Andersons pediatric cardiology 686
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (57.74 KB, 3 trang )
whentheincompleteleftventricleisright-sided.Theatrioventricularconduction
tissuesarebizarrewhenthereisasolitaryandindeterminateventricle.29
CardiacPosition
Anunusualpositionoftheheartshouldalwaysraisethesuspicionofisomerism.
Thelocationoftheheart,andthepositionofitsapex,however,failto
discriminatebetweenrightandleftisomerism.
FunctionalCardiacAbnormalities
Arrhythmias
Arrhythmiascanbepresentinthosewitheitherrightorleftisomerism,with
20%ormoreexperiencingarrhythmias.30Thisshouldbeofnoparticular
surpriseconsideringthepreviousdiscussionofabnormalitiespresentinthe
formationoftheconductionsystemitself.Inthosewithrightisomerism,the
mostfrequentarrhythmiaissupraventriculartachycardia,accountingfor85%of
arrhythmiasinthispopulation.Inthosewithleftisomerism,atrioventricular
blocksrepresentthemostcommonarrhythmias.Ofthosewithleftisomerism
whohaveanarrhythmia,69%willhaveatrioventricularblock.Themost
frequentisfirstdegreeatrioventricularblock,whichisnotedin32%ofthose
withleftisomerismandarrhythmias.Seconddegreeatrioventricularblockis
notedin12%ofthosewithleftisomerismandarrhythmias,whilecomplete
atrioventricularblockisnotedin26%.Ajunctionalrhythmisnotedin12%of
thosewithleftisomerismandanarrhythmia.Onsetofarrhythmiadoesnotseem
todifferbetweenthosewithrightorleftisomerismwithageofonsetgenerally
between3and4yearsofage.Amajority(80%)ofarrhythmiasinchildrenwith
isomerismwhodeveloparrhythmiaswilloccurby5yearsofage.When
ablationsareattemptedinthesepatients,theyaregenerallysuccessfuleven
despitedifficultiesrelatedtosystemicvenousanomaliesinthesepatients.
Implantedpacemakersarenecessaryinapproximately6%ofthosewithright
isomerismand13%ofthosewithleftisomerism.30–47
Anecdotally,thosewithleftisomerismwhodevelopsinusorjunctional
bradycardiacanbesafelymonitoredwithoutneedforpacingaslongasthe
rhythmishemodynamicallytolerated.Childrencanthrivewithsuchbradycardia
withavoidanceofthepotentialcomplicationsaffordedbyanimplanted
pacemaker.Whileprophylacticallyleavingleadswithoutapacemakergenerator
atthetimeofascheduledsurgerymayinitiallyseemlikeausefulpropositionin
thesepatients,itshouldbeavoided.Such“jailed”leadscanbeproblematicwhen
magneticresonanceimagingstudiesneedtobeconductedduetomanufacturer
concernsofoverheating.Althoughthereareseveralreportsofpatientswith
“jailed”leadswhosuccessfullyandsafelyundergosuchimagingstudies,itcan
addtotheoverallconcernoftheimagerandancillarystaff,subsequentlycausing
suchstudiestobedelayedorevenentirelyavoided.
MyocardialFibrosisandMyocardialInfarction
Necropsystudiesofheartsfromthosewithisomerismdemonstratemyocardial
fibrosisin16%withfrankischemiain10%ofspecimensfromthosewith
isomerism.Itisunclearastohowthesefindingsmaytranslateintoissueswith
ventricularfunctioninthefutureandisalsounclearhowthesefindingsmay
impactmyocardialinfarctioninadultswithisomerism.48Astudyonadultswith
myocardialinfarctiondemonstratedthatwhilethereweredifferencesinthe
locationofinfarctsinthosewithisomerismthatage,abilitytostentand
mortalitybecauseofmyocardialinfarctiondidnotdifferbetweenthosewithor
withoutisomerism.49
