AORTIC ARCH ANOMALIES

कपा�क�DR. UMESH KHEDKARD.M. CARDIOLOGY RESIDENT.LTMGH , MUMBAI.

Account for 15% to 20% of all congenital cardiovascular diseases.

Result from errors in the embryologic development of the branchial arches, including errors of involution or migration, or abnormal persistence of vascular structures.

Strong associations of arch anomalies with chromosomal and genetic abnormalities are

supported by studies demonstrating a deletion within chromosome 22q11associated with arch anomalies .

INTRODUCTION

Can be discovered when there are symptoms of airway or esophageal compression produced by vascular rings, or anomalies can be found incidentally on imaging studies obtained for other reasons

Anomalous RSCA-Hunauld,1735Double aortic arch-Hommel 1737Right aortic arch –Fioratti,Aglieti-1763Interrupted aortic arch-Steidele-1788Bayford,1787-dysphagia by vascular ring-

coined term dysphagia lusoria.Gross,1945-first division of a vascular ring.

History

Heart is first seen in the form of two endothelial heart tubes-18th day of foetal life.

Fusion results in a single tube with a series of dilatations - beat by 22nd day.

Bulbus cordis represents arterial end of the tube-prox part conus,distal truncus arteriosus.

Embryology

Portion ventral to foregut - ventral aorta

Portion dorsal to foregut- dorsal aorta

• First arteries to appear are right and left primitive aorta connected to the endothelial heart tubes

After fusion of heart tubes,ventral aorta fuse - aortic sac

During 4th and 5th week, successive arterial arches appear in 2nd to 6th pharyngeal arches.

Each connects ventrally to aortic sac& dorsally to dorsal aorta.

Greater part of 1st &2nd arch arteries disappear

5th arch artery regress completely 3rd-common carotid and prox.int.carotid 4th –Lt.-aortic arch b/w LCCA and LSCA.

◦ Rt-prox RSCA 6TH –prox part –prox pulmonary artery

◦ distal part-ductus on left and right side involutes Lt dorsal aorta-aortic arch distal to LSCA Rt dorsal aorta-cranial portion-RSCA distal

to 4th arch.distal portion-involutes

Portion of dorsal aorta b/w 3rd and 4th (ductus caroticus)disappear

Each 6th arch artery connects to the pulmonary vascular Tree.

Portion b/w this connection and dorsal aorta-ductus arteriosus-regresses on right side

Spiral septum formed in truncus in the 5th week extends to aortic sac. Blood from pulmonary artery goes to 6th arch artery,from aorta to 3rd &4th arch arteries

Dorsal aorta gives lateral intersegmental branches to body wall - 7th cervical intersegmental supplies upper limb bud

Innominate artery - right branch of truncoaortic sac

Right common carotid artery - right third arch

Right subclavian - right fourth arch and right dorsal aorta proximally and right seventh intersegmental artery distally

Left carotid - left third aortic arch. Left subclavian - left seventh

intersegmental artery.

Brachiocephalic Branches Of The Arch

AORTIC ARCH ANOMALIES

Anomalies of aortic arch to be conceptualized as variations in regression of different segments from a “hypothetical double arch”.

The concept of “hypothetical double aortic arch” emphasises the potential contribution of nearly all embryonic arches to components of definitive arch system.

Demonstrate possible embryologic explanations for each arch anomaly.

Edward s double aortic arch model

Totipotential aortic arch diagram

Normal left aortic arch is derived from Aortic portion of the embryonic truncus

arteriosus Left branch of the truncoaortic sac Left fourth arterial arch Left dorsal aorta

Normal left arch development

Left and right arch refers to which bronchus is crossed by the arch

Echo or angio-branching pattern of brachiocephalic vessels

First arch vessel that contains carotid artery opposite side of arch or Retroesophageal or isolated vessels-opp to side of arch

MRI and CT-conclusive

Sidedness of the arch

AORTIC ARCH ANOMALIES CLASSIFICATION

Abnormalities of branching. Abnormalities of arch position-cervical arch,

right arch

Supernumerary arches-double aortic arch and persistent 5th arch

Interrupted aortic arch Anomalous origin of pulmonary artery

branch

Anatomical classification

Vascular rings. Non-ring vascular compression. Non-compressive arch malformations. Ductal dependent arch anomalies-

Inturrupted aortic arch , Isolated subclavian,carotid or innominate arteries.

Clinical classification

Aortic arch anomaly in which trachea and esophagus surrounded by vascular structures.

The vascular structure need not to be patent e.g. ligamentum arteriosum.

Double aortic arch most common(40%) Rt.Aortic arch with left.ligamentum(30%) Aberrant RSCA(20%) Anomalous innominate(10%)

Vascular ring

Symptoms-◦ Stridor,Pneumonia,bronchitis◦ Reflex apnoea or choking on eating.◦ Posture of Hyperextension of neck in infant.◦ Increased respiratory distress a/w intercurrent

respiratory infections.◦ Swallowing difficulty . ◦ Occasionally, in patients with associated

intracardiac anomalies ,the respiratory symptoms may be mistakenly be attributed to cardiac disease.

The Vascular ring may be suspected from combination of the History and plain chest film .

When all elements of the ring are patent, visualization, especially by tomographic imaging, is straightforward.

In cases where the ring is completed by an atretic segment of aorta or ligamentum arteriosum, those segments cannot be visualized with current imaging technologies.

However, these rings are recognizable by the presence of one of three “D” opposite the side of the aortic arch.

3 d΄s opposite to side of arch-diverticulum,dimple,descending aorta

Diverticulum –large vessel from desc.aorta giving rise to a smaller calibre vessel with a sudden taper

Dimple –tapered blindly ending outpouching Descending aorta in upper thorax opp.to

side of arch-connected by ligamentum arteriosum

Idantification of vascular rings

Common brachiocephalic trunk (Bovine Arch)◦ Right innominate and left carotid from single origin◦ 10% of normal ◦ Compression of trachea possible

Separate origin of left vertebral artery◦ 10%◦ Prox to LSCA◦ 3rd arch vessel smaller than 4th

◦No Functional significance

Variants of left aortic arch

The second most common pattern of human aortic arch branching has a common origin for the innominate and left common carotid arteries.

K.F. Layton et al. AJNR Am J Neuroradiol 2006;27:1541-1542

©2006 by American Society of Neuroradiology

a) Lt arch with retroesophageal RSCAb) Lt aortic arch and retroesophageal

diverticulum of Kommerellc) Lt aortic arch,rt.descending

aorta,rt.ductus(circumflex aortic arch)d) Lt aortic arch & isolated RSCAe) Lt aortic arch with cervical origin of Rt

subclavian.

Abnormal Left Arch

Also known as anomalous or aberrant right subclavian artery .

Bayford linked such case with history of difficulty in swallowing and coined term “Dysphagia Lusoria” 0.5% incidence in general population. m.c. aortic arch anomaly Incidence in down’s syndrome with CHD Is

very high (38%).

Lt Arch with Retroesophageal RSCA

Disappearance of Rt 4th arch-distal Rt dorsal aorta becomes prox RSCA forming its retroesophageal portion. Rt 6th arch (ductus) disappear. Usually asymptomatic. Barium –smaller fixed filling defect on post

aspect of esophagus slanting upward to right

Angio-earlier filling of Rt carotid on aortic root injection.

First vascular ring to be diagnosed during life with barium study.

Similar to previous except for persistent right 6th arch-ligamentum which completes a vasc . Ring

Prox.RSCA dilated to form diverticulum.

Lt Aortic Arch and Retroesophageal Diverticulum of Kommerell

Branching pattern similar to earlier Arch retroesophageal RSCA the last arch vessel . Descending aorta connected to RPA by

ligamentum-forms vasular ring Embryology: disappearance of rt 4th arch

but with left distal dorsal aorta forming definitive distal arch and passing retroesophageally to a descending aorta beginning to right of vertebral column.

Lt Aortic Arch,Rt.descending Aorta,Rt.Ductus(Circumflex Aortic Arch)

Plain chest film : left sided aortic arch with right sided upper descending aorta.

Barium esophagography : Large posterior indentation from retroesophageal aorta .

Angiography will confirm the course of aorta.

In symptomatic patients the Ring is divided via right thoracotomy approach.

RSCA arises only from rt ductus. Right 6th arch persists with dossolution of

right 4 th arch and right dorsal aorta. RSCA and vertebral fills from PA in foetal life When ductus closes-retrogradely from circle

of willis◦ Vertebrobasilar insufficiency◦ Congenital subclavian steal◦ Absent rt arm pulse

Lt Aortic Arch & Isolated RSCA

Angiography : Delayed filling of RSCA after aortic root shoot .

With phase encoded velocity mapping ,retrograde flow in the vertebral artery can be detected on MRI.

Symptomatic patients are treated with implantation of subclavian artery into aorta.

Lt Aortic Arch & Isolated RSCA

Marker of 22q11 deletion. (Marker of CATCH 22) Innominate trifurcates in the neck-RSCA

travels back to thorax Subclavian artery arises from 3rd arch in

stead of 4 th . 3 rd arch being more cephalad gives origin

to RSCA in the neck.

Lt Aortic Arch with Cervical Origin of Rt Subclavian Artery.

A single aortic arch that crosses rt mainstem bronchus

13-34% in TOF 30-40% in truncus arteriosus 20% in pul.atresia with VSD 8-10% in transposition.

Right Aortic Arch

a) Right aortic arch-mirror image type branching

b) Rt aortic arch with retroesophageal diverticulum of Kommerell

c) Rt arch with retroesophageal LSCAd) Rt arch with Lt desc aorta and Lt

ligamentum

Right Aortic Arch Types

Sequence of arch vessels-lt.innominate,rt carotid,RSCA.

Ligamentum lt sided. No vascular ring. Almost always associated with CHD (48% TOF)

Right Aortic Arch-Mirror image type

Dissolution of left dorsal aorta distal to the origin of left 7 th intersegmental artery

So, left 4th arch becomes proximal left subclavian artery.

Left Sixth arch persists- left ductus arises from underside of left innominate artery and passes to LPA .

Alternatively right ductus persists giving true mirror image of normal.

Second most common vascular ring . Sequence –lt carotid,rt carotid ,RSCA,a large

retroesophageal vessel( diverticulum) from which LSCA arises

Lt ligamentum completes the ring Disappearance of Lt 4th arch and

persistence of 6th arch Should be differentiated from rt aortic arch with retroesophageal subclavian artery.

Rt Aortic rch with Retroesophageal Diverticulum of Kommerell

Symptoms of vascular ring with right sided aortic arch on plain chest film should raise the suspicion of this anomaly .

Barium study reveals a large posterior indentation on the esophagus.

Branching pattern of arch vessels on echo. Angiography reveals characteristic branching

pattern and abrupt change in calibre from diverticulum to subclavian artery.

MRI ideal for diagnosis . Surgical division of ductus in symptomatic

patients via left thoracotomy.

Management.

Similar to previous one except for the absence of retroesophageal diverticulum.

Sequence –lt carotid,rt carotid ,RSCA, retroesophageal LSCA.

Ductus is rt sided. No vascular ring. Involution of left 4th and 6th aortic arches. Associated with conotruncal anomalies . Higher incidence of 22q11 deletion.

Rt Arch with Retroesophageal LSCA

Also known as circumflex right aortic arch. Aortic arch itself crosses midline to the left

at the level of T4 vertebral body -connects to lt ductus to form vascular ring

Sequence –lt innominate,rt carotid ,RSCA or lt carotid,f/b right carotid,right subclavian,finally left subclavian.

Aortic arch is retroesophageal and not the subclavian artery.

Rt Arch with Lt Descending Aorta and Lt Ligamentum

Embryology : Dissolution of either left dorsal aorta distal to takeoff of the left subclavian artery or the left fourth arch. Persistent left sixth arch connects to the left sided dorsal aorta completing vascular ring .

Barium study :downward slanting left oesophageal indentation .

Mobilisation of retroesophageal aortic segment and reanastomosis of asc and dec aorta using tube graft may be needed in symptomatic adults in addition to simple division of ligamentum.

Sequence : right carotid, right SCA,f/b retroesophageal left innominate artery .

Ductus or ligamentum connects LPA with base of innominate a. completing vascular ring.

Embryology : dissolution of left branch of truncoaortic sac and left 4 th arch .The left dorsal aorta supplies left 7th IS artery and left 3 rd arch.

Clue for diagnosis is single carotid artery arising from proximal aorta.

In symptomatic patients surgical division of ligamentum with implantation of innominate artery to ascending aorta is required.

Rt Aortic Arch with Retroesophageal Innominate Artery.

Vessel arises exclusively from pulmonary artery via ductus arteriosus but without connection to aorta.

3 forms : Isolation of LSCA (m.c.),Isolation of left carotid and isolation of Left innominate .

CHD in more than 50% (m.c. TOF).

Presentation: diminished pulse amplitude or blood pressure in left arm , subclavian steal syndrome,pulmonary artery steal (if duct patent)

The dignosis should be suspected in pt with right sided aortic arch with diminished pulse amplitude or blood pressure in left arm .

Delayed filling of LSCA via vertebral artery during aortic arch shoot confirms diagnosis.

Rt Aortic Arch with Isolation of Contralateral Arch Vessel

Arch found above level of clavicle Two categories- 1.normal branching pattern 2.anomalous subclavian artery and vascular ring with descending aorta contralateral to arch or retroesophageal diverticulum. 2nd group-divided according to carotid origin

(bicarotid trunk or separate origin of ext & int carotid)

First group usually has left sided arch while second group has right sided.

Separate origin of vertebral artery can be seen in both groups.

Cervical Aortic Arch

o Mechanism--Failure of normal descent of aortic arch system-Persistence of ductus caroticus & involution of 4th arch-3rd arch becomes definitive aortic arch with separate origin of ext &int carotid from it.

oPresentation : - Pulsatile mass in supraclavicular fossa or the neck.- Symptoms of vascular ring - Subclavian steal in patients with stenosis or

atresia of LSCA .oPresumptive diagnosis can be made by notation

of loss of femoral pulse during brief compression of the mass.

Both rt and lt arches present. Both arches can be patent or one hypoplastic or

atretic(usually left) Persistence of both rt and lt 4th arch which join TA

sac to their respective dorsal aortae Only one 6th remain. Symmetric origin of 4 arch vessels from respective

arches when both patent Rarely a/w other CHD, when present-TOF most

common. Form complete vascular rings. When both arches are patent, rings typically tight

and present with sridor in first week of life.

Double Aortic Arch

Diagnosis can be made on plain chest film when both arches are patent.

Tracheal air column is indented by more superior right sided arch and inferior left sided arch.

Confirmation with further imaging is important to identify atretic segment.

Surgical division of ring in symptomatic.

Management

First reported by Van praagh in 1969 Double lumen aortic arch in which both

arches appear on same side of trachea. Frequently associated with CHD; however

can be incidental finding without clinical significance .

2 common sub categories-◦ Subway vessel beneath normal arch(4th arch)that

extend from innominate to take off of LSCA◦ Double lumen aortic arch with atresia of superior

arch with patent inferior arch-common origin of all brachiocephalic vessels from asc.aorta

Persistent 5th arch

-4 th arch persists as superior arch connecting TA sac with dorsal aortaand 5th inferior arch does the same.

– With Atresia of superior arch,4 th arch serve as a connection between carotid and subclavian artery similar to innominate artery but ipsilateral to the definative arch which is 5 th arch .

Defined as complete separation of ascending and descending aorta

Celoria and Patton classification(1959)◦ Type A-interruption distal to SCA that is ipsilateral

to 2nd carotid artery◦ Type B-interruption b/w 2nd carotid and ipsilateral

subclavian◦ Type C-interruption b/w carotids.

Each of the types subcategorised to 3 types◦ 1.without retroesophageal or isolated subclavian

artery◦ 2.with retroesophageal subclavian artery◦ 3. with isolated subclavian artery

Interrupted aortic arch

Type A-aorticopulmonary septal defect,TGA Type B- most common a/w conotruncal anomaly with large

malaligned VSD with subaortic obstruction, DiGeorge syndrome.

Type C-rare

Interrupted rt arch seen only in DiGeorge syndrome.

Associations..

Type A-Involution of both dorsal aorta distal to 4th arch and prox to persistent 6th arch which supplies descending aorta .

Type b-Involution of one 4th arch and one dorsal aorta b/w 4th and 6th.

Type C-Involution of one limb of truncoaortic sac,associated proximal 3 rd arch and entire 4 th arch with persistence of dorsal aorta between 3rd and 4 th arch.

Embryology

AAAaa

Type A Type B

Present with acute cardiovascular collapse or heart failure after closure of ductus in first days of life.

Absence of all limb pulse with strong carotid pulse suggest type B with anomalous subclavian.

2 D echo is most important diagnostic tool . 3 D reconstructive MRI is useful for

identifying branching pattern and site of inturruption.

Surgical approch depends on the degree of subaortic obstruction .

1.If subaortic diameter > 5 mm primary intracardiac repair.2.If subaortic diameter < 3mmbypass subaortic region – associate MPA with ascending aorta using homograft augmentation to complete aortic reconstruction. Aortic arch is reconstructed by liberal

dissection around two arch components with direct anastomosis of two ends.

Anomalous pulmonary artery branch arising from ascending aorta in presence of a MPA arising separately

Anomalous RPA-◦ More common◦ Embryonic branch pul.artery joins rt side of TA

sac,but fails the leftward migration to join MPA before septation

◦ High incidence of aorticopulmonary septal defect Anomalous LPA

◦ a/w TOF in 74%◦ Embryonic branch pul.artery fails to join TA sac

CCF in infancy f/b early development of pulmonary vascular disease.

Anomalous origin of pulmonary artery from ascending aorta

LPA arises from RPA and passes b/w trachea and esophagus-Pulmonary artery sling.

Only Anomaly in which a major vascular structure passes between trachea and esophagus.

Tracheal compression-Severe respiratory distress and stridor,Milder forms may exists

Isolated anomaly, rarely a/w TOF Anterior indentation on barium swallow. Bronchoscopy needed prior to surgery to rule

out complete cartilagenous ring .

Anomalous origin of LPA from RPA

Systemic to pulmonary shunts are best carried out using side with innominate artery.

Knowledge of sidedness of aorta may be very useful in the repair of eosophageal atresia or tracheo-esophageal fistula.

Anatomical variations or anomalies in brachiocephalic arteries my pose difficulty in Carotid artery stenting as well as may increase complication rates..

Surgical Implication of Aortic Arch Anomalies

Aortic arch anomalies and vascular rings can be interpreted on the basis of embryology

With the develpoment Of MRI and CT, 3-D reconstruction is possible.

Intervention required only when symptomatic or when a/w other cardiac anomalies.

Summary

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