This anomaly consists of a single arterial trunk
exiting from the heart through a common valve, giving
origin to aorta (systemic circulation), pulmonary
artery (pulmonary circulation) and coronary arteries
Failure of normal septation and division of the
embryonic bulbar trunk into the pulmonary artery &
aorta, which results in development of a single vessel
that overrides both ventricles. Blood from both the
ventricles mixes in the common great artery which
leads to desaturation and hypoxemia.
Blood ejected from the heart flows preferentially to
the lower pressure pulmonary arteries, so the
pulmonary blood flow is increased & systemic blood
flow is reduced.
It affects males & females equally & accounts for
about 1% of all CHD cases. Almost always associated
• Truncus arteriosus communis
• Common arterial trunk
• At 4 weeks of gestation two spiral ridges appear
which separate common truncus into aorta &
• Failure of septation of the cono-truncal segment
gives rise to this anomaly.
•Infants of diabetic mothers
• Embryonic exposure to retinoic acid
•Deletion of 22q11
•Siblings of children born with truncus
•High association with truncus and DORV
•Association with CHARGE syndrome, Digeorge
syndrome and CATCH 22
• Type I : A single pulmonary trunk arises near the
base of the truncus and divides into the left and
right pulmonary arteries.
• Type II : The left and right pulmonary arteries arise
separately but in close proximity & at the same level
from the back of the truncus.
• Type III : The pulmonary arteries arise
independently from the sides of the truncus.
• Type IV : No pulmonary artery arise from common
truncus and lungs are supplied by pulmonary
collaterals called pseudo truncus arteriosus .
When one pulmonary artery arises from ascending
aorta and other comes off normally from main
pulmonary artery arising from the RV.
Blood ejected from the left and right ventricles enters the
common trunk, so that pulmonary & systemic circulations are
mixed. Blood flow is distributed to the pulmonary and systemic
circulations according to the relative resistances of each
system. The amount of pulmonary blood flow depends on the
size of the pulmonary arteries and the pulmonary vascular
resistance. Generally resistance to pulmonary blood flow is
less than systemic vascular resistance, which results in
preferential blood flow to the lungs. Pulmonary vascular
disease develops at an early age in patients with truncus
Both ventricles pump into the common trunk which
overrides the VSD. Therefore the systolic pressure in
ventricles, aorta and pulmonary artery are same.
Blood flow to pulmonary bed and systemic bed depends
on the resistance to flow in their respective
Soon after the birth :- SVR increased and PVR
decreased increased pulmonary flow, if pulmonary
flow is adequate, systemic saturation becomes normal.
Truncal regurgitation contributes to volume overload
of both ventricles. Volume overload in ventricles and
pulmonary circulation Obstructive changes of
pulmonary vasculature Increased PVR
Pulmonary hypertension Eisenmenger’s complex.
But later, because of increased pulmonary blood
flow increased pulmonary venous return to LA and
LVCCF within 1st
week of birth. The cyanosis is mild
CCF in early pregnancy FTT, feeding difficulties,
excessive sweating, tachypnea Repeated respiratory
infection Hyperdynamic precordium, cardiomegaly,
hepatomegaly Minimal cyanosis(not detected in rest,
detected only in crying)
High volume pulse
Auscultation: Loud single 2nd
heart sound( Loudness-
dilation of trunk, Single – closure of one set of
valves), Prominent ejection click (Due to opening of
truncal valve), loud ejection systolic
murmur(increased blood flow through the truncal
ECG: Tall, peaked P wave in leadII, III and aVF shows
RAE, right axis deviation and RVH.
Radiography: cardiomegaly, a high origin of a dilated
left pulmonary artery may give rise to comma sign
Echo : most helpful diagnostic tool.
Cardiac catheterization : used to clarify doubt about
Control of CCF with diuretics and digoxin
Correction of acidosis
Treatment of respiratory infections
No oxygen to minimize pulmonary blood flow
If interruption in aortic arch, prostaglandin infusion
to keep ductus arteriosus patent. I E prophylaxis
Definite treatment : surgical repair Early surgery is
necessary Definite repair using conduit from RV to
PA and closure of VSD.
Optimum age : Before 3 months. As the child grows this
conduit tends to degenerate and calcify, so it needs
replacement in future
Palliative surgery: Pulmonary artery banding. It is
indicated in infants with large pulmonary blood flow
Repeated respiratory infection
Increased cyanosis and hypoxemia
Complications of surgery
Truncal valve dysfunction
RV conduit obstruction
• Mortality is high if not corrected early
• 75% die with in 1st
month of life
• Average lifespan is 5 week
• Survival up to one year is seen only 15%
• If survived, features of pulmonary vascular
obstructive disease and develops Eisenmenger’s
Govt. College of