Andersons pediatric cardiology 788
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pulmonaryvenousandvestibularcomponentsofthedividedleftatrium.
Thereiscontinuousflowathighvelocity,suggestingseverestenosisand
pulmonaryvenoushypertensionsecondarytopeakandmeangradientsof
44and19mmHg,respectively.
DifferentialDiagnosis
Ininfantsandchildren,thislesionmustbeconsideredwhenthereisunexplained
pulmonaryhypertensionorpulmonarycongestion,althoughcareful
echocardiographicassessmentusuallyestablishesthediagnosispromptly.In
olderchildren,adolescents,andadults,inwhomechowindowsmaybemore
challenging,eithertransesophagealechocardiographyortomographicimaging
shouldbeconsideredifthediagnosiscannotbeexcluded.
Treatment
Theonlyappropriatetreatmentissurgical.Thedividingpartitionisresectedon
cardiopulmonarybypass.Thisisusuallyachievedbyarightatrialincision,
visualizingthepartitionthroughtheovalforamenoranatrialseptaldefect.The
shelfcanalsoberemovedbyaleftatrialincision.Anecdotally,surgerycarries
anexcellentprognosis,althoughreportsoflong-termoutcomearelacking.
DivisionoftheMorphologicallyRight
Atrium(Video30.1)
Hemodynamicallysignificantdivisionofthemorphologicallyrightatriumis
considerablyrarerthanthatoftheleft.Itresultsfrompersistenceofthevalvesof
theembryonicsystemicvenoussinus.1,10Thedividingpartitionistherefore
placedbetweenthesystemicvenoussinusandthedistalpartoftherightatrium,
madeupofthevestibuleandappendage.Theembryonicvalvarstructures,
whosesignificanceduringfetallifeistodirecttherichlyoxygenatedinferior
cavalvenousbloodacrosstotheleftatriumandthencetotheaorta,normally
regressinlatefetallifeandearlychildhood.Theypersistastheeustachianand
thebesianvalves,thevalvesoftheinferiorcavalveinandcoronarysinus,
respectively.Thesevalvescanretaintheirfetalproportionsinabnormal
conditionsanddividetherightatrium.Thedividingpartitioncanitselfbe
fenestratedandnotproducemajorobstructiontotheflowofblood.Thisis
termedaChiarinetworkandusuallydoesnotcauseproblems(Fig.30.6).If,in
contrast,thepersistingvalvarstructuresarenotfenestrated,theycanproduce
partitionswithintherightatrium.Mostexamplesseeninpostnatallifehave
coexistedwithatresiaorstenosisofthepulmonaryvalveorwithtricuspidatresia
(Fig.30.7).10
FIG.30.6 Heartshowingvalvesoftheembryonicvenoussinusthathave
persistedinpostnatallife,buthavebecomefenestrated,producingthesocalledChiarinetwork.
