biology

Persistent truncus arteriosus

Persistent truncus arteriosus is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Persistent truncus arteriosus rather than just read about it. In short: Persistent truncus arteriosus (PTA), often referred to simply as truncus arteriosus, is a rare form of congenital heart disease that presents at birth. In this condition, the embryological structure known as the truncus arteriosus fails to properly divide into the pulmonary trunk and aorta.

Key takeaways

Persistent truncus arteriosus belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Persistent truncus arteriosus to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Persistent truncus arteriosus from memory before moving on to harder problems.

Reference excerpt

Persistent truncus arteriosus (PTA), often referred to simply as truncus arteriosus, is a rare form of congenital heart disease that presents at birth. In this condition, the embryological structure known as the truncus arteriosus fails to properly divide into the pulmonary trunk and aorta. This results in one arterial trunk arising from the heart and providing mixed blood to the coronary arteries, pulmonary arteries, and systemic circulation. For the International Classification of Diseases (ICD-11), the International Paediatric and Congenital Cardiac Code (IPCCC) was developed to standardize the nomenclature of congenital heart disease. Under this system, English is now the official language, and persistent truncus arteriosus should properly be termed common arterial trunk.

Causes Most of the time, this defect occurs spontaneously. Genetic disorders and teratogens (viruses, metabolic imbalance, and industrial or pharmacological agents) have been associated as possible causes. Up to 50% (varies in studies) of cases are associated with chromosome 22q11 deletions (DiGeorge Syndrome). The neural crest, specifically a population known as the cardiac neural crest, directly contributes to the aorticopulmonary septum. Microablation of the cardiac neural crest in developing chick embryos and genetic anomalies affecting this population of cells in rodents results in persistent truncus arteriosus. Numerous perturbations affecting the cardiac neural crest have been associated with persistent truncus arteriosus, some of which include growth factors (fibroblast growth factor 8 and bone morphogenetic protein), transcription factors (T-box, Pax, Nkx2-5, GATA-6, and Forkhead), and gap junction proteins (Connexin). The cardiac neural crest also contributes the smooth muscle of the great arteries.

Pathophysiology

Anatomical changes associated with this disorder includes:

single artery arising from the two ventricles which gives rise to both the aortic and pulmonary vessels abnormal truncal valve right sided aortic arch in about 30% of cases (not shown) large ventricular septal defect pulmonary hypertension complete mixing occurring at level of the great vessel right-to-left shunting of blood

Diagnosis The diagnosis is based on:

Cyanosis presents at birth Heart failure may occur within weeks Systolic ejection murmur is heard at the left sternal border Widened pulse pressure Bounding arterial pulses Loud second heart sound Biventricular hypertrophy Cardiomegaly Increased pulmonary vascularity Hypocalcemia (if associated with DiGeorge syndrome)

Classification A well-known classification is the fourfold system developed by Collett and Edwards in 1949. Collett/Edwards Types I, II, and III are distinguished by the branching pattern of the pulmonary arteries:

Type I: The branch pulmonary arteries arise from a single "main pulmonary artery" arising from the lateral surface of the common trunk Type II: The branch pulmonary arteries arises separately, but near each other posteriorly off the common trunk Type III: The branch pulmonary arteries arise separately and far apart off the common trunk Type IV: The branch pulmonary arteries arise distally off the aorta, or the lungs are supplied by multiple aortopulmonary collaterals. Type IV is now considered a form of Tetralogy of Fallot and not Common Arterial Trunk. Another well-known classification was defined by Stella and Richard Van Praagh in 1965. In this classification scheme, the preceding letter ("A" or "B") refers to the presence or absence, respectively, of a ventricular septal defect. Type B common arterial trunk is extremely rare; so below, only Type A is considered:

Type A1: The branch pulmonary arteries arise from a single "main pulmonary artery" arising from the lateral surface of the common trunk (Collett & Edwards Type I) Type A2: The branch pulmonary arteries arise separately off the common trunk (includes both Collett & Edwards Types II and III). Type A3: One branch pulmonary artery arises off the common trunk, and one branch pulmonary artery is isolated, arising from a patent ductus arteriosus. Type A4: Common arterial trunk in association with interrupted aortic arch. As both of the above schemes involve four numerals, they can be easily confused. For this reason, the Collette & Edwards scheme usually uses roman numerals while the Van Praagh system uses arabic numerals and the preceding "A". Ambiguity as to the system being used can lead to misunderstanding. The classification in the International Paediatric and Congenital Cardiac Code (IPCCC) attempts to eliminate this source of confusion with the following nomenclature scheme, which removes the use of numbered types:

Common arterial trunk with aortic dominance and both pulmonary arteries arising from trunk (includes Collette & Edwards Types I, II, and III and Van Praagh types 1 and 2). Common arterial trunk with aortic dominance and one pulmonary artery absent from trunk, isolated pulmonary artery (Van Praagh type 3). Common arterial trunk with pulmonary dominance and aortic arch obstruction (Van Praagh type 4)

Treatment Treatment is with neonatal surgical repair, with the objective of restoring a normal pattern of blood flow. The surgery is open heart, and the patient will be placed on cardiopulmonary bypass to allow the surgeon to work on a still heart. The heart is opened and the ventricular septal defect is closed with a patch. The pulmonary arteries are then detached from the common artery (truncus arteriosus) and connected to the right ventricle using a tube (a conduit or tunnel). The common artery, now separated from the pulmonary circulation, functions as the aorta with the truncal valve operating as the aortic valve. Most babies survive this surgical repair, but may require further surgery as they grow up. For example, the conduit does not grow with the child and may need to be replaced as the child grows. Furthermore, the truncal valve is often abnormal and may require future surgery to improve its function. There have been cases where the condition has been diagnosed at birth and surgical intervention is an option. A number of these cases have survived well into adulthood.

Epidemiology Persistent truncus arteriosus is a rare cardiac abnormality that has a prevalence of less than 1%.

Additional images

See also Truncus arteriosus (embryology) Patent ductus arteriosus

References

External links A.D.A.M. Medical Encyclopedia from NCBI site. Truncus arteriosus

Illustrations

Worked examples

Example 1 — a first encounter with Persistent truncus arteriosus

Start with the simplest possible case. Write down what Persistent truncus arteriosus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Persistent truncus arteriosus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Persistent truncus arteriosus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Persistent truncus arteriosus

In research: Persistent truncus arteriosus appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Persistent truncus arteriosus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Persistent truncus arteriosus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Congenital heart defects, Rare diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Persistent truncus arteriosus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Persistent truncus arteriosus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Persistent truncus arteriosus means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Persistent truncus arteriosus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Persistent truncus arteriosus in simple terms?

Why does Persistent truncus arteriosus matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Persistent truncus arteriosus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Persistent truncus arteriosus.