Truncus arteriosus

Question 1

What is a persistent truncus arteriosus

Answer 1

• Failure to partition fetal truncus
  o Large VSD allow blood flow btw ventricles
  o Single large vessel above defect
  o Single semi-lunar valve
   2/3 of cases: 3 leaflets
   1/3 of cases: 2 or 4 leaflets

Question 2

TA physiology

Answer 2

ventricular blood mixes in common artery → distribution to systemic, pulmonary and coronary circulation
o Non restrictive VSD roofed by truncal valve
 RVP = LVP = SVR
o Consequences depend on PVR and size of PAs
o Blood flow from ventricles tend to cross
 O2 content in Ao > PA
 Systemic O2 is ↑ when PVR is ↓ and pulmonary blood flow is increased → LV volume overload

Question 3

PE findings

Answer 3

o Wide pulse pressure:
 ↓PVR → diastolic runoff from truncus into pulmonary bed
 Rapid rate of rise → rapid ejection of large volume during systole
o Decrescendo systolic murmur, harsh, blowing type
 Prominent 2nd heart sound: enlarged truncus closer to chest wall

Question 4

what is pseudotruncus arteriosus

Answer 4

extreme form of Tetralogy of Fallot
o Pulmonary atresia + VSD
o Distinction resides in blood flow to pulmonary circulation: from PDA or bronchial circulation

Question 5

Ductus arteriosus w/ TA

Answer 5

not present in 50-70% of cases
o Fetal ductus not needed to bypass pulmonary circulation

Question 6

Coronary arteries w/ TA

Answer 6

defined by relationship to truncal sinuses and epicardial course

Question 7

Van Praagh classification

Answer 7

Depend on # of PAs originating from truncus

Question 8

Type 1 Van Praagh

Answer 8

most common
o Short main PA originating from truncus
o Gives rise to R and L PAs

Question 9

Type 2 and 3 Van Praagh

Answer 9

o R and L PA arise from separate ostia on side/back of truncus
o 15% of cases: R or L PA is absent/hypoplastic

Type 2 arises closer at the back of truncus vs type 3 on the sides

Question 10

Type 4 Van Praagh

Answer 10

not used anymore.
o Reconsidered as pulmonary atresia + VSD (pseudotruncus arteriosus)

Question 11

Anderson classification

Answer 11

aortic or pulmonary dominant