Andersons pediatric cardiology 1913
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (111.97 KB, 3 trang )
Summary
ThedominantarrhythmiapostFontanisatrialtachycardia,withcomplexatrial
reentrycircuits.Theirappearanceiscommonlycoincidentwithhemodynamic
deteriorationandthearrhythmiatypicallycontributesfurthertolowercardiac
output,formingaviciouscyclethatmaybelethal.Atrialfibrillationcommonly
alternateswithotheratrialtachycardias.Currentmanagementistendingtoward
earlyconversionoftheatriopulmonaryFontantoanextracardiacconduit,with
concurrentatrialarrhythmiapreventionsurgery.
FollowingalltypesofFontansurgeries,medicalmanagementisusuallynot
sustainableformorethan2to3yearsand,althoughamiodaroneisthemost
effectivemedication,sideeffectsarecommon.Invasiveelectrophysiology
studiesandcatheterablationstrategiescanbeveryhelpfulandarerecommended
earlyintheabsenceofgrossatrialdilationandtodiagnoseandtreatconcurrent
congenitalarrhythmiasubstratesincludingaccessorypathways.
HematologicandImmunologic
Complications
ItiswellrecognizedthattheFontancirculationpresentsahypercoagulablestate,
withtheincidenceofthromboemboliceventsreportedtovarybetween8%and
20%ofthepopulation.127–129Thisislikelyanunderestimation,inviewofthe
occurrenceofsilentthromboembolisminthisgroup.130Aprospective
multicenterrandomizedcontrolledtrialassessingseveralanticoagulantregimens
reportedatotalthrombosisrateof23%over2years.131Onlyone-thirdofthese
events(8%)weresymptomatic,withtheremainderbeingdetectedduring
intensivesurveillanceaspartofthestudydesign.Studieshavedescribedapeak
thromboticriskinthefirstyearfollowingFontancompletion,whichplateaus
overthenext3to4years,beforeasecondpeakafter10years.129,132Moreover,
theincidenceofthromboemboliccomplicationsishigherinadultscompared
withchildren,suggestinganincreaseinriskwithtimethatmightrelatetoa
gradualdeteriorationinvascularandliverfunction,exacerbatedbyatendencyto
amoresedentarylifestyleinolderandmoredebilitatedpatients.
Theetiologyofthisprothromboticstateismultifactorialandinvolvesallthree
factorsoftheVirchowtriad,namelyabnormalhemodynamics,a
hypercoagulablestate,andendothelialdysfunction(Fig.73.17).Potentialfactors
includethelow-velocityflowinthesystemicveins,cavopulmonaryconnection
andpulmonaryarteries,atrialarrhythmias,persistentcyanosisrelatedtoright-toleftshunts,andanimbalanceofintrinsicprocoagulantandanticoagulantfactors.
FIG.73.17 FactorscontributingtoprothromboticstateinaFontan
circulation.
RiskFactorsforThromboembolism
OlderageatthetimeoftheFontanoperationisariskfactorforsilent
thromboembolism.130,133Surprisingly,thereappearstobeasimilarriskof
thromboembolismamongthedifferentvariantsoftheFontan(Fig.73.18;Video
73.2).134–136Althoughthepresenceofaright-to-leftshuntisknowntoincrease
theriskofcerebralvascularembolization,thepresenceofafenestrationhasnot
beenassociatedwithincreasedthromboembolic134orstrokerisk.137This
suggeststhatintrinsichematologicabnormalitiesmaybethemostsignificant
factorsintheprothromboticstateintheFontancirculation.Comparedwith
healthycontrols,Fontanpatientshavereducedlevelsofprocoagulantfactors,
