Venous anomalies

Question 1

Clinical significance of venous anomalies

Answer 1

→ Rarely clinically significant

Question 2

Embryology of venous system: embryonic venous system

Answer 2

• Earliest form of venous return to embryonic heart
  o Paired cardinal venous system: cranial and caudal cardinal veins
  o Join sinus venosus

Question 3

What forms CrVC? Which parts of the embryologic system regresses

Answer 3

o L cranial cardinal vein regresses → anastomosis to R cranial cardinal vein

o R cranial and common cardinal veins remain and enlarge → form CrVC

Question 4

What forms from L common cardinal vein persists

Answer 4

→ form coronary sinus
 Drain coronary circulation

Question 5

Supracardinal system and species differences

Answer 5

o R supracardinal vein form R azygos (Hu, dog, cats, horses)
o Absent in swines and cattles → will have hemiazygos on L side formed by L supracardinal vein
o Azygos (R) or hemiazygos (L) depending on species
 Join proximal segment of corresponding R or L CrVC

Question 6

Which species normally have L CrVC

Answer 6

Rabbits/rats/mice

Question 7

Which species normally have L azygos

Answer 7

Po

Question 8

Which species normally have R azygos

Answer 8

Ca/Fe

Question 9

Which species normally have R and L azygos

Answer 9

Bo

Question 10

Breed reported for pLCrVC

Answer 10

German Shepherds

Question 11

From which structure coronary sinus is a remnant

Answer 11

embryonic L Cr cardinal vein

Question 12

Features of pLCrVC

Answer 12

o Can be single CrVC or both L and R CrVC present
o Can be associated with other congenital diseases (TOF, ASD, mitral atresia, juxtaposition of RA appendage)
o Should not be ligated → appropriately return venous blood to RA
 Not clinically significant hemodynamically
o Size is iα to co existent R CrVC

Question 13

Types of pLCrVC described by buchanan

Answer 13

o Complete → enter CS
 Receive blood from veins cranial to the heart
o Incomplete → L azygos drain into it before entering CS
 Proximal portion of L CrVC receives vein draining the costocervical-vertebral trunk

Question 14

In Hu, pLCrVC can be associated w/

Answer 14

unroofed CS
 If so, persistent L CrVC drain into LA
 R to L shunting → cyanosis

Question 15

Anatomy

Answer 15

o Starts at jct of L jugular and subclavian vein
o Penetrates pericardium → follow posterior wall of LA to CS

Question 16

Where does pLCrVR empty

Answer 16

coronary sinus
o Enters RA in caudodorsal part
o CS normally receive blood from vein of Marshall + coronaries

Question 17

Angio

Answer 17

injection of contrast in L jugular vein → enters heart in caudodorsal RA → RV → PA

Question 18

• Clinical importance

Answer 18

o L thoracic exploration → may interfere with surgical exposure
 Especially for PRAA correction: L CrVC will cross over and can obscure ligamentum arteriosum
o Cardiac KT of L jugular vein → unexpected direction
 Harder to get into RV
o No known functional significances

Question 19

Echo

Answer 19

o Dilated coronary sinus
 Significant of ↑ coronary sinus blood flow
* Persistent L CrVC
* Total anomalous pulmonary venous connection to CS
* Infrahepatic interruption of CaVC with L azygos continuation
o Persistent L CrVC may be visualized in its course behind LA to RA

Question 20

Contrast echo study

Answer 20

agitated saline into cranial vein visible into CS
 R cephalic injection:
* See in RA = normal = confirm R Cr VC present
* See in CS = abnormal = no R Cr VC
 L cephalic injection
* See in RA = no persistent L CrVC = normal
* See in CS = confirm L CrVC
 L saphenous
* See in CS = L azygous

Question 21

Necropsy findings

Answer 21

o Size varies (diameters of LCrVC and LIV vary inversely)
o Starts at junction of L jugular and L subclavian veins descending in front of Ao arch → penetrating the pericardium and following posterior wall of LA to CS
o Leads to CS enlargement and posterior displacement on RA floor

Question 22

significance of a left azygous vein

Answer 22

• Present normally in some species
  o Absent in dogs/cats
  o Cow/pig: large L azygos, absent or ↓ R azygos
  o Sheep: equal size R and L azygos

Question 23

L azygos is a remnant of which structure

Answer 23

L supracardinal system

Question 24

Where does is enter the heart

Answer 24

coronary sinus
 Normally atrophies and become ligament of Marschall

Question 25

How does CaVC develop

Answer 25

anastomosis of 3 paired segments
 Caudal cardinal vein
 Subcardinal vein
 Supracardinal vein

Question 26

What is the course of normal R azygos vein

Answer 26

o Course on the R ventrolateral aspect of thoracic vertebral bodies
o Turn ventrally around root of R lung
o Empties at right angle into termination of CrVC
o Receives intercostal veins from 5th IC space to 2nd or 3rd lumbar vertebrae

Question 27

Features of L azygos vein

Answer 27

• Occasionally sole source of caudal venous return if concurrent interruption of CaVC

Question 28

CTX L azygos vein

Answer 28

o Enlarged Ao arch
o Unusual vascular structure at heart base
 More caudally then expected Ao arch

Question 29

L azygos vein angio

Answer 29

contrast injection in L saphenous vein
o Large opacified caudal vein course toward heart
 // to descending Ao
 Positioned where usual azygos vein in pigs and ruminants
o Extended ventrocranial → tracheal bifurcation → curved caudally

Question 30

L azygos vein AUS

Answer 30

small CaVC

Question 31

L azygos vein echo

Answer 31

normal heart size and function
o Dilated coronary sinus on SAX and LAX R parasternal views
o L azygos vein visible

Question 32

L azygos vein contrast study

Answer 32

injection of microbubbles into L saphenous vein → bubbles visible into CS