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

Question 12

TA gross exam

Answer 12

• Single arterial trunk exiting the heart
  o Give origin to coronary, systemic, pulmonary circulations
  o Dilated truncus
• Large VSD from absence of infundibular septum
  o Roofed by truncal valve cusp
• Single truncal valve (2-3 cusps)
  o Fibrous continuity w/ MV
  o Deformed, functionally insufficient (50%)
   Thickened, nodular dysplastic cusps
   Prolapse of unsupported cusps
   Shallow raphe, inequal cusp size
   Commissural abnormalities
   Annular dilation → poorly developed sinuses
  o Overriding septum: biventricular origin in 60-80% (or RV>LV)
• DA absent in 50% of cases, 2/3 of cases w DA will have PDA
• CA abnormalities common

Question 13

What defines types of TA

Answer 13

Origin of PAs, differentiate from PA atresia

Question 14

Pseudotruncus

Answer 14

• PA atresia w/ VSD (extreme TOF)

Question 15

Hemitruncus

Answer 15

• 1 PA from ascending Ao
• 1 PA from RV
• PA well developed

Question 16

Collett and Edwards classification

Answer 16

~ Type I: short pulmonary trunk originating form TA gives rise to both PA
~ Type II: both PA separate from the TA with no vestige of an MPA and arise close together
~ Type III: both PA separate from TA with no vestige of an MPA and arise at some distance from one another
~ Type IV: type of pulmonary atresia with VSD
~ Incidence: I > II > III > IV

Question 17

Van Praagh classification

Answer 17

~ Type A1: short pulmonary trunk originating form TA gives rise to both PA
~ Type A2: both PA separate from the TA with no vestige of an MPA and arise close or at some distance from one another
~ Type A3: absence of truncal origin of one PA with blood supply to that lung from DA or collateral
~ Type A4: underdevelopment of aortic arch, including tubular hypoplasia, discrete coarctation or complete interruption

Question 18

Pathophys

Answer 18

• Large L → R shunt
  o LVP = RVP
  o Pulmonary overcirculation from ↑ pulmonary flow
• Biventricular hypertrophy +/- dilation if valvular insufficiency

Question 19

C/s

Answer 19

from pulmonary overcirculation or CHF (early in life)
o Exercise intolerance
o Tachypnea
o Bounding/accentuated pulses → diastolic runoff in pulmonary vascular bed
* Cyanosis if stenosis of PA

Question 20

PE

Answer 20

o Pansystolic murmur at L based + low pitched apical diastolic murmur
o S1 w systolic ejection click: maximal opening of truncal valve
o If truncal insufficiency: diastolic high-pitched murmur

Question 21

ECG

Answer 21

normal

Question 22

CTX

Answer 22

• Moderate cardiomegaly
• ↑ pulmonary vascular markings
• R Ao arch in 33% of cases

Question 23

Echo DDX single GA

Answer 23

o Truncus arteriosus
o PA atresia + VSD
o Extreme TOF

Question 24

Natural hx

Answer 24

Px grave