Truncus Arteriosus Alan Graham, M.D.
CHLA
Critical Care
Medicine
Truncus Arteriosus
Definition
Embryology
Anatomy and Classification(s)
Pathophysiology
Repair
Complications
Truncus Arteriosus
Definition:
– Systemic, Pulmonary, and Coronary
circulations all arise from one great artery
with a single semilunar valve
– VSD
Rare: 0.4 to 2.8% of all Congenital
Heart Disease
Truncus Arteriosus
Embryology
Failure of septation of truncus arteriosus
and the conal septum
Endocardial spiral ridges begin at 27
days gestation
Normally, the Truncus forms:
– Proximal Aorta and Pulmonary Artery
– Semilunar valves
Failure of conal septum results in VSD
Embryology
Truncus Arteriosus
Colette & Edwards Classification
Type IV - “pseudotruncus” with single
Aortic trunk and pulmonary flow
dependent on aortopulmonary
collaterals
– Now considered a variant of Tetralogy of
Fallot with pulmonary atresia.
The Van Praagh classification
Type A1 - same as Collett-Edwards Type I (50%)
Type A2 - Right and left PAs arise separately from the truncus (Collett-
Edwards Types II and III). (21%)
Type A3 - A single PA (usually the right) arises from the truncus, while
the opposite lung is supplied by collaterals. (8%)
Type A4 - A hypoplastic aortic arch with a large patent ductus
arteriosus arises from the truncus and supplies the descending aorta.
Right and left pulmonary arteries originate from the posterior aspect of
the truncus. (12%)
Van Praagh R, Van Praagh S: The anatomy of common aorticopulmonary trunk (truncus arteriosus
communis) and its embryologic implications. A study of 57 necropsy cases. Am J Cardiol 1965;16:406-425.
The Van Praagh classification
The Van Praagh classification
Truncus arteriosus is classified into two types, based on the presence (type A) or absence (type B) of a
ventricular septal defect. The 2 types are further subclassified into 4 subtypes, depending on the orientation
of the great arteries. In subtype 1 (Left), the aorticopulmonary septum is incompletely formed, resulting in a
partially separate main pulmonary artery. In subtype 2 (Middle left), the aorticopulmonary septum is entirely
absent with both pulmonary arteries arising directly from the truncus. In subtype 3 (Middle right), one
pulmonary artery is absent and that lung is supplied by collateral arteries from the descending aorta. In
subtype 4 (Right), hypoplasia, coarctation, atresia, or absence of the aortic arch is associated with a large
patent ductus arteriosus.
Truncus Artery
Truncus Artery overrides VSD, most
often toward the RV
Branch Pulmonary Artery stenosis can
protect the lungs from overcirculation
Coronary Arteries Abnormal origin not uncommon
Arise from Truncal Sinuses of Valsalva
– 2/3 pts similar to normal
– LCA arises from L posterior of truncus
– RCA arises from R anterior
Variations:
– Single ostium, high ostium, pulmonary
artery origin, LAD may cross RVOT
– Obstruction from acute angle or slit-ostium
Truncal Valve
5% bicuspid, 25% quadricuspid
myxomatous thickening may occur and
be a/c severe incompetence
Leaflet redundancy may obstruct a
proximal pulmonary artery
Associated Abnormalities
Right Aortic Arch(30%), anomalous
subclavian(10%), L SVC(10%),
ASD(10%)
DiGeorge’s syndrome
– hypertelorism, low ears, short philtrum,
micrognathia
Pathophysiology
Main problem: Pulmonary
overcirculation with LV vol overload and
RV pressure overload
At 1-2 weeks of age, PVR drops and
Qp:Qs becomes >1
Valve insufficiency may raise volume
load (earlier presentation)
Pathophysiology
Coronary flow may be decreased by:
– narrowed ostia
– low coronary perfusion pressure due to
pulmonary run off
Presentation
Signs: Tachypnea, tachycardia,
irritability, poor feeding, poor wt gain,
pneumonias, may be cyanotic
PEx: diaphoresis with rapid pulse with
large pulse pressure, LLSB holosystolic
murmur, loud click from truncal valve
CXR: cardiomegaly with increase pulm
vascular markings
EKG: biventricular hypertrophy
Echo reveals large LA and Pulm Arteries
arising from the single Truncus
Preoperative care
Anticongestive therapy
Avoid torrential pulm Q: Fi02=0.21,
normocapnia, afterload reduction
Watch for coronary ischemia
Stabilize for early repair: (<2 months)
before pulm vascular disease develops
(may be inoperable if >8 Wood
Units/m2)
Surgical Repair
Surgical Repair Goals:
1. Create RV to PA continuity
2. Closure of VSD
3. Correct associated anomalies:
– truncal valve insufficiency
– interrupted Aortic Arch
Surgical Repair
As bypass begins: Pulm Artery snared
to prevent overcirculation and to
enhance systemic/coronary perfusion
Truncus with Interrupted Aortic Arch
Repair of interrupted Arch &
VSD
Creation of RVOT & Aortic Arch
Truncal Valve Insufficiency
May require:
– Resuspension of leaflets
– Valve replacement
– Konno technique to place prosthesis
Left, Relationship between the great arteries. The origin of the descending thoracic aorta has a caudal
direction. Middle, Schematic representation of the potential compression of the right pulmonary artery after
surgical correction. The descending thoracic aorta, connected to the underface of the ascending aorta,
creates a narrow neoaortic arch. Right, Anterior translocation of the right pulmonary artery over the
ascending aorta prevents compression of the origin of the right pulmonary artery and provides more space
for the left main bronchus.
J THORAC CARDIOVASC SURG 1996;111:672-4
Postoperative Care
Possible complications:
– Tamponade
– Bronchial compression
– Coronary compression
– Conduction injury
– Desaturation with pulmonary HTN (via
PFO)
– RV dysfunction after ventriculotomy