教学材料《季节性流感英文》-Unit2

Text1AnatomyandPhysiologyoftheHeartOxygenatedbloodreturningfromthelungsenterstheleftatriumviathepulmonaryveins,passesintotheleftventricle,andisthenejectedtotheaorta.Figure2-1showsthedetailofthevalvesintherighthalfoftheheartseenfromobliquelybeneath.Thelargevalveintheforegroundisthetricuspidvalvethatpreventsbackflowfromtherightventricletotherightatrium.Thesmallroundvalveyouseenearthetopisthepulmonaryvalve,wherethepulmonaryarterycomesoutoftherightventricle(youarelookingatitalmoststraightupintothepulmonaryartery).下一页上一页返回Text1AnatomyandPhysiologyoftheHeartFigure2-1showsthedetailofthevalvesinthelefthalfoftheheart.Youarelookingobliquelyatthetopofthelargemitralvalveintheforegroundthroughthesemi-transparentatrialandventricularwalls.Themitralvalvepreventsthebackflowofbloodfromtheleftventricletotheleftatrium.Behindthemitralvalve,youcanseeacircularvalveinanendonview.Thatistheaorticvalve,wheretheaortacomesoutoftheleftventricle.Inthebackground,thetricuspidvalvecanbeseen.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartTheinneredgeofthetricuspidandthemitralvalvesendsinfilamentousconnectivetissue(chordaetendineae).Theseareattachedtosmallcolumnsofmuscle(papillarymuscles)arisingoutoftheinnersurfaceoftheventricles.Asthepressurebuildsintheventricles,thevalvessnapshut,andthepapillarymusclespreventthevalvesfromblowingintotheatriumandopening.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartPumpingActionoftheHeartThepumpingactionstartswiththesimultaneouscontractionofthetwoatria.Thiscontractionservestogiveanaddedpushtogetthebloodintotheventriclesattheendoftheslowfillingportionofthepumpingcyclecalled“diastole.”Shortlyafterthat,theventriclescontract,markingthebeginningof“systole.”Theaorticandpulmonaryvalvesopenandbloodisforciblyejectedfromtheventricles,whilethemitralandtricuspidvalvesclosetopreventbackflow.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartAtthesametime,theatriastarttofillwithbloodagain.Afterawhile,theventriclesrelax,theaorticandpulmonaryvalvesclose,andthemitralandtricuspidvalvesopenandtheventriclesstarttofillwithbloodagain,markingtheendofsystoleandthebeginningofdiastole.Itshouldbenotedthateventhoughequalvolumesareejectedfromtherightandtheleftheart,theleftventriclegeneratesamuchhigherpressurethandoestherightventricle.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartElectricalActivityoftheHeartWhenvertebratemusclesareexcited,anelectricalsignal(calledan“actionpotential”)isproducedandspreadstotherestofthemusclecell,causinganincreaseinthelevelofcalciumionsinsidethecell.Thecalciumionsbindandinteractwithmoleculesassociatedwiththecell’scontractilemachinery,theendresultbeingamechanicalcontraction.Eventhoughtheheartisaspecializedmuscle,thisfundamentalprinciplestillapplies.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartOnethingthatdistinguishestheheartfromothermusclesisthattheheartmuscleisa“syncytium,”meaningameshworkofmusclecellsinterconnectedbycontiguouscytoplasmicbridges.Thus,anelectricalexcitationoccurringinonecellcanspreadtoneighboringcells.Anotherdefiningcharacteristicisthepresenceofpacemakercells.Thesearespecializedmusclecellsthatcangenerateactionpotentialsrhythmically.下一页上一页返回Text1AnatomyandPhysiologyoftheHeartUndernormalcircumstances,awaveofelectricalexcitationoriginatesinthepacemakercellsinthesinoatrial(S-A)node,locatedontopoftherightatrium.Specializedmusclefiberstransmitthisexcitationthroughouttheatriaandinitiateacoordinatedcontractionoftheatrialwalls.Meanwhile,someofthesefibersexciteagroupofcellslocatedattheborderoftheleftatriumandventricleknownastheatrioventricular(A-V)node.TheA-Vnodeisresponsibleforspreadingtheexcitationthroughoutthetwoventriclesandcausingacoordinatedventricularcontraction.上一页返回Text2RisksEvaluatedfor

HeartImplantsLikealotofcardiologistswhospecializeinarrhythmia,WilliamMaiselreceivesregularnoticesaboutproblemsinsomeofthelifesavingdevicesimplantedinhispatientschests.These“DearDoctor”lettersconfrontaffectedpatientsandtheirdoctorswithharddecisionsaboutwhetherornottoreplaceapotentiallyflaweddevicewithanotheroneofunknownreliability.下一页返回Text2RisksEvaluatedfor

HeartImplantsPhotobyGrahamRamsayWilliamMaiselfoundthatthereliabilityofpacemakersisup,whilethatofimplantabledefibrillatorsisdown.Inhispractice,Maiselimplantsadiversearrayofdevicessothatfewerpatientsaresubjecttoanygivenrecall.下一页上一页返回Text2RisksEvaluatedfor

HeartImplants“Suddenly,I’msittingwithalistofpatientsthatmighthavedefectivedevices,”saidMaisel,HMSassistantprofessorofmedicineanddirectorofthePacemakerandDeviceServiceatBethIsraelDeaconessMedicalCenter.“Evenifalettersaysthereisaonein1,000chanceoffailurefromthisspecificmechanism,wearen’ttoldabouttheexpectedfailurerateofthereplacementdevice.Oneofthemissingpiecesofinformationistheriskofreplacingadevice.”下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsSeveralyearsago,Maiselsetouttofillinthemissinginformationandfindoutiftheincreaseinadvisoriesmeantthatthedeviceswerebecominglessreliableorthatfederaloversightonsafetyissueswasbecomingbetter.PartoftheanswerispublishedintwostudiesintheApril26JournaloftheAmericanMedicalAssociation.From1990to2002,thepopularityandreliabilityofpacemakergeneratorshasimproved,andthemalfunctionreplacementratehasdecreased,Maiselreports.Generatorsforimplantablecardioverterdefibrillators(ICDs),ontheotherhand,hadbeenmostlyreliableuntilthelastfewyearsofthestudy,whentheirmalfunctionandreplacementratesspiked.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsMaiselpresentedhisresultsatameetingofdevicemakers,electrophysiologists,andFDAofficialsinSeptember.Themeetingwasprompted,inpart,bythepublicitytriggeredbythedeathofa21yearoldcollegestudentwithhypertrophiccardiomyopathy,whodiedwhenhisdefibrillatorshortcircuited.Asrequiredbylaw,Guidant,themanufacturer(whichwasrecentlyacquiredbyBostonScientificCorp.),alertedtheFDAthat25similardevicesofthesamemodelhadfailedinpatients.ButthecompanyalertedphysicianslastMay,onlythedaybeforeTheNewYorkTimesreportedtheseevents.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsThedevicemakermaintainedthattheobservedfailureratewassolowthatanalertcouldhaveunnecessarilyexposedpatientstotheriskofdevicereplacementsurgery,includinginfection.Thestatisticalargumentangeredthestudentsdoctors.“Patientshaveafundamentalrighttobefullyinformedwhentheyareexposedtotheriskofdeathnomatterhowlowthatriskmaybeperceived,”theywroteintheSept.27,2005Circulation.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsSincethefallmeeting,manufacturershaveaddedimportantdetailstotheirlatestpublicannualreportsondeviceperformance,Maiselsaid,thoughnosinglecompanyincludesallthedesiredinformationforinformeddecisionmaking.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsOnthesamedayMaisel’spaperscameoutinJAMA,theHeartRhythmSocietyreleaseditsdraftrecommendationsurgingthatmanufacturersestablishhigherperformancestandardsforitsdevices,publishmoredetailedannualdataonmalfunctions,andmaketheinformationpubliclyavailable,amongotherchanges.ThestatementalsourgesphysicianstoreportallproblemsdirectlytotheFDA’sonlineMedWatchprogramat/medwatch.MaiselandhiscolleaguesatthesocietypresentedtherecommendationsonMay17inBostonatthesociety’sannualmeeting.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsNetBenefitsNonethelessForthevastmajorityofpeoplewhohavereceivedorareconsideringoneoftheseimplants,thebenefitsstilltrumpanyrisksbyawidemargin,Maiselsaid.Thestudyresultsonlyapplytothesmallgroupofpatientswithdevicesthatarethetargetofarecalloradvisory.“Thisallowsthemtohaveabetterunderstandingoftherisksandbenefitsofreplacingapotentiallydefectivedevice,”hesaid.下一页上一页返回Text2RisksEvaluatedfor

HeartImplants“Manytrialshavedemonstratedtheclinicalbenefitofthesedevicesincertainpatients,”Maiselsaid.“Nothinginthesestudiesoverridesthatbenefitinthatwelloutlinedgroupofpatientswhohavebeenadvisedtohaveadeviceimplanted.Forthosepatientswhoalreadyhaveimplanteddevices,nothinghererequiresanythingdifferentfromtheirroutineregularcheckupswithphysicianstohavethedeviceschecked.”下一页上一页返回Text2RisksEvaluatedfor

HeartImplants“Manytrialshavedemonstratedtheclinicalbenefitofthesedevicesincertainpatients,”Maiselsaid.“Nothinginthesestudiesoverridesthatbenefitinthatwelloutlinedgroupofpatientswhohavebeenadvisedtohaveadeviceimplanted.Forthosepatientswhoalreadyhaveimplanteddevices,nothinghererequiresanythingdifferentfromtheirroutineregularcheckupswithphysicianstohavethedeviceschecked.”下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsSuddencardiacdeath,usuallyfromasuddenfastheartrhythm,istheleadingcauseofdeathinthiscountry,edgingoutfatalheartattackscausedbyinflamedandcloggedarteriesandkillingmorepeoplethanallcancerscombined.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsICDscansenseandshockamalfunctioningheartbackintoitsnormalbeat.SeveralclinicaltrialshaveshownthatICDsreducetherelativeriskofdeathinselectedhighriskpatientsbyathirdandlowertheabsoluteriskofdeathfrom19percentto14percentinoneyear,whichaddsuptoalotofpeopleavoidingthemostcommoncauseofdeath.Pacemakersaresimplerdevicesthatcontinuouslyoroccasionallypulsetoensurenormalbeatingofadangerouslyslowheart.Thedevicestypicallylastfivetosevenyearsandnormallyarereplacedduetoagingbatteries.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsImplantReplacementRates

MalfunctioningbatteriesandelectricalissuesaccountedformostoftheprematuredevicereplacementsinMaisel’sstudies.Inonepaper,heteamedupwithcoauthorsintheFDA’sCenterforDevicesandRadiologicHealth.(Inthecourseofproposingthestudy,MaiselbecameanFDAconsultant;hechairstheFDACirculatorySystemMedicalDevicesAdvisoryPanel.)ThestudyanalyzedthemandatoryannualreportssentfrommanufacturerstotheFDAforthenumbersofdeviceimplantsandthenumbers,types,andcausesofmalfunctions.ThesedetailsarenotavailableonthepubliclysearchableFDAwebsite.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsFrom1990to2002,U.S.doctorsimplanted2.25millionpacemakersandalmost416,000ICDs.Duringthesametime,theyremoved8,834pacemakersand8,489ICDsduetoaconfirmeddevicemalfunction.Toidentifytrends,theresearchersdividedconfirmedmalfunctionsbytheannualnumberofnewimplantsforanoverallannualreplacementrateof4.6per1,000pacemakersand20.7per1,000ICDs.Malfunctionswereconfirmedbythedevicemakers.下一页上一页返回Text2RisksEvaluatedfor

HeartImplantsThemanufacturersdonotactivelyseekoutdeviceproblemsandinsteadassumepatientsarealiveanddevicesworkingunlesstheyhearotherwise.Toaddressthepossible