Andersons pediatric cardiology 1373
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FIG.52.9 (A)Echocardiogramand(B)computedtomographicscanina
patientwithsecondarycardiacB-lymphoblasticlymphoma/leukemia
(asterisk).Notethecrossingoftissueplanesfromtherightatriumtothe
rightventricle.RA,Rightatrium;RV,rightventricle.
MRIallowsforbettervisualizationofcardiacstructuresthan
echocardiographyinpatientswithpooracousticwindows.Italsoprovidesa
widerfieldofviewthanechocardiography,allowingforclearervisualizationof
theheartandtumorrelativetotheadjacentmediastinum,lungs,orvascular
structures.ThespatialandtemporalresolutionofMRImaybelimitedcompared
withechocardiography,whichmaybebettersuitedforanatomicvisualizationin
thesmallestpatientsandincaseswithsmallmobilemassesandverythin
attachments.MRIishighlysensitivetoferromagneticartifactfromcertain
implantabledevicesandmaybecontraindicatedinpatientswithdevicessuchas
pacemakers,defibrillators,andcochlearimplants.66MRIcanbetimeconsuming
anddifficulttoobtaininpatientswitharrhythmiasandrequiresdeepsedationor
generalanesthesiainpatientsyoungerthan8years.Comparedwithcomputed
tomography(CT),ithastheadvantageofnotrequiringradiationoriodinated
contrast.
CTscanningallowsformultiplanarimagingwithexcellentspatialresolution.
ItissuperiortoMRIforassessmentofcalcificationsbutotherwisemorelimited
initsabilityfortissuecharacterization.ItisalsogenerallypreferabletoMRIfor
assessmentofcoronaryarteriesandtheirpotentialrelationshiptotumor.Modern
high-pitchCTscannersallowforexaminationusingaminimumofradiation
exposureandareoftenfastenoughtoobtaindiagnosticimagesinyounger
patientswithoutsedation.67,68
CatheterizationandAngiocardiography
Onceacceptedasthegoldstandardfordiagnosis,angiocardiographyhaswaned
inimportanceasaresultoftheavailabilityandreliabilityofnoninvasive
imaging.Angiocardiographyremainsthegoldstandardforassessmentofthe
coronaryarterialrelationshiptotumorincaseswhereCTandMRIare
equivocal.69Incertainselectcircumstances,endomyocardialbiopsymaybe
preferabletosurgicalbiopsy.Catheterizationcarriestheinherentriskofplacing
acatheternearoracrossafriabletumor,aprocessthatmayleadto
embolization.70
TypesofTumor
Rhabdomyomas
Rhabdomyomasarebyfarthemostfrequenttumorsfoundinfetuses,infants,
andchildren.Theyoccuralmostexclusivelyinpatientsyoungerthan15years,
andapproximately75%areseeninpatientsyoungerthan1year.1,71Thereisa
strongassociationbetweenrhabdomyomasandTSC.Rarely,rhabdomyomas
havebeenreportedinassociationwithcongenitalheartdefectssuchastetralogy
ofFallotandEbsteinanomaly.
Rhabdomyomasarehamartomascharacterizedbygrotesquelyswollen
myocytes,whichpresentanalmostemptycytoplasmtraversedbytinystrandsof
cross-striatedsarcoplasm.Thenucleusmaythusappearsuspendedwithinthe
cell,givingrisetotheso-calledspidercell(Fig.52.10).Rhabdomyomaspresent
ascircumscribednonencapsulatedlesions,varyinginsizefromafew
millimeterstoseveralcentimeters.Occasionally,thelesionmayoutgrowthesize
oftheheart(seeFig.52.1).Rhabdomyomasareusuallymultipleandhavea
distinctpreferencefortheventricles(Fig.52.11).1,31,72,73Singleandatrial
rhabdomyomasarelesscommon.Thelesionsmaybelimitedtothemyocardium
orextendfromtheirintramurallocationtooccupyanintracavitaryposition(see
Fig.52.11).
