Andersons pediatric cardiology 2259
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FIG.88.2 Neurologicconsequencesofuncorrectedcongenitalheart
disease.(A)Frameofaplaincomputedtomographicscanofthebrainofa
9-month-oldchildfollowingaseverecyanoticspell.Thereislarge
watershedinfarctintheleftcerebralhemisphere.Althoughthechild
“recovered”fromthecyanoticspell,hewasdeclaredbraindeadasaresult
ofthislargeinfarct.(B)A10-year-oldchildwithuncorrectedsingleventricle
physiologywithabrainabscessinvolvingtherighttemporallobe.
Right-to-leftshuntsthatbypassthepulmonarycirculationconstitutea
substrateforcerebralabscess(seeFig.88.2).Thisproblemhaslargely
disappearedineconomicallyadvancednationsbecauseitisrareforchildren
withcyanoticheartdiseasetoremainunaddressedbeyond3to4yearsoflife.
However,itisquitecommonforchildreninLMICswithcyanoticheartdefects
toremainunoperatedinchildhood,andbrainabscessisthereforenot
uncommon.Severehypoxemiaandelevatedhematocritareassociatedwitha
highlikelihoodofdevelopmentofbrainabscess.39Itiswidelyrecognizedthat
long-standinghypoxemiaandpolycythemiaareassociatedwithavarietyof
adverseneurodevelopmentalconsequences.40–42
Cardiacconsequencesoflong-standinghypoxemia.
Bothsystolicanddiastolicfunctionsworsenwithlong-standinghypoxemiain
childrenwithcyanoticdisease,andthisadverselyimpactspostoperative
recovery.43,44Histologicstudiesofmyocardialbiopsyspecimensobtained
duringsurgicalrepairhaveshownthatpreexistingcardiomyocyteinjury
accompaniedbymitochondrialdamageandfibrosisisfoundtobemore
pronouncedinolderpatientswithtetralogyofFallotandlong-standing
hypoxemiacomparedwiththosewithlesshypoxemiaand/orofshorter
duration.45Patientswithafunctionaluniventricularheartandlong-standing
hypoxemiatendtohaveunacceptableelevationsinend-diastolicpressuresthat
sometimesprecludeFontancompletion.44Thesuggestedunderlying
mechanismsofimpairedventricularperformanceincludeimpairedfreefattyacid
metabolism,46ahighprevalenceofcardiomyocyteapoptosis,47andreduced
myocardialadenosinetriphosphatelevelsinthemyocytes.43
Patientswithseverelong-standinghypoxemiamaydemonstrateseverely
diminishedventricularfunctionthatmaycomplicatedecision-makingbecauseit
isnotoftenclearhowmuchofthedysfunctionwouldreverseaftercorrectionof
hypoxemia.Insomeofthesepatientsitmaybenecessarytoperformapalliative
proceduretoimproveoxygensaturation,allowingforrecoveryofventricular
functionpriortocorrectivesurgery.Forexample,inadultswithuncorrected
tetralogyofFallot,itissometimesnecessarytoundertakeapalliativeballoon
pulmonaryvalvotomytofacilitaterecoveryofimpairedleftventricularfunction.
Likewiseabidirectionalcavopulmonaryshuntmayhelptoreverseventricular
dysfunctioninpatientswithafunctionallyuniventricularheartandlong-standing
hypoxemia.
Effectofhypoxemiaanderythrocytosisonotherorgansystems.
Hypoxemiaandtheattendantsecondaryerythrocytosisaffectmultipleorgan
systems(Table88.3)thatmaygetoverlookedinabusyclinicalsetting.48As
patientswithcyanoticCHDgetolder,theeffectsoferythrocytosisdominatethe
clinicalpictureandaccountformostofthepatients’symptoms.
Table88.3
EffectofHypoxemiaandErythrocytosisonVariousOrganSystems
Pathophysiologic
Derangement
Secondaryerythrocytosis
Manifestations
Hyperviscositysymptoms,relativeiron,folicacidandvitaminB12deficiency,
hyperuricemia,andgout
Bleedingdiathesis
Hemoptysis,cerebralhemorrhage,menorrhagia,epistaxis
Alteredredcellrheologyand Cerebrovascularaccidents(strokeortransientischemicattacks),intrapulmonary
thromboticdiathesis
thrombosis,andelevatedpulmonaryvascularresistance
Renaldysfunction
Glomerularabnormalities,hyperuricemia,andgout
Hepatobiliarydysfunction
Calciumbilirubinategallstones,cholecystitis
Infections
Skeletaldisease
Endocarditis,cerebralabscess,pulmonarytuberculosis
Scoliosisandhypertrophicosteoarthropathy
AdverseEffectsofLong-StandingVolumeandPressureOverload.
UncorrectedCHDwithchronicpressureorvolumeoverloadresultsinvarying
degreesofirreversiblechangesthatcontributetoresidualproblemsthatpersist
aftersurgicalcorrection.49Volumeoverloadcanresultfromleft-to-rightshunts
thatoccasionallypersistformanyyearswithoutsignificantelevationinPVR.50
Chronicventricularenlargementpredisposestoheartfailurefromventricular
dysfunctionand,sometimes,atrioventricularvalveregurgitation.Thepictureis
oftencomplicatedbyatrialenlargementwithresultantatrialflutterand
fibrillation.Severeventricularhypertrophyresultsfromuncorrectedoutflow
obstructionsandisoftenassociatedwithresidualdysfunctionafterreliefofthe
obstructionbecauseofmyocardialfibrosis.51,52
UndernutritionandItsImpactonCongenital
HeartDisease
Thereisasignificantburdenofchildhoodundernutritioninlow-andmiddleincomenations.ThecoexistenceofCHDgreatlyincreasesthelikelihoodand
severityofundernutrition,andthisaddssignificantlytotheexistingchallenges
thatincluderesourceconstraints,latepresentation,andperioperativeinfection.
Intheinitialpublicationof15,049patientswithCHDfromtheInternational
QualityImprovementCollaborative(IQIC),morethanhalfthechildrenwere
severelyundernourished(weightz-scoresof−3orless)and12%hadan
emaciatedappearancepriortotheirsurgery(Fig.88.3).53
