Br Heart J 1983; 49: 324-7

Accessory tricuspid valve tissue causing obstruction ofthe ventricular septal defect in tetralogy of FallotGIUSEPPE FAGGIAN, CARLA FRESCURA, GAETANO THIENE, UBERTO BORTOLOTTI,ALESSANDRO MAZZUCCO, ROBERT H ANDERSON*From the Departments ofCardiovascular Surgery, Paediatrics, and Pathology, University ofPadova Medical School,Padova, Italy; and The Cardiothoracic Institute, Brompton Hospital, London

SUMMARY Among 61 heart specimens of tetralogy of Fallot with or without pulmonary atresia, fourpresented with an accessory tricuspid valve leaflet. This structure caused partial or almost completeobstruction of the ventricular septal defect. Depending on the morphology, the accessory tissue wasclassified into "mobile" or "fixed" types.The "mobile" variety was tethered by long chordae tendineae which permitted a wide excursion

of the leaflet through the ventricular septal defect into the left ventricular outflow tract where itrepresented a potential cause of obstruction. The "fixed" variety was attached to the edges of thedefect by short chordae which reduced considerably its movements. This type created a fixedobstruction of the ventricular septal defect without involving the subaortic left ventricular outflowtract. The precise morphology of the accessory tricuspid valve tissue is of considerable surgicalsignificance. When mobile, the tissue must be resected at the time of surgical repair. When fixed itcan be used as a suture anchorage during closure of the ventricular septal defect.

In congenital heart malformations presenting with aninterventricular shunt, the degree of mixing betweenthe pulmonary and systemic circuits is directly relatedboth to the size of the ventricular septal defect and thepresence of an obstruction to ventricular outflow.

In tetralogy of Fallot, the septal defect is usuallylarge because of malalignment of the outlet septum.Restrictive defects have been reported rarely. 1-3 Insuch cases the obstruction was usually caused byaccessory tricuspid valve leaflets or fibrous valve-liketissue derived from the membranous septum or itsremnants.We have reviewed our anatomical collection of

heart specimens with tetralogy, including cases withpulmonary atresia, so as to evaluate the nature, inci-dence, and surgical significance of such anatomicalstructures which may restrict the ventricular septaldefect.

*During the course of this investigation RHA was visiting professor at the Uni-versity of Padova, supported by the Departments of Pathology, Cardiology,Paediatrics, and Cardiovascular Surgery.

This work was supported in part by a grant from the Consiglio Nazionale delleRicerche, Rome, Italy, and by Opera "Martino Arrigoni", Belluno, Italy.

Accepted for publication 23 December 1982

Material and methods

All heart specimens of patients with tetralogy of Fal-lot, including those with pulmonary atresia, collectedat the Department of Pathology, University of PadovaMedical School, were reviewed. Some of the patientshad undergone surgical procedures during life; othershad not. In all specimens geometric measurementswere performed with particular reference to the size ofthe ventricular septal defect, the ratio between thethickness of the right and left ventricular free walls,and the degree of the aortic overriding.

Results

Among 61 specimens studied, four (6.6%) presentedwith accessory valve-like tissue which partially obs-tructed the ventricular septal defect. Three of themshowed a patent pulmonary outflow tract and one hadpulmonary atresia (case 2).

All hearts showed laevocardia, situs solitus,atrioventricular concordance, and normally relatedgreat vessels. Moreover, in all cases both systemic andpulmonary venous drainages and the distribution pat-terns of the coronary arteries were normal. The septal

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Table Main pathologicalfmdings

Case Age (y) Cause of death RV LV VSD diameter (mm) Aortic Nature ofNo. thickness (mm) thickness (mm) and % of obstructiondextroposition (%) obstrctive ksion

1 30 Multiple cerebral abscesses, 9 11 16 50 Freely mobilepulmonary tuberculosis 3(D/o inverted hammnock

(Fig. 1)2 '/12 Operative death; creation of 5 6 16 60 Dysplastic but

Blalock-Taussig shunt 90% mobile hammock3 2 Cerebral infarction after 7 6 9 50 Anchored and

repair of tetralogy 30D/o paired hammocks(Fig. 2)

4 2 Pneumonia 11 6 6 40 Single anchored80% hammock (Fig. 3)

RV, right ventricle; LV, left ventricle; VSD, ventricular septal defect.

defect was of perimembranous malalignment type,typical of tetralogy.

Further details, together with the measurementstaken, are given in the Table. The pertinent findingsin the four hearts were the accessory tricuspid valveleaflets. These showed two distinct patterns. The firstpattern found in cases 1 and 2 was that of an invertedhammock, secured by long chordae tendineae to themedial papillary muscle and the crest of the ventricu-lar septum (Fig. 1). The hammock lesion not onlypartially obstructed the septal defect (Fig. la), butwas free to float into the subaortic outflow tract, pro-

ducing obstruction in this region also (Fig. lb). Theobstructing leaflet illustrated is that from case 1. Thestructure in case 2 was sirftilar but the leaflet tissuewas more dysplastic. The second pattern found incases 3 and 4 differed in that the accessory leaflettissue was firmly anchored to the septum and lackedthe mobility of the first type. The obstructive lesionwas duplicated in case 3 but was a solitary lesion incase 4 (Fig. 2). In both instances the accessory leafletparticularly blocked the septal defect but did not obs-truct the subaortic outflow tract from the left ventri-cle.

X; ~~~~~~MedialA

igjhtentricnle

Kentricl t ~~~~~~~ventricle SO&Fig. 1 Case 1. (a) View from the right ventricular inflov. An accessory leaflet (arrows) attached by long weUformed chordae tendineae to the medialpapillary musck obstructs the ventncular septal defect. (b) View ofthe kftventicular outflow: the accessory leaflet is seen to protrude to the left side of the ventricular septal defect,potentially obstructing the left outflow tract. Note some chordae tendineae inserted on the posteroinferior rim ofthedefect.

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Faggian, Frescura, Thiene, Bortoloui, Mazzucco, Anderson

Lventr.icleFig. 2 Case 4. View ofthe aortic outletfrom the right ventricleshows a solitary andfixed pobpousfibrous valve-like tag(arrows) which is attached to the crest of the ventricular septaldefect and by short chordae tendineae to the medial papillarymuscle.

Discussion

The anatomical features of tetralogy particularlyrelevant to surgical repair have been well described.4The peculiar morphological lesions described hereseem to be relatively rare, though they have been welldocumented previously. 1-3 Surprisingly, they werefound in one fifteenth of the cases in our car-diopathological collection. They are highly significantfrom the clinical and haemodynamic standpoint sincethey may mimic severe pulmonary stenosis or atresiawith intact intraventricular septum. Indeed, theaccessory valvular tissue originating from the tricus-pid valve may during systole almost completelyocclude the large ventricular septal defect.

Such accessory tissue tags arising from valvar orfibrous tissue in the environs of the ventricular septaldefect have been more extensively described when thedefect is isolated,5 6 accompanying complete7 or cor-rected8 transposition or is part of an atrioventricularseptal defect.6

In these other anomalies, the tissue tags have beenobserved to originate either from the membranous

septum, from its remnants, or from the left atrioven-tricular valve (the right sided valve in corrected trans-position). In contrast, in our cases together with thosepreviously reported in tetralogy, the accessory tagswere always found to originate from the tricuspidvalve. A single case of corrected transposition with atag originating from the left sided morphologicallytricuspid valve has also been observed.9The surgical significance of our findings derives

from the observation of two discrete morphologicalpatterns, not discussed previously to our knowledgeand which can be conveniently differentiated as fixedand mobile types, respectively.The mobile type (cases 1 and 2) is a large hammock

like leaflet anchored to the ventricular septum by longchordae. This gives it freedom to protrude into thesubaortic region producing a potential cause of leftventricular tract obstruction. Since in tetralogy of Fal-lot the ventricular septal defect is also the aorticoutflow from the right ventricle, the structure hereindescribed created also a more or less severe obstruc-tion of the right ventricular outlet to the aorta.The clinical significance of this feature should not

be underestimated, particularly in tetralogy where itmay be favoured by the increased right ventricularpressure and the aortic overriding. In this respect,Sellers and associates6 described two cases of isolatedventricular septal defect having tricuspid valve tissuetags which, from the anatomical point of view, pre-sented the possibility of left side obstruction. Thedanger of obstruction, however, in an isolated defectuncomplicated by pulmonary vascular obstructivedisease is remote, since the pressure gradient is usu-ally from left to right.The anatomical features of the fixed type of lesion

(cases 3 and 4) was the anchoring of the morerudimentary tissue tag to the interventricular septumby short chordae. The mobility was thus reduced incomparison with the other type. As a consequence,the fixed lesion produced an obstacle which decreasedthe size of the defect without involving the left ven-tricular outflow tract.From the surgical standpoint it seems wise to resect

the mobile variety at the time of the surgical repair,since it may result in left ventricular outflow tractobstruction if permitted to remain on the left ven-tricular aspect of the patch at the end of the proce-dure. In contrast, the fixed variety need not necessar-ily be excised. It may be left in situ and used as firmanchorage tissue for the placement of sutures securingthe patch.

References

1 Fischer EA, Thanopoulos BD, Eckner FAO, HastreiterAR, DuBrow IW. Pulmonary atresia with obstructed

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ventricular septal defect. Pediatr Cardiol 1980; 1:209-17.

2 Scott 0, Macartney FJ, Deverall PB. Anomalous acces-sory tricuspid valve tissue causing reduction in the size ofventricular septal defect [Abstract]. EurJ Cardiol 1976;4: 529.

3 Neufield RH, McGoon DC, DuShane JW, Edwards JE.Tetralogy of Fallot with anomalous tricuspid valvesimulating pulmonary stenosis with intact septum. Circu-lation 1960; 22: 1083-90.

4 Anderson RH, Allwork SP, Ho SY, Lenox CC, Zuber-buhler JR. Surgical anatomy of tetralogy of Fallot. JThorac Cardiovasc Surg 1981; 81: 887-96.

5 Gomes AS, Nath PH, Singh A, et al. Accessory flapliketissue causing ventricular outflow obstruction. J ThoracCardiovasc Surg 1980; 80: 211-6.

6 Sellers RD, Lillehei CW, Edwards JE. Subaortic stenosis

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caused by anomalies of the atrioventricular valves. JThorac Cardiovasc Surg 1964; 48: 289-302.

7 Riemenschneider TA, Goldberg SJ, Ruttenberg HD,Gyepes MT. Subpulmonic obstruction in complete (d)transposition produced by redundant tricuspid tissue.Circulation 1969; 39: 603-9.

8 Levy MJ, Lillehei CW, Elliott LP, Carey LS, AdamsP Jr, Edwards JE. Accessory valvular tissue causingsubpulmonary stenosis in corrected transposition of greatvessels. Circulation 1963; 27: 494-502.

9 Anderson RH, Becker AE, Gerlis LM. The pulmonaryoutflow tract in classically corrected transposition. JThorac Cardiovasc Surg 1975; 69: 747-57.

Requests for reprints to Dr G Thiene, Istituto diAnatomia e Istologia Patologica, Via Gabelli 61, 35100Padova, Italy.

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