Br Heart J 1982; 48: 240-8 Absent left atrioventricular connection with right atrium connected to morphologically left ventricular chamber, rudimentary right ventricular chamber, and ventriculoarterial discordance Problem of mitral versus tricuspid atresia ANGELO RESTIVO, SIEW YEN HO, ROBERT H AN,,, kSON, HUGH CAMERON, JAMES L WILKINSON From the Department of Paediatrics, Cardiothoracic Institute, Brompton Hospital, London; the Department of Pathology, Birmingham Children's Hospital, Birmingham; and Department of Paediatric Cardiology, Royal Liverpool Children's Hospital, Liverpool SUMMARY Four cases of absent left atrioventricular connection are reported. The observations from these cases have been used to emphasise problems concerning the use of the confusing terms "tricuspid" and "mitral'' atresia to describe such hearts. One of the four cases represents a very uncommon condition since the rudimentary chamber was contralateral to the side of the absent atrioventricular connection. The morphology of the conduction system has been elucidated with emphasis given to the surgical implications of these anomalies. Atrioventricular valve atresia has become the subject of increased interest since the development of innova- tive surgical treatment. ' Only recently, however, has the anatomy of these syndromes been clarified with emphasis to the differentiation of an absent atrioven- tricular connection and an imperforate atrioventricu- lar valve.2 It has also been pointed out that when one atrioventricular connection is absent, the morphology of the patent atrioventricular valve is highly variable and poorly identifiable. Consequently it has been sug- gested that it is more accurate to distinguish these cases as absent right or left atrioventricular connec- tion rather than tricuspid and mitral atresia.2 More recently, however, the advisability of this concept has been questioned.3 In the light of this correspondence, we report here four pertinent cases with absent left atrioventricular connection. The findings in these hearts strongly support the remarks of one of us in an earlier paper.4 All the hearts had main ventricular chambers of left ventricular type. Two cases had the rudimentary right ventricular chamber on the same RHA and SYH are supported by the British Heart Foundation together with the Joseph Levy Foundation. Accepted for publication 19 May 1982 side of the absent connection, the usual pattern. One case, in contrast, had the rudimentary chamber on the opposite side to the absent atrioventricular connec- tion.56 The final case is even more fascinating since the rudimentary right ventricular chamber was more or less directly anterior. Case reports CASE 1 The heart was situated in the left hemithorax, with the apex to the left. There was a left aortic arch (Fig. la). Atrial situs solitus was present with normal ven- ous connections. The right atrium was enlarged. The left atrium showed an accessory superior chamber into which four pulmonary veins drained. It was ob- structed at its junction with the main atrial chamber, which received two large pulmonary veins. The left atrial floor was completely muscular, having no con- nection with the ventricular mass (Fig. lb). The atrial septum showed a patent foramen ovale. The ventricu- lar mass was largely made up of a left ventricular chamber. It was connected with the right atrium through an atrioventricular valve of uncertain mor- phology (Fig. lc) Two leaflets were tethered by large 240 on April 21, 2021 by guest. Protected by copyright. http://heart.bmj.com/ Br Heart J: first published as 10.1136/hrt.48.3.240 on 1 September 1982. Downloaded from
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Br Heart J 1982; 48: 240-8
Absent left atrioventricular connection with rightatrium connected to morphologically left ventricularchamber, rudimentary right ventricular chamber, andventriculoarterial discordanceProblem of mitral versus tricuspid atresia
ANGELO RESTIVO, SIEW YEN HO, ROBERT H AN,,, kSON, HUGH CAMERON,JAMES L WILKINSON
From the Department ofPaediatrics, Cardiothoracic Institute, Brompton Hospital, London; the Department ofPathology, Birmingham Children's Hospital, Birmingham; and Department ofPaediatric Cardiology, RoyalLiverpool Children's Hospital, Liverpool
SUMMARY Four cases of absent left atrioventricular connection are reported. The observations fromthese cases have been used to emphasise problems concerning the use of the confusing terms"tricuspid" and "mitral'' atresia to describe such hearts. One of the four cases represents a veryuncommon condition since the rudimentary chamber was contralateral to the side of the absentatrioventricular connection. The morphology of the conduction system has been elucidated withemphasis given to the surgical implications of these anomalies.
Atrioventricular valve atresia has become the subjectof increased interest since the development of innova-tive surgical treatment. ' Only recently, however, hasthe anatomy of these syndromes been clarified withemphasis to the differentiation of an absent atrioven-tricular connection and an imperforate atrioventricu-lar valve.2 It has also been pointed out that when oneatrioventricular connection is absent, the morphologyof the patent atrioventricular valve is highly variableand poorly identifiable. Consequently it has been sug-gested that it is more accurate to distinguish thesecases as absent right or left atrioventricular connec-tion rather than tricuspid and mitral atresia.2 Morerecently, however, the advisability of this concept hasbeen questioned.3 In the light of this correspondence,we report here four pertinent cases with absent leftatrioventricular connection. The findings in thesehearts strongly support the remarks of one of us in anearlier paper.4 All the hearts had main ventricularchambers of left ventricular type. Two cases had therudimentary right ventricular chamber on the same
RHA and SYH are supported by the British Heart Foundation together with theJoseph Levy Foundation.
Accepted for publication 19 May 1982
side of the absent connection, the usual pattern. Onecase, in contrast, had the rudimentary chamber on theopposite side to the absent atrioventricular connec-tion.56 The final case is even more fascinating sincethe rudimentary right ventricular chamber was moreor less directly anterior.
Case reports
CASE 1The heart was situated in the left hemithorax, withthe apex to the left. There was a left aortic arch (Fig.la). Atrial situs solitus was present with normal ven-ous connections. The right atrium was enlarged. Theleft atrium showed an accessory superior chamberinto which four pulmonary veins drained. It was ob-structed at its junction with the main atrial chamber,which received two large pulmonary veins. The leftatrial floor was completely muscular, having no con-nection with the ventricular mass (Fig. lb). The atrialseptum showed a patent foramen ovale. The ventricu-lar mass was largely made up of a left ventricularchamber. It was connected with the right atriumthrough an atrioventricular valve of uncertain mor-phology (Fig. lc) Two leaflets were tethered by large
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Fig. 1 The cardiac morphology incase 1. (a) The anterior view of theheart. The dotted line shows theposition of the rudimentary rightventricular chamber. (b) The absentleft atrioventricular connection. (c)The right atrium connected to a leftventricular chamber. (d) The openedrudimentary right ventricularchamber, the right atrioventricular(AV) valve being seen covering overthe interventricular communication(IVC).
anterior and posterior papillary muscles. The inter-ventricular communication, which looked obstructedsince it was covered by the atrioventricular valvemural leaflet, led to a hypoplastic right sided andanterior rudimentary chamber of right ventriculartype which showed a prominent trabecular portionand extremely short infundibular segment (Fig. ld).The aorta arose from the rudimentary chamber, beinganterior and to the right of the pulmonary trunkwhich arose from the main left ventricular chamber.The pulmonary valve was in fibrous continuity withthe solitary atrioventricular valve. The ascendingaorta and the arch appeared moderately hypoplastic.A persistent ductus arteriosus was present.
Fig. 2 shows a diagrammatic representation of theconduction system as judged from inspection of the
heart. The atrioventricular bundle was not in directrelation with the posterior pulmonary outflow tract.
CASE 2The aortic arch and cardiac apex were to the left (Fig.3a). Atrial situs solitus with normal venous connec-tions was found. The left atrium had no connectionwith the ventricular mass. A patent foramen ovale waspresent. The main left ventricular chamber was con-nected with the right atrium through an atrioventricu-lar valve of atypical morphology which showed threeleaflets (Fig. 3b). A third papillary muscle wasattached to the trabecular septum. The interventricu-lar communication was displaced leftwards, leading toa rudimentary chamber of right ventricular typewhich was mostly on the left (Figs 3a, 3c). The
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Fig. 2 A reprsentation of theconduction tissue disposition in case 1.The main drawing shows the site of theatrioventrlar conduction axis as wouldbe seen through an incision in the left sideof the left ventricular chamber (comparewith Fig. 3d). The inset shows the courseof the bundle relative to the ightatrioventrcar and pulmonary valves aswould be seen by the surgeon approachingvia the right atrium.
Fig. 3 The cardiac morphology ofcase 2. (a) The anterior view of theheart. Despite the left sided position ofthe rudimentary right ventricularchamber (dotted lines) the aorta is tothe right of the pulmonary trunk. (b)The right atrioventricular valveconnecting right atrium to a leftventricular chamber. (c) The openedrudimentary right ventricularchamber. (d) The main leftventricular chamber opened through aleft sided incision. The site of theconduction tissues has beensuperimposed (compare with Fig. 2).
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Fig. 4 Representation of thePulmonary conduction tissue disposition in case 2.
<1\>Trunk //< The main drawing shows the view asillustrated in Fig. 3d while the insetgives the surgeon's view as seenthrough the right atrioventricular
Fig. 5 The cardiac morphology ofcase 3. (a) An anterior view with thedirectly anterior position of therudimentary right ventricular chambermarked. (b) The absent leftatrioventricular connection. (c) Theopened rudimentary chamber. (d) Themorphology of the nghtatrioventricular valve.
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Fig. 6 The conduction tissues from case4. (a) The regular atrioventricular node atthe apex of the triangle ofKoch whichmakes no connection with the ventricularconduction tissues. (b) The anterolateralnode giving rise to the penetrating bundle.(c) The bundle running intramyocardiallyaround the anterior quadrant of thepulmonary trunk. (d) Thebundle-branches to either side of theinterventricular septumn.
rudimentary chamber showed a prominent trabecularportion and a very short infundibular segment, givingorigin to a normally sized aorta, there being no ob-struction of the interventricular communication (Fig.3c). Despite the leftward position of the rudimentarychamber, the aorta was found to be on the right andanterior to the pulmonary trunk (Fig. 3c). The pul-monary trunk arose from the main left ventricularchamber in fibrous continuity with the patentatrioventricular valve (Fig. 3b). A ductus arteriosuswas also present in this case.
In Fig. 4 the course of the conduction tissue is
shown as judged from the gross examination of theheart. Note that the non-branching bundle encirclesthe subpulmonary outflow tract.
CASE 3There was left sided position of the aortic arch andcardiac apex (Fig. Sa). Atrial situs solitus with normalvenous drainage was encountered. The left atrioven-tricular connection was absent (Fig. Sb). The atrialseptum showed evidence of balloon septostomy. Theright atrium communicated with the main left ven-tricular chamber through an atrioventricular valve
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which showed two leaflets (Fig. 5c). Anterior andposterior papillary muscles were present. A goodsized interventricular communication was found to beanterior and to the left of the ventricular mass leadingto a rudimentary chamber of right ventricular typewhich showed a prominent trabecular component andvery short infundibular segment (Fig. Sd). Therudimentary chamber was more or less anterior inrelation to the main chamber; the rudimentarytrabecular component, however, was unequivocallyon the right. The aorta arose from the rudimentarychamber and was anterior and to the right of the pul-monary trunk (Fig. 5a). The pulmonary trunk, takingorigin from the main chamber, was in fibrous con-tinuity with the patent atrioventricular valve. Bothgreat arteries were of normal size and a persistentductus arteriosus was present.The conduction tissue disposition was as illustrated
in Fig. 4.
CASE 4The aortic arch and cardiac apex were to the left.Atrial situs solitus with normal venous connectionswas present. Absence of the left atrioventricular con-nection was found, with a patent foramen ovale on theatrial septal surface. The right atrium connected withthe main left ventricular type chamber through anatrioventricular valve which was of mitral morphol-ogy, having paired papillary muscles. The interven-tricular communication was to the left of the ventricu-lar mass and was somewhat restrictive. It led to a leftsided rudimentary chamber of right ventricular typewhich showed the same prominent trabecular compo-nent and a very short infundibular segment asencountered in the three previous cases. The aorta,arising from the rudimentary chamber, was anteriorand to the left of the pulmonary trunk. Aortic archand isthmal hypoplasia were found. The pulmonarytrunk arose from the main chamber with the atrioven-tricular valve. Persistent ductus arteriosus was alsopresent.
In this case the entire right atrioventricular junctionwas sectioned to show the disposition of the conduc-tion tissues. The regular node in the atrial septummade no contact with the ventricular myocardial tis-sues, being a blind-ending structure (Fig. 6a).Instead, an anomalous anterolateral node was found(Fig. 6b) which gave rise to a penetrating atrioven-tricular bundle. This penetrated to the right of thepulmonary trunk. A long non-branching bundle (Fig.6c) then encircled the anterior quadrant of the pul-monary valve before descending into the right marginof the interventricular septum, where it branched onits left ventricular aspect well below the septal crest(Fig. 6d). A right bundle-branch then penetratedthrough the septum into the rudimentary right ven-
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tricular chamber while the left bundle-branch rami-fied on the left ventricular surface. The overall dis-tribution of atrioventricular conduction tissue was asshown in Fig. 4.
DiscussionIn the past it has been customary to classify theatrioventricular valve atresias simply as tricuspidatresia and mitral atresia. Only recently has the fullanatomy of the lesions been discussed with regard tothe clinical ability to differentiate an absent atrioven-tricular connection from an imperforate atrioventricu-lar connection.2 In the light of these findings, it hasbeen suggested that, when one atrioventricular con-nection is absent, it is preferable to distinguishabsence of the right sided and left sided connectionsrather than nominating the conditions as tricuspid ormitral atresia. This is because, since the essence of theanomaly is absence of the atrioventricular connection,it can never be known with certainty whether, had theconnection developed, it would have been guarded bya mitral or a tricuspid valve.
In the hearts herein described, the right atriumcommunicated always with a left ventricular chamberand always there was ventriculoarterial discordance.The difference in the four cases related only to theposition of the rudimentary right ventricularchamber. In two cases the chamber was left sided, asusually described in this entity, but in one it was rightsided and in the other it was directly anterior. All thisis vital information in the light of the recent sugges-tion by Gittenberger-de Groot and Wenink3 that allhearts with valve atresia should be distinguished ashaving mitral or tricuspid atresia according to the ven-tricular architecture present. They indicated that ven-tricular architecture could be deduced from knowingthe ventricular relations, and then from this informa-tion the nature of the atretic valve could be inferred.If we apply this process to our cases, then presumablya diagnosis of "mitral atresia" would be made in thecase with right sided rudimentary chamber and"tricuspid atresia" in the cases with left sidedrudimentary chamber. But what of the case withdirectly anterior chamber? Furthermore, if weexamine the case with right sided rudimentarychamber (presumed d-bulboventricular loop), onewould expect the solitary atrioventricular valve to beof tricuspid morphology. Instead, we find it to bemore reminiscent of mitral morphology. Conversely,considering the second case with a left sided rudimen-tary chamber (presumed 1-loop), a solitary mitralvalve would be expected. Surprisingly, the valve pres-ent is reminiscent of a tricuspid valve.What this shows is that the conclusion that one can
categorise all valve atresias as mitral or tricuspid frominferential evidence concerning ventricular architec-
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ture is palpably incorrect. In the cases we studied,architecture could certainly not be predicted withaccuracy from knowledge of the ventricular relations.It may be possible to make a more accurate judgementknowing the morphology of the atrioventricular valvepresent, but this information is unlikely to be avail-able to the clinician. Thus, the concept offered byGittenberger-de Groot and Wenink3 may be of valueto the morphogeneticist, but is unlikely to be of greathelp to the clinician, since it is not based upon mor-phological features as observed by the clinician. Wesubmit that it is far more accurate, more comprehen-sive, and more useful simply to describe absence (oratresia) of the right or left atrioventricular connectionand then to describe the chamber combinations pres-ent. This gives the information required by the clini-cian, and at the same time gives all the evidencerequired by the morphogeneticist to make deductionsconcerning the nature of the atretic connection if thisis so desired.From this discussion, it can be seen that in no way
do we deny the value of the looping concept promotedby Van Praagh et al.7 as a mechanism for the under-standing of congenital heart disease. Indeed, Wein-berg, working with Van Praagh and others,8 hasshown more recently how it is essential to describe theloop (ventricular architecture) in those rare caseswhere it is incongruous for a given atrial situs andatrioventricular connection. Our own group9 hasfurther emphasised the need for describing the ven-tricular architecture in hearts with ambiguousatrioventricular connection. But the feature of allthese hearts (that is those with biventricular atrioven-tricular connections) is that the architecture can bereadily identified in terms of the imaginary placementof the palmar surface of the observer's hand on theseptal surface of the morphologically right ventriclewith the thumb in the inlet, the wrist in the trabecularcomponent, and the fingers in the outlet.I0 In thisway, right hand (typical for the normal) and left hand(typical for "ventricular inversion") patterns can beeasily appreciated. It is much harder to determineventricular architecture when the atria connect to onlyone ventricular chamber (univentricular atrioven-tricular connection), particularly when the ventricle isof left ventricular or indeterminate morphology. Thisis because the inlets in such hearts are either con-nected to the same ventricle, or else one inlet isabsent. It is not therefore possible to "anchor one'sthumb" when trying to "place the imaginary hand"on the septal surface of the morphologically right ven-tricular chamber (or, in the indeterminate hearts, tofind a septum). Because of this we find it difficult toapply the "loop convention" in hearts with univen-tricular atrioventricular connection such as presentlydescribed. Moreover, we can see neither a need nor
any relevance, from the clinician's or surgeon's viewpoint, to attempt so to identify the "loop' or theimagined morphology of the absent valve. The firstcase presently described deserves particular commentsince it represents a very uncommon condition. Usu-ally absence of one atrioventricular connection isassociated with presence of the rudimentary ventricu-lar chamber on the same side as the absent connec-tion. Two cases, however, were reported by Quero,5 6with the rudimentary chamber on the opposite side tothe absent connection. Subsequently a few additionalcases have been described' 1-13 and angiocardio-graphic documentation has been reported.'4 In hisoriginal report, Quero indicated that the right sidedposition of the rudimentary right ventricular chamberpointed to the existence of mitral atresia, again usingthe loop to predict the nature of absent connection.He then suggested that this was most unusual, sincewith mitral atresia it would be expected for the leftventricular chamber to be hypoplastic and the rightventricular chamber to be the main ventricularchamber. He expressed this in terms of normaldevelopment, rather than hypoplasia, of the topo-graphically homologous ventricle. At that time, how-ever, the distinction had not been made betweenatrioventricular valve atresias with biventricular anduniventricular atrioventricular connections. If thecases described had possessed imperforate valvemembranes, Quero's comments5 6 would be entirelyappropriate. But in fact the cases had absence of anatrioventricular connection. When an atrioventricularconnection is absent and the other atrium connects toa main ventricular chamber, the relation of therudimentary ventricular chamber is an independentfactor. So, when the left connection is absent and theright atrium connects to a left ventricular chamber,the rudimentary right ventricular chamber is usuallyleft sided, but as we have seen may be right sided oreven directly anterior. When the right atrioventricularconnection is absent with similar chamber connec-tions, then usually the rudimentary right ventricle isright sided, but it may be directly anterior or even tothe left. In hearts with univentricular atrioventricularconnection to a left ventricular chamber, it has beenemphasised that, though there is a basic disposition ofthe atrioventricular conduction system, the precisecourse of the non-branching atrioventricular bundlewithin the ventricles is dependent upon the positionof the rudimentary chamber. Fl1 The findingsencountered in the cases here reported further sup-port these remarks. In the first case with right sidedrudimentary chamber there was an anterior node fromwhich a very short bundle arose going down immedi-ately along the main chamber aspect of the trabecularseptum.'8 In contrast, in the cases with left sidedrudimentary chambers, there was an anterior node, in
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the same position as in case 1, from which an elon-gated atrioventricular bundle coursed towards thetrabecular septum in close proximity to the posteriorpulmonary outflow tract.
These morphological features are of considerablesurgical signifcance. If surgical "correction" is to beattempted in hearts such as these, it will probably bedone using a Fontan type procedure. The position ofthe node will not be a major feature, since always itwill be necessary to preserve the right atrioventricularorifice. It is the relation of the conduction tissues tothe interventricular communication which is para-mount. If there is ventriculoarterial discordance, as isusually the case, it may be necessary to enlarge thiscommunication. If there is ventriculoarterial concor-dance, a rare happening,5 it will be necessary to closethe communication if an atrioventricular conduit is tobe constructed.'9 Whichever option is attempted, itmust be known that the branching bundle is carriedon the left ventricular aspect of the septum away fromthe septal crest, and that the non-branching bundledescends on to the right margin of the foramen. Therim of the foramen formed by the outlet septum neverharbours conduction tissue, and the left margin is alsoa safe area for resection. These rules hold good what-ever the position of the rudimentary right ventricularchamber (Fig. 7). It must be emphasised, however,that we speak of the right and left margins of theinterventricular communication relative to its anatom-ical position. These margins may not always be per-ceived as being in right sided or left sided position,this depending entirely upon the approach taken bythe surgeon.
Finally, the rare occurrence of ventriculoarterialconcordance5 in these anomalies is worthy ofemphasis. This arrangement permits the pulmonaryvenous blood to be switched into the main left ven-tricular chamber via an intra-atrial baffle. Therudimentary chamber can then be opened and theinterventricular communication closed, a valved con-duit being placed between the right atrium and therudimentary right ventricular chamber. This proce-dure, which represents a modification of the Fontanoperation, has been successfully performed in onecase.'9 The reason for incorporating the rudimentarychamber into the pulmonary circuit is the possibilityof growth and development of the chamber. Such amodified Fontan procedure could be performed evenin cases in which the rudimentary chamber is leftsided, providing there is ventriculoarterial concor-dance. If ventriculoarterial discordance is present,however, as in the cases here reported, a baffle proce-dure and the classical atriopulmonary Fontan bypasswould be the only possible option other than combin-ing an atrioventricular bypass with an arterial switchprocedure.20
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Right-sided rudimentary RV chamber
Safe area for resection
Left-sided rudimentary RV chamber
Fig. 7 Diagram illustrating the vital relation of theat?ioventncular conduction axis to the interetularcommunication as seen by the surgeon approaching through therudimentary ight ventricular chamber. Note that the position ofthe nudimentary chamber does not alter the basic disposition oftheconduction axis, and that the safe area for widening thecommunication is the same in both arrangements.
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