TGA

Question 1

Types of TGA

Answer 1

• PA from morphologic LV, Ao from RV
  o Complete: normal AV concordance
   Situs solitus, D looping, anterior/R Ao
  o Congenitally corrected transposition: AV discordance
   Double discordance = corrects the transposition
  o Lethal if not corrected

Question 2

Pathophys

Answer 2

2 independent circulations in //
o Needs shunting at some level to survive: ASD, VSD, PDA

Question 3

Mx management

Answer 3

o Maintain DA patency → PGE2
 Improve arterial saturation + ↑ mixing at atrial level

Question 4

Palliative sx correction

Answer 4

 Balloon atrial septostomy or sx creation of ASD
* Neonates, via umbilical/femoral vein
 Partial venous return repair: Baffes = connect CVC → LA w conduit
 Pulmonary artery banding
 Systemic-pulmonary anastomosis
 Rastelli operation: TGA w large VSD and severe LVOTO
* Intraventricular repair + extracardiac shunt → complete bypass of LVOT

Question 5

Definitive sx correction

Answer 5

 Atrial switch operation: physiologic correction
* Redirection of blood at atrial level: Dacron, pericardium or atrial flaps
* Systemic venous return → MV → subpulmonary LV
* Pulmonary venous return → TV → subsystemic RV
o Morphologic RV supports systemic circulation
 Arterial switch operation:
* Arterial trunks transected → anastomosed to contralateral root
* Transposition of CAs on neoAo
* VSD closed if present
* Advantage: restoration of LV as systemic pump

Question 6

D-TGA gross exam

Answer 6

• Discordant ventriculoarterial connection
  o Ao originate from morphologic RV
   Morhphologic Ao: coronary ostia + cranial vasculature (BcT and L subCl)
  o PA originate from morphologic LV
   Morphologic PA: bifurcation and sharp angulation toward lungs
• VSD type
  o Perimembranous: fibrous continuity of MV + PV
  o Malalignment/outlet: conoseptal hypoplasia
  o Doubly committed subarterial: fibrous continuity Ao → PV
• SubAo conus arising from RV
• RV is a morphologic RV
• GA arise in // opposed to normally spiraled fashion
• Coronary abnormalities can be present

Question 7

Pathophys D-TGA

Answer 7

• 2 independent circulations in // → pure form of lesion is lethal
  o Systemic veins → RV → Ao
  o PVs → LV → PA
• Survival depends on presence of shunting: 1 or > communication
  o VSD (50%), ASD/PFO
  o PDA → only allow L to R shunting
   Another communication must be present
   Patency maintained by
• PGE2
• Balloon atriotomy

Question 8

4 combinations of lesions D-TGA

Answer 8

o Intact IVS
o VSD
o VSD + LVOTO
o Intact IVS + LVOTO

Question 9

Embryology 2 theories for formation D-TGA

Answer 9

o Lack of spiral rotation of the aorticopulmonary septum
o Subaortic conus enlarges, while the subpulmonary conus is resorbed (normally opposite)

Question 10

PE D-TGA

Answer 10

o Cyanosis
 Reverse differential cyanosis: PDA + PH with shunt reversal
* Cranial cyanosis with adequate caudal perfusion
o Continuous murmur (from PDA)

Question 11

ECG D-TGA

Answer 11

• RAE: tall P waves
• RVH: R axis deviation

Question 12

CTX D-TGA

Answer 12

• Cardiomegaly: egg on a string appearance of cardiac silhouette
• Enlarged MPA
• Pulmonary overcirculation

Question 13

Echo d-TGA

Answer 13

• 2D: // Ao and PA
• Doppler
  o Color flow through shunting lesions (ASD, VSD, PDA)

Question 14

Cardiac KT angio

Answer 14

o Nonselective contrast study: R heart → Ao
o Selective injection in Ao: Ao → PDA → PA → LV → VSD → RV → Ao

Question 15

Cardiac KT oximetry

Answer 15

o ↓ O2 tension in RV vs proximal Ao
 Suggest VSD