Truncus arteriosus

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Truncus arteriosus is a cyanotic congenital heart anomaly in which a single trunk supplies both the pulmonary and systemic circulation, instead of a separate aorta and a pulmonary trunk ³. It is usually classified as a conotruncal anomaly.

It accounts for up to 2% of congenital cardiac anomalies and is almost always associated with a VSD to allow circulatory flow circuit completion¹.

Epidemiology

The estimated incidence is 1 in 10,000 births.

Pathology

There is a lack of normal separation of the embryological truncus into a separate aorta and pulmonary trunk. This results in a single arterial vessel that originates from the heart. It may also result in a common truncal valve which can contain 2-4 cusps.

Sub typesSubtypes

There are many types of classification.

One system includes division into three main types:

type I: both aorta and pulmonary arteries arise from a common trunk
type II: pulmonary arteries arise from posterior aspect of trunk, close to each other just above the truncal valve (negligible main pulmonary artery segment)
type III: ~~pulmonary~~ (least common) pulmonary arteries arise independently from either side of trunk

Associations

right sided aortic arch
interrupted aortic arch ⁸
persistence of primitive aortic arches
DiGeorge syndrome

Radiographic features

RadiographsChest radiograph

Often shows moderate cardiomegaly with pulmonary plethora (mainly as a result of collateral formation) and widened mediastinum.

However, ~~widened~~the main pulmonary artery (arising from common trunk) may be small/unusual in position which may result in narrow mediastinum,. This along with moderate cardiomegaly and ~~right~~pumonary plethora gives an appearance that is similar to D-loop transposition of great arteries⁹.

Right-sided aortic arch may be seen ².

Echocardiography/prenatal ultrasound

Allows direct visualisation of a single trunk. Outflow tract views are the most useful. Colour Doppler may additionally show flow across both ways through an associated VSD.

CT/CTA

Allows direct visualisation of anomalous anatomy.

MRI

Allows direct visualisation of anomalous anatomy. SSFP cine sequences can offer additional functional assessment.

Prognosis

Due to parallel fetal circulation, truncus arteriosus doesn't cause any haemodynamic problem in utero. However it is a major problem postnatally and, if left untreated, approximately 80% of infants die within the first year.

Differential diagnosis

Consider:

aortopulmonary window/fenestration

-<p><strong>Truncus arteriosus</strong> is a <a href="/articles/cyanotic-congenital-heart-disease">cyanotic congenital heart anomaly</a> in which a single trunk supplies both the pulmonary and systemic circulation, instead of a separate <a href="/articles/aorta">aorta</a> and a <a href="/articles/pulmonary-trunk">pulmonary trunk </a><sup>3</sup>. It is usually classified as a <a href="/articles/conotruncal-cardiac-anomalies">conotruncal anomaly</a>.</p><p>It accounts for up to 2% of congenital cardiac anomalies and is almost always associated with a <a href="/articles/ventricular-septal-defect-vsd">VSD</a> to allow circulatory flow circuit completion<sup>1</sup>.</p><h4>Epidemiology</h4><p>The estimated incidence is 1 in 10,000 births.</p><h4>Pathology</h4><p>There is a lack of normal separation of the embryological truncus into a separate aorta and pulmonary trunk. This results in a single arterial vessel that originates from the heart. It may also result in a common truncal valve which can contain 2-4 cusps.</p><h5>Sub types</h5><p>There are many types of classification.</p><p>One system includes division into three main types:</p><ul>
+<p><strong>Truncus arteriosus</strong> is a <a href="/articles/cyanotic-congenital-heart-disease">cyanotic congenital heart anomaly</a> in which a single trunk supplies both the pulmonary and systemic circulation, instead of a separate <a href="/articles/aorta">aorta</a> and a <a href="/articles/pulmonary-trunk">pulmonary trunk </a><sup>3</sup>. It is usually classified as a <a href="/articles/conotruncal-cardiac-anomalies">conotruncal anomaly</a>.</p><p>It accounts for up to 2% of congenital cardiac anomalies and is almost always associated with a <a href="/articles/ventricular-septal-defect-vsd">VSD</a> to allow circulatory flow circuit completion<sup>1</sup>.</p><h4>Epidemiology</h4><p>The estimated incidence is 1 in 10,000 births.</p><h4>Pathology</h4><p>There is a lack of normal separation of the embryological truncus into a separate aorta and pulmonary trunk. This results in a single arterial vessel that originates from the heart. It may also result in a common truncal valve which can contain 2-4 cusps.</p><h5>Subtypes</h5><p>There are many types of classification.</p><p>One system includes division into three main types:</p><ul>
~~-<strong>type II:</strong> pulmonary arteries arise from posterior aspect of trunk</li>~~
+<strong>type II:</strong> pulmonary arteries arise from posterior aspect of trunk, close to each other just above the truncal valve (negligible main pulmonary artery segment)</li>
~~-<strong>type III:</strong> pulmonary arteries arise from either side of trunk</li>~~
+<strong>type III:</strong> (least common) pulmonary arteries arise independently from either side of trunk</li>
-</ul><h4>Radiographic features</h4><h5>Radiographs</h5><p>Often shows moderate <a href="/articles/cardiomegaly">cardiomegaly</a> with <a href="/articles/pulmonary-plethora">pulmonary plethora</a> (mainly as a result of collateral formation), widened mediastinum, and right-sided aortic arch <sup>2</sup> .</p><h5>Echocardiography/prenatal ultrasound</h5><p>Allows direct visualisation of a single trunk. Outflow tract views are the most useful. Colour Doppler may additionally show flow across both ways through an associated VSD.</p><h5>CT/CTA</h5><p>Allows direct visualisation of anomalous anatomy.</p><h5>MRI</h5><p>Allows direct visualisation of anomalous anatomy. <a href="/articles/steady-state-free-precession-mri-2">SSFP</a> cine sequences can offer additional functional assessment. </p><h4>Prognosis</h4><p>Due to parallel fetal circulation, truncus arteriosus doesn't cause any haemodynamic problem in utero. However it is a major problem postnatally and, if left untreated, approximately 80% of infants die within the first year. </p><h4>Differential diagnosis</h4><p>Consider:</p><ul><li><a href="/articles/aortopulmonary-window-fenestration">aortopulmonary window/fenestration</a></li></ul>
+</ul><h4>Radiographic features</h4><h5>Chest radiograph</h5><p>Often shows moderate <a href="/articles/cardiomegaly">cardiomegaly</a> with <a href="/articles/pulmonary-plethora">pulmonary plethora</a> (mainly as a result of collateral formation) and widened mediastinum.</p><p>However, the main pulmonary artery (arising from common trunk) may be small/unusual in position which may result in narrow mediastinum. This along with moderate cardiomegaly and pumonary plethora gives an appearance that is similar to D-loop <a title="Transposition of the great arteries" href="/articles/transposition-of-the-great-arteries">transposition of great arteries</a> <sup>9</sup>.</p><p>Right-sided aortic arch may be seen <sup>2</sup>.</p><h5>Echocardiography/prenatal ultrasound</h5><p>Allows direct visualisation of a single trunk. Outflow tract views are the most useful. Colour Doppler may additionally show flow across both ways through an associated VSD.</p><h5>CT/CTA</h5><p>Allows direct visualisation of anomalous anatomy.</p><h5>MRI</h5><p>Allows direct visualisation of anomalous anatomy. <a href="/articles/steady-state-free-precession-mri-2">SSFP</a> cine sequences can offer additional functional assessment. </p><h4>Prognosis</h4><p>Due to parallel fetal circulation, truncus arteriosus doesn't cause any haemodynamic problem in utero. However it is a major problem postnatally and, if left untreated, approximately 80% of infants die within the first year. </p><h4>Differential diagnosis</h4><p>Consider:</p><ul><li><a href="/articles/aortopulmonary-window-fenestration">aortopulmonary window/fenestration</a></li></ul>

References changed:

9. Textbook of radiology and imaging. Churchill Livingstone. ISBN:0443071098. <a href="http://books.google.com/books?vid=ISBN0443071098">Read it at Google Books</a> - <a href="http://www.amazon.com/gp/product/0443071098">Find it at Amazon</a><span class="ref_v3"></span>

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