Dextrocardia-value of segmental analysis in its categorisationDextrocardia Solitus- 16 cases Arnbiguus with dextro isomerism-2cases Inversus-11 cases^S.llt A Ambiguus with laevo isomerism-4

British Heart Journal, 1979, 42, 497-507

Dextrocardia-value of segmental analysis in itscategorisationGIUSEPPE CALCATERRA', ROBERT H. ANDERSON2, KAI C. LAU3, ANDELLIOT A. SHINEBOURNEFrom the Department of Paediatrics, Cardiothoracic Institute, Brompton Hospital, London

SUMMARY Dextrocardia can be defined as a heart in the right chest with the major axis to the right.This definition, however, conveys no information regarding the chamber arrangements and internalanatomy of the heart.

Of 40 patients satisfying this definition in the files of the Brompton Hospital, 33 had angiocardio-graphic data adequate for complete analysis in terms of connections, relations, and morphology ofcardiac segments. They form the subject of this report.

There were 16 (48%) patients with situs solitus, 11 (33%) with situs inversus, and six (18%) withsitus ambiguus. Of the cases of situs ambiguus, four exhibited laevoisomerism and two dextroisomerism.Ofthe 16 patients with situs solitus, six had two ventricles and 10 had univentricular hearts; two patientshad concordant and three discordant ventriculoarterial connections, seven had double outlet ventricle,and four a single outlet heart. Of the 11 patients with situs inversus, nine had two ventricles and twoa univentricular heart of right ventricular type; the arterial connection was concordant in two,discordant in two, double outlet in six, and single outlet in one. Of the six patients with situs ambiguusand laevo or dextroisomerism, four had two ventricles, and two univentricular hearts; the arterialconnection was concordant in one, double outlet in three, and single outlet in two.

Segmental analysis and the use of basic descriptive terms are essential to define the complexanatomy of such hearts.

The term dextrocardia is used by some authors(Van Praagh et al., 1964; Van Praagh and Vlad,1978) to describe the situation where on plainchest x-ray the heart is predominantly in theright hemithorax. Others use the term to describethe situation where the apex or major axis of theheart (Lev et al., 1968; Squarcia et al., 1973) pointsto the right. As a right-sided position of the hearthas no implications for the internal anatomy,controversy about the precise definition or use ofthe term dextrocardia, or such terms as dextro-position, dextroversion, dextrorotation, or dextro-torsion, is unhelpful. As Van Praagh and colleagues(1964) and Squarcia et al. (1973) have shown,segmental analysis is essential for completedescription of such hearts. In this paper wedescribe an analysis of cases from the BromptonHospital, fulfilling these definitions for dextro-

'Visiting Fellow from Ospedale Maggiore della Carita, Novara, Italy.2Supported by the Joseph Levy Foundation and the British HeartFoundation.3Heinz Fellow, British Paediatric Association.

Received for publication 16 February 1979

cardia, but have used a system of analysis whichdistinguishes the connections of the cardiacchambers and great arteries from their spatial inter-relations (Shinebourne et al., 1976) and which, inaddition, describes abnormal morphology withoutresort to embryological considerations (Tynan etal., 1979).

Patients studied

We have analysed the radiographic, angiographic,and, where appropriate, necropsy data in 40 patientson file at the Brompton Hospital as having theirhearts within the right hemithorax, with the majorcardiac axis pointing to the right (Fig. 1). Theradiographic examination was particularly import-ant since from it information was derived aboutthe disposition of the bronchi and abdominal viscerawhich permitted the determination of atrial situs,vital knowledge in the analysis of patients withdextrocardia.

In only 33 were the data adequate for definitiveand complete analysis and they form the subject of

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this report. Each of these patients was analysed interms of connections, relations, and morphologyusing the system described elsewhere in detail(Tynan et al., 1979).

Findings

The anatomy of the hearts in the patients studiedis shown in the Table. There were 16 patients withsitus solitus (48%), 11 (33%) with situs inversus,and six (18%) with situs ambiguus (Fig. 2). Four

ofthe cases of situs ambiguus exhibited laevoisomer-ism, and two dextroisomerism.

SITUS SOLITUSIn all patients we found visceral, thoracic, and atrialsitus to correspond.

Atrioventricular junction (Fig. 3)Of 16 patients with situs solitus, two hadconcordant and four discordant atrioventricularconnections. The remaining 10 patients had

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Dextrocardia

Solitus- 16 cases

Arnbiguus withdextro isomerism

-2 cases

Inversus- 11 cases

^S.llt

A

Ambiguus withlaevo isomerism-4 cases

Fig. 2 Diagram illustrating bronchial anatomy.RAA, right atrial appendage; LAA, left atrialappendage.

ventricles (concordant atrioventricular connection),to the left in four (discordant atrioventricularconnections), and anterosuperior to the leftventricle in one (concordant atrioventricularconnections).

Arterial junctionOne of the two patients with concordant atrio-ventricular connections had concordant ventriculo-arterial connections, the aorta being anterior andto the right of the pulmonary artery. The otherhad a truncus arteriosus with a right-sided originof the pulmonary trunk.Of the four patients with discordant atrioventri-

cular connections, the arterial connections werediscordant in one, the aorta being anterior and tothe left, and double outlet right ventricle in three.In the latter cases the aorta was anterior and to theleft in two and directly anterior in one; all hadbilateral infundibula.Of the 10 patients with univentricular heart,

only one, with a main chamber of left ventriculartype, had concordant arterial connections. Twouniventricular hearts of left ventricular type exhi-

RA rALA LA

AV Concordance- 2onxses AV Discordarice-4cases

univentricular hearts, six with absent rightatrioventricular connection and four with doubleinlet connections.Of the 10 patients with univentricular hearts,

four had univentricular hearts of left ventriculartype, two with double inlet and two with absentright atrioventricular connection. Three patientshad univentricular hearts of right ventricular type,two with absent right connection and one withdouble inlet, while three had univentricular heartsof indeterminate type, one with double inlet andtwo with absent right atrioventricular connection(Fig. 3). The seven univentricular hearts of right orleft ventricular type all possessed rudimentarychambers, four of which were outlet chambersgiving rise to a great artery while three weretrabecular pouches, having neither inlet nor outletportions.The right ventricle was to the right of the left

ventricle in one of the six patients with two

Double nlet ventricle4 cases

Ventricle - LV type 2RV type 1Indeterminate 1

Absent Rt cornection6 cases

\Vntricle - LV type 2RV type 2Indeterminate 2

Fig. 3 Diagram illustrating atrioventricularconnections found in cases with situs solitus.RA, right atrium; LA, left atrium; MRV, morpho-logically right ventricle; MLV, morphologically leftventricle; V, ventricle in univentricular heart; AV,atrioventricular; Rt, right.

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Table Distribution and anatomy of patients studied; every heart was analysed in terms of connections, relations, andmorphology (see text)Case Atrialno. situs

1 Solitus2 Solitus

3 Solitus

4 Solitus

5 Solitus

6 Solitus

7 Solitus

8 Solitus

9 Solitus

AVjunction VentricularAV Mode of morphologyconnection connectionConcordant 2 AV valves 2 ventriclesConcordant 2 AV valves 2 ventricles

Discordant

Discordant

Discordant

Discordant

Doubleinlet

Doubleinlet

Double

inlet

10 Solitus Doubleinlet

11 Solitus Absent RAV connectio






17 Inversus18 Inversus19 Inversus20 Inversus

21 Inversus

22 Inversus

23

24

25

26

27

28

29

ConcordantConcordantConcordantConcordant

Concordant

Discordant

Inversus Discordant

Inversus Discordant

Inversus Discordant

Inversus Doubleinlet

Inversus Doubleinlet

L ambiguus Ambiguus

L ambiguus Ambiguus

30 L ambiguus Ambiguus

31 L ambiguus Doubleinlet

32 R ambiguus Ambiguus

2 AV valves

2 AV valves

2 AV valves

2 AV valves

R AV valvestraddling

CommonAV valve

L AV valvehypoplastic

2 ventricles

2 ventricles

2 ventricles

2 ventricles

UV heartLV type

UV heartLV type

UV heartRV type

2 AV valves UV heart in-determinatetype

UV heartin LV type

UV heartin LV type

UV heartin RV type

UV heartin RV type

UV heart in-

in determinatetype

UV heart in-in determinate

type

2 AV valves 2 ventricles2 AV valves 2 ventricles2 AV valves 2 ventricles2 AV valves 2 ventricles

2 AV valves 2 ventricles





2 AV valves UV heart RVtype

Common UV heart RVAV valve type


Common 2 ventriclesAV valve

Common * 2 ventriclesAV valve

Common UV heart ind-AV valve determinate

typeCommon 2 ventriclesAV valve

33 R ambiguus Double Commoninlet AV valve

Relation of ventricles and ofrudimentary to main chamber

RV superior to LVRV to right of LV and

anterior

RV to left of LV andanterior




OC to right of MC andanterior

Pouch to right of MC

Pouch posterior to MC

No rudimentary chamber

OC anterior to MC

OC to right of MC andanterior

Pouch to right of MC andposterior

Pouch to right of MC andposterior



RV anterior and left of LVRV anterior and left of LVRV anterior and left of LVRV anterior and left of LV

RV to left of LV

RV to right of LV andposterior



RV anterior and superior toLV

Pouch posterior to MC

Pouch to left of MC

RV posterior to LV

RV to left of LV




UV heart OC to left of MC andLV type anterior

Arterial junctionArterial Relation ofconnection arteriesConcordant ARSingle out-

let truncus

Discordant AL

DORV A

DORV AL side-by-side

DORV AL side-by-side

Concordant RP

Double Aoutlet

Single out- Alet-aorta;pulmonaryatresia

Double Aoutlet

Discordant A

Discordant A R

Double A Routlet

Single out- Alet-aorta;pulmonaryatresia

Double A Loutlet

Single out-let-aorta;pulmonaryatresia

Concordant P LDORV A LDORV A LDORV A L

Single out- A Rlet-aorta;pulmonaryatresia

Concordant P

Discordant A R

Discordant A R

DORV A

Double Aoutlet

Double A Routlet

Concordant P

DORV A R side-by-side

Single out-let-truncus

Double A Loutlet

DORV A

Single out- A Llet-aorta;pulmonaryatresia

500

Infundibularmorphology

SubpulmonaryMitral-truncal

continuity

Subaortic

Bilateral

Bilateral

Bilateral

Subaortic

Subaortic

Subaortic

Subaortic

Subaortic

Subaortic

Subaortic

Bilateral

Subaortic

Bilateral

SubpulmonaryBilateralBilateralBilateral

Subaortic

Subpulmonary

Subaortic

Subaortic

Bilateral

Subaortic

Subaortic

Bilateral

Bilateral

Mitral-truncalcontinuity

Subaortic

Bilateral

Subaortic

Abbreviations: AV, atrioventricular; A, anterior; R, right; P, posterior; L, left; UV, univentricular; RV, right ventricle; LV, left ventricle;DORV, double outlet right ventricle; PS, pulmonary stenosis; VSD, ventricular septal defect; ASD, atrial septal defect; IVC, inferior vena cava;SVC, superior vena cava; MC, main chamber; OC, outlet chamber

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Dextrocardia

Aorticarch

RightLeft

Left

Left

Left

Left

Right

Right

Right

Associated anomalies

Ventricular septal defectAscending aorta gives R-L

pulmonary arteries; ductus-descending aorta

Ventricular septal defect;pulmonary stenosis

Ventricular septal defect

Ventricular septal defect;pulmonary stenosis

Ventricular septal defect;persistent ductus arteriosus

Persistent ductus arteriosus

Persistent ductus arteriosus

Left Pulmonary stenosis

Left Atrial septal defect; pulmonarystenosis

Right Left juxtaposition of atrialappendages; pulmonary stenosis

Left Left juxtaposition of atrialappendages

Left Patent foramen ovale; persistentductus arteriosus

Left Severe pulmonary stenosis

Left Persistent ductus arteriosus

Right Aneurysm of membranous septumLeft Severe pulmonary stenosisRightLeft Supulmonary stenosis; persistent

ductus arteriosusLeft PDA; VSD; left SVC

Visceral situs Thoracicsitus

Solitus SolitusSolitus Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus

Solitus Solitus

Solitus

Solitus

Solitus

Solitus

bited discordant arterial connections and the otherof left ventricular type had double outlet mainchamber. One of the univentricular hearts of rightventricular type had double outlet main chamber, theother two having single outlet with pulmonaryatresia. Of the univentricular hearts of indeter-minate type, two had double outlet and the othersingle outlet with pulmonary atresia.

Aortic archThe aortic arch was left sided in 11 patients (70%)and right sided in five (30%).

Associated anomaliesPersistent ductus arteriosus, ventricular septaldefect, and pulmonary stenosis were the commonestanomalies. Two patients had left juxtaposition ofthe atrial appendages.

SITUS INVERSUSIn all cases we found visceral, thoracic, and atrialsitus to correspond.

Solitus Solitus Atrioventricular junction (Fig. 4)Eleven patients had situs inversus, of whom fiveSolitus Solitus had concordant and four discordant atrioventricular

connections. The remaining two patients haddouble inlet ventricles, in both of which the

Solitus Solitus ventricular morphology was of a univentricularheart of right ventricular type with a posterior

Solitus Solitus right-sided trabecular pouch of left ventriculartype.The right ventricle, in the nine cases with two

Inversus Inversus ventricular chambers, was to the left of the leftInversus Inversus ventricle in five (all with concordant atrioventricularInversus Inversus connections) and to the right in four (with discord-Inversus Inversus ant atrioventricular connections).

Right ASD; right juxtaposition of atrialappendages; left IVC-azygos-left SVC

Right Ventricular septal defect

Pulmonary stenosis

Right SVC; ASD

Severe pulmonary stenosis

Pulmonary stenosis

VSD; ASD; severe PS; leftjuxtapostion of atrial appendages

Left IVC-azygos-left SVC

Right IVC-azygos-right SVC

Subaortic stenosis; right IVC-azygos-right SVC

Inversus

Inversus

Inversus

Inversus

Inversus

Inversus

Right liver,left stomach

Midline liver,left stomach

Right liver,left stomach

Midline liver,left stomach

Left Bilateral SVC; right IVC receives Asplenia, mid-R and L inferior pulmonary veins line liver,

left stomachLeft Persistent ductus arteriosus Asplenia, left-

midline liver,left stomach

Arterial junctionInversus The ventriculoarterial connection in the five patients

with concordant atrioventricular connections' wasInversus concordant in one, double outlet right ventriqle inInversus three, and single outlet in the other (aorta with

pulmonary atresia). Of the four patients who hadInversus discordant atrioventricular connections, one hadInversus concordant ventriculoarterial connections (Fig. 5).

This chamber arrangement has been termedInversus 'isolated atrial inversion' by other workers (ClarksonLambiguus et al., 1972), and was confirmed at operation in ourLambiguus case. Of the remaining patients, two had discordant

ventriculoarterial connections and one double outletLambiguus right ventricle. In both the patients with univentri-Lambiguus cular hearts the arterial connection was double

outlet from the main chamber.Rambiguus In the group as a whole the aorta was anterior to

the pulmonary artery in two cases, anterior and toR ambiguus

Right

Right

Right

Right

Right

Left

Left

Left

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AV concordance AV discordance5 cases 4 cases

Double2 ca

("RV ty

the right in four cases, anterior and to the left inthree, posterior and to the left in one, and posteriorin one.

Aortic archThe aortic arch was right sided in eight patients(73%) and left sided in three (27%).

Fig. 5 Angiocardiogram (injection into right atrium) ofpatient with situs inversus, atrioventricular discordance,and ventriculoarterial concordance viewed in anteroposteriorprojection. At operation for atrial septectomy aorta wasfound to be posterior and to right of pulmonary artery.The chamber connections deduced from theangiocardiogram were confirmed. Note alsomorphologically right atrial appendage (RAA)juxtaposed behind pulmonary artery (not seen) andcatheter entering right atrium via azygos continuation ofinferior vena cava. RA, right atrium (left sided);MLV, morphologically left ventricle; Ao, aorta.

^ inlet Fig. 4 Diagram illustratingises atrioventricular connections in situspe') inversus. Abbreviations as for Fig. 3.

Associated anomaliesPulmonary stenosis and ventricular septal defectwere the commonest lesions. The patient withdiscordant atrioventricular connections and con-cordant ventriculoarterial connections (isolated atrialinversion) had right juxtaposition of the atrialappendages with azygos continuation of the inferiorvena cava to the left superior vena cava (Fig. 5).

SITUS AMBIGUUS, LAEVOISOMERISMIn four patients atrial laevoisomerism was suggestedby the bronchial anatomy on the chest x-ray film,confirmed by necropsy in one (Fig. 6). In two ofthese patients the liver was central (visceral situsambiguus) but in two the liver was right sided(visceral situs solitus).

Atrioventricular junction (Fig. 7)Three patients had two ventricles and one auniventricular heart of indeterminate type (withoutrudimentary chamber). In the biventricular heartsthe right ventricle was to the right in one case andto the left in two cases.The mode of connection was through a comrmon

atrioventricular valve in three cases and via twoperforate atrioventricular valves in one case.

Arterial junctionzOf three patients with two ventricles, one hadconcordant ventriculoarterial connection, one doubleoutlet right ventricle, and one single outlet (truncusarteriosus). The remaining patient had doubleoutlet from the sole indeterminate ventricularchamber.The aorta was anterior and to the right in one

case, anterior and to the left in one case, and to theleft in one case. The remaining case had a truncuswith the aortic component posterior to the pulmon-ary component.

Aortic archThe aortic arch was left sided in three patients andright sided in one.

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Dextrocardia

Fig. 6 Posterior view of specimen with laevoisomerismdissected to show bilateral hyparterial (morphologicallyleft) bronchi. Both lungs were bilobed and atrialappendages were of left morphology. The bronchi arehyparterial as both upper lobe bronchi (ULB) passbelow lower lobe pulmonary arteries (LLPA).

Associated lesionsThree patients had azygos continuation of theinferior vena cava. One patient had left juxtapositionof the atrial appendages (Fig. 8).

SITUS INVERSUS, DEXTROISOMERISMIn two patients atrial dextroisomerism was present,

as suggested from the chest x-ray film and confirmedat necropsy in both. Both also had asplenia. In onethe liver was central (visceral situs ambiguus) butin the other the liver was left sided (visceral situsinversus).

Atrioventricular junction (Fig. 9)Two ventricles were present in one patient. Theother had a univentricular heart of left ventriculartype with outlet chamber of right ventricular typewhich was anterior and to the left of the mainchamber.

Arterial junctionThe patient with two ventricles had double outletright ventricle with the aorta directly anterior, andthe patient with a univentricular heart had singleoutlet (pulmonary atresia), the aorta arising fromthe outlet chamber.

Aortic archBoth patients had a left-sided aortic arch.

Associated anomaliesPartial anomalous pulmonary venous return wasfound in one patient.

Discussion

Our study endorses the findings of others (VanPraagh et al., 1964; Squarcia et al., 1973) that avariety of chamber combinations can be found inhearts situated in the right chest with their long axisorientated to the right. We concur, therefore, withthe opinion that the term dextrocardia conveys noinformation regarding chamber organisation andinternal anatomy of the heart but should be usedonly for description of this cardiac position, afeature easily discernible from the plain chestradiograph. In this investigacion our cases not onlyhad the greater part of the heart within the righthemithorax but also had the long axis and apexdirected to the right. It is possible that cases werenot included that others might have categorised

Ambiguus connections1 case

RV to right and posteriorof LV

Ambiguus connectiDns2 cases

RV to left and anteriorof LV

Double ilet1 case

Indeterminate type

Fig. 7 Diagram illustratingatrioventricular connections in cases withsitus ambiguus and laevoisomerism.Abbreviations as before. IV,univentricular heart of indetermninatetype.

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Giuseppe Calcaterra, Robert H. Anderson, Kai C. Lau, ana Elliot A. Shinebourne

Fig. 8 (a) Angiocardiogram from a patient with situs ambiguus with laevoisomerism showing left-sided juxtapositionof atrial appendages (AA) as demonstrated by atrial injection. Ao, aorta. (b) The necropsy specimen of this patientconfirming presence ofjuxtaposed atrial appendages, both having left morphology. The patient had single outlet of heartwith pulmonary atresia, and surgical correction with conduit (Con) was unsuccessful.

as dextrocardia. However, as we have indicated,arguments concerning the precise definition ofdextrocardia are unproductive, the importantfeature being the segmental arrangement in a heart.In this respect only two of our cases had 'normal'chamber arrangements, compared with 30 per centofthose analysed by Van Praagh et al. (1964), thoughonly 7 per cent of those studied by Lev et al. (1968)had normal chamber connections. It is possiblethat these differences reflect the mode of selection

of cases. Thus, as shown by the earlier investiga-tions, it is essential to utilise a segmentalapproach in order adequately to diagnose andclassify the cases. We have not, however, foundprevious approaches (Van Praagh et al., 1964;Squarcia et al., 1973; Van Praagh and Vlad, 1978)to be universally applicable to the anomaliesencountered. In contrast, utilisation of the systemadvocated by Tynan et al. (1979) has enabled allhearts to be described simply and unambiguously.

Ambiguus connections 1 caseRV to the right and posterior of LV

Double inlet 1 caseLVtype

Fig. 9 Diagram illustrating theatrioventricular connections found intwo patients with situs ambiguus anddextroisomerism.

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Dextrocardia

The hearts investigated here highlight the de-

ficiencies in diagnostic approaches which do notdistinguish clearly between anatomical connectionsand spatial relations.

In the hearts we examined, atrial situs was deter-mined from bronchial anatomy on plain chestradiography. In this way not only could situs solitusand inversus be identified but the laevoisomericand dextroisomeric forms of situs ambiguus couldbe distinguished. Atrial situs was confirmed in thecases coming to necropsy. We believe this methodof categorising situs to be preferable to thoserelating atrial morphology to the state of the spleen.Furthermore, if there is doubt from the plain film,bronchial morphology can easily be confirmed bytomography (Partridge et al., 1975) and there isbetter correlation between atrial and bronchialanatomy than between atrial morphology andpresence or absence of splenic tissue or multiplespleens (Macartney et al., 1978).When describing the ventricular segment of the

heart, we found it necessary to be able to describeconnections of the atria to the ventricles independ-ently both of spatial relations of chambers withinthe ventricular mass and of the morphology of theventricular chambers. Thus, in our cases we foundall five types of atrioventricular connection con-sidered possible by Tynan et al. (1979), namelyconcordant, discordant, ambiguus, double inlet,and absence of one atrioventricular connection. Inthe last category absent right but not absent leftatrioventricular connection was seen. The provisionof the category for ambiguus connection wasnecessary to describe the connections in the heartswith situs ambiguus and two ventricles, as the termsconcordance and discordance are inappropriate forthis arrangement (Tynan et al., 1979). Our casesalso illustrated the usefulness of describing type ofconnection separately from mode of connection,since the ambiguus connection was effected througha common valve in five cases, but through separateright and left valves in one case.

These cases also serve to illustrate what webelieve to be a further refinement (Shinebourne etal., 1978) of our initial approach to this connection(Shinebourne et al., 1976). Following Van Praagh'slead, we initially described ventricular relationswith ambiguus connection in terms of the loop, aswas recently commented upon by Freedom et al.(1978). However, because of the additional con-notations of 'd- and 1-loop', we now prefer todescribe the ventricular relations simply in termsof right/left and antero/posterior orientation. Onereason for this is the possibility of a 'criss-cross'heart (Anderson et al., 1974) with an ambiguusconnection. Previously in a criss-cross heart, we

had used 'd-loop' to describe the relation wherethe morphologically right ventricle was right sided.However, if a criss-cross situation were found withan ambiguus connection, would the relation bedescribed as 'd-loop' or 'l-loop'? As Freedom et al.(1978) indicate, the current concept of the loop(Van Praagh and Vlad, 1978) makes it independentof situs. As such, in situs ambiguus it is simplybeing used to describe ventricular relations. Thus,in the criss-cross situation the left-sided rightventricle, having achieved its position as a conse-quence of cardiac rotation, can still be recognised asbelonging to a d-loop. Is it not, however, simpler todescribe the ventricular position in terms of right/left and antero/posterior position rather than askingthe observer to interpret the presumed embryo-logical looping of the heart tube? We also submitthat simple usage of the right/left and antero/posterior co-ordinates is more useful and moreaccurate than the terms 'inversion' and 'non-inversion'. The 'inverted' ventricles of classicalcorrected transposition in situs solitus are rarely,if ever, the mirror image of the normal ventriculararrangement: in the presence of atrioventriculardiscordance the ventricles tend to be more side byside with horizontal inclination. Furthermore, thereis no consensus as to what 'ventricular inversion'describes. For some authors, 'ventricular inversion'in situs inversus describes ventricles occupying thenormal position for the solitus individual with anormal heart, with the right ventricle anterior andto the right (Espina-Vela, 1978). Such differentinterpretations are avoided by the use of simpleadjectives such as right, left, anterior, and posterior.The value of describing ventricular morphology

independently of the connection is well illustratedby our cases with absence of the right atrioventricu-lar connection ('tricuspid atresia'). These heartsillustrate the wide variability found in hearts havingthe atrial morphology of classical tricuspid atresia,a possibility predicted in our previous studies(Anderson et al., 1977). Thus, univentricular heartsof right ventricular type, left ventricular type, andindeterminate type were found with absent rightatrioventricular connection. We find it difficult todescribe these hearts using the loop concept. Thefinding of such variability in ventricular morphologyin hearts with 'tricuspid atresia' has considerablesurgical significance. Rudimentary chambers maybe posterior or anterior, right sided or left sided, orabsent. Most posterior chambers are not suitablefor incorporation into the circulation in 'corrective'procedures. We also do not know the effect thatventricular morphology will have on the possibleoutcome of a Fontan procedure, and clearly this isanother factor which must be considered when

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assessing these cases for possible operation (Fontanet al., 1978).

It is of note that several hearts in our series hadthe morphology of a main chamber of right ventri-cular type with a rudimentary chamber of leftventricular type. Five cases were identified (16.5%),three with double inlet connection, and two withabsence of the right atrioventricular connection. Webelieve that in part this relatively high prevalenceis the result of an awareness of the anomaly, sincewe are now finding this malformation with increas-ing frequency in hearts both with and withoutdextrocardia (Keeton et al., 1979). Again, identifi-cation of this type of ventricular morphology in theuniventricular heart is important since it affords agood guide to the likely disposition ofthe conductingsystem (Anderson et al., 1978).

Juxtaposition of the atrial appendages was notinfrequent in our series. Otero Coto et al. (1978)have also pointed to an association between right-sided apex and juxtaposition with a left-sided aorta.However, the aorta was left sided in only one ofour cases. All the cases were identified during life,a possibility discussed by Deutsch et al. (1974).At the arterial junction we again found categorisa-

tion to be facilitated by describing separately theconnections, the arterial relations, and infundibularmorphology. It seems to us that if this is donethere can be little room for controversy concerningsuch matters as 'transposition' or the 'conus'.

In conclusion, we have studied a series of patientswhose hearts were within the right hemithoraxwith their long axes orientated to the right, thisbeing the only information to be drawn from theterm 'dextrocardia'. The identification and categor-isation of the extremely varied chamber arrangementwithin these hearts was greatly facilitated by use ofa descriptive system accounting separately forconnections, relations, and morphology.

References

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Requests for reprints to Dr R. H. Anderson,Department of Paediatrics, Cardiothoracic Institute,Fulham Road, London SW3 6HP.



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