Andersons pediatric cardiology 1815
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overridingthereisdouble-inletleftventricle(LV)witharight-sided
incompleterightventricle.Incontrast,asshowninthelowerpanels,the
spectrumisbetweendiscordantAVconnectionsanddouble-inletLVwith
left-sidedincompleterightventriclewhenthetricuspidvalveisleftsided.
FIG.69.20 Comparablespectratothoseillustratedforstraddlingofthe
tricuspidvalveinFig.69.19.Inthisinstance,themitralvalveisstraddling,
leadingtospectrabetweenconcordantatrioventricular(AV)connections
anddouble-inletrightventricle(RV)withtheleft-sidedincompleteleft
ventricle(upperpanels)anddiscordantconnectionsandadoubleinletwith
theright-sidedincompleteRV(lowerpanels).
FIG.69.21 (A)Amorphologicallytricuspidvalvestraddlesandoverrides
(arrows)theinferiorandinletpartoftheapicalventricularseptum(star).
Becauseofthemalalignmentbetweentheatrialseptumandtheapical
muscularventricularseptum,theconductionaxis(redline)takesorigin
fromananomalousatrioventricularnodelocatedintheinferior
atrioventricularjunction(cross-hatchedoval).(B)Themitralvalve
morphologicallystraddlesthroughananterosuperiorseptaldefectthat
openstotheoutletoftherightventricle.Inthisinstance,asshownwith
concordantatrioventricularconnections,theatrioventricularconductionaxis
maintainsitsoriginfromtheregularatrioventricularnode.
Solitaryatrioventricularvalvescanstraddleandoverridewhenoneofthe
atrioventricularconnectionsisabsent.Thesolitaryvalvecanberightorleft
sidedandcanexistinthesettingofeitherright-orleft-sidedventricular
topology(Fig.69.22).Thesearethecombinationsthatproducetheuniatrialbut
biventricularatrioventricularconnections.Becauseoftheabsenceofoneofthe
atrioventricularconnections,suchpatientswillbesuitableonlyfortreatmentby
conversiontotheFontancirculation.Thearrangementsareoftendescribedin
termsofdouble-outletatrium,butallpatientswithstraddlingatrioventricular
valveshaveadoubleoutletfromoneortheotheratrium.Such“doubleoutlets”
canalsobefoundinthesettingofatrioventricularseptaldefectwithacommon
atrioventricularjunctionwhenthereisgrossmalalignmentoftheatrialseptum
versustheventricularseptum.Furthercomplicationscanbeproducedwhenthe
solitarystraddlingatrioventricularvalvehasdualorifices,withtheconnecting
tongueofvalvartissueattachedtothecrestoftheventricularseptum.This
seeminglyproducesanintactventricularseptum,butventricularseptationisof
necessitydeficientwhenthereismalalignment,asfoundwithstraddling
atrioventricularvalves.
