Andersons pediatric cardiology 679

Introduction
Ithaslongbeenrecognizedthatcongenitalabsenceofthespleen,orthepresence
ofmultiplespleens,isassociatedwithseverecongenitalmalformationsofthe
heart.1Someofthemostcomplexformsofcongenitalcardiacdiseaseare
associatedwiththesesplenicabnormalities.Prognosisformanypatientswith
theselesionsremainspoor,eveninthemoderneraofcongenitalcardiovascular
surgery.Ifprogressistocontinueinthecareofthesechildren,thecardiac
abnormalitiesneedtobedeterminedwithprecisionineachcase.More
importantly,theyneedtobedescribedinunambiguousfashiontothesurgeon
attemptingcorrectionorpalliation.Descriptionoftheso-called“splenic
syndromes,”however,continuestobethecauseofmuchconfusionand
controversy.Itisnowestablishedthatcardiacstructuresarebestidentifiedonthe
basisoftheirmostconstantcomponents,followingtheso-calledmorphologic
method.2Whenconsideringtheatriums,itistheappendagethatismost
constantlypresent(seeChapter1).Thepresenceofisomericatrialappendagesis
themostaccuratefeaturewithwhichtostratifythepatientspreviouslylabeledas
having“splenicsyndromes,”ormorerecentlyashavingeither“situs
ambiguous,”or“visceralheterotaxy.”3–5Tosetthesceneforclarification,we
beginthisaccountbyreviewingsomeofthehistoricallandmarksinthe
recognitionofthecardiacmalformationsseeninthesyndromes.Wethenseekto
clarifysomeoftheconfusingnomenclaturethathasevolvedoverthelastfew
decades.Wethendescribeindetailthemorphologicandclinicalfeaturesof
thesecardiacmalformations,takingadvantageofourownextensiverecent
researches,correlatingthecardiacfeatureswiththefindingswithintheother
systemsoforgans.Wethenfocusattentionontheprogressmadeinrecentyears
inthediagnosisandtreatmentofpatientswiththesecomplexmalformations.


HistoricalNotesandDefinitions
Absenceofthespleenisanobviousautopsyfinding.Itisunlikelytobemissed,
andwasnotedaslongagoasthe16thcentury,butverylikelyasthe

consequenceoftuberculousinfection.Theearliestrecordedexamplesof
congenitalabsenceareprobablythoseappearingin1826.Multiplespleens
occurringasacongenitalmalformationhadbeenrecordedover30years
previously.Theseearlyaccountsrecognizednotonlythesplenicanomalies,but
alsotheabnormalarrangementsofotherorgans,includingthecardiac
malformations.Overrecentdecades,therehasbeenamoresystematicanalysis
ofthecardiacandextracardiacmalformationsseeninpatientswithcongenital
splenicanomalies.Thishasresultedinrecognitionthattheentirebodily
arrangementofinvolvedpatientsdiffersfromboththeusualarrangement,or
“situssolitus,”anditsmirror-imagedvariant,typicallydescribedas“situs
inversus.”Itisofnotethatinhisclassicaldescription,Ivemarkintroducedthe
phrase“asplenia,ateratologicsyndromeofvisceralsymmetry.”1Shortlyafter,
PutscharandMannion,withremarkableprescience,stated:“Therelationshipof
agenesisofthespleentodisturbeddevelopmentoflaterality,however,goes
beyondthemanifestationsofobvioussitusinversus.Betweenthenormalsitus,
whichisasymmetrical,andthesitusinversus,whichistheasymmetricalmirror
imageofnormality,asymmetricalsitussometimesexists,exhibiting
symmetricalrightnessorleftnessonbothsides.”Itishardtofindanysubsequent
accountthatsowellexpressestheconceptofbiologicisomerismthatisthe
essenceofthe“splenicsyndromes.”6
Thisfactisthemoresurprising,sincenotehadbeentakennotonlyof
isomerismoftherightatrialappendagesandsinusnodesinpatientshaving
absenceofthespleen,butalsotheobviousbilateralleftsidednessinpatients
withmultiplespleens.7Theapproachinwhichthecardiacmalformations
continuetobegroupedundertheheadingsof“asplenia”and“polysplenia”by
some,withinanoverallgroupingof“situsambiguous,”islessthanidealata
timewhenmostcentersdealingwithcongenitalcardiacdiseaseuseasequential
segmentalapproachtodiagnosis.7,8Suchanalysis,ofnecessity,muststartwith
accurateidentificationofthearrangementoftheatrialchambers.Whenthe
essenceofthemalformationsisnowproventobeisomerism,ratherthan

lateralization,oftheatrialappendages,thereisnothingambiguous,oruncertain,


concerningtheatrialmorphology.Intermsofthescientificrigor,itisalsothe
casethatmolecularadvanceshavemadeitpossibletogenerateknockoutmice
withunequivocalisomerismoftheatrialappendages.9Weseenoreasonfor
continuingtouse“situsambiguous,”eventhoughadefinitionfortheentitywas
suggestedbytheinternationalworkinggroupdealingwithnomenclature.5We
recognizethatisomerismisnotuniformlypresent.Indeed,itisthecasethatonly
thethoracicorgansshowevidenceofisomerism.Providingeachsystemof
organsisdescribedseparately,allquestionsofambiguityareremovedby
accuratedescription.