truncus arteriosus communis intact ventricular - heart.bmj.com filebritish heartjournal, 1979, 42,...

British Heart Journal, 1979, 42, 97-102

Truncus arteriosus communis with intact ventricularseptum1IAN CARR, SAROJA BHARATI, V. S. KUSNOOR, AND MAURICE LEV

From the Divisions of Pediatric Cardiology and Pathology, Cook County Children's Hospital, Chicago, Illinois;and The Congenital Heart Disease Research and Training Center, Hektoen Institute for Medical Research,Chicago, Illinois, USA

SUMMARY This is the first documented case of truncus arteriosus conununis with intact ventricularseptum in which extensive clinical, haemodynamic, angiographic, and pathological data are available.Angiography suggested the presence of two discrete semilunar valves but necropsy showed a basicallysingle semilunar valve.

This case fills a gap in the spectrum of aorticopulmonary, truncal, and infundibular septal defects, andreinforces the belief that the essence of truncus arteriosus communis is a single semilunar valve, commonto both ventricles, which need not be associated with the defects in the adjacent parts of the structuralcontinuum.

In the common forms of truncus arteriosus commu-nis, as the term is used in cardiology, a single greatartery arises from the heart above a single semilunarvalve, gives origin in its ascending portion tocoronary and pulmonary arteries, and continues asthe aorta. Though an infundibular septal deficiencyis not a necessary component of truncus arteriosuscommunis, instances of this anomaly in which theinfundibular septum is intact are very rare. We areaware of no previous report describing a heart withtruncus arteriosus communis and intact ventricularseptum in which extensive clinical, haemodynamic,and angiographic data, as well as pathological dataare available. The purpose of this report is both todescribe and to discuss such a case and to commenton its implications with respect to the embryology,definition, and classification of truncus arteriosuscommunis.

Case history

A 3-month-old boy had been born at term bycaesarean section, to a diabetic mother; his birth-weight was 4252 g (9 lb 6 oz). On the second day ofextrauterine life he was noticed to have a heartmurmur. Mild central cyanosis and congestive

'This study was supported by a grant from the Children'sHeart Research Foundation and by grants from the NationalInstitutes of Health, Bethesda, Maryland. USA.

Received for publication 14 November 1978

heart failure were first detected at the age of 3 weeks.He had frequent respiratory infections and per-sistent congestive heart failure in spite of fullmedical treatment.

PHYSICAL EXAMINATION AT AGE 3 MONTHSThe infant was in mild respiratory distress with arespiratory rate of 60/minute. There was slightcentral cyanosis and no clubbing. Pulse rate was160/minute, regular in rhythm, and bounding inform. Femoral pulses were neither diminished nordelayed. There was mild intercostal retraction oninspiration, and easily visible cardiac pulsation onthe left side. The apex beat was in the 5th leftinterspace beyond the mid-clavicular line. Therewas a slapping parasternal impulse and a systolicthrill maximal in the 3rd and 4th spaces at the leftsternal edge. On auscultation the first sound com-plex was of normal intensity. The second soundappeared to be split but a phonocardiogram was notobtained. A third heart sound was heard at theapex. A grade 4/6 harsh systolic murmur wasmaximal in the 3rd and 4th spaces at the left sternaledge. A grade 2/4 mid-diastolic murmur was heardat the apex. The lungs were clear. The liver waspalpable 2 cm below the right costal margin.

CHEST X-RAYThe cardiomediastinal shadow was moderately en-larged and the pulmonary vascularity was increased.

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Ian Carr, Saroja Bharati, V. S. Kusnoor, and Maurice Lev

ELECTROCARDIOGRAMThis showed regular rhythm with a mean frontalplane QRS axis of + 1500. The patterns of left atrialenlargement and combined ventricular hypertrophywere present (Fig. 1).

CARDIAC CATHETERISATIONCatheterisation at the age of 3 months (Table)showed that neither the aorta nor the pulmonaryartery was entered from the right ventricle.

ANGIOCARDIOGRAMSInjection into the root of the great artery arising

I II III aVR aVL aVF

V4R Vi V2 V4 V5 V6

Fig. 1 Electrocardiogram at age 3 months.

Table Cardiac catheterisetion data at age 3 months

Site 0, saturation (%) Pressure (mmHg)

Superior vena cava 54Right atrium, high 52Right atrium, middle 58 a= 10 mean= 7Right atrium, low 68Inferior vena cava 62Right ventricle 68 124/0-1Right upper pulmonary

vein 95Left pulmonary vein 94Left atrium 91 a = 15,v = 25mean = 17Left ventricle 89 110/0Aorta 81 mean = 52

Note: Difference in right ventricular and left ventricular sys-tolic pressures is consistent with lack of interventricular com-munication and some degree of right ventricular infundibularstenosis. Aortic pressure was overdamped. The left atrialoxygen saturation, lower than that in the pulmonary veins thatwere entered, is presumably caused by the perfusion of under-ventilated lung whose pulmonary vein was not entered. Thesame explanation may apply to the left ventricular saturationwith the additional factor of semilunar valve regurgitation.

from the base of the heart showed that it gave rise tothe coronary, pulmonary, and systemic arteries in itsascending portion. An unopacified area at the root ofthis great artery, best seen in the lateral projection,was interpreted as a septum between 2 semilunarvalves (Fig. 2 and 3). No reflux into either ventriclewas seen.A left ventriculogram showed opacification of the

root of the great artery but not of the right ventricle.A right ventriculogram showed opacification of

the root of the great artery via a well-defined but

Fig. 2 Angiogram in root ofgreat artery showingfilling defect caused by dysplastic truncal valve tissue ofanterior leaflet (shorter arrow). Longer arrow indicatesanterior sinus of Valsalva.

narrow infundibulum. Opacification of the leftventricle was seen in this injection.The diagnosis of an unusual form of truncus

arteriosus, or aorticopulmonary septal defect with 2semilunar valves, was made on the basis of thesedata.

SUBSEQUENT COURSEThe infant continued in severe congestive heartfailure with poor weight gain, and at the age of 5months was submitted to operation. It was plannedto attempt construction of separate aortic and pul-

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Truncus arteriosus communis with intact ventricular septum

Fig. 3 Angiogram in root of great artery showingfilling defect caused by dysplastic truncal valve tissue ofanterior leaflet (shorter arrow). Contrast medium istrapped in anterior sinus of Valsalva (longer arrow) givingthe false impression of a rudimentary main pulmonaryartery with its own semilunar valve.

monary channels or, if this proved to be impractic-able, to band the pulmonary arteries. Duringinduction of anaesthesia he developed cardio-respiratory arrest. All resuscitative measures wereunsuccessful.

NECROPSY FINDINGSThe heart was enlarged. From the base of the hearta single great artery emerged. There was hyper-trophy, enlargement, and endocardial thickening ofall the cardiac chambers. A patent foramen ovalewas present.The architecture of the infundibulum of the

right ventricle was abnormal. The septal band groupproceeded to the base and met the parietal band toform an arch. This arch, however, was somewhatnarrowed superiorly. This was related to thepresence of the single great artery emerging fromboth ventricles, straddling the ventricular septum.The valve of this artery was quadricuspid, with oneeach of anterior, posterior, right, and left leaflets.The right was slightly larger than the posteriorleaflet which in turn was larger than the left; theanterior leaflet was the smallest. The commissure ofthe left and anterior leaflets was also at the anterior,

Fig. 4 Anterior view of heart showing the outflow tractof the right ventricle. RV, right ventricle; PB, parietalband; SB, septal band; V, truncal valve; T, commonarterial trunk; LPA, left pulmonary artery. Arrowpoints to the truncal valve tissue extending over theventricular septum. Note the absence of a ventricularseptal defect.

right, side of the ventricular septum so that theleft leaflet also bridged the ventricular septum.The crest of the muscular ventricular septum layin the same plane as the arterial valve (Fig. 4 and5). Valve tissue arose from this crest and wasconfluent, with the commissure of the right andposterior leaflets, posteriorly, and with the left leaflet,near its conmmissure with the anterior leaflet,anteriorly. The left leaflet close to its junctionwith the posterior, non-coronary, cusp was relatedto the mitral valve. The valve tissue was very thick-ened throughout, with many single and confluentnodular formations. The right coronary ostiumemerged from the sinus of Valsalva of the rightbridging cusp and the left coronary ostium fromthat of the left bridging cusp. These ostiaappeared obstructed by the much thickened nodularformation of the valve tissue. This arterial trunk

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Fig. 5 Left ventricular view: the linear cuts in the leftventricle indicating the areas from which microscopicalsections were studied. LV, left ventricle; MV, mitralvalve; V, truncal valve; T, common arterial trunk.Arrow points to much thickened nodose truncal valvewhich extends on the summit of the ventricular septum.Note the absence of a ventricular septal defect from theleft ventricular view.

gave off the pulmonary trunk anteriorly, which inturn divided into right and left pulmonary arteries.The main arterial trunk then proceeded into a leftaortic arch giving off the brachiocephalic vessels.The left coronary artery gave off 2 anterior de-

scending branches but formed no left circumflexartery. The right coronary artery formed theposterior descending branch.At a gross level all walls of the left ventricle on

section presented a variegated picture of red andwhite areas. Microscopical sections through allwalls of this chamber presented areas of recent andold infarction.

Aside from the findings in the heart the patho-logical diagnoses were partial pulmonary atelectasis,bilateral, with chronic passive hyperaemia of thelungs and liver.

Discussion

PREOPERATIVE DIAGNOSISIn the angiocardiograms, the unusual diastolic con-figuration of the dysplastic tissue of the anteriortruncal leaflet gave the false impression that itrepresented a septum separating an anterior rightventricular outlet valve from a posterior left ven-tricular outlet valve. Two semilunar valves weretherefore believed to be present. Necropsy showedonly one semilunar valve though the dysplastic tissueon the crest of the ventricular septum suggests anearly stage of division into 2 semilunar valves. Toavoid this angiographic misinterpretation in thefuture we need to remember this patient, and torecall how thick and fleshy the dysplastic valvetissue can be in truncus arteriosus communis.

SURGERYSurgically, it seems that this heart may have beenaccessible to a procedure similar to that described byDaily et al. (1975). An eccentrically placed channelmight have been created from the right ventricularoutlet to the main pulmonary artery orifice withoutobstructing the channel from the left ventricularoutlet to the aortic arch. The small size of the struc-tures and the doubtful effectiveness of the dysplasticvalve tissue at the right ventricular and left ventri-cular outlets after such a procedure would havemade its success a considerable tour de force.

PATHOLOGYThe old and recent infarcts have not, to our know-ledge, been previously described as complications oftruncus arteriosus communis and may be related tothe proximity of this valve tissue to the coronaryorifices.

EMBRYOLOGY, DEFINITION, ANDCLASSIFICATIONThe remarkable thing about this case is the absenceof an infundibular septal defect. In addition, thoughthere is a clearly differentiated truncal valve with 4circumferential leaflets, valvular tissue is alsopresent on the crest of the septum extendingacross the diameter of a root of the great artery; thistissue is not formed into leaflets. Similar cases havepreviously been described by Bharati et al. (1974)and Rosenquist et al. (1976). We believe thesefeatures to have possible implications with respectto the embryology, definition, and classification oftruncus arteriosus communis.The definition and classification of truncus

arteriosus communis are still the subject of con-siderable controversy. On the one hand there is thenatural desire to relate posmatal appearances to

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Truncus arteriosus communis with intact ventricular septum

prenatal development, as evidenced by the use ofembryological terms to describe postnatal struc-tures, and on the other hand the pathologicalembryology of these defects is not known.The normal embryonic structures whose mal-

development is believed to be relevant to truncusarteriosus communis are the aorticopulmonaryseptum, the truncus arteriosus, and that part of thepartition between the right ventricular and leftventricular outflow tracts immediately below the2 semilunar valves, which becomes the infundi-bular septum. The term 'truncus arteriosus com-munis', as used by most cardiologists, includes boththe single great artery arising from the heart andthe semilunar valve at the root of this great artery.Some embryologists (Van Mierop et al., 1978) usethe term only for the precursor of 'the truncalsinuses of Valsalva and valve cusps, not the commonarterial trunk distal to it'; what cardiologists call thecommon arterial trunk is derived from the aorticsac. The ascending aorta and pulmonary artery areformed from the aortic sac when it is partitioned byan invagination of the posterior wall called theaorticopulmonary septum. This implies that defec-tive partition into aorta and pulmonary artery wouldrepresent, embryologically, an aorticopulmonaryseptal defect which may or may not be associatedwith persistence of the embryological truncusarteriosus communis. This also means that the termaorticopulmonary septum as used by cardiologistscorresponds to the embryological aorticopulmonaryseptum but not the embryological truncal septum.We believe a distinction has to be made betweenthe term truncus arteriosus communis as used todescribe a prenatal, embryological structure, andtruncus arteriosus communis as used to describe apostnatal structure.

If the above 3 artificial subdivisions of thestructural continuum always functioned, in ab-normal states, as a single developmental unit, wewould not need to draw any fine distinctions be-tween one part and another for the purposes ofdefinition and classification. However, they do notalways function as a single developmental unit inabnormal states, as evidenced, for example, by ourcase in which infundibular septation is apparentlycomplete, but embryonic truncal septation is in-complete.

Fig. 6 represents a spectrum of hearts previouslyreported to have defects in this region, including thepresent heart. Though this artificially arrangedsequence may not correspond completely to anembryological sequence, it may clarify the problemof definition and classification of truncus arteriosuscommunis for the clinician and surgeon. At one endof this spectrum (Fig. 6.1) lies truncus arteriosus

J L

A2

Fig. 6 Diagrammatic representation of spectrum ofhearts reported to have defects in the region of thetruncus arteriosus. See text. The pulmonary artery isdrawn on the right side of the aorta only because of theconstraints imposed by representing 3D in 2D.

communis (cardiologists' term) with no main pul-monary artery (left and right pulmonary arteriesarise separately), a single semilunar valve, andfailure of the infundibular septum to reach the planeof the semilunar valve, leaving what is effectively asubvalvar ventricular septal defect. This corres-ponds to Collett and Edwards Type 3 (Collett andEdwards, 1949) and may be regarded, embryologi-cally, as truncus arteriosus communis with asso-ciated aorticopulmonary and infundibular septaldefects. In Fig. 6.2 arterial septation has resulted inthe main pulmonary artery but is otherwise thesame as in Fig. 6.1. Embryologically we regardFig. 6.2 as depicting truncus arteriosus communiswith an infundibular septal defect and partialabsence of the aorticopulmonary septum. The heartreported here (Fig. 6.3) exemplifies a further degreeof truncus arteriosus communis (cardiologists' term)in which the infundibular septum is fully formed,there is no ventricular septal defect, truncal valvetissue is present on the crest of the infundibular

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septum, but differentiation into right ventricular andleft ventricular outlet valves has not occurred.Embryologically this is truncus arteriosus communiswith partial absence of aorticopulmonary septum.Fig. 6.4 represents 'pure' truncus arteriosus com-munis with well-formed aorticopulmonary septum,embryologically, as exemplified by case 4 ofRosenquist et al. (1976) and Fig. 6.5 truncusarteriosus communis with no aorticopulmonaryseptal defect, embryologically, but with ventricularseptal defect, as exemplified by case 1 of Rosenquistet al. (1976) The hearts described by Bain andParkinson (1943), Van Praagh and Van Praagh(1965) and Daily et al. (1975) are represented byFig. 6.6. This seems to correspond to another degreeof defect in which there is little aorticopulmonaryseptation embryologically but separate right andleft ventricular outlet valves have developed andthere is no ventricular septal defect. The fact that 2semilunar valves are present precludes the idea thatthere is persistence of the truncus arteriosus com-munis, as it is understood by embryologists. Untilcontrary data are available, it seems preferable to usto regard this kind of heart as an example ofaorticopulmonary septal defect both embryologi-cally and anatomically. The strictly arterial portionof these hearts is indistinguishable to us from thoserepresented by Fig. 6.2 and 6.3. Finally (Fig. 6.7),aorticopulmonary septation progresses to the pointat which the abnormality would clearly be regardedas an aortopulmonary window by the cardiologistand would correspond to an aorticopulmonaryseptal defect embryologically. Fig. 6.8 representsthe normal.

It seems that though most instances of truncusarteriosus communis have both infundibular andaorticopulmonary septal defects as part of the com-plex from the embryological standpoint, suggestinga high degree of interdependence between theseartificial subdivisions of the structural continuum,in rare instances, as exemplified both by this andother reported cases, one or both of these associateddefects may be absent.We believe that there are sound reasons, both

embryological and surgical, for regarding aorto-pulmonary window, or any other instances of in-complete differentiation into ascending aorta and

pulmonary artery, with 2 semilunar valves, asrepresenting aorticopulmonary septal defect ratherthan a variant of truncus arteriosus communis.Edwards (1976) and Crupi et al. (1977) have reachedthe same conclusion, but whereas they regard asingle semilunar valve as an essential part of thetruncus arteriosus we prefer the perspective of VanMierop et al. (1978) that the single semilunar valveis the only essential for truncus arteriosus.

We are grateful for the assistance of Drs GertrudeNovak, Avinash Mondkar, and ConstantineTatooles.

References

Bain, C. W. C., and Parkinson, J. (1943). Common aorto-pulmonary trunk: a rare congenital defect. British HeartJournal, 5, 97-100.

Bharati, S., McAllister, H. A., Rosenquist, G. C., Miles,R. A., Tatooles, C. J., and Lev, M., (1974). The surgicalanatomy of truncus arteriosus communis.Journal of Thoracicand Cardiovascular Surgery, 67, 501-510.

Collett, R. W., and Edwards, J. E. (1949). Persistent truncusarteriosus: a classification according to anatomic types.Surgical Clinics of North America, 29, 1245.

Crupi, G., Macartney, F. J., and Anderson, R. H. (1977). Per-sistent truncus arteriosus. American Journal of Cardiology,40,569-578.

Daily, P. O., Sissman, N. J., Lipton, M. J., and Shumway,N. E. (1975). Correction of absence of the aortopulmonaryseptum by creation of concentric great vessels. Annals ofThoracic Surgery, 19, 180-190.

Edwards, J. E. (1976). Persistent truncus arteriosus: a com-ment. American Heart Journal, 92, 1-2.

Rosenquist, G. C., Bharati, S., McAllister, H. A., and Lev,M. (1976). Truncus arteriosus communis: truncal valveanomalies associated with small conal or truncal septal de-fects. American Journal of Cardiology, 37, 410-412.

Van Mierop, L. H. S., Patterson, D. F., and Schnarr, W. R.(1978). Pathogenesis of persistent truncus arteriosus.American Journal of Cardiology, 41, 755-762.

Van Praagh, R., and Van Praagh, S. (1965). The anatomy ofcommon aorticopulmonary trunk (truncus arteriosus com-munis) and its embryologic implications. A study of 57necropsy cases. AmericanJournal ofCardiology, 16, 406-426.

Requests for reprints to Dr Ian Carr, Division ofPediatric Cardiology, Cook County Hospital, 1825West Harrison Street, Chicago, Illinois 60612,USA.

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