare collectively named valve diseases. As properties ofnormal diseased not sufficiently under-stood, no drugs available treat cure dis-eases. only curative solution perform open-heartsurgery replace artificially engi-neered devices. substitutes nonliving ma-terials fashioned form reestablishinitial mechanical functions restore functionalityof However, these devices eventually failbecause imperfections design, composition, or bio-compatibility. Once device shows signs failure, thepatient requires open-heart surgery replace-ment device. Reoperations generallyrisky pose additional problems children who nat-urally outgrow their implants.Thus, long-term goal biomedical engineering tofind better methods treating valvular diseases andthus impact lives millions patients worldwide. Thisdaunting effort bringstogether multidisciplinary team ofspecialists medicine, biology, engineering, mechan-ics. chapter describes structure, function, biology,and pathology valves; information on current re-placement devices; necessary prerequisites forconstructing an ‘‘ideal’’ replacement valve. Ongoing re-search aimed at improving existing by enhanc-ing biocompatibility, as well pioneering work noveltissue-engineering approaches, which would facilitatecomplete regeneration tissues.2. NATURAL HEART VALVES ARE SPECIALIZEDCARDIOVASCULAR TISSUESThe action similar tothat two-cylinder engine. Four natural valvesmaintain direction within circulatorysystem (Fig. 1). tricuspid mitral (collec-tively called atrioventricular valves) allowblood tofilltheventricular cavities.Thesetwo‘‘admission’’(inflow) connected subjacent mus-cle via fibrous extensions (chordae tendinae). When theinflow closed, forced theaortic pulmonary (collectively semi-lunar valves). ‘‘ejection’’ (outflow) openin response immediately close after ejec-tion. Although initially apparent, structural andfunctional correlation between muscle thevalves exists A 3-D network extra cellular ma-trix (mainly collagen fibers), formally known ‘‘car-diac skeleton,’’ maintains spatial structure andfunction muscle. cardiac skeleton in-cludes large structures (macro-skeleton), such