alan graham, m.d. chla critical care medicine

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.



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

alan graham, m.d. chla critical care medicine

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