Ao arch anomalies

Question 1

Embryology aortic arch system

Answer 1

• Aortic arches: paired arteries from aortic sac on ventral surface of embryo
  o Paired dorsal aorta
• Total of 6 paired Ao arches develop, not present at same time
• Surround esophagus and trachea
• Modified during development to form major component of arterial system
  o All of mature Ao arch structures lie on L side of esophagus/trachea
   Except birds: normally have R Ao arch

Question 2

Which arch regress

Answer 2

1,2,5

Question 3

3rd arch becomes

Answer 3

internal common carotids

Question 4

L 4rth arch become

Answer 4

portion of Ao root, join persistent L dorsal Ao

Question 5

R 4rth arch become

Answer 5

R subclavian artery

Question 6

6th arch become

Answer 6

R: RPA
L: LPA + DA

Question 7

Dorsal Ao become

Answer 7

L: desceding Ao
R: portion of R subclavian

Question 8

7th intersegmental arteries become

Answer 8

L subclavian

Question 9

Which species do 5th Ao arch do not regress

Answer 9

Reptiles

Question 10

Species differences in BCT

Answer 10

• Eq, Bo: 1 BCT
• Ca, Fe, Po, rabbits/mice: BCT + L subclavian
• Hu, Rat: BCT + L subclavian + R common carotid

Question 11

most common vascular anomaly

Answer 11

PRAA

Question 12

Breeds PRAA

Answer 12

o ↑ incidence: German Shepherd, Irish Setter
o Also reported in Geart Dane

Question 13

Pathophys PRAA

Answer 13

o Absence of L aortic arch → R Ao arch persists
o Ring formed w/ L sided DA + PA → entrapment of esophagus btw PA, trachea and ligamentum/PDA

Question 14

DDX PRAA

Answer 14

o Double Ao arch
o Retroesophageal L or R subclavian artery
o R ligamentum arteriosum

Question 15

C/s PRAA

Answer 15

typically swallowing difficulties
o Young animal
o Regurgitation after meal
o Thin/emaciated animal with normal heart/lungs

Question 16

CTX changes PRAA

Answer 16

• Radiographs: air, fluid filled esophagus cranial to heart
  o Dilation starts at thoracic inlet
  o End abruptly at heart base
  o On DV: mediastinal dilation cranial to heart with S shaped trachea on right

Question 17

PRAA 1/3 of dogs also have

Answer 17

retro L subcl.

Question 18

Histo PRAA

Answer 18

o Normally: Ao, ductus arteriosus and PA are on the L of trachea
o PRAA: Ao arch on the R while ductus arteriosus and PA on the L side
 Leftward deviation of trachea
 Compression by vascular structures → deformed, overlapped cartilages

Question 19

Tx PRAA

Answer 19

o Dissection of ligamentum/ductus → relieve obstruction
o Survival rate is 80%
o Post op care: small, frequent meals at elevated levels
o Prognosis is variable depending on if dog regurgitation frequently/aspiration pneumonia

Question 20

Double Ao arch: features

Answer 20

• Persistence of both 4th aortic arches
  o Ascending aorta branching into R and L branches
   R commonly larger
  o Course along either side of esophagus and trachea
  o Reunite caudally to form descending Ao

Question 21

vascular ring formed by XX in double Ao arch

Answer 21

o Ao arches
o Ligamentum

Question 21

Tx double Ao arch

Answer 21

o Divide one of the persistent Ao arch → least functional/atretic
o Leave the other as the functional arch

Question 21

Double Ao arch associated w/

Answer 21

malformed tracheal rings

Question 21

Normal subclavian anatomy

Answer 21

• Normally, R subclavian leaves brachiocephalic trunk on the L and course to the R front leg below esophagus

Question 22

Retroesophageal left subclavian artery features

Answer 22

* L 7th intersegmental artery fails to reach L 4th Ao arch before it separates from dorsal Ao o 1/3 of dogs with PRAA * Dorsal compression of esophagus + compression from PRAA

Question 23

Retroesophageal right subclavian artery features

Answer 23

* R 7th intersegmental artery fails to reach R 4th Ao arch before it separates from dorsal Ao * Results in R subclavian arising from dorsal Ao → crossing over esophagus * Similar compression to PRAA * Reported in 4 Bulldogs

Question 24

Tx anomalous Subclavian

Answer 24

ligation

Question 25

Right ligamentum arteriosum features

Answer 25

* Remnant of R 6th caudal Ao arch o Normally ductus will arise from L 6th Ao arch o Can coexist with other arch abnormalities o Can also be functional R PDA

Question 26

Ring formed from Right ligamentum arteriosum

Answer 26

* Vascular compression of esophagus o Ventrally attached to RPA o Dorsally attached to  Ao  Retroesophageal R subclavian artery  R 4th Ao arch

Question 27

Coarctation of Ao feature

Answer 27

* Ridge at jct of arch and descending Ao o Site of ductus arteriosus attachment

Question 28

Coarctation of Ao cause

Answer 28

unclear, but thought to be secondary to ectopic ductal tissue or abnormal preductal flow

Question 29

Coarctation of Ao clinical significance

Answer 29

o Poor perfusion of descending Ao o Hypertension of cranial limbs o LVH o Collateral development

Question 30

PE coarct Ao

Answer 30

differential pulse o Front limbs: systolic > diastolic o Back limbs: systolic < diastolic

Question 31

Tubular hypoplasia def

Answer 31

segmental narrowing >50%

Question 32

Interruption of Ao

Answer 32

Extreme form of coarctation * Perfusion of distal limbs from PDA + collateral vessels o ↑ R heart pressure: RVE + RVH

Question 33

Aortic aneurysm

Answer 33

* Ao dilation → compared to Marfan syndrome in Hu o Fibrillin gene-1 * Older cats (mild) or large breed dogs

Question 34

Aortocardiac fistula

Answer 34

* Eq: often btw Ao root → RA/RV o Can be associated w aneurysm of sinus Valsalva

Question 35

Persistent L CrVC

Answer 35

* Commonly seen with vascular ring anomalies * Normal in rabbits and rodents * Can be single or have L and R cava * 2 types: incomplete vs complete (enters CS at caudal RA) * No clinical significance

Question 36

L azygos vein

Answer 36

* Remnant of L supracardinal vein * Enters CS

Question 37

Anomalies of the CaCV

Answer 37

* Double CaVC: sacrocardinal and subcardinal vein remain * Absent CaVC: R subcardinal vein fails to connect to liver o Blood goes from caudal body → azygos → CrVC and heptic vein → RA

Question 38

How would you interpret the presence of 3 cranial arch vessels in a dog with a left-sided fourth arch?

Answer 38

L sided aortic arch with anomalous R subclavian artery (image E)