Br Heart J 1992;68:481-4

Use of casts in the necropsy diagnosis of fetalcongenital heart disease

Andrew C Cook, Nuala L K Fagg, Lindsey D Allan

AbstractObjective-To evaluate a casting

technique in the interpretation of fetalcardiac anatomy.Design-In 32 fetuses, the echocardio-

graphic and cast features were comparedand correlated.Patients-Three normal fetal heart

specimens from spontaneous abortusesand 32 specimens from spontaneous or

induced abortions with congenital heartmalformation.Results-There was close correlation

between the echocardiographic andanatomical features in 32 abnormalfetuses studied. In some, additionalfeatures of diagnosis could be displayedon the cast and the relative sizes of thecardiac structures could be appreciatedand defined.Conclusions-With increasing echo-

cardiographic detection of congenitalheart disease in early prenatal life, an

increasing number of fetal heartspecimens of small size are dissected for

Department ofPathology, Guy'sHospital LondonA C CookN L K FaggDepartment of FetalCardiology, Guy'sHospital, LondonL D Allan

Correspondence to:Professor L D Allan,Department of Fetal

Cardiology, 15th Floor,Guy's Tower, London SE19RT.

Accepted for publication9 June 1992.

pathological confirmation. The use ofsilicone rubber casts to reproduce theinternal anatomy proved a useful addi-tion to dissection, providing a threedimensional model of the cardiac defect.

(Br Heart J 1992;68:481-4)

Fetal echocardiography has become establi-shed as a reliable technique for the evaluationof the normal and abnormal fetal heart. 1-3

Echocardiographic and anatomical correlationhas formed an important part of the learningexperience in this new field.34 The formation ofcasts of the cardiovascular system has beendescribed since the 16th century. Leonardo daVinci referred to the use of wax for casting thecavity of a bull's heart in his notebooks and a

number of other materials have been used.Thompsett achieved very accurate representa-

tion of the cardiac chambers by using resinsand then dissolving the surrounding tissues inacid.' As this involves destruction of theanatomical specimen, the technique has not

been generally applied to clinical practice.More recently, silastic polymers mixed with

Data on cases

GestationCase Echocardiographic diagnosis (weeks) Additional cast finding

1 Distal arch hypoplasia 20 Extent of hypoplasia defined2 HLHS, arch hypoplasia 20 1-5 mm VSD3 Critical AS 19 Coarctation4 Critical AS 20 Arch hypoplasia, bicuspid AoV5 Critical AS 23 Unicuspid AoV, coaretation6 Mitral atresia, DORV 23 Size of VSD and LV defined7 Critical AS 18 Imperforate AoV, intact atrial septum8 HLHS 22 Unicuspid AoV, coarctation9 VSD 23 Coarctation, isthmal hypoplasia10 Critical AS 21 Isthmal hypoplasia11 Critical AS, arch hypoplasia 18 Extent of hypoplasia defined12 Aortic atresia, Corr TGA 20 Coarctation13 HLHS 18 Aorta and LV size defined14 HLHS 19 Arch hypoplasia, coarctation15 Severe coarctation 20 1 mm subaortic VSD16 HLHS 19 Coarctation, arch size defined17 HLHS 22 'T'ubular aortie hypoplasia18 RV > LV, trisomy 13 20 Normal arch19 HLHS 21 Coaretation20 Normal heart, hydrops 26 Isthmal hypoplasia21 HLHS, VSD 20 'I'wo VSDs, coaretation, aortic override22 Critical AS 20 LV size defined23 Pulmonary atresia, IVS 23 Sinusoid identified24 HLHS, LAI, azygos vein 18 Azygos defined25 Critical AS 24 LV size defined26 HLHS 19 Coaretation. 2 mm subaortie VSD27 AVSD, DORV, LAI 19 Azygos vein defined28 Corr 'TGA, aortie atresia 23 Coaretation29 Corr 'VGA, Ebstein's 22 Arch hypoplasia30 Corr 'VGA, Ebstein's 22 Severe coarctation31 TGA, VSD 19 Corr 'TGA, severe arch hypoplasia32 Coarctation 19 Isthmal stenosis

HLHS, hypoplastic left heart syndrome; VSD, ventricular septal defect; AS, aortic stn(nosis; AoV, aortic valvc; DORV, doublc outlctright ventricle; LV, left ventricle; Corr ''GA, corrected transposition of the great arteries; RV, right vcntricle; I VS, intact vcntricularseptum; LAI, left atrial isomerism; ASVD, atrioventricular septal defect.

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Cook, Fagg, Allan

Figure 1 Casts of right and left ventricular cavities are photographed with their septalsurface against the background. Morphology, shape, and size of ventricles can becompared in this case of coarctation of the aorta in a 19 week fetus.

catalysts have been used in postmortem

material to study examples of congenital heartdisease and to assist in the interpretation ofspecimens after surgical reconstruction of car-

diac malformation.6 We adapted this methodfor use in the analysis of cardiac abnormalitiesin the fetus.

Patients and methodsThree specimens of normal fetal hearts fromspontaneous abortions were casted to evaluatethe cardiac anatomy. Of a series of fetalspecimens obtained after termination of preg-

nancy for congenital heart disease, 32 were

selected for silicone cast injection. The ges-

tational age of the cases studied was from 18 to26 weeks with a mean of 20-6 weeks. Both freshand formalin fixed specimens were used.Anatomical dissection was carried out toexpose the intrathoracic organs in situ. Exter-nal appraisal of the anatomy was performed. In

Figure 2 Arch anatomy can be compared in twofetuses of 19 weeks gestation.Coarctation of the aorta is shown on the left and a normal arch on the right. Thetransverse arch and arterial duct are of similar size normally with the pulmonary rootslightly larger than the aorta at its origin. In this example of coarctation, the transversearch is less than half the normal width and there is an acute angle between the isthmusand descending aorta at the site of a coarctation shelf. The origin of the pulmonaryartery is nearly twice the size of the ascending aorta.

cases where it appeared possible that castingwould improve the definition of cardiovascularanatomy, a small incision was made down-stream to the anatomical structure to be inves-tigated. The incision was in the left atrium in13, the aorta in 12, the pulmonary trunk in five,and other sites in five. Blood clots were washedout ofthe cavities and vessels with a water filledsyringe. The casting material used was a com-mercially available silicone rubber sealant(Dow Corning house seal). This compoundwas found to be self setting over a period of oneday in formalin. The material was injectedgently from a syringe through a small pipettepositioned in the incision. Distension of thechambers and vessels was observed as theinfusion took place. In some cases, the castingmaterial was massaged along the vessel understudy until it reached the descending aorta. Itwas important to ensure that vessels and cham-bers of interest were filled with the material toavoid artefacts. The heart and lungs wereremoved from the thorax 24 hours after the castinjection. The cardiac anatomy was then dis-sected according to a standard method.7 Thecast was removed carefully from the atrium,ventricle, and great artery in progressive order,preserving the integrity of valvar tissue,papillary muscles, and small vessels.

ResultsFigures 1-6 illustrate some examples of thespecimens that were obtained from the 35cases. The table lists the echocardiographicdiagnosis and the additional findings in thecases of congenital heart disease studied. Thecase illustrated in figs 1 and 2 left is one ofcoarctation of the aorta. The echocardiogra-phic findings at 19 weeks of gestation were theright ventricle larger than the left; the pulmon-ary artery larger than the aorta; and distal archhypoplasia in transverse sections. Figure 1compares the casts obtained from each ven-tricular chamber, clearly showing the rightventricle to be nearly twice the size of the left.Figure 2 right shows a normal aorta, aorticarch, pulmonary artery, and duct in a 19 weekspecimen. Normally the pulmonary artery isslightly larger than the aorta but in fig 2 left,this difference is seen to be much greater thannormal. The distal arch narrows considerablyafter the common carotid branch and theisthmus shows an acute angle at the junctionbetween the duct and the descending aorta.The coarctation shelf indents the posterioraspect of the cast at this point. Figures 3A, B,C, and D show some of the varieties of coarcta-tion which can occur. In the case illustrated infigure 3A, there is only a discrete shelf oppositethe junction of the duct with the aorta. Figure3B illustrates that there is isthmal hypoplasia ina fetus with a subaortic ventricular septal defectand a hypoplastic left ventricular cavity. Figure3C shows more diffuse transverse arch hypo-plasia extending from before the brachioce-phalic artery to the isthmus. Figure 3D showstubular hypoplasia from the aortic valve to theisthmus before the coarctation shelf. Figure 4shows a whole cardiac cast with mitral atresia

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Use of casts in the necropsy diagnosis offetal congenital heart disease

Figure 5 Renal veins are seen joining the venous systembelow the diaphragm. The azygos vein lay behind theaorta and connected to a left superior vena cava at itsjunction with the left atrium (arrow).

Figure 3 This series shows variation in arch abnormalities. (3A) Arch structures areof comparable sizes but a discrete coarctation shelf is seen indenting the cast in thejuxtaductal position. (3B) A castfrom the mitral valve to the descending aorta isshown. The left ventricle was hypoplastic although this is difficult to appreciate withoutthe right for comparison. Cast material has crossed a suboartic ventricular septal defect(arrow). Hypoplasia of the arch is limited to the isthmus and there is a mild coarctationlesion. (3C) The arch becomes hypoplastic just before the origin of the brachiocephalicartery and remains so until the junction with the arterial duct. (3D) Tubularhypoplasia of the whole aorta to the junction with the duct is seen, most obvious in theascending aorta.

Figure 4 Whole cardiaccastfrom the atria to thedescending aorta. Thepulmonary artery isdivided at its origin andreflected to the right todisplay the hypoplastic leftventricle. A trabecularand subaortic ventricularseptal defect are seen. Theaorta arises astride theventricular septum. Thedistal arch is hypoplasticand a coarctation lesion isalso seen.

and left ventricular hypoplasia, and a muscularsubaor-tic ventricular septal defect. The aortaarises astride the ventricular septum and thereis transverse arch hypoplasia before a coarcta-tion shelf. A visual understanding of the com-parative ventricular sizes can be readilyappreciated in the cast specimen. Figure 5illustrates a case in which there was interrup-tion of the inferior vena cava on echocardiogra-phic examination of the abdominal vesselsbelow the diaphragm in a 18 week fetus. Therewas a venous structure lying behind the aortathat could be seen on colour flow mapping tojoin a left sided superior vena cava at itsjunction with the left atrium. Figure 5 showsthe cast of an azygos system obtained from thisfetus, which correlated completely with theprenatal findings. This delicate vessel is oftendamaged or even destroyed on removing thethoracic viscera from the body. Figure 6 illus-trates a case in which there was a hypertrophiedright ventricle with a small cavity found onechocardiography at 24 weeks' gestation. Thepulmonary outflow tract was atretic from theinfundibulum to the pulmonary valve. The castinjection confirmed those findings but alsoshowed a large fistulous connection betweenthe left anterior descending coronary arteryand the trabecular portion of the right ven-tricular cavity. Measurement of the castedstructures and chambers showed a closecorrelation with those obtained by echocar-diography in all cases where measurementswere made.

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Figure 6 Small rightventricular cavityfrom thetricuspid valve to theatretic infundibulum(arrow). Left circumflexand anterior descendingcoronary arteries are seenarisingfrom the aorticroot. A sinusoidalconnection between themidtrabecular portion ofthe right ventricle and theleft anterior descendingcoronary artery is seen.

DiscussionThis newly described technique proved par-ticularly useful in the correlation of fetalechocardiography with pathological specimensin our series. The technique is simple and canbe applied routinely. It has the advantage ofmaintaining the integrity of the specimen itselfand producing a three dimensional picture ofthe cardiac cavities. Despite the small size ofthe fetal specimens, we achieved exquisitedetail of structures less than one millimetre insize. We found that casts enhanced the inter-pretation of morphology, displayed paths offlow, and avoided the distortion that can occurduring a standard pathological demonstration.Cast models were particularly useful as a teach-ing aid. Defects could be detailed in theirentirety by the cast. The frequency of aortic

arch lesions as underlying or associated find-ings in the hypoplastic left heart syndrome wasdemonstrated in cast material and the extent ofhypoplasia of the left ventricle and arch wasdefined.

Echocardiographic diagnosis could be con-firmed and in some cases extended-for exam-ple, in the case of the coronary artery sinusoid.More faithful representation of the cardiovas-cular system was obtained where casting wasperformed in situ; this is a practical techniquein the fetal specimen. We are currently assess-ing the possibility of using the cast modelto examine in closer detail the characteristicsof valve morphology in cases of fetal valvarstenoses.

In summary, casting has proved a usefuladdition to the morphological analysis of fetalheart specimens. It is easy and practical to use.It provides a three dimensional model that isideal as an aid to understanding the nature andextent of congenital heart malformations,particularly in the early fetus.

AC and LDA are supported by the British Heart Foundation.

1 Lange LW, Sahn DJ, Allen HD, Goldberg SJ, Anderson C,Giles H. Qualitative real-time cross-sectional echocar-diographic imaging of the human fetus during the secondhalf of pregnancy. Circulation 1980;62:799-806.

2 Kleinman CS, Hobbins JC, Jaffe CC, et al. Echocardio-graphic studies of the human fetus: prenatal diagnosis ofcongenital heart disease and cardiac dysrhythmias.Pediatrics 1980;65:1059-67.

3 Allan LD, Tynan MJ, Campbell S, Wilkinson J, AndersonRH. Echocardiographic and anatomical correlates in thefetus. Br Heart J 1980;44:444-51.

4 Allan LD, Crawford DC, Anderson RH, Tynan MJ.Echocardiographic and anatomical correlations in fetalcongenital heart disease. Br Heart J 1984;52:542-8.

5 Thompsett DH. Anatomical techniques. 2nd ed. London:Churchill, 1970:153-61.

6 Kilner PJ, Ho SY, Anderson RH. Cardiovascular cavitiescast in silicone rubber as an adjunct to postmortemexamination of the heart. Int J Cardiol 1988;22:99-107.

7 Devine WA, Debich DE, Anderson RH. Dissection ofcongenitally malformed hearts, with comments on thevalue of sequential segmental analysis. Pediatr Pathol1991;11:235-59.

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