JACC Vol . 19, No. 7June 1992 :1561-76

PEDIATRIC CARDIOLOGY

Mitral Atresia With a Large Left Ventricle and an Underdeveloped orAbsent Right Ventricular Sinus: Clinical Profile, Anatomic Data andSurgical ConsiderationsHIDETO SHINPO, MD, STELLA VAN PRAAGH, MD, IRA PARNESS, MD,

STEPHEN SANDERS, MD, MARIAN MOLTHAN, MD, FACC,

ALDO CASTANEDA, MD, PHD, FACC

Boston, Massachusetts

In mitral atresia with a large left ventricle, the tricuspid valve iseither straddling and biveutricular or entirely left ventricular . T olearn how to assess the identity of the tricuspid voice in such cases15 heart sv oimms were examined as well as the echocardiogramsof 10 living patients . When the right ventricular sinus wasunderdeveloped (11 cases), a straddling Iekuspid valve waspresent ; when it was absent (14 cases), the tricuspid valve wasentirely left ventricular.

Regardless of biventricular or exclusively kit ventricular at-ta hments, the tricuspid valve was tricommissnral (at postmortemexamloadon or on echocardiography) in 22 cases (88%). Itschordal attachments showed considerable variations but wereusually par'aseplal or on the ventricular septa) crest a conalseptum . When biventricular, the tricuspid valve straddledthrough an Intel ventricular septal defect. Clinical or anatomic

As a rule, atresia of the mitral or tricuspid valve is associatedwith extreme underdevelopment of the corresponding ven-tricle. Yet atresia of the mitral valve has been reported (1-7)to occur with a normal-sized or even a larger than normal leftventricle . In such cases, the single patent atrioventricular(AV) valve entering the morphologically left ventricle repre-sents the tricuspid valve.

What is the underlying morphogenelic process of thisapparent paradox? How can one differentiate a left ventric-ular tricuspid valve from a left ventricular mitral valve? Doesa left ventricular tricuspid valve function normally? If it doesnot function normally, what are the surgical implications and

therapeutic options in patients with this condition? Thisstudy, which includes the largest series of patients with thisrare cardiac malformation to date, attempted to answerthesequestions.

From the Departments of Cardiology, Cardiovascular Surgery and Pathol-ogy, C.iidrcos Hospital, Boston, Massuhusetls.

Menuw6l t remind July 29, 1991 ; revised maause,ipt received Novem-ber 14, 1991, accepted December 5, 1991.

Adtaovrfor rcpdu5 : Stalls Van Praagh, Mn, children's Hospital, 309

Lonawood Avenue, Boston, Massachusetts 02115.

01992 by the American College of Cardiology

1561

evidence, or both, of tricuspid regurgitation was present in 14cases (56%).

It is concluded that 1) the Identity of the atrioventricular valvesis reflected in their chordal attachments ante aenurately than intheir leaflet morphology and dey : s;s primarily an the type ofventricular loop present; 2) as a role, the tlitsrspid valve isright-sided in D-looped and tuft-sided to Ldonped ventricles ;3) valve identity expressed as the number and position of thepapillary muscle attachments is generally recognizable echocar-diographically and can be used to diagnose the type of ventricularloop that is present; and 4) the presence and degree of tricusaldregurgitation deserve attention when choosing oplimad initiativesurgery.

(J Am Col Cordial 1992;19:1561-76)

Methods

Study cases and petlents. Among the 3,052 heart speci.mens from the Cardiac Registry of the Children's Hospital inBoston, we identified 15 cases of mitral valve atresia asso-ciated with a well developed or enlarged left ventricle and anunderdeveloped or absent right ventricular sinus . In addi-tion, we compared the morphology of what we considered tobe the left ventricular or straddling tricuspid valve in thecases from this series with the morphology of the leftventricular mitral valve in 72 postmortem cases of tricuspidvalve atresia and with the morphology of the AV valves in 55autopsy cases with a double-inlet left ventricle .

We also searched our computerized echocardiography

data base for the diagnosis of AV or ndtral valve atresiaduring the years 1991 to 1990. We then reviewed the recordsof those patients whose left ventricle was reported as normalor enlarged in size . On the basis of the apparent ventricularlooping, as well as the morphology of the patent AV valve,we identified nine patients whose atretic valve was consid-ered to be the mitral valve . All nine patients had a large leftventricle and an underdeveloped or absent right ventricularsinus; all nine are alive . One additional patient (Case 25,Table I) was diagnosed angiocardiographically as having a

0735-1997192,55.01)

Table

1.Mi

tral

Atr

esia

Wit

h a

Larg

e Le

ft V

entr

icle

: An

atom

ic D

ata,

Sur

gica

l Pr

oced

ures

and

Cli

nica

l Co

urse

in

25Ca

ses

A73-78,

(5,0,5),RAE.

6.51eF

em i

ll R

V,LA

H. L

VE

Lmmg,

8 yr, F

(s,D,S),

RAE,

abse

nt R

Vas

, IA

E,LYE

Tric

uspi

d Va

lve

snad

dlin

gant

If,t

Mmeu

niss

urel

,attechtS On RVFW, VS

real

and

PMPM

Soad

mlng

ant

If,

oic

ommi

ssur

at,

atta

ches

an

RVLW

. VS

cre

stand PMPM

Stra

ddli

ng a

n II

, oi

cott

Mifs

aral

,edandanr, attaches on RVSep,

LVSe

pi.

ALPM

and

PMP

M,TR

Large argical

Entire)y into LV, triwmmlorord,

ASD

mi1d

7R

Serg

taol

A5D

(15 x IS)

Enur

elym

laLV

lrav

mmss

uml,

re4erdanl,noTR

Srtaddlirgantlf,bOannannssurd,

thick mdunamt Se, attaches oa

CS, VS erect and PMPM

Sbad

dlhg

ant

and

eep

ret

bs,

tric

anas

ssor

el,

shed

, on

RVFW, VS

eres

tand

PMP

Mof

LV

Stra

ddli

ng a

m st

d re

peal

bs,

Rimmmsraml rote datee

Ifs,a.a

d,on

APM

and

PPM

a IRV

, VS

cre

st a

nd P

k1PM

of

LV,TR

fontp

wvLS

ofmst;

vrodemte to severe

TR

A. Let -Sided Mint A.-

in

VSD

(nor

,)

AVC

type

and

CS mat,

ant

I(x2~

TV

AVCC,peobso

TV x 5)

AVC

type

obo

eby TV

(19

. 16

)

Smell BVF, mid

.)stake Isege

VSDCTV

attathaxnts

Out it

sloner

run

8 mo

to

17yr.cyenalr dmrczad sranona, an

dd~

.17 yr.

ree

unem

P PAA

,qu

itei

dier

A

22, LV 9S5Ao -

S3%.

ASR Lang

biop

sy =

nor

mal

pd--

y ve

ssel

s 23

yr:

pomp NVA preame

-10

. 26 yr.

attempted

~'oWlmmemy amslomosis.

Imp

osei

bkd

perfonR blouse ofnY

SO«b

onof

9PV

5d

W--.,k.-

28Rx

yr. letetmitreot aotal Sseer

Work

s as

a p

rvxt

r. MaKed, one cbad

.No

rati

on. Rapid deterioration dspgt

eiwogrsdve manes,.

Ded

3 d

ays

aner

cardiac ntheteNZataunt

.2011

: ASR,Wete0055ehusLtmprovedfore

Rw d

ays,

die

d 22

day

s po

etop

.

0

N

D Dy D

Sy D

B em

: AS

R an

d PA

R d

impr

tmme

oe o

f CH

F",yr.

modified Foneee proeemne

diachargod 13 days pmmp, remand m 7

days dy_pneie, acitlak, b large pleural

Rus)orsand died 0 the ER

.25

sen

t AS

R an

d PA

R. 5

yr . and syaorYs

.mbdydetrea

xdc,ceraaelok0Mry

SStayr

..OASUSSestedaodovetsewn,

LSVC

eaee

lama

ncdI

OLPA

.644,yrsubfo

mu5m

aere

eeoo

sisd

paas

uteg

eadl

ene7

R-a0.

krrtyr,sobAO sbaosis remeeon

W TV

ppGwy

.Osrtop

t5ae

edte

ddcy

Clubbing

..ah

persis

t.Straddling, eeimremioseeral

AVC

type

d a

ntBOA

band

5 w«

lest

bou

nce

acri

d se

ptos

t«tPAR'

ex omens

an.sn

ows

RAo2, [A= tl

y. .Ble

de a

but

-at rA,

LVH+E

ledge

erpe

oeom

yrtw

dmin

RA=6

,fA=

9atd

,.C

ksse

dogo

[(7I

P.7mo:

nthstmwsbfPA

band

gae

dies

t-70

. RA= 7, LA = 12,

PA-25

. ASR.

Poaop PA

-18

.^o

Living,

291S

tyr.M

(S,D,S),RAE,

absent RV

LVH+

E

Lvg

orpr

alASD

bA6a-268,

10days, M

7GA,

(S,D

,D),

RAE,

55100RV

.LV

H+E

ASDN(6

x3.5)

7A7

1-11

1,TC

2A,(

S,D,

D),

Surg

irnl

ASD

23da

y,m

RAE,

Sma

ll R

V.LA

H,LV

H(73 x 16)

8A8

1-50

,95

1, y

r, M

DORV, (&DiD),

RAE,

lar

ge,

iif

RV l

td,

LAH+

E

sr Wca1 AS

9Lsnng,

7'Vnyr,F

TGA,

(S,D

,D).

RAE,

amd

tRV,

LAE, LVH

Larg

e -p

ea!

ASD

10Lt

wng,

7 mo, M

TGA,

15,D

,D7,

RAE,

Sma

ll R

V,Saeeiod

ASD

Csse No

.PM

No

.,Ag

e,'G

endc

rCl

ards

eSeg

ment

san

d Ch

ambe

rsPF

O or

ASD

(rose)

IAS

S-16

3,2 days, M

C72-

107

2.5 mo, M

RAE

..a

ll R

V

(S,D,S),RAH+E,

all RV

.LAH, LVE

PFO

PFO,

sep

e 1°

bulges

,RA

Grear Aredea

0650

0Cardlte

Fhtd

ieg,

AgreeOp

era=

,Staideal Pmcedam and

Clmlml (rare,

Smell

PA,

bP5

Natm

d

Mild

ca

arcs

MPA

band

Small FDA, coemheoo

BC tmnk

Car

Iria

biat

unr,

ein

gda

LOrtst(um.

inttamural LCA

FDA, COS mifira

..la

a re

enge

ede

fbw.LSVC

-etna-

.RSV

C-.R

A

N omap

emtionn,Cy mareo

d se

vere

dys

pne,

teap

an

Medi

cal

trea

tme n

t.

Noopemtion

.Cyarmsisandseveredyspota,

SVTd

urln

gcan

dmcn

tbet

enra

tioe

,liv

edIn

an O

atent for 3 ma

2 mo

t PA

R, (

HF d

e-ad

. 6

yr. A

511

and

repe

GOfu

nesp

ecte

dmrt

rien

tatu

nr,a

nemp

,to repair a$ if it Were CAVC.

Died 7 b

poatop

.25 mot ASR and PAR

. CHF partly con5Olled

;PAD migmtivn, te1Wtog is RPA

5500

01a and

LPAh

ypct

eeer

dos.

6'.leoroImage, PD

.AOIdedwith etamvtSdnvimLPA0000

pee_ foB from 701.

33. M

ild

TR. 7

yr:

RSVC to RPA anastoetoeis (Gkrm).

Doi

ngweb 10

dqpoelop

.Sm

all

reot

riat

veBVF

Nuance

LSVC

to

CoS,

RPV5

Reor )with

AYCbyeab

soby

TV

(S o

5)

AVCtyptand

posstt

e for C

An isthmus

hypop

Puan

onae

yol

eeel

a

LSVC

to

Imge

GS,

osBC=

PDA

(9 x

7)

AVE type

SOW'S

SupemirMenar

(29 x 21)

acquired

v+at

rird

esrr

osts

oiti

dive

=IPA

Larg

e AV

C ty

peMPA band

LSVC to COS.

RAVE

"d-sad-

supe

roin

frei

ave

nldd

es

Table 1.

Con

thwe

d

C- 15

A%,

In

Living

.

MR T7,

II

AWLp

l3,

"IN

71111,

LVINE

17111~1~1

TGA.,

RA

RAE, uhsc^1

111

a 11

Gin-

ofil

l,ah

em I

IV'

LEE

RUE

:d1.s.

'nr

RV s

imw,

LAI

l,

SLIl

,,,.IA

Sf)

Ill

x Il

l

PFn

FGA,

I&L

.Ll.

PFD

RAL,

1111

1RV

.

TGA~

L.~ 1~

.

PEE

%al.aiV.

scail

LA.,E

.

Rvm

!ul

hlcl

ws o

nVS ass

"HIE

IRVLV,,,,...

otlC

T6..

.p,d V,l-

vsv(.

.)

G-1A,..k

,

Findings

A.

,,"

,V~i

1,

1-fla-.

LsL

1,1~W

I.IL

'S.

PDA

LAIR

dvIM

iwlA

lrct

ir

wall

mlA,

free

IsubPO)

count

MPA

LSVC

1,C

CoS

81'

bx hl

,,IAO1

A -1

in RA, small PDA

R"F,

poll

MPANO

1tv.2"

,t

11.%TAL111

P,M'M.

Tp,

mP,

d,&1

-S.

I-!ty I

C

BYE

F C

Pun,

PS-d

.bps

dALP,

.

'i,

,

ly-, L%'~."-'

' PM-

.".l.

],,1

S1A

Aruches nnL

'i,

-euEr

AL'.

17 x

3,andAM

Nor-

PS

.0 bPS

IL Ri1IIISidcd Mind Allan,

.

AVC

lypu

l,2S HI

AVC

11

D,

I

!_

v

sluddfng

.lri

cwnm

iaw:

,l

1111)11

VC

lypc

PV1. UDA

CImI

CUIC

uvrx

N.

7%ce

k.,:

1,11WA auiJl

mud:naysmwr,

n: 5

511

and

PAR;

rap

id d

o:eriurad,n

-A, AIR -d

fur

2n then CW

I'F

r ccvn

cd.

AI

ASR

.LA

1.5

24,PA=AS.Ny1,ASR,Urumulm

wmuMPA

N1, -ii-

Mild

cyAn-and d--6

I 27.

"1

lfar

dM.V

.

scvvc

MPA h-

S .lbA" '-=

ONE

r. n

nmoo

Roa

n

Fund -ed

rdll

et,.p Y.MW n-z

Died

%

PS"ev.!

,

FD~A

i I-

:L

BYlb-

. I y,

.-h:

L "-

P-

iubps.

PA =

11,

11"

_""'

V' 5T""'

nub

.

AY

MIA

1111A

'vandxnmina much

d-

Table1.

Continued

Age

at O

pera

tion

. Surgmi Pnxedurc:

mdCl

inic

al C

oars

e

Noopcntion.4

'Cyr.developedmvereCHF

wish peripheral edema-usciles and Sinai

amEythmias

.V'0:,

:cardiac ones) during

cash

, re

cove

red.

Died at home attar u

rspiratory infection

.Ncopemtion

. Treated tenCHF

. Developed VF

during each. Cardieroond

. Di

ed t

he n

ext

dayy

5'h. a

nal: PAR, heart failure and growth

improved

. Pos top oath at 4 yr showed

mums

) PA

pre

ssur

e an

d ar

teri

al 0

.saturation 8931

.4.9

y r: fl-Wed Fonlan c

rcevenlful recovery.

Pnmo

:surgalASD(BIalenk

.Hanlon)and

PAD,

hea

p fa

ilur

e im

prov

ed,

rema

ined

cyanotic

.31V

Cyr

. BT

shunt modified, &,

yr: e

ach: LVED = 6, PA = 12, nonrenrzi

VSD. aT chum occluded, MPA ecnnewn,

dire

ct a

nasm

mosi

n of

RA

with

RPA

,•

vcntfulrcw

very

.ISy

r:asymptomatie

.2 days and again at l mo

: coar

cIre

pair.

8 da

ys:

PAR

4 ma

: ASR_

345:

yry oath shows 60

grsd

ient

at

BVF.4Y

ryn

anaa

lomo

sis

oflmnseenedPM

I,MPA to asaading aorta

and

modi

fied

Fon

tan.

Diur

etic

dnt

gs s

addigondn for 2 yr

. At present dningwell

.11

1to 5 yr:

ryallmic,d

ecre

ased

sta

mina

. 5yr

:•

rrent brain abscess, R hcmiparesis

.s.

SM.yr

.L BT shunt.

16yr

:R BT

,hum

.33 ye markedly cyarmed.

Her

70%

,al

CHF

. Ca

thRA

= I1

, LA

= 1

1, L

V =

145/18PA = 12, ferevmted Fm- c

d-4. impnwementofeyannsrand

stam

ina.

'Age at death for the postmortem cases and present age for the living patients

. Al

l pr

essu

res

in m

m Hg

; al

l di

mens

ions

in

cm.

ALPM

= e

aler

olat

eral

pao

illa

ry m

uscl

e of

the

LV;

ant = anterior;

Ao = sonic;

AmV

=ao

nicvalve

; AP

M =a

nterior papillary muscle of the RV

; AS

D=at

ria)

sep

tal

defe

ct;ASD2a =secundum alrial sepml defect

; AS

R= a

tria) septal resection

; AV

C =

atri

oven

trie

ular

cana

l; RC= bmchececphalic, bil=bilateral

;BT

shu

nt =

Bla

lock

-Tau

ssig

shu

nt; BVF = hullxwentneala

r fo

rame

n; c

= with

; ca

sh =

car

diac

cat

hete

nzar

ion;

CAVC = common aeciovemricular canal

; CHF = congestive head failure;

coa

rct

= co

arcl

aden

of

aort

a;ca

r =

coro

nary

; Co

S = co onary sinus

; CS

=an

al s

eptu

m; DCRV = double-chamber right ventricle

; DO

inf

= d

oubl

e-ou

tlet

inf

undi

bulu

m; D

ORV)S,D,D)

= doubleoulkt right ventricle with solims aria, D-ventricular

loop and Dmalposed a

orta

; E = enlargement; ER = emergency room

; F

= fe

male

; Ho

t =

hema

tocr

il;

hypo

pl =

hyp

opla

stic

or

hypo

plae

ia;

IAA=

int

erru

pted

Ion

ic a

rch;

Iof

= i

ofun

dibu

lum;

Ins = innmninate vein; L=

Iof; LA = laR atrium;

LAE = left aerial enlargement

; LAH = left aerial hypertmphy

; LC

A =

left

cor

onar

y ar

tery

, If

= l

eafk

gs);

LPA

= l

eft

pulm

onar

y ar

tery

; LS

VC =

lef

t su

peri

or v

ersa

cave

;LV

= le

ft v

entr

icle

;LV

E =

left

vem

rcul

ar e

nlar

geme

nt;

LVED

= l

eft

vent

ricu

lar end-diastolic pressure

; LVH = left vemrcular hypenmphy

; LV

sept

= f

elt

vent

cula

r so

ared

sur

face; M = male

; an

d =

mala

ligm

nent

; MPA = main pulmonary

arte

ry;

obst

r= o

bstr

ucted;

0,

= ox

ygen

; Osat = oxygen saturation

; PA = pulmonary artery; PAR = pulmonary artery band;

PAT

= paroxysmal aerial tachyeardir;

PDA

= pa

ten)

duc

tus

arte

rios

us;

PFO

= pa

tent

for

amen

male

;plasry =valvu

loph

sty;

PM =

pos

tmor

tem;

pro = papillary muscle(

.); PMPM = poslernmedial papillary muscle of the LV

; po

stop

= p

osto

pera

tive

ly,

PPM

= po

ster

ior

papi

llar

y mu

acle

(s)

of t

he R

V; PS = pulmonary

valv

e sm

nosi

c; R

= r

ight

; RA = right atrium;

RNA = right a

trial appendage

; RA

E =

righ

t uo

ial

enla

rgem

ent;

RAH

= ri

ght

aeri

al h

yper

trop

hy;

RPA

= ri

ght

pulm

onar

y ar

tery

; RP

Vs =

rig

ht p

ulmo

nary

vet

m. RSVC = right

supe

rior

aa;

RV = right ventricle;RV

FW= right venrcular free wall;

RVsepr = light venelicalar settled surface;

SBE = sub

acut

e ba

neri

al e

ndoc

ardi

fis;

{S,D,S}

= so

litu

s at

ria.

D-loop ventricles, solbus normally

'l'i

edgreatarteries; s

ept

I' =

sep

tum

prim

m;{

S,L,

E)=

solk

as a

tria

, L-

loop

ven

tric

les,

Dlr

ansp

osed

or

malp

osed

aor

ta; {S, L, L} = solitus atria, L-loop ventricles, L-Bansposed coma

: subAo = subsonic;

subP

S =

subp

ulmo

nary

ste

nosi

s; S

VT =

sup

mven

tric

ular

tac

hyca

rdia

; TGA = transposition of the great arteries;

TR

= tr

icus

pid

regu

rgit

ation; TV = tricuspid valve

; VF

= v

entr

icul

ar f

ibri

llat

ion;

VS

= ve

ntri

cula

r se

ptum

; VS

D =

ventricular septet def

ect:

und

erde

v =

unde

rdev

elop

ed; unicorn = unkommissuml

;-r = imo.

Cuss No

.PM M,

Age

.'

Gender

Carom Sagmcnls

and Chenbo

PFOo

r,(S

DIm

mlTr

icus

pid

Valv

eVS

D1mm

)GrimArtcrus

Othe

r Ca

rdia

cFi

ndin

gs

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flatl Vol . 19, No. 7

loot 1992 :ISb1-76

single L-looped left ventricle to the rghi and posterior of aleft-sided double-outlet infundibulum . atresia of the right-sided mitral valve and dextrocardia Echocardiographicstudy of this patient was considered unsatisfactory becauseof very poor imaging windows . He was the oldest patient inthis series and the only one with dextrocardia .

The ventriculoatrial malalignment in 12 of the 15 postmor-tem cases was the subject of a brief presentation in theSecond World Congress of Pediatric Cardiology (8). One ofthese postmortem cases was also reported (9) as an exampleof subaortic stenosis recognized after banding of the mainpulmonary artery .

There were 16 male and nine female patients (ratio 1 .11 :1) .Because the right-or left-sided position of the Kinetic mitralvalve has different hemodynamic consequences, we sepa-rately calculated the range and median age at death in eachof the two groups . In the I 1 postmortem cases with left-sidedmitral atresia (D-loop ventricle) . the median age at death was2 months (range 2 days to 12 111/r years) . In the four postmor-tem cases with right-sided mitral valve atresia (L-loop ven-tricle), the median age at death was 41/Is years (range 21 daysto 27 years),

Anatomic evaluation, The atrial sifts in the postmortemcases was diagnosed on the basis of the systemic andpulmonary venous connections, the relation of the septumprimum to the septum secundum (when the septum primumwas not surgically resectedl and the size and shape of theatria] appendages. In the IO living patients, atrial situs wasdiagnosed on the basis of the echocardiographic or angiocar-diographie appearance, or both, of the systemic and pulmo-nary venous connections . and was confirmed in all bysurgical observations .

The type of rentricrdar loop present was diagnosed in allcases according to the position of the left ventricle in relationto the ventricular septum . It was concluded that a D-loopwas present when the left ventricle was to the left andposterior to the characteristic left ventricular septal surface.An L-loop was considered present when the left ventriclewas to the right and posterior to the left ventricular septalsurface. Because this surface can be recognized echocardio-graphically (10), the same criteria were used for 9 of the 10living patients . In one living patient (Case 25, Table I I withan unsatisfactory echocardiogram, the diagnosis of the ven-tricular loop was based on the findings on his angiocardio-gram .

The patent AV calve (t/tat is, the tricuspid ralre) wasevaluated for leaflet morphology (normal, redundant orthickened with rolled edges indicative of regurgitation) .papillary muscle attachments (entirely into the left ventricle,on the crest of the ventricular septum, straddling the ven-tricular septum or attaching on both ventricles) and thenumber of its commissures (postmortem cases) or points ofchordal attachments (living patients) .

The position of the ventricular septam (inlet portion) inrelation to the crux of the heart was determined in the 15postmortem cases by inserting a long needle at the site where

SHINTO ET AI. .

1555MI r KAt. A IAESIA WITH A LARGE LITT VENTRICLE

the atrial septum met the AV groove and by observing thedistance between the needle and the posterior end of theventricular septum . The direction of the needle was perpen-dicular to the posteroinferior (diaphragmatic) surface of theheart.

The reruriealar .septal defect was assessed in all casesaccording to its position in the left ventricular septal surface,its size and the presence or absence of straddling of thetricuspid valve . A large ventricular septat defect in the inletportion of the left ventricular septet surface associated witha straddling tricuspid valve was described as a ventricularseptal defect of the AV canal type (3,9-11) . This defectresembled the ventricular septal deficiency seen in heartswith a common AV canal, in that it extended over the entirewidth of the ventricular septum and the left ventricularsepta[ surface had a shorter inlet than outlet dimension111 .12). It differed from the AV septal defect in cases with acommon AV canal in that it was not associated with acommon AV valve or an ostium primum septal defect, orboth (Fig . ID and 2B) . In addition, probably because of theunderdevelopment or absence of the right ventricular sinus,the posterior border of the ventricular septum did not meetthe crux or the heart as it does in cases of a common AVcanal .

A rentricolar septat defect in the area of The owlet

ventricular septmu, usually small and never associated witha straddling tricuspid valve, has been described as a butbo-ventricular or infundibuloventricular foramen (that is . a defectallowing communication between the infundibulum [the em-bryonic bulbus cordisl and the left ventricle) (Fig, 3, B to D and4, B and CI . When this defect was confluent with or close to theaortic valve, it was also described as subaortic.

Enlargenrene and hypertrophy of the cardiac chambers inthe postmortem cases were evaluated by comparison withthe normal heart of persons of the same age. In the livingpatients, atrial and ventricular enlargement was assessed onthe basis of electrocardiographic (ECG), echocardiographicand angiocardiographic data .

Tile ight ventricular sinus was considered absent whenthe tricuspid valve was entirely left ventricular (Fig- 3B and4B) .

Clinical evaluation. Hospital records were available forreview in all patients . Chest X-ray films or reports and atleast one ECG were available in all but one patient (Case 1,Table 1) . Echocardiograms with Doppler studies were avail-able for review in 9 of the 10 living patients .

Cardiac catheterization data were obtained in 12 post-mortem cases and in all living patients .

ResultsAnatomic findings (Table 1, Fig. I to 5) . The 25 cases

included in Table I are arranged according to 1) the type ofventricular loop (cases with a 0.1oop with left-sided mitralatresia precede those with an L-loop) : 21 the type of ventric-uloarterial relation (cases with normally related great arter-

1 566

SHINI't) CT AL .WE RAI . AIRRSIA WITH A LARGE LEFT VENTRICLE:

Figure 1. Case 7. The heart of a 23-day old boy with solitus atria .D-loop ventricles, D-transposed aorta . mitral atresia. a straddlingtricuspid valve (TV) and pulmonary atresia. A . The opened rightatrium (RAI is very large . AS = surgical atrial septa] defect . III, Thetricuspid valve straddles the ventricular septum and attaches on thefree wall and the septa) surface of the small . underdeveloped rightventricular sinus (RV ). The opening of the Waterston anastomosis isseen in the wall of the ascending aorta lAo) . CS = canal septum :SB = septa) band . C, A small left atrium with worked hypcrtmphvof its wall and the wall of the pulmonary veins IPVsI has thesurgically created atria) septa) defect (ASD) as its only exit . Theleft atrial appendage (LAA) and atreli,: mitral orifice (M All areseen . D, Opened left ventricle (LV).'the tricuspid valve straddlesthe ventricular septum (VS) and attaches only to the posteromedialpapillary muscle . The anterolateral papillary muscle is representedby the trabeculations seen in (he free wall (RV) of the left ventricle .The main pulmonary artery IMPA) is small but patent down to thelevel of the atretic pulmonary valve (P An. This wax the only casein this series with congenital pulmonary valve atresia .

ies precede cases with transposition or t double-outlet rightventricle) ; and 3) the presence or absence of straddling of thetricuspid valve (cases with a straddling tricuspid valve

JACC Vet . In . No .7Juae 1992..061-ru

precede those in which the tricuspid valve is entirely in theleft ventricle) .

Left-sided mitral atresia and normally related great arter-ies were present in Cases I to 5 . Left-sided mitral atresia anda double-outlet right ventricle or transposition of the greatarteries were present in Cases 6 to 16 . Finally, right-sidedmitral valve atresia and transposition of the great arteries ora double-outlet infundihulum were present in Cases 17 to 24 .In all of these subgroups. the postmortem cases precede theliving patients .

The left veatrlrle it-as either of normal size or enlarged(Teth(r 1) . Left ventricular hypertrophy was present in 15patients (60%) (Fig. ID. 2B . 3C and 4C).

The right rrabirulor sieos was absent in 14 cases (56%))Fig. 3B and 411) and underdeveloped in 11 (44%) (Fig. IBand 2C).

The posterior limit ofthe inlet ventricular sepumn did notmeet the crux of the heart in any of the 15 postmortem cases .It was located to the right of the crux in all the patients witha D-loop ventricle and to the left of the crux in all thepatients with an L-loop ventricle .

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Figure 2. Case 17. The heart of 27-roar old man with olimatria, L-loop venhricles and an L-lrmspoceJ aorta . A, Openedright atrium IRA). The right-sided mitral calve onfice is urencINI At IRIt. PFO = patent foramen ovals . e, Opened right-sidedleft ventricle (LV IRI). There is hvpern ophv of the left ventricularfree wall IFWI . The ventricular septum IVSI display's the charac-tefisiic smooth surface and a large atriovenuicnlar canal typeventricular sepud defect . The Tricuspid salve l IV) . which allots,communication between the left atrium and left ventrice,

is tortabnormal . II attaches on a very wide multiheaded posteriorpapillary muscle and on the posterior pare of the Iowa rim of thelarge ventricular .:eplal defect . The edges of the tricuspid value arcIhick and rolled . indicative of significant tricuspid regurgitation .The pulmonary valve (PV) is in direct fihrous continuity with thetricuspid valve . C. The extremely underdevelupal right ventricu-lar sinus (RV) and infundihulum Iloll are lefl-sided and showmarked hvpcnrophv . The left-Wed tricuspid stdro straddles theposterior part of the lunge ventricular septal defect and apaches tothe right ventricular serial surface. The aorta IAol originates fromthe infundibulum .

The single parent AV' i ahr ams rrironurtissurel by post-mortem or echocardiographic assessment in 11 patients(RR%) (Table I, Fig . 2B : 3 . C and D: 5. A and C . and 6) . Itsleaflet and papillary muscle attachments were not like thoseof the mitral valve in cases at' tricuspid atresia (Fig. 71 . norwere they like those of the normal right ventricular tricuspidvalve . The leaflets tended to be redundant . with papillarymuscle attachments varying from case to case . When thevalve straddled the ventricular septum, it straddled througha ventricular septal defect of the AV canal type and insertedinto the underdeveloped right ventricular sinus, the crest ofthe ventricular septum and the posteromedial papillary mus-cle of the left ventricle (Fig . I . B and D: 2. B and C : 5 . A andC . and RA). The papillary muscle attachments resembledthose of a straddling tricuspid valve with a patent (normal orstenotic) mitral valve (Fig . RBI.

Clinical profile. Cyanosis was universally present . Itsonset or severity was not affected be the left- or right-sidedposition of the alretic mitral valve .

Near) (iuilure, often with particularly severe dyspnea dueto pulmonary venous congestion. was observed in all pa-tients who did not have significant pulmonary stenosis or an

all ial septal defect. or birth. The severity and onset of heartfailure were also unrelated to the left- or right-sided positionof the at, tic mitral valve .

Chest V-ran films were available in all but one patient(Case I . Table II . All chest X-ray films showed mild tomm"ked cardiac enlargement . The vascularity of the lungfields was increased in 19 (79%I of the 24 patients withavailable chest X-ray studies .

Flit rrw'urdiograms were available in all but one patient(Case I Table I L All 24 patients with an available ECG hadnormal sinus rhythm when first seen at The Children'sHospital . Four patients (two in the group of living patients)developed atria) arrhythmias .

All 24 patients had very prominent P waves indicative ofright atrial enlargement in the standard and precordial leads .A superior frontal QRS axis and a counterclockwise vectorloop in the frontal plane were present in five of the sevenpatients with a D-loop ventricle . a straddling tricuspid valveand a ventricular septal defect of the A V canal type (Cases 2,3.6 to R . Table 1), Similar FCG findings have been reportedt11) in patients with a straddling tricuspid valve . mitralstenosis and D-loop ventricles .

1588

SHINTO FT AL.MITRAL ATRFSIA WITH A LAR(iL: LFFI' VENTRICLE.

Figure 3. Case 13. The heart of a N2-year old boy with arial sitarsolitus . D.loop ventricles, Ieh-sided mural 1 .trvsia (M At) andD-transposition of the great arteries . A, Opened left atrium . Thewall of the pulmonary veins (PVc) is markedly hypertrophied .A surgically created attial .sepia] defect (ASD) is present . Coronarysinus (Co SI orifice atresia has resuftl in a dilated coronarysinus . LAA = left atria) appendage . B, Opened infundihularchamber (Inil, The transposed aorta lAo) and bulboventricularforamen (BVF) are seen . C. Opened left ventricle (LV) . Thetricuspid valve (TV) is entirely left ventricular with three chordalattachments and three leaflets . Two of its attachments are to theanterefaterai and posteromedial papillary muscles of the leftventricular free wall and the third one is into the conal septum .A very small membranous pouch is identified close to the leftventricular free wall and under the atretic mitral orifice . Itrepresents the abortive mitral valve IMVI. PV = pulmonary valve .D, Magnification of the tricuspid valve and its attachments . a s wellas the membranous pouch representing the mitmi valve . CS = copalseptm.

IACC VII . 19. Nu. 7June 19921551_7 5

In the cases with the tricuspid valve opening entirely inthe left ventricle and an outflow ventricular septal defect andin all the patients with L-loop ventricles and right-sidedmitral atresia, the frontal QRS axis ranged from 45' to 120'and the vector loop in the frontal plane was clockwise . In themajority of patients, the precordial leads exhibited an rS orRS pattern.

EC/tocesrdiogrants with Doppler interrogation were avail-able in 9 of the l o livine patients (Cases 4, 5, 9,10.16, 19 and22 to 24, Table I). The echocardiogram of Patient 25 wasconsidered unsatisfactory because of poor imaging windows.

The echocardiographic studies accurately demonstratedthe atrial sites, the ventricular loop, the site of the Arcticmitral valve, the morphology of the patent AV valve, thesize and position of the ventricular septal defect or defects,the presence of pulmonary valve or subpulmonary stenosis

tALC VA . 19 . 1, 1June 1997.1%1-'5

Figure 4. Case 14. The heart of a 127c-r, old buy with solitulatria. D-loop ventricles . left-sided mitral atresia IM At) . D-Imnspo-silion of the great arteries and subpulmonary stenosis . .A. Openedleft atrium (LA), displaying a surgically created atrial sepal defect(ASDI and the attachments of the septum primum to the left arildsepta) surface. B, The interior of the infundibular outflow chamber(InfOC). The aorta (Act and bulboventriculer foramen (BVF) areseen . C, Opened left ventricle ILVI . The tricuspid valve (TV) isentirely left ventricular, with chordal attachments to the posterome-dial papillary muscles and an abnormally small and posteriorlylocated anterolateral papillary muscle . The thickened rolled edges ofthe anterior commissure reflect tricuspid regurgitation, which clini-cally was severe. Posterior conal seplal malalignment :md a promi-nent free wall IFWI trabeculation produce subpulmonary stenosis(PS( . Ao V = aortic valve ; VS = ventricular septum.

and the type of ventriculoarlerial relations . In three of theechocardiographically studied patients, a straddling tricus-pid valve was observed (Cases 9. 10 and 19). Dopplerinterrogation revealed moderate tricuspid regurgitation inCases 9 and 19. The youngest of our living patients (Case 10)had a competent straddling tricuspid valve . In the remainingsix living patients, the tricuspid valve was large- entirely leftventricular and had redundant leaflets . Careful review usingslow motion and stop fratne analysis revealed three points ofattachment (Fig. 6) . In four of the six (Cases 4, 16, 22 and24), Doppler interrogation showed mild tricuspid regurgita-tion . All four patients were >3 years of age when tricuspidregurgitation was first observed .

Cardiac catheterization . This was performed in 24 of the25 patients (Cases 2 to 25, Table 11 . On the basis of thecatheterization data alone, the correct diagnosis of mitralvalve atresia was accomplished in 12 of the 16 patients witha left-sided atretic mitral valve . Patient 3, who underwentcardiac catheterization in 1973 . was erroneously diagnosedas having a common AV canal instead of mitral valve atresiawith a straddling tricuspid valve .

Pulmonary artery hypertension due to pulatottaev venous

SHINPO ET At. .

1569SIIIR.-V . ArarAlA WITH A LARGE LEFT VENTRICLE

hypertension was found in three patients with left-sidedmitral atresia despite the coexistence of subpulmonary orpulmonary valve stenosis (Cases 5, 14 and 16). In two ofthese patients (Cases 5 and 16). pulmonary artery pressurewas found to be normal during cardiac catheterization I yearafter atrial septectomy . Patient 14 did not undergo cardiaccatheterization after operation .

The patients with right-sided AV ralvc atresia who hadrecently undergone cardiac catheterization (Cases 18, 19 and22 to 25) were correctly diagnosed as having mitral atresiawith a large left ventricle on the basis of the echocardio-graphic appearance of the patent AV valve and type of theventricular loop present .

Regurgitation of the tricuspid vah ,e was detected angio-cardiographically in sc -veu patients (Cases 3, 4, 8, 9, 14, 16and 24), three with a straddling tricuspid valve . The young-est patient with angiocardiographic evidence of tricuspidregurgitation was 3%Iryears old .

Atresia of the coranarv sinus orifice and retrograde flowof blood into the left superior vena cava, innominate vein,right superior vena cava and right atrium were well demon-strated by angiocardiography in Case 4 (Fig . 9) .

1570

..HINW11T AL .\71TRA1 . AtahS1A WITH A Aver III'' VINTRR 1 1:

Balloon atrial .septostonnv attempted in two patients(Cases 4 and 11) was unsuccessful . Blade atria] septotomyfollowed by KO',) m dilation in four other patients (Cases 5 .

10, 16 aid 741 ::riled to eliminate the pressure gradientbetween the left and right atria . All four patients subse-quently underwent surgical atrial septectomy . In the post-mortem cases, examination of the septum primum indicateda markedly increased thickness so that it could not be tornby the balloon . Blade septotomy may succeed in incising theseptum primum, but the markedly increased septa ; thicknesslimits its mobility and consequently the effectiveness of theseptotomy . In addition, the cavity of the left atrium in thevery young patients is often small and the risk of incising theatrial free wall is very real .

DiscussionDevelopmental and Morphologic' Considerations

It is generally accepted that after ventricular looping, theundivided AV canal is entirely located above the primitiveventricle, which is the precursor of the morphologically leftventricle (13-16( .

isec Vol. 19 . Nn. 7June 199'- .1551- 76

Figure 5. Case 2. The heart and lungs of a 2'h-month old boy withsolitus atria. D-loop ventricles and normally related great arteries,left-sided mitral atresia and a straddling tricuspid valve . A, Theright an'ium (RA) communicates with the large left ventricle (LV)and the small right ventricular sinus (RV) by way of the straddlingtricuspid valve 0'V) . The ventricular septum (VS) is transected atthe level of the ventricular sepml defect, so that the right ventric-ular attachments of the tricuspid valve can he seen . B, The leftatrium has a dimple on its floor, representing atresia of the mitralorifice IM Al( . The wall thickness of the left atrium is markedlyincreased. The left atrial appendage (LA) is distended and pointsposteriorly. The atrial septum is intact. LL and RL = left and rightlungs . respectively . C, The outlet of the left ventricle (LV) towardthe aena is widely patent and there is direct fibrous continuitybetween the straddling tricuspid valve (TV) and the aortic valve(AoV). VS = the crest of the ventricular septum .

In embryos with a crown-rump length of 6 mm . "theatriuventricular canal still gives access only to the primitiveleft ventricle and is separated from the cones cordis by thebulbo- (cono-) ventricular fold . With further development,the central portion of This fold recedes and blood can nowenter the primitive right ventricle directly from the atrium"(14) . Another factor that has been considered to contributeto the approximation of the right atrium with the growingright ventricle is the expansion and rightward movement ofthe AV canal (13) .

Underdeveloped or absent right ventricular sinus . In ad-dition, we and other investigators (7) think that the growth ofthe right ventricular sinus plays an important role in the finalnormal alignment of the atria with the appropriate ventricles .This view is supported by the anatomic finding of AVmalalignment in several cardiac malformations in which theright ventricular sinus is underdeveloped or absent . Becausemovement of the AV canal is limited by the relative immo-bility of the atria, which are "anchored" by the systemic and

pulmonary veins. the approximation of the tricuspid orificeand right ventricle is probably influenced more by the growthof the right ventricular sinus and the resulting leftward shift

1AC(' Vat. iv . No. 7Jlmc 10)2 :I]M1I-7v

Figure 6. Case 4 . Echocardiogram from an 8-year old girl withsolims atria . D-loop ventricles. normally related great arteries andleft-sided mitral atresia . Subxiphoid short-axi, views in diastole (A)and systole 1B) show the tricuspid valve (TV) in the left ventricle(L V) . Note the three ccmmisemes of the tricuspid valve (arrow-heads) . The large inlet ventricular septa) detect (VSD) is seen indiastole . p = posterior: s = superior.

of the ventricular se plum than by the rightward movement ofthe AV canal. Thus, it is not surprising that in all themalformations that share the characteristic of nigh: ventric-ular sinus underdevelopment (double-inlet left ventricle,straddling tricuspid valve with normal or stenotic mitralvalve, tricuspid atresia with normally related or transposedgreat arteries and mitral atresia with a large left ventricle),the inlet ventricular septum does not meet the crux of theheart. On the basis of the anatomic findings of these cardiacmalformations, it appears that if the right ventricular sinusdoes not develop after ventricular looping, both AV valveorifices maintain their early embryonic position above theprimitive ventricle and double-inlet left ventricle results. Ifthe right ventricular sinus is partly developed and the inlet

tiN19PU1;r-

1 57 151110 V . i7iIISIAwrrll :\ 1, AKGr rrFI VP.NIt,III I

ventricular septum is deficient . the tricuspid orifice is placed.ho" both ventricles and the tricuspid valve exhibits biven-tricular papillary muscle attachments .

Role of straddling of the tricuspid valve . Depending on thedegree of the straddling of the tricuspid notice, the mitralvalve orifice may be displaced close to or exactly above theleft ventricular free wall . resulting in mitral stenosis oratresia. In other words, a straddling or left ventriculartricuspid valve often interferes with the normal developmentof the mitral valve . which may become stenotic (II) oratretic (3) . In the cases in this series . underdevelopment ofthe right ventricular sinus was associated with marked AVmalalignment and alignment of the tricuspid orifice entirelyor pertly with the left ventricle . The dimple of the atreticmitral valve orifice in all our postmortem cases was abovethe left ventricular free wall (Fig . 10), Because the tricuspidorifice remained partly or completely above the left v entri-cle . i t allowed blood flow to stimulate normal growth . Thisresulted in the apparent paradox of mitral atresia with anormal-sized or large left ventricle .

Atrioventrieular valve identity . One might have expectedthe left ventricular tricuspid valve to have the morphologicfeatures of the mural valve (Fig . 7). but this did not occur inthe patients in this series or in previously reported cases11-4 .( .7) . The left ventricular tricuspid valve remained sep-tophilic and usually attached to papillary muscles close tothe ventricular septum or to the lower rim of the ventricularseptal defect or to the tonal septum- or both (Fig . I- B andD: 2 . B and C: 3, C and D : 5 . A and C . and 8A).

When this single AV valve straddles the ventricularseptum, it is always through a ventricular septa) defect of theAV canal type as has been observed with the straddlingtricuspid valve (17) (Fig. ID : 2 . B and C, and 8A) . Incontrast. the mitral valve is known to straddle through anoutflow ventricular septa) defect due to conal septa) mal-alignment (17). Hence . although the leaflet morphology of

the partly or entirely left ventricular tricuspid valve hassome similarities with the leaflet morphology of the mitralvaive (probably for hemodynamic reasons) . its mode ofstraddling and papillary muscle attachments are not likethose of the mitral valve (Fig. 7) .

These anatomic facts led us to conclude that the truenature of the AV valves is expressed in their papillarymuscle attachments and proximity to the ventricular septum,rather than their leaflet morphology . Our data also indicatethat, as a rule . the right- or left-sided position of the tricuspidvalve depends on the type of the ventricular loop that ispresent (that is, the tricuspid valve is right-sided in D-loopsand left-sided in L-loops), In addition, the cases in this andother reports (1-4.6,7,9) support the conclusion that theidentity of an AV valve does not always depend on theidentity of the ventricle that receives it ; otherwise, onewould have to postulate that in the hearts with a double-inlet

ventricle . the two AV valves are both mitral and that astraddling tricuspid valve has tricuspid and mitral compo-nents .

1'72 0I11N1O 11 AL .M1fo41M

vrm-SIA o,I1'H 41 .00111 : Lfl'1 'I . .vtlfl I I

'igure 7- A, Gee 57'-1)6 . 1 he leant of a1 4 1 yc-veal ofd her k lhohms mina, D-loop vwirisicp. Ddmndpasnd 111cul 'artrca andfight-sided rrinrspid atre+i, . Opened Ielt-sided Ief1 se01111Ie 11-VIhoses marked hvpcrtrophv .1 its trio well (l-W 1 and the popi€lira'nuccles of the normal milrul valve [MV] The in flmdlhulosen!liciiu' foramen [IVFI Ks Iron surgically enlnreed . PV = pulma iv 1-0cave'. VS = ventricular ,puma If . Case A51-'-U . tie heir: u4-henrold hoe with .lita, carol . L-1-1p cemticles- I : nimspua•,1red arteries and a lull-tilled ;102114 Iricaspid oriEci lt= lifhlLou in communicates N'ith the ilghhsided leis venlrdu IL VIhh AIo111141 nphl-sided mural o' ilve I hVlOil erhlhilr the usual normalnachmems an the too papillay muscle snaps of the lice .all ofhe left venlncle . The inl'uuiihnlourmriculur foramen is 11011 ldc-c and can ba seen to the tell tdthc pnnnepull Pal illurv I11selc,

-he left ventricle is en1mgcd'and hypertntphied, Soft I - 11,114imum .

In Case 1} in this series (Fig . q . the thint In-n-, rot orhe left ventricular tricuspid valve mimics a clef" of thenlcrior leaflet of a mi1ral valve . Careful obxrvalicn irJi-ales that Ibis cleft hair cllurdul altachoiculs to the runalopium instead of the most inferior par[ of the told vznitic-dar sepmm . In addition . there is a, very small membr nauscouch below' the atrelic left all ii outlet and adjacert to aleell vemricu!nr free wall that must represent in this D •I nnped

la('[' 1'rl . Iv. Hu .',acme 114+ .151,1=1•

hear) rite "shadow ' of the mitral'active that tamed Ut develop(Fig. 1DI, Its prcuence stteurtthens (lie conelnvilrn that therelent AV vdve is the tricuspid valve .

kiguruNA .Cece8 .Thenpunod cftveniricleofa94c-yaanddtmv,iii- ;ulnas clha- lehaidod initial uacsia . D-loop venlricler :md'adrools-eudcl right vrnn'iele with a D-m :dposed auna. The snarlIII Iri :wpic'amts IINI Htmehcs 111 the miller rim of the largeven'deticr sep'l,al tenet 1V .5DI of the ausuvemricular IAVI canaltype and o the pesrsomedial papillary muscle of the loft ucniricleILVI. Sole the thickened cdgesoftlu Iricuspid salve indiculivr ofr[urgifaliun . fW = fee oval : VS = ccn .ricular septum . It. ThecpeaeJ efveiIClu'Ifa25.manIholdcirlwitinAultipleconpeniIalenunalini viscn',J heteretazyi tuAv,rlenia . ;.liras atria, D-loopvin :ticles sand nurmafly 'dated great urtcrio.. The aneurysmalvmdTing '.ricuspid rata's is attached In the crest of the large AV

""RIloin ventrieuhc'septal detect and the posteromedial papillary

mamlc of the loll ventricle . The milrnl valve is hypoplarlfc andShTrlic 1 Vi 51 anti its lc;ittrlo are fined with tell scrilrirolar fit' walltnofceahtlinn, lair the al11eIim papillary musclel . None II€ : mi ni ladlylil'11t vcnlriatlar septul detect and Ills nnpillon• allachmtems of thealr•¢idlike teieusp€d solve to the case shown in A . In both cases . thetrines pillvalve Leached to the free wail and ventricular septum I VSIufa slighllr underdeveloped right ventricular ,mw tnot shown l. Wesp_aahtle'.hat a similar mnrphopcnclic process differing only indcurvc twilled in mitl :d .11-11 11a the cave in Amid IN1ml daemonin tie case In It .

JACC Vet, 19. No . 7lone 1952:ISrd-7a

Figure 9. Case 4. Selective innominate vein angiocardiogram (an-teroposterior view) from a patient with atresia of the coronary sinusICoSI orifice and a persistent small superior vera cava . Contrastmaterial fills the innominate vein . left superior vena cava ILSVC) .part of the coronary sinus and two large cardiac veins (CVI . Theextension of the coronary sinus toward the right atrium and itsestium were never visualized . Blood flows in a retrograde directionfrom the coronary sinus to the left superior vena cava . innominatevein. right superior vena cava and finally into the right atrium . Aclamshell device used to obliterate a large patent due uuureriosus isseen under the junction of the left superior vent, cava and in-mi .note vein .

Papillary muscle attachments. We compared the papillarymuscle attachments and the type of ventricular septa) defectin cases of straddling tricuspid valve with mitral stenosiswith findings in the cases in this series with straddlingtricuspid valve and mitral atresia (Fig . 8) . The observedsimilarity favors the conclusion that both malformationsresult from a similar morphogenetic process . varying only inthe degree of AV malalignment and the degree of theresulting approximation of the mitral valve orifice with thefree wall of the tell ventricle . The straddling tricuspid valvewith mitral alresia or stenosis presents certain similarities inits papillary muscle attachments with a common AV valve .Yet the absence of a foramen primum type atrial septa)defect and especially the presence of an atretic or stenoticorifice at the expected position of the mitral valve stronglyindicate that the AV valves are not in common .

To further substantiate the septophilir and .septophobircharacteristics of the tricuspid and mitral valves . respec-tively, we examined 55 heart specimens with a double-inletleft ventricle and 72 heart specimens with tricuspid orificeatresia from the Cardiac Registry of the Children's Hospitalin Boston. We found that in all 72 specimens with tricuspidatresia (with normally related or transposed great arteries) .

SHR7PU FT AI ..

1 57 3ivross ITRFSI :xWITH5 nefFLFFTvENTRICLF

the mitral valve attached on papillary muscles originatingfrom the free wall of the left ventricle (Fig . 7). We also foundthan the right- or left-sided position of the sepiophilic AVvalve (that i,, the tricuspid valve) in the 55 cases of double-inlet left ventricle accurately predicted the type of venivev-lar loop present .

1-lern e . the nuaehnrenrs of the AV rah'e ar rnlres and thetvpe of the remriralar septal defect drrmigh whit -It the i n/i'estraddles can be used to diagnose the ideniny of the AVvalve or valves . In addition, as a role . a right-sided tricuspidvalve is indicative of D-looped ventricles and a left-sidedtricuspid valve is indicative of L-looped ventricles. Conse-quently . identification of the AV valves can indirectly diag-nose the type of ventricular loop more accurately than canthe position of the infundibular outflow chamber or theposition of the transposed aorta . By using the same principlein reverse . i t is possible to diagnose the identity of the AVvalve or valves when the ventricular loop that is present isknown . We found that these conclusions apply accurately tohearts with two ventricles. as well as to hearts with a singleleft ventricle, excluding some very rare cases with atrial andventricular valpositinr ssnciated with juxtaposition of theatrial appendages (18-20) .

Tricuspid and mitral versus left and right AV valves . Theatypical leaflet morphology of the AV valves in double-inletleft ventricle and cases of mitral atresia with a large leftventricle tempted us and other colleagues (21-28) to use theterms right and left AV valve, rather than tricuspid andmitral valve. This approach gave primary concern to thehemodynamie consequences associated with atresa of tineright or left atria] outlet rather than to the identity of theatretic valve . Yet the findings of this and other studies (10)indicate that AV valve identification is almost always possi-ble by echocardiography in living patients and at postmor-tem study in heart specimens .

Hence . we propose the use of the terms tricuspid ormitral atresia- rather than right or left AV valve atresia .when one of the two AV valves is atretic . As other investi-gators (2_91 have pointed out . unnecessary simplification ofterminology creates a situation where "the material becomesless accessible to those who try to understand the develop-mental background of cardiac malformations ."

In the cases in this series, a clinically important consid-eration aided by accurate AV valve identification is therealization that in this unusual type of mitral atresia, thepartly or entirely left ventricular tricuspid valve is oftenincompetent or may become regurgitant even when it iscompetent in early infancy . Although the overall incidenceof tricuspid regurgitation in our 25 cases was 56%, 12 (86%)of the 14 patients >2 years of age had echocardiographic,engiocardiographic or anatomic evidence of some degree oftricuspid regurgitation . In 6 of the 13 patients with tricuspidregurgitation, the tricuspid valve was straddling (Cases 3 . 8,9 and 17 to 19, Fig. 2. B and C and 8A). and in 7 it openedentirely into the left ventricle (Cases 4 . 13 . 14. 16, 20 . 22 and24 . and Fig . 3- C and D and 4C) . lit contrast, the left

1574

SHINTO CT AL,MI IAAL AIRESIA WITH A LARGE LEFT VENTRICLE

C.

ventricular mitral valve in cases of tricuspid atresia (regard-less of the type of ventricular loop present and the type ofventriculoarterial relation), is very seldom regurgitant unlessit is cleft in association with a partial AV canal septa] defect(30) .

Coronary sinus orifice or lumen atresia . The presence ofatresia of the coronary sinus orifice or lumen in 3 of the 16cases with left-sided mitral valve atresia represents a high(19%) incidence of this rather rare malformation (Fig . 9)(31-34). One wonders if the etiology of this defect is relatedto the obstruction of the left atrial outlet so early in embryo-genesis that the resulting high left atrial pressure compressesand obliterates the lumen of the coronary sinus. The pre-operative diagnosis of this anomaly is important, so that the

(ACC Vnl. 14 .N,7lone IY4_iSM1 I-7n

Figure 10. Diagrammatic demonstodion of ventriculoatdal malalignment and abnormalvenlriculoalrial sepia] angle in three postmortem cases . The normal angle between theventricular (VS' and the atrial septum (ASI is approximately 10' . A. Case 3 . This patienthad solilus atria, D-loop ventricles . normally related great arteries and a straddlingtricuspid valve . The ventricular part of the hear! is malaligned far to the right relative tothe atrial pan of the heart . The expected site of the mural orifice (x) is located above theleft ventricular free wall (LVFW) . resulting to mural atresia (MAtt . The vcntriculoatrialseptal angle is abnormally large (6ll°I . B, Case 12 . This patient had sulilus atria. D-loopventricles . D-transposition of the great arteries and a tricuspid valve entirely in the leftventricle . There is marked rightward malalignmenl of the ventricular segment relative tothe atrial segment . The expected site of the mitral orifice-the mitral dimple (xl-islocated above the left ventricular free wall, reselling in mitral atresia . The eontriculoetrialseptal angle is very abnormally large 170°1 . indicating that although the atria] septum LAS)was normally vertical. the ventricular septal plane was almost horizontal . IOC =infundihular outlet chamber. C, Case 21. This patient had solilus atria, L`leep ventricles,D-transposed great arteries and an entirely left ventricular tricuspid valve . There wasmarked malalignment of the ventricular part of the heart to the left relative to the atria .Consequently . the right-sided mitral dimple was located above the left ventricularfree wallIx I. The ventriculoatrial septal angle was much larger than normal (60'). All threediagrams are analogous to short-axis two-dimensional echocardiographic views, theventral surface being toward the top, the dorsal surface toward the bottom . the patient'sright toward the viewer's left and the patient's left toward the viewer's right .

surgeon can avoid the ligation of the left superior vena cava,which usually is very small . If the atretic coronary sinusreceives the major cardiac veins, ligation of the left superiorvend cave can he fatal (35) .

Atrioventricular and ventriculoarterial relations. Vis-ceroalrial silus solilus occurred in all cases in this series .Hence, the 16 patients with D-loop ventricles had AV situsconcordance. In all 16 patients, despite the presence of AVsilos concordance, the right atrium opened partly or com-pletely into the large left ventricle by way of the right-sidedtricuspid valve, resulting in AV alignment discordance (Fig .SA), In the patients with L-loop ventricles (that is . AV sinusdiscordance) . the left atrium by means of the left-sidedtricuspid valve opened partly or entirely (depending on the

JACC Vol . 19, Na. 7June 1992 :1501-7G

presence or absence of straddling oft he tricuspid valve) intothe large left ventricle, resulting in AV alignment concor-dance (Fig. 21. It is obvious then that in this type ofmalformation, the segmental situs concordance (that is .solims atria and D-loop ventricles) results in segmentalalignment discordance . For the same reasons, segmentalsinus discordance (that is . solicits atria and I- loop ventricles)results in segmental alignment concordance .

Surgical ConsiderationsThe surgical procedures performed in 17 of the patients in

this series are described in Table I . Several subsets ofpatients who died before 1973 were I) patients who were notsurgically treated in = 8). 2) patients with atrial septectomyor main pulmonary artery banding, or both in = 41 . and3) patients with atria) septectomy and systemic to pulmonaryartery shunt In = 1) . All but 2 of the 12 patients who wereoperated on after 1973 (Cases 8 and 18) are alive andimproved clinically or hemodynamically. or both.

Atrial septectomy and pulmonary artery banding . Whenthe atretic mitral valve is left-sided. surgical atrial septec-tomy is essential in early infancy . Case 16 is •a rare exampleof a patient with left-sided mitral atresia with a restrictiveforamen ovale who grew normally and survived to the age of24 years without surgery. When blade atrial septotomy wasperformed during her cardiac catheterization in our hospital,she described her sensation as "the first time in my life that1 could take a deep breath." Nevertheless . her left atrialhypertension was abolished only after surgical atrial septec-tomy. Increased pulmonary blood flow necessitates a mainpulmonary artery band that should be placed at the same timeof the surgical septectomy . It is well known 136) that handing ofthe main pulmonary artery may be associated with progressivenarrowing of the bulboventricular foramen. A less frequentfinding after banding or transection of the main pulmonarvartery is the development of muscular stenosis within thesubaortic infundibulum . It occurred in two cases in this series .both with a straddling tricuspid valve and a large ventricularsepta) defect . In Case 9, it was correctly diagnosed andsurgically resealed. In Case 18. it was diagnosed as restrictionof the bulboventricular foramen . which led to the placement ofa left ventricle to descending aorta conduit . The patient died20 h after operation (9).

In the cases of coexisting pulmonary atresia (Case 7 . Fig .ID) or severe subpulmonary stenosis (Cases 19 and 25) . asystemic to pulmonary artery shunt becomes necessary veryearly in life,

Fontan procedure. When more definitive palliative ther-apy is contemplated (one of the modifications of the Fontonprocedure) (37.38) . the presence of significant tricuspidregurgitation, atrial arrhythmias or pulmonary venous con-nections to the superior vena cava may constitute important

complicating factors. In this s eries . no patient with left-sidedmitral atresia has successfully undergone any of the varia-tions of the Fontan procedure, although a classic Glenn

SHINPO FT AL

157 5sit rcAL A[RrSLs WITH A I .ARGE LEFT vENTRICLE

procedure (39) and bidirectional cavopulmonary shunt wereperformed in two patients (Cases 4 and 9, Table 1) .

Three patieats lCases 19. 23 and 24, Table II with aright-sided atretic mitral valve underwent atriopulmonary anas-tomosis 140) before the introduction of the more recent modi-fications of the Fontan procedure (37 .38) . All three are alive,acvanotic and have considerably improved exercise tolerance .

Two additional patients with right-sided mitral valveatresia Cas es 22 and 25 . Table 1) . recently underwent afenestrated Fontan procedure and had an uneventful recov-ery . Patient 25 (a 33-year old father of three and grandfatherof two) had a dramatic decrease in severe cyanosis andincrease in exercise tolerance after the operation .

Cavopulmonary artery anastomosis. A most importantdecision for patients with either left- or right-sided mitralvalve atresia is the timing of the cavopulmonary anastomo-sis . which is the final surgical therapeutic objective . Thesingle AV valve in the heart of these patients is the tricuspidvalve with abnormal left ventricular or hiventricular attach-ments . The presence of mild or moderate tricuspid regurgi-tation in 86C3 of the patients >2 years of age in this seriesmust not he overlooked. Can the development or progres-sion of Tricuspid regurgitation be avoided by performing acavopulmonary anastomosis as early as possible? If some ofthe tricuspid regurgitation is due to the left ventricularvolume overload, will this lessen or disappear when allsystemic venous return is rerouted directly to the pulmonaryartery and pulmonary blood flow is reduced? Although wewould intuitively answer these questions in the affirmative .the number of patients in this series who underwent atria-pulmonary or cavopulmonary anastomosis is too smail toprovide reliable answers to these questions . At present, weconsider the patients who have a competent or mildlyregurgitant tricuspid valve and are free of atrial arrhythmiasfavorable candidates for a fenestrated cavopulmonary anas-tomosis . For the patients with significant tricuspid regurgi-tation. we recommend a bidirectional cavopulmonary shuntas the first stage of surgical palliative treatment . If thetricuspid regurgitation improves significantly after this pro-cedure. a fenestrated cavopulmonary anastomosis can beundertaken to complete the surgical treatment .

Conclusions. The patients in this series provide clinicaland anatomic data for the understanding and preoperativerecognition of this unusual type of mitral valve atresia . Webelieve that it is important to differentiate between muraland tricuspid valve atresia in patients with AV valve atresiaand a normal-sized or large left ventricle . This approachallows the identification of subgroups of patients at risk forproblems such as tricuspid regurgitation or coronary sinusatresia. In addition, it provides data for better understandingof the morphogenesis of such cases .

We thank Emily Flynn-McIntosh far artwork . Melanie Fdedman for photog-raphy ned Shumn Heim f r,euitence in the preparation of the manuscript.

1576

SHINPO01 AL .MURAL Al IIESIA WITH A LARGE LEFT VENTNICLF

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