Ao arch anomalies Flashcards
Embryology aortic arch system
- 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
Which arch regress
1,2,5
3rd arch becomes
internal common carotids
L 4rth arch become
portion of Ao root, join persistent L dorsal Ao
R 4rth arch become
R subclavian artery
6th arch become
R: RPA
L: LPA + DA
Dorsal Ao become
L: desceding Ao
R: portion of R subclavian
7th intersegmental arteries become
L subclavian
Which species do 5th Ao arch do not regress
Reptiles
Species differences in BCT
- Eq, Bo: 1 BCT
- Ca, Fe, Po, rabbits/mice: BCT + L subclavian
- Hu, Rat: BCT + L subclavian + R common carotid
most common vascular anomaly
PRAA
Breeds PRAA
o ↑ incidence: German Shepherd, Irish Setter
o Also reported in Geart Dane
Pathophys PRAA
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
DDX PRAA
o Double Ao arch
o Retroesophageal L or R subclavian artery
o R ligamentum arteriosum
C/s PRAA
typically swallowing difficulties
o Young animal
o Regurgitation after meal
o Thin/emaciated animal with normal heart/lungs
CTX changes PRAA
- 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
PRAA 1/3 of dogs also have
retro L subcl.
Histo PRAA
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
Tx PRAA
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
Double Ao arch: features
- 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
vascular ring formed by XX in double Ao arch
o Ao arches
o Ligamentum
Tx double Ao arch
o Divide one of the persistent Ao arch → least functional/atretic
o Leave the other as the functional arch
Double Ao arch associated w/
malformed tracheal rings
Normal subclavian anatomy
- Normally, R subclavian leaves brachiocephalic trunk on the L and course to the R front leg below esophagus
Retroesophageal left subclavian artery features
- 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
Retroesophageal right subclavian artery features
- 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
Tx anomalous Subclavian
ligation
Right ligamentum arteriosum features
- 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
Ring formed from Right ligamentum arteriosum
- Vascular compression of esophagus
o Ventrally attached to RPA
o Dorsally attached to
Ao
Retroesophageal R subclavian artery
R 4th Ao arch
Coarctation of Ao feature
- Ridge at jct of arch and descending Ao
o Site of ductus arteriosus attachment
Coarctation of Ao cause
unclear, but thought to be secondary to ectopic ductal tissue or abnormal preductal flow
Coarctation of Ao clinical significance
o Poor perfusion of descending Ao
o Hypertension of cranial limbs
o LVH
o Collateral development
PE coarct Ao
differential pulse
o Front limbs: systolic > diastolic
o Back limbs: systolic < diastolic
Tubular hypoplasia def
segmental narrowing >50%
Interruption of Ao
Extreme form of coarctation
* Perfusion of distal limbs from PDA + collateral vessels
o ↑ R heart pressure: RVE + RVH
Aortic aneurysm
- Ao dilation → compared to Marfan syndrome in Hu
o Fibrillin gene-1 - Older cats (mild) or large breed dogs
Aortocardiac fistula
- Eq: often btw Ao root → RA/RV
o Can be associated w aneurysm of sinus Valsalva
Persistent L CrVC
- 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
L azygos vein
- Remnant of L supracardinal vein
- Enters CS
Anomalies of the CaCV
- 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
How would you interpret the presence of 3 cranial arch vessels in a dog with a left-sided fourth arch?
L sided aortic arch with anomalous R subclavian artery (image E)
