Heart Sounds Topic Review | Learn the Heart - Healio

S4 Heart Sound BacktoHealio ECGInterpretation QuizzesandCases CardiologyReview LearnTheHeart CardiologyReview TopicReviewsA-Z TopicReviewsA-Z Save HeartSoundsTopicReview S1HeartSound | S2HeartSound | S3HeartSound | S4HeartSound | ExtraHeartSounds Introduction Heartsoundsareproducedfromaspecificcardiaceventsuchasclosureofavalveortensingofachordaetendineae. Manypathologiccardiacconditionscanbediagnosedbyauscultationoftheheartsounds.Notethatheartsoundsarediscrete,shortaudibleeventsfromaspecificcause—differentfromaheartmurmur.Amurmurisduetoturbulenceofbloodflowandcan,attimes,encompassallofsystoleordiastole. ThemainnormalheartsoundsaretheS1andtheS2heartsound.TheS3canbenormal,attimes,butmaybepathologic.AS4heartsoundisalmostalwayspathologic. Heartsoundscanbedescribedbytheirintensity,pitch,location,qualityandtiminginthecardiaccycle. Intensity: Heartsounds canbedescribedasincreasedinintensity(loud),decreasedinintensity(soft)orabsent. Pitch: Heartsoundscanbedescribedashighpitched(heardbestwiththediaphragmofthestethoscope). Location: Thelocationoftheheartsoundcanhelpdeterminetheetiology.Thestandardlisteningposts(aortic,pulmonic,tricuspidandmitral)applytobothheartsoundsandmurmurs.Forexample,theS1heartsound—consistingofmitralandtricuspidvalveclosure—isbestheardatthetricuspid(leftlowersternalborder)andmitral(cardiacapex)listeningposts. Enlarge  Timing: Thetimingcanbedescribedasduringearly,midorlatesystoleorearly,midorlatediastole. Althoughtermssuchas“click,”“snap”or“knock”aresometimesused,theyhavenospecificqualityormeaning.Theywillbereferencedinthefollowingsections. FirstHeartSound(S1) Thefirstheartsoundresultsfromtheclosingofthemitralandtricuspidvalves.ThesoundproducedbytheclosureofthemitralvalveistermedM1,andthesoundproducedbyclosureofthetricuspidvalveistermedT1.TheM1soundismuchlouderthantheT1soundduetohigherpressuresintheleftsideoftheheart;thus,M1radiatestoallcardiaclisteningposts(loudestattheapex),andT1isusuallyonlyheardattheleftlowersternalborder.ThismakestheM1soundthemaincomponentofS1. CLINICALPEARL:AsplitS1heartsoundisbestheardatthetricuspidlisteningpost,asT1ismuchsofterthanM1. TheM1soundoccursslightlybeforeT1.Becausethemitralandtricuspidvalvesnormallyclosealmostsimultaneously,onlyasingleheartsoundisusuallyheard.However,inabout40%to70%ofnormalindividuals—aswellasincertaincardiacconditions—a“splitS1”soundcanbeappreciated.Thisoccurswhenthemitralvalvecloses significantly beforethetricuspidvalve,allowingeachvalvetomakeaseparateaudiblesound.Inspirationdelaystheclosureofthetricuspidvalveinanormalperson,duetoincreasedvenousreturn,therebyenhancingthesplittingoftheS1sound. AsplitS1soundiscommoninthesettingofarightbundlebranchblockorventriculartachycardia/prematureventricularcontractions,orPVCs,witharightbundlebranchblockmorphology.ARBBBcausestheelectricalimpulsetoreachtheleftventriclebeforetherightventricle.Dyssynchronythenoccurs,resultingintheleftventriclecontractingbeforetherightventricle,thusthepressuresintheLVrisebeforethatoftherightventricle. Thisdelaystheclosureofthetricuspidvalve,resultinginasplitS1sound.AleftbundlebranchblockhastheoppositeeffectonS1.Inthissetting,theelectricalimpulsereachestheRVbeforetheLV,thusthepressureintheRVrisesbeforethatoftheLV.Thisforcesthetricuspidvalveclosedearlier,resultingincompleteoverlapofM1andT1,andthusnoaudiblesplitS1sound. CLINICALPEARL:ARBBBresultsinawidenedsplitS1,whereasaLBBBresultsintheabsenceofasplitS1. Fourfactorsaffecttheintensityofthefirstheartsound.BecausetheM1portionofS1ismuchlouderthanT1,itisonlyimportanttodiscusswhataffectstheintensityofM1. Chestwallthickness:Thefirstfactoristhethicknessofthechestwall.IndividualswithobesitywillhaveasoftS1,whereasthinnerpeoplewillhaveamoreintenseS1.Thegreaterthedistanceseparatingtheleafletsofthemitralvalveatthebeginningofsystole,theloudertheS1;thisisaffectedbythedurationofthePRintervalontheECG. LengthofPRinterval:RememberthatthePRintervalrepresentspartofdiastole,meaningalongerPRintervalwouldresultinalongerdiastolicfillingtime.AstheLVfills,thepressuregraduallyincreases.Thisgradualincreaseinpressurecausesthemitralvalveleafletstoslowlydrifttogether.Therefore,whenventricularsystoleoccursinthesettingofalongPRinterval,theleafletswillbeseparatedbyasmallerdistance,andtheS1soundwillbesofter.Theconverseisalsotrue.AshortPRintervalresultsinanaccentuatedS1,asthemitralvalveleafletswillbefurtherapartattheonsetofventricularsystole. CLINICALPEARL:AshortPRintervalresultsinanaccentuatedS1,whereasalongPRintervalresultsinasoftS1. Valveleafletmobility:ThemobilityofthevalveleafletsisanotherfactorinfluencingtheintensityofM1.Inmildtomoderatemitralstenosis,theincreasedleftatrialpressurecausesthemobileportionsofthemitralvalveleafletstobemorewidelyseparated,resultinginanaccentuatedM1sound.Inseveretocriticalmitralstenosis,thevalveleafletsaresocalcifiedandimmobilethattheM1soundisdiminishedorabsent. CLINICALPEARL:MildtomoderatemitralstenosisresultsinaloudS1,whereasseveretocriticalmitralstenosisresultsinasoftS1. Ventricularcontractionrate:TherateofventricularcontractionalsoaffectstheintensityofS1.Thefastertheheartrateandthefastertheriseinventricularpressure,theloudertheS1.Thus,highflowstatessuchasanemia,thyrotoxicosisorsepsiswouldresultinanaccentuatedS1.Also,duringexerciseoranyothersettingoftachycardia,theS1willbeaccentuated. SecondHeartSound(S2) Thesecondheartsoundisproducedbytheclosureoftheaorticandpulmonicvalves.ThesoundproducedbytheclosureoftheaorticvalveistermedA2,andthesoundproducedbytheclosureofthepulmonicvalveistermedP2. TheA2soundisnormallymuchlouderthantheP2duetohigherpressuresintheleftsideoftheheart;thus,A2radiatestoallcardiaclisteningposts(loudestattherightuppersternalborder),andP2isusuallyonlyheardattheleftuppersternalborder.Therefore,theA2soundisthemaincomponentofS2. CLINICALPEARL:AsplitS2isbestheardatthepulmonicvalvelisteningpost,asP2ismuchsofterthanA2. LiketheS1heartsound,theS2soundisdescribedregardingsplittingandintensity.S2isphysiologicallysplitinabout90%ofpeople.TheS2heartsoundcanexhibitpersistent(widened)splitting,fixedsplitting,paradoxical(reversed)splittingortheabsenceofsplitting.TheS2heartsoundintensitydecreaseswithworseningaorticstenosisduetoimmobileleaflets.Insevereaorticstenosis,theA2componentmaynotbeaudibleatall. CLINICALPEARL:Inseverehypertension,aloudS2maybeprolongedandslurred—falselymimickingasplitS2. PhysiologicSplitS2 Normally,A2occursjustbeforeP2,andthecombinationofthesesoundsmakeupS2.AphysiologicsplitS2occurswhentheA2soundprecedesP2byagreatenoughdistancetoallowbothsoundstobeheardseparately.Thishappensduringinspirationwhenincreasedvenousreturntotherightsideoftheheartdelaystheclosureofthepulmonicvalve(majoreffect),anddecreasedreturntotheleftsideofthehearthastenstheclosureoftheaorticvalve(minoreffect),therebyfurtherseparatingA2andP2.Duringexpiration,thedistancenarrows,andthesplitS2isnolongeraudible. ParadoxicalSplitS2 AparadoxicalsplitS2heartsoundoccurswhenthesplittingisheardduringexpirationanddisappearsduringinspiration—oppositeofthephysiologicsplitS2.AparadoxicalsplitS2occursinanysettingthatdelaystheclosureoftheaorticvalveincludingsevereaorticstenosisandhypertrophicobstructivecardiomyopathy,orinthepresenceofaleftbundlebranchblock. CLINICALPEARL:AparadoxicalsplitS2isheardinAS,HOCMorinthepresenceofaLBBB. Enlarge  Persistent(Widened)SplitS2 Persistent(widened)splittingoccurswhenbothA2andP2areaudibleduringtheentirerespiratorycycle,andthesplittingbecomesgreaterwithinspiration(duetoincreasedvenousreturn)andlessprominentwithexpiration.ThisdiffersfromafixedsplitS2,whichexhibitsthesameamountofsplittingthroughouttheentirerespiratorycycleandisexplainedbelow. Anyconditionthatcausesanonfixeddelayintheclosureofthepulmonicvalve,orearlyclosureoftheaorticvalve,willresultinawidesplitS2.Therefore,apersistentsplitS2wouldoccurinthesettingofaRBBB,pulmonaryhypertensionorpulmonicstenosis(delayedP2)orseveremitralregurgitation/ventricularseptaldefect(earlyA2closure). ARBBBcausesadelayintheclosureofthepulmonicvalve,andthusadelayinP2,withoutanyeffectonA2.InsevereMRorinthesettingofaVSD,theA2occursearly.Inmitralregurgitation,thisisduetoalargeproportionoftheleftventricularstrokevolumeenteringtheleftatrium,causingtheleftventricularpressuretodecreasefaster.InaVSD,alargeproportionofthestrokevolumegoesintotheRV,similarlydecreasingLVpressurequickly.TheP2isnotaffectedinsevereMRorVSDunlesspulmonaryhypertensionispresent. CLINICALPEARL:Apersistent(widened)splitS2occursinthesettingofaRBBBorsevereMR. Enlarge  FixedSplitS2 AfixedsplitS2isararefindingoncardiacexam;however,whenfound,italmostalwaysindicatesthepresenceofanatrialseptaldefect.AfixedsplitS2occurswhenthereisalwaysadelayintheclosureofthepulmonicvalve,andthereisnofurtherdelaywithinspiration;comparethistoawidenedsplitS2,asdescribedabove. ToexplorewhyanASDresultsinafixedsplitS2,wemustconsiderthealteredcardiachemodynamicspresent,whichresultinafixeddelayinPVclosure.Duringinspiration,asusual,thereisanincreaseinvenousreturntotherightsideoftheheartandthusincreasedflowthroughthePV—delayingitsclosure.ThealterationinapersonwithanASDoccursduringexpiration.Asthepersonexpires,thepressureintherightatriumdecreasesbecausethereislessvenousreturn.ThedecreasedpressureallowsmorebloodtoflowabnormallythroughtheASDfromthehighpressuredleftatriumtotherightatrium,ultimatelyresultingagaininincreasedflowthroughthepulmonicvalve—again,delayingitsclosure. CLINICALPEARL:AfixedsplitS2ispathognomonicforthepresenceofanASD. Enlarge  ThirdHeartSound(S3) Thethirdheartsound,alsoknownasthe“ventriculargallop,”occursjustafterS2whenthemitralvalveopens,allowingpassivefillingoftheleftventricle.TheS3soundisactuallyproducedbythelargeamountofbloodstrikingaverycompliantLV. CLINICALPEARL:AS3heartsoundisproducedduringpassiveleftventricularfillingwhenbloodstrikesacompliantLV. Enlarge  IftheLVisnotoverlycompliant,asisinmostadults,aS3willnotbeloudenoughtobeauscultated.AS3canbeanormalfindinginchildren,pregnantfemalesandwell-trainedathletes;however,aS4heartsoundisalmostalwaysabnormal. CLINICALPEARL:AS3heartsoundisoftenasignofsystolicheartfailure,howeveritmaysometimesbeanormalfinding. AS3canbeanimportantsignofsystolicheartfailurebecause,inthissetting,themyocardiumisusuallyoverlycompliant,resultinginadilatedLV;thiscanbeseenintheimagebelow. Enlarge                     NormalLVvs.DilatedLV(S3Present) S3isalow-pitchedsound;thisishelpfulindistinguishingaS3fromasplitS2,whichishighpitched.AS3heartsoundshoulddisappearwhenthediaphragmofthestethoscopeisusedandshouldbepresentwhileusingthebell;theoppositeistrueforasplitS2.Also,theS3soundisheardbestatthecardiacapex,whereasasplitS2isbestheardatthepulmoniclisteningpost(leftuppersternalborder).TobesthearaS3,thepatientshouldbeintheleftlateraldecubitusposition. FourthHeartSound(S4) Thefourthheartsound,alsoknownasthe“atrialgallop,”occursjustbeforeS1whentheatriacontracttoforcebloodintotheLV.IftheLVisnoncompliant,andatrialcontractionforcesbloodthroughtheatrioventricularvalves,aS4isproducedbythebloodstrikingtheLV. Enlarge  CLINICALPEARL:AS4heartsoundoccursduringactiveLVfillingwhenatrialcontractionforcesbloodintoanoncompliantLV. Therefore,anyconditionthatcreatesanoncompliantLVwillproduceaS4,whileanyconditionthatcreatesanoverlycompliantLVwillproduceaS3,asdescribedabove. AS4heartsoundcanbeanimportantsignofdiastolicHForactiveischemiaandisrarelyanormalfinding.DiastolicHFfrequentlyresultsfromsevereleftventricularhypertrophy,orLVH,resultinginimpairedrelaxation(compliance)oftheLV.Inthissetting,aS4isoftenheard.Also,ifanindividualisactivelyhavingmyocardialischemia,adequateadenosinetriphosphatecannotbesynthesizedtoallowforthereleaseofmyosinfromactin;therefore,themyocardiumisnotabletorelax,andaS4willbepresent. Itisimportanttonotethatifapatientisexperiencingatrialfibrillation,theatriaarenotcontracting,anditisimpossibletohaveaS4heartsound. CLINICALPEARL:AS4heartsoundisoftenasignofdiastolicHF,anditisrarelyanormalfinding(unlikeaS3). LikeS3,theS4soundislowpitchedandbestheardattheapexwiththepatientintheleftlateraldecubitusposition.BelowiscomparativeinformationforS3andS4. S3–“ventriculargallop” Occursinearlydiastole OccursduringpassiveLVfilling Maybenormalattimes RequiresaverycompliantLV CanbeasignofsystoliccongestiveHF S4–“atrialgallop” Occursinlatediastole OccursduringactiveLVfilling Almostalwaysabnormal RequiresanoncompliantLV CanbeasignofdiastoliccongestiveHF ExtraHeartSounds Thereareafewcommonextraheart soundsthattheclinicianmayencounter.TheseincludeejectionsoundsthatoccurwithpulmonicorASheardinearlysystole, “clicks”thatareheardinmitralortricuspidvalveprolapse occurringlaterinsystole,aswellas“snaps,”“knocks”and“plops.” Systolicejectionclick: Asystolicejectionclickfrequentlyindicatesabicuspidaorticvalve.ThissoundisheardjustaftertheS1heartsound.Usually,theopeningoftheaorticvalveisnotaudible;however,withabicuspidaorticvalve,theleafletsdomesuddenlypriortoopeningandcreateasystolicejectionclick.TheclickmaybedifficulttohearinthepresenceofsignificantAS. Mitralvalveprolapseclick: Mitralvalveprolapseproducesamidsystolicclick,usuallyfollowedbyauniform,high-pitchedmurmur.ThemurmurisactuallyduetoMRthataccompaniestheMVP;thus,itisheardbestatthecardiacapex.MVPrespondstodynamicauscultation.Aftersuddenstanding,preloadisdecreased,andtheclickmovesearlierinsystole.Withsuddensquatting,preloadincreases,andtheclickmoveslaterinsystole. Openingsnap: InthesettingofMS,the increasedleftatrialopeningpressurescauseanopeningsnaptooccurwhenthemitralvalveleafletssuddenlytenseanddomeintotheLVinearlydiastole.Thishigh-frequencysoundisbestheardattheapex. Tumorplop: Atumorplopisanearlydiastoliclow-pitchedsoundjustaftertheS2heartsound.Thisisincontrasttotheopeningsnapofrheumaticmitralvalvestenosis,whichishighpitched.Atumorplopmaybefollowedbyalow-pitcheddiastolicmurmur.Ifthemitralvalveinflowobstructionissignificantenough,physicalexamfindingsofcongestiveHFwillbepresent. Pericardialknock: Apericardialknockcanbepresentinpatientswithconstrictivepericarditis,astheearlyfillingoftheLVislimitedfromtheconstrictiveprocess.TheknockoccursearlierthanaS3heartsound.whichisthedistinguishingfactor;thisisbecausetheS3heartsoundoccursfromastretchofaverycompliantLV,whichtakesashorttimelonger. RelatedContent: HeartSoundsQuiz Readmoreabout auscultation Facebook Twitter LinkedIn Email Print Comment ContinueReading RelatedContent Save Save Save We’resorry,butanunexpectederrorhasoccurred. Pleaserefreshyourbrowserandtryagain.Ifthiserrorpersists,[email protected]. Close