Andersons pediatric cardiology 557
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fluoroscopyinpediatricEPs.Multiplesystemsareavailable,andacomplete
discussionbeyondthescopeofthischapter.Briefly,however,thesesystemsuse
electroanatomicfieldstoidentifythelocationofcathetersinthree-dimensional
space.Thecardiacchamberofinterestisanatomicallydefinedandthencolorbasedtimingmapsaresuperimposedontheanatomicmaps.
FIG.22.29 Ablationofanaccessorypathway.Fluoroscopyintheleft
anterior(A)andrightanterior(C)obliqueprojections.(B)Electrograms
recordedduringablationwithabolitionofconductionacrosstheaccessory
pathwaywithV-to-Ablockandterminationofthesupraventricular
tachycardia.CS,Coronarysinus;HRA,Highrightatrium;RF,
radiofrequency;RV,rightventricle.
CatheterAblation
Oncethesubstratehasbeenidentifiedwithmapping,itisoftenfeasibleto
proceedwithacatheterablationtogetridofthesubstratethatiscausingor
potentiallycouldcauseatachyarrhythmia(Figs.22.30and22.31).The
developmentofradiofrequencyenergyasatoolforablationwasenhancedwith
thedevelopmentofsteerableelectrodecatheterssothatdiscretecontrolled
amountsofenergycouldbedeliveredaccuratelytothetargetwhileavoiding
damagetootherstructures.Deliveryofenergyisgradualandsteadyratherthan
theexplosiveinstantaneousdeliveryproducedbydirect-currentablation,andit
canbeappliedrepeatedlyuntileffective.Radiofrequencyablationisrelatively
painlessandcanbeperformedunderlocalanesthesia.Althoughcatheterablation
wasinitiallydevelopedtocreatecompleteheartblock,thisisseldomrequiredin
children,inwhomradiofrequencyablationisusuallyusedtoeffectadirectcure
ofarangeofarrhythmias.
FIG.22.30 (A)A2-Frquadripolarelectrodeintherightcoronaryartery
(RCA)throughacoronaryguidecathetertoassistablationofaright-sided
manifestaccessorypathwayafterapreviousattempthadfailed.(B)
Electrogramsfromsurfaceandintracardiacleadsshowthattheshortest
atrioventricularconductiontimeisatthedistalpairofelectrodesonthe
catheterwithintherightcoronaryartery.Theablationcathetershows
continuousatrioventricularsignalsatthesiteofsuccessfulablation.CS,
Coronarysinus;HRA,highrightatrium;RV,rightventricle.
