Andersons pediatric cardiology 2132
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thrombosisascomparedwithwarfarin.Itdoesnotcrosstheplacentaand
thereforeissafeforthefetus.Manyofthereportedcasesofthrombosisin
womentreatedwithLMWHoccurredsecondarytoinadequatedosingand
monitoring.IfLMWHisusedduringpregnancy,dosingbyweightisnot
adequate,andcarefulmonitoringofanti-Xalevelsisrequired.Low-doseaspirin
issafeandmayenhancetheeffectivenessofheparinandofwarfarininpregnant
womenwithmechanicalvalves.Bothheparinandwarfarinaresafeinthe
breastfeedingmother.Thereisnoperfectregimeforanticoagulationinpregnant
womenwithmechanicalvalves,norhaverandomizedtrialsbeendone,sothe
choiceshouldbetailoredtotheindividualafterrisksandbenefitsarediscussed
indetail.Guidelines,predominantlybasedonexpertopinion,havebeen
publishedbytheAmericanHeartAssociation/AmericanCollegeof
Cardiology,66theAmericanCollegeofChestPhysicians,67andtheEuropean
SocietyofCardiology.9
PeripartalManagement
Recommendationsfortheevaluationandmanagementofpregnancyinwomen
withcongenitalheartdiseaseareavailablefromtheEuropeanSocietyof
Cardiology,9theAmericanHeartAssociation,68theCanadianCardiovascular
Society,69–71andothersources.72,73Forwomenwithcongenitalheartdiseaseat
significantriskforadversecardiacorneonatalcomplications,thereshouldbea
timelymultidisciplinaryassessmentandaplanshouldbedevelopedfor
managementthatprovidesrecommendationsforvariouscontingenciesincluding
allcommononesaswellasrareonesthatimparthighrisk.Thisplanmustbe
availabletothemedicalteamwhomaybetaskedwiththecareoflaborand
deliveryatunpredictabletimesandeveninunpredictableplaces.Theplan
shouldthereforebewrittenandwidelydistributed,withacopygiventothe
patienttoensuretimelyaccess.
Generalprinciplesofmanagementoflaboranddeliveryforwomenwith
congenitallymalformedheartsofmoderateorgreatercomplexityincludeearly
effectiveanalgesiabyregionaltechniquesandvaginaldeliveryinalmostevery
caseunlessobstetricconsiderationsrequirecesareandelivery.Inductionis
consideredsafeinwomenwithcardiacdisease.Assistedvaginaldeliveryis
oftenindicatedinordertolimitoravoidmaternalexpulsiveefforts.Forcardiac
reasons,cesareandeliveryisrarelyindicated.Guidelinesdonotrecommend
prophylaxissolelytopreventendocarditisforuncomplicatedobstetric
deliveries.74
CardiacMedications
Theuseofanydrugduringpregnancyrequiresconsiderationofmanyfactors,
includingpotentialfetaltoxicityaswellaspossiblepregnancy-relatedchangesin
theeffectivenessofthemedication.
Fetaltoxicitydependsontimingofadministration.Priortoimplantation,the
effectisall-or-none.Teratogeniceffectsareseenwithexposurebetween3and
10to12weeks.Laterinpregnancy,effectsaremixedanddependonthedrug
andthemagnitudeofexposure.Generalprincipleswithrespecttoavoidingfetal
toxicityincludechoosingdrugsknowntobesafewhenpossible,usingtheleast
numberofdrugsfortheshortestpossibletimeinthelowesteffectivedose,and
avoidingmedicationsduringthefirsttrimesterwhenpossible,sincethe
teratogeniceffectsofmostdrugsarenotwellknown.Thebalanceofriskto
benefitwithrespecttomaternalandfetalhealthmustbecalculated.Evaluation
subsequenttoexposuremustconsidermagnitudeofrisk.Evenifapotentially
toxicdrughasbeenusedinadvertently,therisktothefetusmaynotbehigh
enoughtowarrantmoreaggressivestepsthanearliestpossiblediscontinuationor
substitution.Mostdrugsexcepthigh-molecular-weightmoleculessuchas
heparinarenotheldbackinanimportantwaybytheplacentalbarrierand
equilibrateinthefetalcirculationovertime.
Pregnancyaffectsthematernalresponsetoadrugthroughchangesindrug
absorption,transport,binding,metabolism,andexcretion.Theimpactofthese
pregnancy-relatedchangesonaspecificdrugneedsindependentconsideration.
Forexample,drugspredominantlyexcretedthroughthekidneywillcallforan
increasedfrequencyofadministrationbecauseofthepregnancy-associated
increaseinglomerularfiltrationrate.
Certaincommoncardiacdrugshaveknownfetaltoxicityandshouldbe
avoided.9Blockersofangiotensinreceptorsandinhibitorsofangiotensinconvertingenzymecausesecond-trimesterfetalnephrotoxicity;inaddition,
inhibitorsofangiotensin-convertingenzymehavebeenshowntobeteratogenic.
Warfarinfetaltoxicitiesaretosomeextentdoserelatedandmustbebalanced
againstthematernalneedforthedrug.
