Andersons pediatric cardiology 175
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VentriculovascularCoupling
FetalSystemicPressures
Directmeasurementsofintraventricularpressurehavebeenmadeinthenormal
heartbetween18and29weeksofgestation.195Thesestudieshaveconfirmed
thatventricularsystolicpressuresincreasewithgestation.Infetusesinwhichit
waspossibletorecordmeasurementsinbothventricles,thepressureswere
equal,asexpected.End-diastolicpressuresthathavepreviouslyonlybeen
inferredfromDopplerassessmentwerealsodirectlymeasured(Fig.6.20).
Speckletrackingtechniqueshavebeenusedtotracetheendovascularborderof
theaortaprofiledinanaxialplaneinthefetalchestatthelevelofthefourchamberviewtomeasuretheaorticfractionalareachange(AFAC).Animal
studieshaveshowngoodcorrelationwithbloodpressureanditsamplitude
measureddirectlyinafetallambmodel.196Inthehumanfetus,intertwinpair
differencesinAFACwerereportedinmonochorionicpregnanciescomplicated
byTTTS,withhighervaluesintherecipienttwinofapaircomparedwithits
donortwin,consistentwithahigherpulsepressure.Nointertwinpairdifferences
wereobservedinuncomplicatedmonochorionictwinpairs.Furthermore,AFAC
correlatedwithcombinedcardiacoutputandventricularfillingpressures,thus
provingitspotentialutilityinmonitoringfetalresponsetotherapies(Fig.
6.21).197
FIG.6.20 Pressuretracesshowingthesystolicandend-diastolic
measurementswithinthehumanfetalventricleat22weeksofgestationfor
theleftventricle(A)andtherightventricle(B).(FromJohnsonP,Maxwell
DJ,TynanMJ,AllanLD.Intracardiacpressuresinthehumanfetus.Heart.
2000;84:59–63.)
FIG.6.21 (A)Theendovascularborderofthemid-thoracicaortainthe
four-chamberviewwastracedmanuallyduringsystolewithtimingguided
byanatomicM-modeandtheaorticfractionalareachangeaveragedover
threecardiaccycles.(B)Asamplearea-timediagramfromafetusacquired
