Conotruncal abn

Question 2

Conotruncal anomalies: conotruncus

Answer 2

= 2 myocardial subsegments
o Conus: myocardial segment btw ventricles and semilunar valves
 Gives rise to subarterial coni
 Inferior to AoV and PV
o Truncus: fibrous segment btw semilunar valves and Ao sac
 Gives rise to great arteries

Question 3

Conotruncal anomalies def

Answer 3

• Abnormality in development of neural crest-derived tissue

= malformation of
o Infundibulum = conus arteriosus
o Great arteries = truncus arteriosus
o Abnormal ventriculo arterial alignment

Question 4

Spectrum of conotruncal abn

Answer 4

o Mild: transposition of GA
 Lack of subpulmonary conus
 Pulmonary mitral fibrous continuity
o Moderate: double outlet RV, subaortic VSD
 Both GA arise from RV
 No fibrous continuity with AV valves
o Severe: Tetralogy of Fallot
 PS + RVH
 Overriding Ao
 VSD
 Mitral-aortic fibrous continuity

Question 5

Embryology of conotruncus

Answer 5

• Paired endocardial cushions in conus/bulbus cordis and truncus
  o Bulbus cordis cushions are ALIGNED with IVS, truncus would be perpendicularly oriented
  o Invagination towards the center to form the spiral septum
   Aorticopulmonary septum = divides truncus arteriosus
  o Orientation is clockwise

Question 6

Conotruncal abn

Answer 6

TGA
DORV
TOF

Question 7

Features of DORV

Answer 7

• Both great vessels exit from RV
  o Associated congenital abnormalities are common
   PS common in Hu
  o Cyanosis depends on
   Origin of Ao
   Presence of PH/PS

Question 8

Pathophys DORV

Answer 8

o Malalignment VSD → provide avenue for LV outflow
 Usually large, not restrictive → R = L systolic pressures
 Beneath Ao or PV
 Pulmonary overcirculation is present
* Unless PS or PH

Question 9

DORV: GA relation

Answer 9

o Normal: Ao caudal and R to PA
o Ao // PA, originate to the R and cranial
o Ao cranial, PA caudal and to R

Question 10

Types of DORV depending on

Answer 10

VSD type

o Subaortic VSD + PS – TOF type
 PA is anterior (>conus) and overriding Ao

o Subaortic VSD – VSD type
 Pulmonary venous return → LV → VSD → Ao
 Physiology mimic a large VSD
 L heart failure early in life, can result in Eisenmenger physiology later in life
* Pulmonary overcirculaton

o Subpulmonic VSD – TGA type
 Ao is anterior (>conus)
 Physiology mimic TGA: LV → VSD → PA → RV → Ao

o Non committed VSD
 Not directly related to one GA

Question 11

GA alignement depends on

Answer 11

Amount of conus beneath GA
>conus => superior and anterior position

Normally PA

Question 12

TOF genetics

Answer 12

• Inherited in some breeds of dogs
  o Keeshond: polygenic trait

Question 13

4 components of TOF

Answer 13

o Non restrictive subaortic VSD
o Dextroposition of Ao (biventricular origin)
o Pulmonary stenosis → RVOTO
 Cats: marked hypertrophy of crista supraventricularis
 Dogs: valvular PS
o Secondary RVH

Question 14

Embryology

Answer 14

o Underdevelopment of subpulmonary infundibulum → PS + overriding Ao
o Malalignment of lower conotruncal septum → overriding Ao + VSD
 Upper part of IVS → forms too far cranially
o Malalignment
 Results in narrow RVOT
 Abnormal PV
 Dextroposition of Ao

Question 15

What is a pseudotruncus arteriosus

Answer 15

Extreme TOF w/ pulm atresia

Question 16

TOF pathophysiology

Answer 16

o R to L shunt through VSD
 PS ↑ resistance to blood flow from RV > systemic resistance
 Amount of shunting depends on relative resistance btw 2 circulations
* Physiologic consequences depend on degree of PS and SVR
* Degree of override is not hemodynamically significant

Question 17

Why is exercise intolerance a c/s of TOF

Answer 17

Induce vasodilation => decr SVR => more shunting
 Infundibular narrowing and hypertrophy → stenosis that worsens with contractile function

Question 18

Why do TOF patients develop cyanosis

Answer 18

o Systemic hypoxemia → cyanosis
 Depend on degree of shunting
 Symptomatic patients have arterial O2 tension <40mmHg

reduced O2 saturation => polycythemia => decr blood flow