Andersons pediatric cardiology 177

FIG.6.23 Samplereportonafetalelectrocardiogramfromasingleton
pregnancyat35weeks’gestation.(FromTaylorMJ,SmithMJ,ThomasM,
etal.Non-invasivefetalelectrocardiographyinsingletonandmultiple
pregnancies.BrJObstetGynaecol.2003;110:668-678.)


FIG.6.24 Representativeaveragedmagnetoelectrocardiographic
waveformsrecordedduringfetallife.(A)Normalfetusat39weeks’
gestation.(B)Normalfetusat37weeks’gestation.(C)Fetusat27weeks’
gestationbutwithventriculartachycardiaat25weeks’gestation.(D)Fetus
at27weeks’gestationwithsupraventriculartachycardia.(E)Fetuswith
supraventriculartachycardiaat31weeks’gestation.(F)Samefetusasin
(C)butwithtachycardiapresentat25weeks’gestation.(G–H)Fetuses
withcompleteatrioventricularblockat30and25weeks’gestation,
respectively.(I)Fetuswithblockedprematureatrialcontractionsat20
weeks’gestation.Allwaveformsaretakenfromthechannelwiththelargest
signalamplitude,theamplitudebeingshowninunitsofferntotesla,with
eachferntoteslaequalto10−15Tesla.(FromZhaoH,StrasburgerJF,
CuneoBF,WakaiRT.Fetalcardiacrepolarizationabnormalities.AmJ
Cardiol.2006;98:491–496.)

Heartratevariabilitymayalsobedescribedusingthestandarddeviationfrom
thetimedomain,aswellasothermeasuresfromthefrequencydomainsand
approximateentropyasameasureofcomplexity.213Twodistinctfractal
structureshavebeenidentifiedwithinthisvariation.Theyshowsignificant
gestationalchangeinthenormalfetusandmaybeusefultoevaluatevariationin
diseasestates.214
Investigationintovariabilityoftheheartrateinthefetusandneonatemay


provideinsightsintodevelopmentalprocessesinhealthanddiseaseandrefine

stratificationoffetusesatriskofintrauterinedeath,aswellastheriskofsudden
infantdeathsyndromeinthosebornpriortoterm.Neonateswhohavesuffered
apparentlife-threateningeventsshowdifferencesinheartratevariability,
suggestingalteredautonomiccontrol.215,216
Fetalheartrateparameterssuchasaverageaccelerationanddeceleration
capacitymayprovemoreusefulinthedetectionofthesmallfordatesfetus,thus
improvingprenataldetectionofpoorfetalgrowthandimprovingoutcomes.217