angiographic signs in isolated valvular pulmonary stenosis

Ir J. Med. Sc. July, 1964, pp. 31%328 Illustrated Printed in the Republic of Ireland

ANGIOGRAPHIC SIGNS IN ISOLATED VALVULAR J'ULMONARY STENOSIS.*

PATRICK ~[cCANN, M.D., M. Rad., F.F.R., D.M.R.D.

SEAN BLAKE, M.D., M.Se., M.R.'C.P. (Lond.), M.R.C.P. (Edin.).

O..C. WARD, M.D., F.R.C.P.I., D:C.H.

Mater Miserivard~e Hospital, Dublin and

Our Lady's Hospital for Sick Children, Dublin

U NTI~L c~)mparatively rccently, pulmonary stenosis was considered r,are, except as part of Tetralogy of Fallot. This belief was based primarily on autopsy studies and antedated the widespread use of

special diagnostic procedures such as angiocardiography and cardiac eatheterisation. In recent years it has become apparent that its incidence is considerably higher than previously estimated and that it is in fact a common lesion. Nadas (1963) estimated that pulmonary stenosis with intact ventricular septum constituted 10:15 per cent of all cases of congenital heart disease who live beyond infancy and Campbell (1960) found an incidence of 10 per cent. In its severe form it may cause death ea sy in life. Since direct surgical treatment is now available early diagnosis and evaluation of the condition is a matter of great importance. In this respect angiocardiography has a valuable part to play, complementary to cardiac catheterisation and frequently yielding information unobtainable by any other method.

Early reports on angiocardiogmphy in pulmonary stenosis referred to the difficulty in visualising the stenosed valve (Dotter and Steinberg, 1951 ; Cooley, 1951) and the necessity of relying :on indirect signs such as delay in emptying of the right ventricle, post-stenotic dilatation of the main pulmonary ,a~tery and narrow peripheral pulmonary artery branches.. The difficulty was due to the fact that the early examinations were non-selective angiocardiograms, the dye being mann,ally injected into a peripheral vein. 'In addition films were taken in the antero- posterior projection only, with relatively few radiographic exposures per second.

5larder and Scott (1953) suggested the right ,anterior oblique projection for visualising the right ventricular outflow tract in profile. Jonsson et al. (1953) recommended selective injection of contrast medium into the right ventricle through a cardiac catheter and considered the lateral view the most useful. 1It is now geneeally accepted that selective angiocardiography is essential and that the dye must be injected under very high pressure. If exposures are to he in one plane on]y this must be the lateral, but ideally there should be simultaneous biplane filming. The rate of filming should be six per second or more.

*Based on a communicat ion to the Section of Radiology of the Royal Academy of Medicine in Ireland by Patr ick McCann, M.D. on 25th March, 1964.

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320 IRISH JOURNAL OF MEDICAL SCIENCE

If it is less than four per second, the infundibulum of the right ventricle may be visualised only in systole and mistaken for infundibular stenosis, or valvular stenosis might evade detection if all films happened to be taken in diastole. Excellenr descriptions of direct angiographic signs of pulmonary stenosis by these methods have been given by Kjellberg ect al. (1959) and Shanks and Kerley (1962).

Material and Method~*

A n g i o c a r d i o g r a p h y h a s been car r ied ou t on 50 eases o f i so la t ed va lvu l a r p u l m o n a r y s tenos is . The re were 29 females a n d 21 males . The i r ages r a n g e d f rom 5 m o n t h s to 32 y e a r s w i t h a n average age o f 11.4 yea rs . The m e t h o d o f choice, a n d t he one u s e d as a r o u t i n e in b o t h hosp i ta l s , c o n s i s t s o f a select ive in jec t ion o f c o n t r a s t m e d i u m in to t h e r i gh t ventr ic le , u s i n g a p r e s su re in jector . T h i s is done fol lowing ca the t e r i s a t ion o f t he r i gh t h e a r t a n d p u l m o n a r y a r t e ry , w i t h p re s su re record ing a n d oxygen s amp l ing in t he v a r i o u s chamber s . The C o u r n a n d ca t he t e r u s e d for t h e s e m e a s u r e m e n t s is t h e n r ep laced b y a th in -wa l l ed c a t h e t e r w i t h o u t a t e r m i n a l opening , b u t w i th sub- t e r m i n a l s ide-holes . The t h i n wal l a l lows of a larger l u m e n for a g iven e x t e r n a l d i a m e t e r a n d t he presence o f s u b t e r m i n a l holes r a the r t h a n a n end -open ing ensu res t h a t t he r e is p rac t i ca l ly no t e n d e n c y for t h e ca the t e r to recoil ou t o f t he r igh t vent r ic le du r ing p re s su re inject ion. I n gene ra l t h e l a rges t c a the t e r wh ich can be inse r t ed in to t he ve in is used . I t is m a n i p u l a t e d in to t he r igh t vent r ic le , a n d t h e p a t i e n t is t h e n p laced in t he t r ue la te ra l pos i t i on w i t h t h e a r m s s t r e t ched cephaled . Th i s m a y have to be modif ied , to some ex ten t , i f one a r m c o n t a i n s t he c a t h e t e r i n se r t ed t h r o u g h a " c u t - d o w n " in t he an t e - cub i t a l fossa . F r o m a pu re ly r ad iog raph ic po in t o f view, i t is p re fe rab le i f a n app roach h a s been m a d e f rom a ve in in t he groin , a n d s o m e of our cases h a v e been done in t h i s way . However , i t is u s u a l l y eas ie r to cu t down on t he a r m , a n d to ea the te r i se t he r i gh t ven t r i c l e a n d p u l m o n a r y a r t e r y w i t h th i s approach .

Genera l a n a e s t h e s i a was u s e d in al l c a se s in t he ch i ld ren ' s hosp i t a l ; i t was induced a f te r c o m p l e t i o n o f t he ca t he t e r s t u d i e s wh i ch were done u n d e r seda t ion . I n t he Mate r Hosp i t a l , ear l ier a n g i o c a r d i o g r a m s were done u n d e r genera l anaes thes ia , b u t more recen t ly , s a t i s f ac to ry r e su l t s h a v e b e e n . o b t a i n e d in a d u l t s a n d co-opera t ive ch i ldren u s i n g seda t ion only.

The r a p i d in jec t ion o f c o n t r a s t m e d i u m is ob ta ined b y u s i n g t he " Ta l l ey " p re s su re in jec to r (Pa t t i son a n d Somervi l le , 1958). A p ressu re o f 100 to 120 p o u n d s pe r squa re inch w a s gene ra l l y used . T h i s e n a b l e d a bo lus o f dye to be in j ec ted in to t he r i gh t vent r ic le w i t h i n a b o u t 2 seconds , d e p e n d i n g on t he size o f t h e ca the t e r wh ich could be used . The c o n t r a s t u sed was H y p a q u e 85 ~o in the ch i ld ren ' s hosp i ta l , a n d Urograf in 76 % in t h e Ma te r Hosp i t a l . The re w a s no pa r t i cu la r r e a son for t h e difference excep t c u s t o m in t he two hospi ta l s . T h e y are v e r y s imi la r in chemica l c o n s t i t u t i o n and v iscos i ty . H y p a q u e 85 % is m a d e u p o f 28 % s o d i u m d ia t r i zoa te a n d 57 % m e t h y l - g l u e a m i n e - d i a t r i z o a t e . Urograf in 76 % is m a d e u p o f 10 % s o d i u m d ia t r i zoa te a n d 66% m e t h y l g h i c a m i n e d ia t r izoa te . T he fo rmer c o n t a i n s 0.43 g r a m s o f iodine pe r m]. t he ' l a t t e r 0.37 g r a m s pe r ml . so t h a t t he r e is v e r y l i t t le d i f ference in radio-opaci ty . As r ega rds p o t e n t i a l r a t e o f in jec t ion, w h i c h is equa l in i m p o r t a n c e to iodine con ten t , Laws a n d F o x (1960) f ound no s ign i f ican t difference be tween t he se two compounds . The dose u sed was �89 to } c.e. pe r p o u n d u p to a m a x i m u m o f 50 e.c. in adu l t s .

Two d i s t i nc t rad iographic t e c h n i q u e s were u sed in th i s ser ies o f examina t i ons . I n t he Ma te r H o s p i t a l conven t iona l r ad iograph ic m e t h o d s were employed , u s ing a m e c h a n i - cal ser ia l f i lm change r to ob t a i n a n u m b e r o f f i lms in quick success ion . I t al lows a max i - m u m o f 6 f i lms pe r second, b u t in p rac t i ce m o s t cases were e x a m i n e d a t 4 f i lms pe r second. Th i s m e t h o d prov ides exce l len t r ad iograph ic deta i l a n d uses large fi lms (14 # X 14") su i tab le for d e m o n s t r a t i n g t he whole a d u l t ches t i f necessary . I n Our L a d y ' s Hosp i t a l , on t he o the r hand , an irr~ge in tens i f ie r was used, a n d a 35 m . m . e ine-f i lm o f t he fluoro- scopic i m a g e t a k e n du r i ng a n d a f t e r t h e in ject ion. Th i s m e t h o d enab les up to 50 in- d iv idua l f r a m e s to be t a k e n per second. I n prac t ice 24 were f o u n d suf~cient in m o s t cases, a n d 32 in smal l babies . T he d i s a d v a n t a g e s o f th i s m e t h o d are t h a t t he flue de ta i l ob t a inab l e b y conven t iona l r a d i o g r a p h y c a n n o t be equa l l ed on eine-film, a n d t he a r ea w h i c h can be e x a m i n e d is l i m i t ed b y t he field-size o f t h e image in t ens i f i e r - - in t he case o f our appa ra t u s , a circle o f 5" d i ame te r . Th i s is a d e q u a t e for sma l l ch i ldren a n d pa r t i cu l a r l y for select ive e x a m i n a t i o n o f t he r igh t ven t r i cu l a r outf low t rac t , w h e n t he whole h e a r t ne ed n o t be v isual i sed . I n t he e x a m i n a t i o n o f p u l m o n a r y s tenosis , t he c ine m e t h o d in our op in ion is super ior , ~s t he large n u m b e r o f f r ames ava i l ab le pe r second is e x t r e m e l y va luab le a n d m o r e t h a n c o m p e n s a t e s for t h e loss o f deta i l per i nd iv idua l " p ic tu re ".

A f u r t h e r po in t o f t e chn ique is the pos i t i on ing of the pa t i en t . W e find t he la te ra l v iew the m o s t va luab l e single project ion, b u t in some of t he earl ier e x a m i n a t i o n s t he an te ro - pos te r io r v i ew was done. This was nece s s i t a t ed b y t he fac t t h a t a p res su re in jec tor was

ANGIOGRAPHIC SIGNS IN 2SOLATED VALVULAR PULMONARY STENOSIS 321

not available to enable a rapid selective injection to be made in to the r ight ventricle t h rough a catheter . These pa t i en t s had manua l inject ions th rough a cannula or shor t wide ca the te r into an a r m vein. I nev i t ab ly by this m e t h o d there is some filling of the r ight a t r i u m a t the t ime the r igh t vent r icular outflow t r ac t is filled, and if the lateral project ion is used, the p u l m o n a r y valve area m a y be obscured b y the r ight atrial appendage. The projections used in th is series of cases were : - -

Antero-pos ter ior only . . 9 c a s e s Lateral on ly . . . . 33 , ,

Both views . . . . 8 ,,

Findings The essenti,al angiographic sign of pulmonary valve stenosis is visual-

isation of a conical or domed membrane formed by the fused valve cusps. This membrane bulges upwards into the pulmonary artery during systole. In all except four of the lateral angioeardiograms in the present series, this systolic dome w.as demonstrated. The "four excep- tional cases were all mild having right-ventrieular systolic pressures of 37,44,44, and 45 m.m. l=[g. In cases of severe stenosis, the fused cusps are so thick and rigid that the dome remains bulging upwards during diastole as well as systole. This occurred in nine of the present series of lateral angiocardiograms. In most cases, however, the cusps are mobile, and arc seen in their normal position in diastole (Fig. 4). When seen in this position only, the appearance could be taken as ~ormal unless definite valve thickening is seen. Thus, it is important to film at a sufficiently rapid rate to ensure that systolic appearances are available. OT our lateral angiocardiograms, twenty-five showed the valve cusps in a normal diastolic position. In some cases, the cusps may have an irregular appearance in diastole, presumably when they are moderately rigid and hence assume an intermediate position between the fixed upward dome and the normal diastolic position. This was observed in seven of the lateral examinations.

The valve orifice is usually central, but may be eccentric, and varies in size with the severity of the case. Apertures as small as 2 m.m. in diameter have been noted at surgery in our most severe cases. The orifice is frequently outlined .at angiocardiography by ,a jet of dye forced through during systole and the width of the jet gives an indica- tion of the size of the opening. The jet is best seen on early films of the angiographic series. We were able to visualise it in 22 of the lateral angiocardiograms including almost all the cine,angiograms. The jet appearance may to some extent be fortuitous, depending on the timing of a particular radiographic exposure in relation to the phase of the cardiac cycle and the start of the selective injection. The higher per- centage of jets seen on the eine-angiograms suggests that timing is an important factor. Cardiac failure is also an important factor; of four very severe cases which showed delayed emptying of the right ventricle and evidence suggestive of right ventrieular failure, only one showed a jet and this was poorly delineated. The clarity with which a jet is demonstrated is not related to the severity of the stenosis.

Definite valve thiekening was seen in 21 of the series of lateral angiocardiograms and doubtful thickening in three further ones. There was no apparent correlation between the severity of the stenosis and the incidence of detectable valve thickening.


FIG. 1.--Lateral film of selective angiocardiogram during systole. Note dome formed by fused valve cusps, jet of contrast medium forced through narrowed orifice, and fusiform post-stenotic dilatation of

the pulmonary artery.

Fie. 2 . - -Fi lm of same pat ient during diastole. Valves have moved towards the normal diastolic position, and are seen to

be thickened.

FIG. 3.--Another case showing dome, jet, post-stenotic dilatation, and considerable narrowing in infundibular

region due to muscle hypertrophy.

FIe. 4.--Same patient showing that valves have returned completely to normal position in early diastole. No valve thickening.

ANGIOGRAPHIC SIGNS IN (ISOLATED VALVULAR PULMONARY STENOSIS 323

Angiocardiography may demonstrate evidence of hypertrophy of the right ventricle especially of the erista supraventricularis and its parietal and septal bands. This secondary infundibular hypertrophy is particularly important as it must be distinguished from true infundibular stenosis which is a primary abnormality. Hypertrophy can cause marked narrowing of the outflow tract of the right ventricle, particularly toward~s the end of systole, but can be distinguished by the fact that unlike infundibular stenosis it allows complete dilatation in diastole. The importance of a rapid series of exposures is obvious, .and in this context, cine-angiography is clearly the best method. Infundibular hypertrophy was seen in 26 of the cases filmed in the lateral position and in general was more marked in the severe cases (as was suggested by W,atson e~t al . , 1960). Exceptions to this were the four cases referred to earlier which exhibited delayed emptying of the right ventricle, and evidence of failure. In these, narrowing of the infundibulum was absent throughout the cardiac cycle; it may be ~hat this is a sign of a failing ventricle with increased diastolic volume. We were unable to confirm the suggestion (Watson eta/., 1960) that systolic infundibular narrowing was of longer duration in relation to the cardiac cycle in severe cases. In many instances it was impossible to assess this feature as extra- systoles are very common during injection of dye into the right ventricle and these alone will have a marked effect on the duration of the systole. Kjellberg er al. (1959) reported a similar finding.

The nine ang.ioeardiograms which were done using the antero-pos,terior projection ~only were the least satisfactory of the series. In seven cases the investigation was aarried out during the early days of angiocardiography when a pressure injector and special catheters were not available and manual injection was made into a vein. In a further case the catheter could not be positioned satisfactorily in the right ventricle. Of the total of fifteen angiocardiograms done in the antero-posterior plane, only four showed a definite systolic dome while a further one showed a doubtful dome. In no case could valve thickening or mobility be assessed. Only three cases showed a jet. Infundibular hypertrophy could not be satisfactorily assessed in any case.

The habitus of a patient appears to play a part in the visualisation of the signs of pulmonary stenosis in the antero-posterior view. ~n a flat- chested person the right ventricular outflow tract and the pulmonary artery run more upwards than posteriorly, but when the chest is deep, the pulmon:ary artery runs more dorsally and overlaps the valve region. Gross right ventricular hypertrophy also causes the pulmonary artery to assume a dorsal course. Brock ~(i1957) :describes how enlargement of the right ventricle upwards and anteriorly "like a pouter pigeon's chest " carries the .origin 'of the pulmonary artery up with .it, so that the pulmonary trunk comes to lie approximately horizontally. In these cases there is no satisfactory visualisa~ion of pulmonary stenosis on an antero-posterior projection.

Post-stenotic dilatation of the pulmonary artery is one of the most constant signs of valvular pulmonary stenosis and was present in all our cases with the excepti, on of four mild ones. It was well demonstrated in both the antero-posterior and lateral projections including those cases


FIG. 5 . - -Another pa t ient i l lustrat ing part icularly the saccular type of post-stenotic dilatat ion, bulging upwards.

Fro. 6.--Case where the individual cusps forming the dome can be

identified.

ANGIOGRAPHIC SIGNS IN ISOLATED VALVULAR PULMONARY STENOSIS 325

in which a manual injection was used and which were unsatisfactory in other respects. In the main pulmonary artery it was of two principal types, fusiform and saccular. The fusiform type was the commoner. ]n the saecular type the pulmonary artery bulged mainly upwards and in these cases the dilatation was very inconspicuous and in some cases invisible in the standard postero-anterior chest film (McCann and Blake, 1963). There was no correlation between the degree of post-stenotic dilatation and the severity of the pulmonary stenosis.

The pulsation ,of the pulmonary artery was studied by comparing systolic and diastolic films. The cine angiograms were particularly helpful for this purpose and Fig. 7 shows superimposed tracings of the systolic and diastelic positions of the infundibulum, valve ring and pulmonary artery. Marked expansion of the pulmonary artery in systole was usually shown. This varied considerably in degree and did not appear to be proportional either to size of the main pulmonary artery or to right ventricular pressure. Fabricius (1959) using kymography also found no correlation between right ventricular pressure and the degree of pulsation ,of the pulmonary artery. The expansion in most cases is due to considerable downward movement of the lower wall of the pulmonary artery (in association with the systolic downward movement of the pulmonary valve ring) while the position of the upper wall usually remains unchanged.

A point of interest in angiography of pulmonary stenosis is its sensi-

2

t . .

FIG. 7.--Superimposed tracings of systolic and diastolic outlines of a lateral angiogram. Heavy line is the systolic outline. 1. Indicates the sternum. 2. Indicates the dilated pulmonary artery. 3 and 4. Diastolic and systolic positions respectively of pulmonary valve, showing extent of downward movement in systole. 5 and 6. Width of infundibular

outline in diastole and systole respectively.


tivity as a test of mild stenosis, although, in practice, few angiocardiograms are done in this type of case. :Campbell (1960) made calculations of the cross-sectivnal areas of the pulmonary orifice in valve stenosis and concluded that if a systolic gradient is detected at the valve, the cross-sectional area must be reduced to about 25 per cent of normal. One would therefore expect that in the presence of a gradient, even if small, the angiocardiograms should demonstrate valve stenosis. In those cases which were studied by cine-angiography all showed evidence of pulmonary stenosis. The mildest case had a systolic pressure in the right ventricle .of only 36 m.m. Hg., and it showed a definite dome, but no apparent jet, valve thickening or impairment of valve cusp mobility. In the cases studied by sconventional angiocardiography, there was one case with a systolic pressure of only 46 m.m. Hg. which showed a dome, a jet, valve thickening and post-stenotic dilatation, but there were four other mild cases with right ventrieular pressures ,of 37 to 45 m.m. Hg., in which there were no detectable signs of stenosis. I t may be that for the diagnosis of mild cases, the cine technique is more sensitive than the conventional method.

Discussion

Angioeardiography, when properly performed, can now provide clear and direct evidence of pulmonary stenosis and it is a very sensitive diagnostic technique. In experienced hands, serious complieatiolls are exceedingly rare.

The great majority of cases of isolated pulmonary stenosis have already been diagnosed before angiocardiography is carried out, as pressure readings have usually been obtained in the right ventricle and pulmonary artery and ~vithdrawal tracings made to show a pressure gradient across the pulmonary valve. In addition, associated lesions such as central shunts have been excluded by appropriate blood-oxygen estimations. Angiographie demonstration of pulmonary stenosis is therefore in most eases a confirmatory investigation and a demonstration of the anatomical detail of a lesion already known to exist. Nadas (1963) expressed the opinion, that," although angiocardiography is a ma~o~ificent teaching and research instrument in the study of pulmonic stenosis, its practical use is limited at present, and it is overshadowed by cardiac catheterisation ". He considered the cardiac catheter more useful than angiocardiography in determining the nature of the stenosis.

However, in certain circumstances, angiocardiography is positively indicated : --

(1) When the right ventricular pressure is approximately at systemic level, and Tetralogy of Fallot must therefore be excluded with certainty.

(2) Where the level of the stenosis (whether valvular, infundibular or ,both) is in doubt after catheterisation.

(3) When the catheter cannot be made to enter the pulmonary artery to establish the presence of a systolic pressure gradient.

The differential diagnosis of Fallot's Tetralogy and isolated pulmonary stenosis is the most valuable function of selective angio-

ANGIOGRAPHIC SIGNS IN ;ISOLATED VALVULAR PULMONARY STENOSIS 327

cardiography in these cases. During the period of collection of the present series, there were two cases which were considered after clinical and catheter studies to be examples of isolated pulmonary valve stenosis, but were found at thoracotomy to be cases of.Fallot's Tetralogy. In fact, one of these had had an angivcardiogram, but this was in the relatively early days of angiocardiography and it was technically unsatisfactory. It was not selective, the contrast medium was injected manually and radiographs were taken in the antero-posterior position only. !In our experience, selective angiocardiography using a pressure injection into the right ventricle and with rapid filming w.ill always reveal Fallot's Tetralogy if present. It may be taken as a general rule, then, that when the right ventricular pressure is found to be in the systemic range, it is advisable to look for evidence of Fallot's Tetralogy by angiocardiography. For absolute safety "systemic range " should be taken as systemic pressure (measured in aorta or upper limb arteries) plus or minus 30 m.m. Hg. (Gotzsche e~ al., 1952).

Stenosis of the outflow tract of the right ventricle may be at valve level or in the infundibulum .or both. The distinction may be made at catheterisation from the appearance of the pressure tracing obtained while the catheter tip is being withdrawn from the pulmonary artery to the right ventricle. However, not infrequently the pressure tracing may be equivocal. This is especially likely to be the case where there is infundibular stenosis without a distinct and sizeable infundibular chamber. Again, in the combined lesion the catheter may fail to dis- tingnish true infundibular stenosis from secondary hypertrophy of the infundibular muscle. I f there are numerous ectopic beats, the pressure tracing may be very difficult to interpret. In the present series some doubt about the site of stenosis ~vas recorded in 23 cases, though in most of these a probable site was suggested and this usually proved to be correct.

In occasional cases of pulmonary stenosis it may be impossible to pass the catheter into the pulmonary artery. It is more likely to occur when the stenosis is very severe, and in small babies when catheterisation is carried out through a femoral vein. This occurred in six cases of our series. In these circumstances angiocardiography is essential to establish the diagnosis.

Summary The angiocardiographic findings in a series of 50 cases of isolated

pulmonary stenosis are described. The distinctive sign is systolic ballooning of the membrane formed by the fused valve cusps. Other helpful signs are jet formation, valve thickening, post-stenotic dilatation of the pulmonary artery and secondary stenosis in the region of the infundibulum. The place of angiocardiography in the diagnosis of pulmonary stenosis is discussed.

: . A c k n o w l e d g e m e n t s

We wish to thank all the clinicians of the Mater and[ Our Lady's Hospitals, and particularly Dr. Malley and Professor Counihan for penuission to include their cases, Thanks are also especially due to Professor E. O'Malley and Mr. Barry O'Donnell for operative findings.


References

Brock, R. (1957). The Anatomy of Congenital Pulmonary Stenosis. Cassell and Company, London.

Campbell, M. (1960). Brit. Heart J., 22, 101. Cooley, R. N. (1951). J. Fac. Radiologists, 2, 249. Dotter, C. T. and Steinberg, I. (1951). Angiocardiography. Paul B. Hoeber Co. Inc.,

New York. Fabricius, J. (1959). Isolated Pulmonary Stenosis. Munksgaard, Copenhagen. Gotzsche, H., Pederson, A., Hansen, A. T., Eskildsen, P. (1952). Acta Med.

Sca.ndinav/ca, supp. 266, p. 445. Jonsson, G., Broden, B. and Karnell, J. (1953). Acta Radiologica, 40, 547. Kjellberg, S. R., Mannheimer, E., Rudhe, U., Jormson, B. (1959). Diagnosis of

Congenltal Heart Disease. Year Book Publishers Inc., Chicago. Laws, J . W. and Fox, J. G. C. (1960). Brit. J. Radiol., 33, 119. McCann, P. and Blake, S. (1963). J . I .M.A . , LII, 181. Marder, S. M. and Scott, W. G. (1953). Radiology, 60, 797. Nadas, A: S. (1963). Pediatric Cardiology W . B . Saunders Co., Philadelphia and

London. Pattison, J . N. and Somerville, W. (1958). Brit. Med. J., 11, 1037. Shanks, S. C. and Kerley, P. (1962). Textbook of X-ray Diagnosis. H. K. Lewis & Co. Watson, H.. Pickard, C., Lowe, K. G. and Hill, G. W. (1960). Brit. Heart J., 22, 706.

angiographic signs in isolated valvular pulmonary stenosis

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