British Heart Journal, I973, 35, II90-I I95.

Persistent left fifth aortic arch in manReport of two cases

T. Izukawa, M. E. Scott,' F. Durrani, and C. A. F. MoesFrom the Departments of Cardiology and Radiology, The Hospitalfor Sick Children, Toronto, Canada

Two cases ofpersistent leftfifth aortic archforming a congenital double lumen aortic arch have been confirmedat necropsy. In the first case, the diagnosis was suspected during life after aortography. An unusual vesselran inferior and parallel to the aortic arch from the innominate artery to the left subclavian artery. It laysuperior to the pulmonary artery.

Both cases were associated with other cardiovascular anomalies. The first case had a persistent ductusarteriosus, and a small membranous ventricular septal defect; the second, coarctation of the aorta, persistentductus arteriosus, bicuspid aortic valve, and a single right coronary artery.

There is disagreement about the existence of thefifth aortic arch in man. In the cat embryo, Hunting-ton (I9I9) depicts a fifth arch forming a vascularchannel beneath the fourth arch. Brown (I9I3) inthe cat embryo, and Buell (I922) in the chickembryo have described the existence of the fiftharch. Congdon (1922) reported that endothelialsprouts arising from the aortic sac ventrally andfrom the descending thoracic aorta correspond tothe upper and lower ends of the fifth arches in man.Sissman (I968) and Hamilton, Boyd, and Mossman(I962) allege that the status of the fifth aortic archesis uncertain. Balinsky (i965), Arey (i965), Langman(i969), and Duckworth (I967) either deny theexistence of the fifth aortic arch in mammals, or be-lieve that it is only present transiently if it does exist.Van Praagh and Van Praagh (I969) described the

first case of duplication of the aortic arch and sug-gested that the smaller caudal arch or 'subway'represented the fifth aortic arch. In this presenta-tion, we describe, to the best of our knowledge,the first case of a persistent fifth aortic arch diag-nosed during life and a third example of this raremalformation in which there were two completeaortic arches of almost equal size arising anterior tothe trachea.

Case reportsCase IA female infant, 44 months old at the time of death, wasborn prematurely at 32 weeks' gestation weighing I705 gReceived 13 June 1973.1 Present address: Craigavon Area Hospital, Craigavon, Co.Armagh, Northern Ireland.

after an assisted breech delivery. The Apgar score was I.Intensive resuscitation was necessary. Initially, clinicalfindings and chest x-ray were compatible with the diag-nosis of respiratory distress syndrome. Respiratorydifficulty persisted, and from the end of the first weekshe required assisted ventilation by intermittent posi-tive pressure. She also had convulsions due to hypogly-caemia and hypocalcaemia.

Case 1 6 .9-72

I II Ill AVR AVL AVF

-AAL

RV3 VI V2 V

a-|' ....| 1....,.....

V5 V6

FIG. I Case I. Electrocardiogram with evidence ofright atrial hypertrophy and combined ventricularhypertrophy.

II

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Persistent leftfifth aortic arch in man 1I9I

In the second week of life a systolic murmur was notedalong the left sternal border and she developed conges-tive cardiac failure. A chest x-ray at this time showedcardiomegaly and pulmonary plethora. An electro-cardiogram showed right atrial hypertrophy and com-bined ventricular hypertrophy (Fig. I). Clinically adiagnosis was made of persistent ductus arteriosus and/orventricular septal defect with pulmonary hypertension.She was treated with digoxin and diuretics.The infant showed an inability to swallow and ab-

normal neurological responses. Tube feeding was re-quired throughout her life because of aspiration when-ever an attempt was made to bottle feed. The dysphagiawas attributed to neuromuscular disorder. A bariumswallow failed to show any compression on the oeso-phagus from a vascular ring. An electroencephalogramshowed non-specific and generalized abnormal changes.At the age of 3 months, a cardiac catheterization was

carried out because of the persisting heart failure andcardiomegaly. The presence of a moderately large per-sistent ductus arteriosus and a small ventricular septalTABLE Cardiac catheterization dataSite

Superior vena cavaRight atriumInferior vena cavaRight ventridePulmonary artery

Left atriumPulmonary vein (left)Left ventricleDescending aorta

Approximate pulmona

02 Saturation (%) Pressure (mmHg)(breathing 28% 02) Phasic Mean6i a=I552.5 V= II 6667382

9292

75/875/34a= ioV= 12

50

8

9I 94/993 95/50 62

ry to systemic blood flow ratio = 2-9: I

FIG . 2 Case i. Aortogram. Three parallel horizontal channels are seen in this lateral view.From the upperfourth aortic arch (IV) arisefrom front to back, the innominate artery (Inn A),the left common carotid artery (LCCA), and the left subclavian artery (LSA). The middlechannel is the persistent left fifth aortic arch (V), and the lower channel is the persistent ductusarteriosus (PDA). The catheter lies in the descending aorta (D. Ao).

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1192 Izukawa, Scott, Durrani, and Moes

defect was confirmed (Table). There was a I2 per centrise in oxygen saturation from the superior vena cava tothe right ventricle and a 9 per cent rise from the rightventricle to 82 per cent in the pulmonary artery. Thepulmonary venous and systemic saturations were 92 and93 per cent, respectively. The pulmonary to systemicflow ratio was approximately 2-9: I.There was pulmonary hypertension with the main

pulmonary artery pressure at 75/34 mmHg (mean 5ommHg). The aortic pressure was 95/50 mmHg (mean62 mmHg).A left ventricular angiocardiogram revealed a small

aneurysm of the membranous portion of the interven-tricular septum with a small defect at the apex of theaneurysm. An injection of contrast medium into the

persistent ductus arteriosus opacified the pulmonaryartery and descending aorta. There was also retrogradefilling of the aortic arch, and an unusual vessel betweenthe aortic arch and the persistent ductus arteriosus wasnoted. An aortogram revealed a normal left aortic archwith normal brachiocephalic arteries and a persistentductus arteriosus in the normal position. Again, a sep-arate channel running parallel to the undersurface of thearch was seen arising from the aorta just beyond theorigin of the innominate artery to rejoin it at the level ofthe left subclavian artery (Fig. 2) (Moes and Izukawa,I973, unpublished observations).

Shortly thereafter, the persistent ductus arteriosus,which measured 4 mm in diameter, was surgically ligated.Dissection along the aortic arch revealed broadening and

FIG. 3 Case I. Specimen to show the two aortic arches; the upper channel has been opened toexpose the bar of tissue ( t ) separating the left fifth aortic arch situated posteroinferiorly (V).The tinnomnnate artery (Inn A), left comnon carotid artery (LCCA), and left subclavian artery(LSA) arise from the left fourth aortic arch.

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flattening from the level of the innominate artery to theleft subclavian artery.The infant survived operation, but had recurrent

aspiration pneumonias and died at 4j months of age.

Necropsy There was an absence of thymic tissuegrossly and on microscopy.The ascending aorta was 20 mm in internal circum-

ference as compared to the larger main pulmonary trunkof 30 mm in circumference. The great arteries were nor-mally related. The brachiocephalic arteries arose fromthe dorsal aspect of the left aortic arch in the usual orderof innominate artery, left common carotid artery, andleft subclavian artery. The aortic arch at the innominateartery level measured I5 mm in internal circumferenceand the descending aorta also measured I5 mm in cir-cumference. Internally, the aortic arch channel frombeyond the origin of the innominate artery to the leftsubclavian artery was divided into an upper and dorsalchannel (measuring 4-5 mm in internal diameter approxi-mately) and a lower and ventral channel measuring3-5 mm in internal diameter. The channels, which weresymmetrical, were separated by a horizontal bar oftissue from anterior to posterior aortic wall along theapex of the arch (Fig. 3). The diameter of the aorta wasincreased at the site of the aortic end of the previouslyligated ductus arteriosus.The aortic valve and coronary arteries were normal.

The interventricular septum was intact and there was notrace ofthe defect in the membranous septum, which hadclosed spontaneously. The foramen ovale was patent as a4 mm slit anteriorly.There were scattered areas of bronchopneumonia,

atelectasis, and haemorrhage in the lungs. The brain wasoedematous withsofteningand cystic formation anteriorlyalong the lateral ventricles.

Case 2A male newborn, weighing 2900 g, was admitted to thehospital 7 hours after delivery. He was the fifth child ofa 42-year-old woman who had had a severe attack of'influenza' during the eighth week ofpregnancy.

In the third trimester she developed hydramnios andthe membranes had ruptured during the 36th week ofpregnancy. Labour was induced 7 days later because offoetal distress. One minute after delivery the Apgar scorewas 3. The baby required resuscitation and was deeplycyanosed until placed in 70 per cent oxygen.

Physical examination revealed a slightly cyanosedinfant. The face was peculiar, with small eyes, low-setears, and a right-sided facial palsy. The neck was shortand the left hand malformed. The heart rate was i6o/minute and the respiratory rate 46/minute with sub-costal retraction. The liver edge was 2 cm below thecostal margin and the tip ofthe spleen was palpable. Thefemoral pulses were very weak. The praecordium washyperdynamic. The first heart sound was normal; thesecond was loud in both aortic and pulmonary areas andsplitting was not discernible. A grade 3/4 ejection systolicmurmur was audible over the lower praecordium and inthe left axilla.

The chest x-ray showed a large heart with a cardio-thoracic ratio of 65 per cent. There was slight accentua-tion of the vessel markings. The electrocardiogram(Fig. 4) showed sinus rhythm, and hypertrophy of bothatria and right ventricle; the mean frontal QRS axiswas + 1400 and the T wave axis was -I5°.

Cose 2

I I1 11

8 870

J444VrAL4*L1^io*'uL$-

III AVR AV L AV F

VI V2 V3 V4 VS

FIG. 4 Case 2. Electrocardiogram reveals rightaxis deviation of the frontal QRS axis (140 degrees),right atrial hypertrophy, and right ventricular hyper-trophy.

The clinical diagnosis was heart failure due to coarcta-tion of the aorta, probably associated with a more com-plex cardiac malformation. Pulmonary infection wasconsidered a probability and cerebral damage a possi-bility. The infant was treated in an incubator with 40per cent oxygen, intramuscular digoxin, frusemide, andvitamin K, and intravenous antibiotics and sodiumbicarbonate. Before further investigations could be per-formed the baby died.

Necropsy Emination of the heart revealed slightright ventricular hypertrophy. No septal defects werepresent, but the foramen ovale was probe patent. Theaortic valve was bicuspid with no discernible raphe torepresent a third commissure. A single coronary arteryarose from the right anterior sinus ofValsalva. The originofthe absent left coronary artery was represented only bya shallow dimple on the floor of the remaining sinus ofValsalva. No coronary artery arose from the pulmonaryartery.The ascending aorta measured 13 mm in internal cir-

cumference and was normally related to, but muchsmaller than, the main pulmonary artery (internal cir-cumference 25 mm). At the origin of the innominate

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1194 Izukawa, Scott, Durrani, and Moes

artery, the aortic arch divided into two separate channelsof equal size (internal circumference of 6 mm in eachcase: Fig. 5). The left common carotid artery and leftsubclavian artery arose, respectively, from the middleand terminal portions of the upper aortic arch. Immed-iately distal to the point where the two arches reunitedthere was a deep indentation in the left side of the aorta,at which point the internal circumference was reducedto 4 mm. Distal to this coarctation, a large persistentductus arteriosus (internal circumference i6 mm) con-

nected the pulmonary artery and descending aorta(Fig. 5).

Histological examination confirmed the two arches tobe entirely separate, each having its own adventitialsheath.

DiscussionIn the mammal, there is clear embryological evi-dence of the existence of a left fifth aortic arch. Inthe cat embryo, Huntington (I9I9) and Brown

FIG. 5 Case 2. Specimen of the area of the aortic arch showing the two arches clearly sep-arated (IV and V). The innominate artery (INNA), left common carotid artery (LCCA),and left subclavian artery (LSA) arise from the left fourth aortic arch. The localized coarcta-tion of the aorta immediately distal to the left subclavian artery and the persistent ductus arter-iosus is noted.

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(1913) and in the chick embryo, Buell (I922) de-scribe a left fifth aortic arch forming a vascularchannel caudal to the fourth aortic arch. Congdon(1922) demonstrated the presence of endothelialsprouts arising from the aortic sac and the descend-ing aorta which were thought to be the ends of thefifth aortic arches in the human embryo. Finally,Van Praagh and Van Praagh (I969) presented thefirst case of a persisting left fifth aortic arch in ahuman postmortem heart.The two cases presented in this report add further

support to the developmental concept that a fiftharch can occur in man. Case 2 is particularly impor-tant because the two arches were clearly separatedby a gap and each arch was surrounded by an ad-ventitial sheath.

Case I is, to the best of our knowledge, the firstpersistent left fifth aortic arch to be recognizedduring life. As suggested by Van Praagh and VanPraagh (I969), the diagnosis was made from theselective angiocardiogram of the aortic arch systemobtained at cardiac catheterization (C. A. F. Moes andT. Izukawa, I973, unpublished observations). Aware-ness that the entity exists is important, as alternativeexplanations for the odd angiographic appearancecan be produced. One possible explanation is that themisplaced vessel is an aberrant brachiocephalicartery, usually a right subclavian artery originatingabnormally from the descending aorta. A routinechest x-ray and haemodynamic data from cardiaccatheterization will not detect the anomaly. A normaloesophagogram will rule out both the existence ofanaberrant right subclavian artery and a double aorticarch (fourth).

In all three cases reported to date, the persistingfifth aortic arch was on the left side and originatedfrom the aortic lumen at or distal to the origin of

the innominate artery and rejoined the aortic lumenat the origin of the left subclavian artery inferiorly.All three cases had other abnormalities of the heartor great vessels. The occurrence of an isolated per-sisting left fifth aortic arch has not yet been re-ported.

ReferencesArey, L. B. (I965). Developmental Anatomy. A Textbook and

Laboratory Manual of Embryology, 7th ed. W. B. Saunders,Philadelphia.

Balinsky, B. I. (I965). An Introduction to Embryology, 2nd ed.W. B. Saunders, Philadelphia.

Brown, A. J. (I9I3). The development of the pulmonary veinin the domestic cat. Anatomical Record, 7, 299.

Buell, C. E., (I922). Origin of the pulmonary vessels in thechick. Contributions to Embryology, 14, II.

Congdon, E. D. (I922). Transformation of the aortic archsystem during the development of the human embryo.Contributions to Embryology, 14, 47.

Duckworth, J. W. A. (I967). Embryology of congenital heartdisease. In Heart Disease in Infancy and Childhood, 2nd ed.,p. I36. Ed. by J. D. Keith, R. D. Rowe, and P. Vlad.MacMillan, New York.

Hamilton, W. J., Boyd, J. D., and Mossman, H. W. (I962).,Human Embryology, 3rd ed. W. Heffer and Sons, Cam-bridge.

Huntington, G. S. (IgIg). The morphology of the pulmonaryartery in the mammalia. Anatomical Record, 17, I65.

Langman, J. (I969). Medical Embryology. Human Develop-ment - Normal and Abnormal, 2nd ed. Williams andWilkins, Baltimore.

Sissman, N. J. (I968). Anomalies of the aortic arch complex.In Heart Disease in Infants, Children, and Adolescents.Ed. by A. J. Moss and F. H. Adams. Williams and Wilkins.Baltimore.

Van Praagh, R., and Van Praagh, S. (i969). Persistent fiftharterial arch in man. American Journal of Cardiology, 24,279.

Requests for reprints to Dr. T. Izukawa, Department ofCardiology, The Hospital for Sick Children, 555 Uni-versity Avenue, Toronto, Ontario MsG iX8, Canada.

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