Andersons pediatric cardiology 898
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entrappedintheleftventricularoutflowtract,themitralvalvemaybecome
regurgitantbecauseofthetractionexertedbytheaccessoryvalvartissueonthe
anteriorleaflet,whichresultsintheopeningofthevalveinmidsystole14;
however,inthatcasetheleftventricularoutflowtractobstructionisthe
predominanthemodynamiclesionandisusuallyresponsibleforthediagnosis.15
Often,theaccessorymitralvalvetissuedoesnotgenerateasignificantgradient
orinsufficiency.
FIG.34.13 Macroscopicviewofaccessorymitralvalvetissueafter
surgicalresection.
SupravalvarMitralRing
Oftenconsideredacongenitalanomalyofthemitralvalve,thesupravalvar
mitralringisafibrousconstructionattachedtotheposteriorannulusofthe
mitralvalve;itrunsacrossbothcommissuresandtothemiddleheightofthe
anteriorleaflet.Thelesionisstenotic,oftentoagreaterextentthanmightbe
suggestedbytheextensionofthering.Thisismorearesultofthelimitationof
theopeningoftheanteriorleafletthanoftheactualdiaphragmeffectofthering
(Fig.34.14).Thesupravalvarmitralringisanacquiredlesionresultingfrom
turbulentflowacrossthemitralvalve.Theprimarylesionofthemitralvalve
responsiblefortheturbulentflowcanbeobvious,stenotic,andregurgitantorit
canbediscreteormildanddifficulttoidentify.Itmayevenbeonlyflowrelated
inthecontextofaleft-to-rightshunt.Itcanberelatedtoaprominentcoronary
sinus,asfoundinapersistentleftsuperiorvenacavadrainingintothecoronary
sinus.16,17Perhapsforthesereasonsthesupravalvarmitralringispronetorecur
aftersurgicalresectionunlesstheunderlyinganatomicanomalyhasbeen
identifiedandcorrected.
FIG.34.14 Anatomicappearanceofsupravalvarstenosingring(A,
arrows)andasurgicalviewofatypicalsupravalvarring(B).Bothpanels
demonstratethemembraneattachedtotheatrialsurfaceofthemural
leafletofthevalve,closetothemitralannulus,andtheextensiontoward
themid-heightoftheanterior(aortic)leaflet.
Strictlyattachedtothemitralvalveannulus,thesupravalvarmitralringmust
bedifferentiatedfromthecortriatriatum,whichisnotacquiredandcanbefound
intheantenatalandneonatalscans.Extremelyrarely,fibrousconstructioncanbe
foundinthevestibuleoftheleftatrium,producingtruesupravalvarrings.
AnomaliesoftheMitralValveinHypoplasticLeft
HeartSyndrome
Themitralvalveisalwayssetwithinaseverelyhypoplasticannulus.Most
valveshavetworecognizablepapillarymuscles.Theleaflettissueismostoften
severelythickenedanddysplastic;occasionallytheleaflettissuehasanormal
aspectandthevalveisaminiatureversionofthestandardone(Fig.34.15).On
thatspectrum,anisolatedrelativehypoplasiaofthemitralvalvewithout
hypoplasiaoftheleftventriclecanalsobeencountered.
FIG.34.15 (A)Absenceoftheleftatrioventricularconnections.(B)How
theleafletsofthemitralvalvecanbefusedtoformanimperforateshelf.
Bothlesionsareseenmostfrequentlyincombinationwithaorticatresia,
whentheyareanintegralpartofthehypoplasticleftventriclesyndrome
(seeChapter69).Intheheartshownin(B),however,theimperforatevalve
isfoundinthesettingofapatentaorticrootanddeficientventricular
septation.
AnomaliesoftheMitralValveWithNormal
Anatomy
IsolatedDilationoftheMitralValveAnnulusand
IsolatedElongationoftheCordsandPapillary
Muscle
Whentheanatomyofthemitralvalveisotherwisenormal,itisdifficultto
ascertainthecongenitaloriginofdilationofthemitralvalveannulusand
elongationofthesuspensionapparatus,buttheyareincludedinmoststudiesof
congenitalanomaliesofthemitralvalve18andaccountfor15%to40%ofthe
patientsinpublishedstudiesofcongenitalmitralvalveregurgitation.19–21
