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1、7.4IMPLANTABLECARDIACASSISTDEVICES1.CLINICALNEEDANDAPPLICATIONS2.VENTRICULARASSISTDEVICEDESIGNANDBLOODCONTACTINGMATERIALS3.COMPLICATIONSANDVADBIOCOMPATIBILITYISSUES4.ROTARYBLOODPUMPSFORCHRONICCIRCULATORYSUPPORT5.CONCLUSION1.CLINICALNEEDANDAPPLICATIONSHeartfailureresultsinmo
2、rethan43,000deathsperyearintheUnitedStatesandcontributestothedeathofanother220,000individuals.Thereareapproximately400,000newcasesdiagnosedannuallyandthosediagnosedwiththisconditionhaveamortalityrateofabout50%at5years(AmericanHeartAssociation,1999).Forend-stagepatientsheart
3、transplantationhasbecomeaneffectivetreatmentoverthepast20years,largelyasaresultoftheintroductionofsuccessfulimmunesuppressiondrugssuchascyclosporine.Actuarialsurvivalratesforhearttransplantpatientsarecurrently75%at3years(UnitedNetworkforOrganSharing,1999).Thesuccessofheartt
4、ransplantationislimited,however,byaninadequateandstagnantdonorsupply.Although35,000–64,000patientscouldpotentiallybenefitfromhearttransplantationannually(Funk,1991),in2003,only2055cardiactransplantswereperformedintheUnitedStates.Whilewaitingforscarcedonororganstobecomeavail
5、able,approximately20%ofindividualslistedforhearttransplantationdieannually(UnitedNetworkforOrganSharing,1999).Toaddresstheneedtosupportthecirculationinpatientswithend-stageheartfailureawidevarietyofmechanicaldeviceshavebeendevelopedoverthepastseveraldecades.Currentdevicesth
6、atarewidelyusedforthepurposeofbridge-to-cardiactransplantationwillbediscussedinthischapter,aswillcirculatorysupportdevicesthatmayenterthemarketinthenearfuture.Thesedevicesdonotreplacethepatient’sheart(aswouldatotalartificialheart),butratherworkasventricularassistdevices(VAD
7、s).ThegeneralconceptbehindaVADcanbeseeninFig.1.2.VENTRICULARASSISTDEVICEDESIGNANDBLOODCONTACTINGMATERIALSVADshaveprovidedcirculatorysupporttoend-stageheartfailurepatientswhootherwisewouldhavealowlikelihoodofsurvivinguntiladonororganbecameavailable.Nearly70%ofpatientsundergo
8、ingVADsupporthavesurviveduntilhearttransplantation(Mehtaetal.,1995).Patientsunderg
