Andersons pediatric cardiology 1063

asynchronousclosureofthevalvarleafletsorproductionofaduplicatesoundby
vibrationswithinthearterialtrunk.Inmostinfants,therewillalsobealoud
ejectionclick,heardbestattheapex,whichcoincideswiththeopeningofthe
truncalvalve.Thereisoftenanejectionsystolicmurmurheardmaximallyatthe
mid-to-upperleftsternalborder,oraharshpansystolicmurmurmaximallyatthe
lowerleftsternalborder.Lesscommonmurmursincludetheapicalmid-diastolic
murmur,whichresultsfromflow,andanearlydiastolicmurmurheard
maximallyalongtheleftsternaledge,indicatingtruncalvalvarinsufficiency.
Surprisingly,inperhapsone-tenthofpatients,nomurmurisheardatallatthe
timeofpresentation.Thisindicatesanabsenceofturbulencewithinthe
ventriclesortheiroutflowtracts.

Electrocardiography
Sinusrhythmisusual,andconductionthroughtheheartissimilarlynormal.The
QRSaxisisextremelyvariableandnonspecificbutisalmostalwaysdirected
inferiorly.Thedistributionofventricularforcesisalsovariable,reflectingthe
variabilityencounteredinventricularhypertrophy.Themajorityofpatientsshow
evidenceofcombinedventricularhypertrophy,withisolatedrightventricular
hypertrophyalsoafrequentfinding.Itisunusualtofindevidenceofisolatedleft
ventricularhypertrophyoranormalpattern.InversionoftheTwavesis
sometimesseenintheleftprecordialleads,probablyreflectingtheimpaired
coronaryarterialdiastolicflow.


RadiologicFeatures
Thechestradiographshowssignificantcardiomegaly,withanincreasein
pulmonaryvascularmarkings(Fig.40.9).Theaorticarchisrightsidedin
approximatelyone-thirdofpatients.Thisfinding,inassociationwithincreased
pulmonaryvascularity,isstronglysuggestiveofcommontrunk.Itmaybe
possibletoseeanunusuallyhighoriginoftheleftpulmonaryarterywithno
interveningconfluentpulmonaryarterialsegment.Althoughthetruncalroot

itselfisdilated,thearterialpedicletendstoappearnarrowsimplybecauseofits
commonality.Whenflowofbloodtothelungsisdecreased,theheartisless
enlargedandthepulmonaryvascularmarkingsareclosertonormal.Pronounced
discrepancybetweenthevascularmarkingsonthetwosidessuggestsunilateral
atresia,orabsence,ofonepulmonaryartery.

FIG.40.9 Chestradiographobtainedfroma4-week-oldinfantwith
commonarterialtrunk,demonstratingincreasedpulmonaryvascular
markings.


Echocardiography
Itispossibleinmostinstancestoevaluatepatientswithsuchprecisionthatonly
cross-sectionalechocardiographyisrequiredpriortocorrectivesurgery.27The
goalsofechocardiographyaretodefinetheventricularoriginandpatternof
branchingofthecommonarterialtrunk,todeterminethemorphologyandany
functionalabnormalitiesofthetruncalvalve,toexcludeanystenosisatthe
originsofthepulmonaryarteries,todistinguishaperimembranousventricular
septaldefectfromonewithamuscularposteroinferiorrim,toexcludeany
abnormalitiesoftheaorta,andtodefineallotherassociatedlesions.
Theparasternallong-axiscutoftheleftventriclewillusuallyshowthe
commonarterialtrunkoverridingtheventricularseptum,withitsvalveforming
thesuperiorborderoftheventricularseptaldefect(Fig.40.10).Thisfeature,of
course,islackingwhenthetrunkhasauniventricularorigin.Ifthepulmonary
arterieshaveaconfluentsegment,itwillbeseenarisingposteriorlyfromthe
commontrunkinthisview.Theleafletsofthetruncalvalvearefrequently
dysplasticandoccasionallyprolapse,causingtheventricularseptaldefecttobe
restrictive.Indeed,theleafletsmayoccasionallycoaptdirectlyonthecrestofthe
ventricularseptum.ColorflowDopplerinterrogationwilldemonstrateflowto
theaortafromboththerightandleftventricleandwilldocumentanytruncal

insufficiency.

FIG.40.10 Echocardiographicimagefromaparasternalwindow
demonstratingthelongaxisoftheheart.Thereisacommonarterialtrunk
(Tr),whichoverridesthecrestofthemuscularventricularseptum.LV,Left
ventricle,RV,rightventricle.