Andersons pediatric cardiology 172
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CharacteristicCirculatoryAbnormalities
inPathologicPregnancies
ComplexMultiplePregnancies
Monochorionictwinshaveanincreasedriskofcongenitalheartdefects,most
oftenpulmonaryvalvestenosis,buttheirsharedplacentalcirculationformsthe
substratefordevelopmentofTTTS,characterizedbyactivationofthereninangiotensin-aldosteronesystemandunbalancedintertwinedtransfusionofthese
vasoactivesubstances,aswellasvolume.111Earlyalterationofcardiacfunction
isreflectedindiscordantdiastolictimeintervalsofthevenousductandinleft
ventricularstraininaffectedpregnanciesbeforeovertsignsofdiseaseare
present.161,162Theincreasedafterloadisreflectedintheinterestingresponseof
theumbilicalarteriesofthecordtoproducehypercoiling(seeFig.6.2).163
Intheabsenceofanobstructedrightventricularoutflowtract,noninvasive
estimatesofthesystemicfetalpressurescanbeestimatedfromthepeakvelocity
ofthejetoftricuspidregurgitation.Importanttricuspidregurgitationis
holosystolic,oftenwithincreaseddurationofthesystolicDopplerenvelope,
withacompensatoryshorteningofthediastolicfillingtime.Itmaybeassociated
withabnormalwaveformsintheperipheralarterialandvenouscirculations(e.g.,
reversalofflowinthevenousductatend-diastole).
Twin-reversedarterialperfusionoccursinmonochorionicpregnancieswhere
earlysplittingoftheinnercellmasspreventsthedevelopmentoftwonormally
formedtwins.UltrasoundDopplerexaminationofthesecirculationscanidentify
reversedperfusionoftheamorphoustwinbythenormalso-calledpumptwin.
Hydropsandcardiacfailuremayresultfromvolumeoverload,andtheexcess
cardiacoutputrequiredtoperfusetheabnormaltwinmaybeestimatedfromthe
relativevolumeflowsoftheumbilicalveinsofbothtwinsusingmathematic
modeling.164Similarcirculatoryfindingsoffetalhydropsandcardiacfailure
mayresultfromvolumeoverloadbecauseofavasculartumorsuchas
sacrococcygealteratomaandplacentalchorioangioma.Adaptationofthis
modelingmayassistinthemonitoringofsuchpregnanciesandguidetimingof
theirtreatmentordelivery.165FlowabnormalitiesassociatedwithveinofGalen
aneurysmincludereversedflowinthefetalaorticarchduetothesteal
phenomenon(seeVideo6.10).
ChestMasses
Displacementoftheheartandelevationofthevenousductintothechestmay
occurindiaphragmatichernia.Subsequentalterationofitsflowpatternsis
believedtoreducetheflowthroughtheovalforamenintotheleftsideofthe
fetalheartandmaycontributetoitsreducedgrowthandcoexistingcoarctation
oftheaorta.166Lungmassessuchasadenomatouscystsandbronchopulmonary
sequestrationmaydisplacetheheartbutusuallyhaveminimaleffectsonfetal
physiology.
DuctalConstriction
Inthehumanfetus,ductalflowmaybecompromisedbymaternalingestionof
inhibitorsofprostaglandins,suchasthenonsteroidalantiinflammatoryagents
andbyfoodsrichinpolyphenols.Dopplerabnormalitiesinthearterialductare
recognizedbyincreaseddiastolicandsystolicvelocities(Fig.6.17)followedby
subsequenttricuspidregurgitationduetoincreasedafterloadofthefetalright
heart.
FIG.6.17 Dopplerprofileofductalconstrictionischaracterizedby
increaseddiastolic(D)andoftensystolic(S)velocities.
FistulaeoftheCoronaryArteries
Itisrelativelyeasytodemonstrateabnormalvascularconnectionbetweenthe
coronaryarteriesandventricularcavities,particularlyinassociationwith
obstructedoutflowtracts(Video6.12).Postnatalcoronaryarterialstealmaybe
predictedbyreversalofflowintheaorticarch,andcoronarystenosesor
occlusionbythefindingofretrogradeflowathighvelocity(seeFig.6.14).
Thesefindingsareimportanttodiscussduringantenatalcounselingbecause
outcomesforthesebabiesmaybepoorandassociatedwithpostnataldeath.
