USMLE题库Cardiology(一)31-46

Cardiology1题库Q31An18-year-oldCaucasianfemaleisreferredtothecardiologistbecauseherprimarycarephysicianheardacardiacmurmurduringaroutinecheck-up.Thepatientishealthyandhasnocomplaints.Herpastmedicalhistoryisunremarkable.Carefulquestioningofthepatientandhermotherrevealsthatseveralfamilymembershavebeentoldthattheyhavemurmurs.Auscultationrevealsamidsystolicclickwhichisfollowedbyashortlatesystolicmurmur.Themurmurdisappearsonsquatting.Thispatient'sconditionismostlikelyrelatedtoanabnormalityof:A.EndocardialliningB.CardiacmuscleC.ConnectivetissueD.CoronaryvesselsE.ParietalpericardiumA31Correctanswer:DSmall(1-5mm),sterile,non-destructivefibrinousvegetationsalongthelinesofclosureofcardiacvalvecuspsarecharacteristicofnon-bacterialthromboticendocarditis(NBTE).Histologically,thesevegetationsconsistofblandthrombuswithoutaccompanyinginflammationorvalvulardamage.Theyaretypicallytheresultofahypercoagulablestate,althoughtheymayalsobecausedbyendothelialinjury.Whencausedbyhypercoagulability,NBTEismostoftenrelatedtosomeunderlyingdisease,suchasacancer.ThereisaparticularlystrongassociationofNBTEwithmucinousadenocarcinomasofthepancreasandadenocarcinomasofthelung,whichmayrelatetoprocoagulanteffectsofcirculatingmucin.NBTEassociatedwithdisseminatedcanceristermed,marantic(ormarasmic)endocarditis,derivedfromthetermforcancer-relatedwastingofbodytissues(marasmus).Byasimilarmechanism,tumor-associatedreleaseofprocoagulantsisthoughtresponsibleforthemigratorythrombophlebitis(Trousseausyndrome)sometimesseeninpatientswithdisseminatedcancers.(ChoiceA)Humoralhypercalcemiaofmalignancy,themostcommoncauseofhypercalcemiainhospitalizedpatients,isduetotheproductionofaparathyroidhormone(PTH)-likesubstancebytumors.Thisparaneoplasticsyndromewouldnotcauseahypercoagulablestateorvegetationsofthesortdescribedinthispatient.(ChoiceB)Cancermetastasestotheheartusuallyinvolvethepericardiumormyocardium.Valvemetastasesarelessfrequentandwouldprobablyhaveshowninvasivecharacteristicsonhistologicexamination.(ChoiceC)Lambert-Eatonsyndromeisanautoimmuneparaneoplasticmyasthenicsyndromethataffectsthepresynapticcalciumchannels,resultingindecreasedpresynapticacetylcholinerelease.Lambert-Eatonsyndromeisassociatedinmostcaseswithoatcellcarcinomaofthelung.(ChoiceE}Raynaud’sphenomenoninvolvesepisodic，ischemicattacksofthedigitsthatproducepallorandnumbness.Theseepisodesmaybeinducedbycoldoremotionalstimuli.Thepathophysiologyisthoughttoinvolveabnormalsensitivityofdigitalarteries/arteriolestovasoconstrictiveinfluences.Raynaud'sphenomenonoccursintheabsenceofanyhypercoagulablestate.Q32A73-year-oldCaucasianmalewithadvancedvisceralcancerdiesofextensivemyocardialinfarction.Autopsyalsorevealssterilenon-destructivevegetationsalongthemitralleafletedges.Thepathogenesisofthispatient'svegetationsismostsimilartothatof:A.HypercalcemiaofmalignancyB.DistantmetastasesC.Lambert-EatonsyndromeD.TrousseausyndromeE.RaynaudphenomenonA32Correctanswer:DThispatientexhibitssignsandsymptomsconsistentwithacutetransmuralmyocardialinfarction.Typicalsymptomsincludeseverechestpainnotrelievedbyrestornitroglycerin,diaphoresis,dyspnea,nausea,lightheadedness，and/orpalpitations.PeakedT-wavesarethefirstECGsign(reflectinglocalizedhyperkalemia),andST-segmentelevationfollowswithinminutestohours.Withinhourstodays,Q-wavesappearintheinvolvedleads.Thepatientinthevignettehaslikelysufferedatransmuralinfarctoftheanterolateralleftventricle,asevidencedbytheECGchangesintheanterior(V1-V3)andlateral(I,aVL)chestleads.Transmuralinfarctionismostcommonlycausedbyanacuteplaquechange(e.g.rupture)whichproducesasuperimposedthrombusthatcompletelyoccludestheinvolvedcoronaryartery.Inthispatient,thethrombusmaybecompletelyoccludingtheleftmaincoronaryartery.(ChoiceA)Anatheroscleroticplaqueobstructing50%ofthelumenandwithoutanyoverlyingthrombuswouldbeunlikelytoproducesymptomaticmyocardialischemia.Symptomsofstableanginadonotbecomeprominentuntilatleast75%ofthecross-sectionalareaofthecoronaryarterylumenisoccluded(ChoiceB)Thepatientinthevignetteissufferinganacutecoronarysyndrome.Acutecoronarysyndromesaregenerallytheresultofanacutechangeinacoronaryarteryplaque,includingulceration,fissuring,orrupture,withformationofanoverlyingthrombus.ThelesiondescribedinanswerchoiceBisastableplaqueproducingafixedobstruction.Thissortoffixedobstructionoccludingmorethan75%ofacoronaryarterylumenwouldtendtoproducestableangina.(ChoiceC)Anulceratedatheroscleroticplaquewithapartiallyobstructivethrombuswouldtendtoproduceunstableangina,subendocardialmyocardialinfarction,orsuddencardiacdeath.(ChoiceE)CoronaryarteryvasospasmoccursinPrinzmetal's(orvariant)angina,anuncommonconditionofepisodicanginathatgenerallyoccursatrest.ThespasmmayoccuratsitesofcoronaryatherosclerosisandcanresultintransienttransmuralischemiawithST-segmentelevationsonECG.Insomecases,thespasmmaycauseQ-wavetransmuralmyocardialinfarction,evenintheabsenceofatheroscleroticlesionsoncoronaryangiography.However,thevasospasmofPrinzmetal'sanginagenerallyrespondspromptlytovasodilators,suchasnitroglycerin.Thus,apatientwithPrinzmetal'