Arch Anomalies (M/A)

Aortic Arch Anomalies (MA36)

Anatomical Classification:

-AbNly of branching

-AbNly of Arch position

-R Ao Arch

-Cervical Ao Arch

-Anomalous origin of PA branch fr Asc Ao or fr contralateral PA

Definitions:

-Arch Sidedness refers to which bronchus is crossed by the arch, NOT which side of midline Ao rt ascends

-Practically, sidedness is usually determined indirectly w echo or angio by brachioceph branchng pattrn

-first arch vessel contains carotid art on the side opposite the arch

-exceptions: retroesophageal or isolate innominate artery

-common source of error: hard to decide which of 2 carotid arteries is first

Embryology:

-6 paired aortic arch vessels connecting to the tuncoaortic sac; each pair for each branchial pouch derived fr embryologic foregut. Migration of neural crest cells into pharyngeal arches play a role...

Dx:

-barium esophogram, MRI/CT

Clinical Classification:

-Vascular rings

-non-ring vascular compression of the trachea, bronchi, esophagus

-noncompressive arch malformations

-ductal-dependent arch anomalies- interrupted Ao arch, isolated SCA, carotid, innominate arts

Chrom 22q11.2 Deletion syndromes

-seen in >80% pts w DiGeorge, velocardiofacial, conotruncal anaomaly face syndromes (CATCH 22)

-...

Vascular Rings:

= trachea and esoph completely surrounded by vessels

-might not be patent (ligamentum arteriosum, etc)

--> stridor, pna, bronchitis, cough; infants w hyperextension of neck, reflex apnea w eating

"noisy breathing since birth" and h/o apparent recurrent bronchitis

-if pt has some cardiac dz, sometimes these Sx are attributed to it but really its a ring

-Sx can continue for yrs post correction bc of tracheomalacia

-if the ring is completed by a nonpatent vessel, then it won't show up well on imaging, so look for one of the following: diverticulum (large vessel arising fr desc Ao giving rise to smaller caliber vessel w a sudden taper), dimple (tapered blind ending pouch off of Ao), Desc Ao (opposite side of the Ao arch)

I Normal L Ao Arch & Variants

-crosses LMSB at level of thoracic vertebra T5, and desc L of midline to diaph

-R innominate artery branches first (--> RCC & RSCA), then LCC and LSCA

-DA/LA usually joins Ao distal to LSCA takeoff, but can insert more prox (espec w TOF)

-L Ao Arch variants:

-Common brachiocephalic trunk- R innom and LCA arise fr single origin (10% of otherwise Nl arch)

--> no Sx/xx, but ? more common to have tracheal compression

-Separate origin of L vertebral art fr Ao arch proximal to the LSCA takeoff, instead of fr LSCA (10%)

-must ddx fr anomalous RSCA (in which you also see 4 vessels off of arch)

-w L vertebral art, the first artery will be Nl (R innom art) and be larger than the 2nd (LCC), and the third artery (the L vertebral) will be smaller than the 4th artery (the LSCA)

--> no Sx/xx

Embryology:

-Nl L arch is formed bc the R 6th Ao arch (ductus) and R dorsal Ao distal to origin of 7th intersegmental artery (which will--> distal subclavian art) both dissolve

--> R 4th arch becomes the proximal SCA, instead of staying an arch connecting the truncoaortic sac to desc ao. And it arises fr the R innominate art.

--> L 4th arch becomes the final Ao Arch

AbNL L Ao Arch:

-L Ao Arch w Retroesophageal RSCA (aka Anomalous/aberrant RSCA)

-Branches = RCCA, LCCA, LSCA, then a 4th to RSCA, arising fr post-med side of distal arch

-Epi- 0.5% of population (#1 arch xx)

-38% of Down's pts that have CHD

-Sx- usually ASx, incidental finding

-Embryology- R 4th arch disappears, so the distal R dorsal Ao becomes prox RSCA instead, and R 6th Ao Arch doesn't form so no RIGHT ductus...

-Dx/Tx- No inonom art, so see 1st & 2nd branches same size,

-UGI--> fixed filling defct slanting up to R, small compared to other xx

-L Ao Arch w Retroesophageal DIverticulum of Kommerell

-L Ao Arch w retro-esoph diverticulum, same as above, except the caliber of the prox RSCA w abrupt decr in size, representing the presence of the ligamentum arteriosum.

-also occurs bc of involuted R 4th Ao Arch, but here the R 6th arch (right DA) does form--> persists and forms a complete vascular ring (unlike above)

-L Ao Arch w R Desc Ao & R Ductus/Ligamentum

-rare, aka circumflex Ao arch; branching pattern similar to L arch w retroesoph RSCA, but the arch itself is retroesoph, so the RSCA is not retroesoph even though it arises as last arch. The desc Ao is connected by the DA/LA to the RPA --> Vasc ring.

-Embryology- R 4th Ao arch disappears and the distal L dorsal Ao forms the definitive distal Ao arch, and passes retroesoph to the desc Ao beginning to the R of the vertebral column. The R 7th intersegmental art arises fr R sided desc Ao. The R 6th arch (DA) connects the RPA of the truncoaortic sac w the distal R dorsal Ao

-Dx/Tx- c/s w pt w Sx of a vasc ring, and find no R Ao Arch

-CXR shows L sided arch and R sided upper desc Ao

-UGI--> large posterior indentation of esoph fr retroesoph Ao

-L Ao Arch w Isolate SCA

-SCA arises only fr the DA - PA supplies SCA and verebral arts; when DA closes, SCA gest Q fr vertebrals via retrograde Q, via circule of Willis

-Embryology- R 4th arch and R dorsal Ao dissolves, but R 6th arch persists

-Dx/Tx-can cause vertebrobasilar insufficiency w "congen subclavian steal", often ASx or have absent R arm pulse - see delayed filling of SCA after Ao root injection

-Tx w implantation of SCA to Ao

-L Ao Arch w Cervical Origin of RSCA