Persistent truncus arteriosus (PTA), often referred to simply as truncus arteriosus, is a rare form of

congenital heart disease A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...

that presents at birth. In this condition, the

embryological Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and ...

structure known as the

truncus arteriosus The truncus arteriosus is a structure that is present during embryonic development. It is an arterial trunk that originates from both ventricles of the heart that later divides into the aorta and the pulmonary trunk. Structure The truncus arterio ...

fails to properly divide into the

pulmonary trunk A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and t ...

and

aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...

. This results in one arterial trunk arising from the heart and providing mixed blood to the

coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ of ...

pulmonary arteries A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and t ...

, and

systemic circulation The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

. 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 A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic 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 22 Chromosome 22 is one of the 23 pairs of chromosomes in human cell (biology), cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and ...

q11 deletions (

DiGeorge Syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent in ...

). The

neural crest Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, per ...

, 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 factor A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regu ...

s (

fibroblast growth factor 8 Fibroblast growth factor 8 (FGF-8) is a protein that in humans is encoded by the ''FGF8'' gene. Function The protein encoded by this gene is a member of the fibroblast growth factor (FGF) family. FGF family members possess broad mitogenic and ...

and

bone morphogenetic protein Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of piv ...

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fu ...

s (

T-box T-box refers to a group of transcription factors involved in embryonic limb and heart development. Every T-box protein has a relatively large DNA-binding domain, generally comprising about a third of the entire protein that is both necessary an ...

Pax Pax or PAX may refer to: Peace * Peace (Latin: ''pax'') ** Pax (goddess), the Roman goddess of peace ** Pax, a truce term * Pax (liturgy), a salutation in Catholic and Lutheran religious services * Pax (liturgical object), an object formerly ki ...

Nkx2-5 Homeobox protein Nkx-2.5 is a protein that in humans is encoded by the ''NKX2-5'' gene. Function Homeobox-containing genes play critical roles in regulating tissue-specific gene expression essential for tissue differentiation, as well as dete ...

, GATA-6, and

Forkhead FOX (forkhead box) proteins are a family of transcription factors that play important roles in regulating the expression of genes involved in cell growth, proliferation, differentiation, and longevity. Many FOX proteins are important to embryon ...

), and

gap junction Gap junctions are specialized intercellular connections between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulate ...

proteins (

Connexin Connexins (Cx)TC# 1.A.24, or gap junction proteins, are structurally related transmembrane proteins that assemble to form vertebrate gap junctions. An entirely different family of proteins, the innexins, form gap junctions in invertebrates. Each ...

). The cardiac neural crest also contributes the

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

of the

great arteries The great arteries are the primary arteries that carry blood away from the heart, which include: * ''Pulmonary artery'': the vessel that carries oxygen-depleted blood from the right ventricle to the lungs. * ''Aorta'': the blood vessel through whic ...

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 The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins a ...

in about 30% of cases (not shown) * large

ventricular septal defect A ventricular septal defect (VSD) is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart. The extent of the opening may vary from pin size to complete absence of the ventricular septum, creating one ...

* pulmonary hypertension * complete mixing occurring at level of the

great vessel Great vessels are the large vessels that bring blood to and from the heart. These are: * Superior vena cava * Inferior vena cava * Pulmonary arteries * Pulmonary veins * Aorta Transposition of the great vessels is a group of congenital A b ...

* right-to-left shunting of blood

Diagnosis

The diagnosis is based on: *

Cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...

presents at birth *

Heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

may occur within weeks *

Systolic Systole ( ) is the part of the cardiac cycle during which some chambers of the heart contract after refilling with blood. The term originates, via New Latin, from Ancient Greek (''sustolē''), from (''sustéllein'' 'to contract'; from ''sun ...

ejection murmur is heard at the left sternal border * Widened

pulse pressure Pulse pressure is the difference between systolic and diastolic blood pressure. It is measured in millimeters of mercury (mmHg). It represents the force that the heart generates each time it contracts. Resting blood pressure is normally approx ...

* Bounding arterial pulses * Loud second

heart sound Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stet ...

* Biventricular hypertrophy *

Cardiomegaly Cardiomegaly (sometimes megacardia or megalocardia) is a medical condition in which the heart is enlarged. As such, it is more commonly referred to simply as "having an enlarged heart". It is usually the result of underlying conditions that make t ...

* Increased pulmonary vascularity *

Hypocalcemia Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. The normal range of blood calcium is typically between 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L) while levels less than 2.1 mmol ...

(if associated with

DiGeorge syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent in ...

)

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 Tetralogy of Fallot (TOF), formerly known as Steno-Fallot tetralogy, is a congenital heart defect characterized by four specific cardiac defects. Classically, the four defects are: *pulmonary stenosis, which is narrowing of the exit from the ri ...

and not Common Arterial Trunk. Another well-known classification was defined by Stella and

Richard Van Praagh Richard is a male given name. It originates, via Old French, from Old Frankish and is a compound of the words descending from Proto-Germanic ''*rīk-'' 'ruler, leader, king' and ''*hardu-'' 'strong, brave, hardy', and it therefore means 'strong ...

in 1965. In this classification scheme, the preceding letter ("A" or "B") refers to the presence or absence, respectively, of a

. 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 ''Patent ductus arteriosus'' (PDA) is a medical condition in which the ''ductus arteriosus'' fails to close after birth: this allows a portion of oxygenated blood from the left heart to flow back to the lungs by flowing from the aorta, which has ...

. * Type A4: Common arterial trunk in association with

interrupted aortic arch In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...

. 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 Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and oxygen to the body. The CPB pump itself is often referred to as a he ...

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 In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

of less than 1%.

Additional images

Image:Gray469.png, Diagrams to illustrate the transformation of the

bulbus cordis The bulbus cordis (the bulb of the heart) is a part of the developing heart that lies ventral to the primitive ventricle after the heart assumes its S-shaped form. The superior end of the bulbus cordis is also called the conotruncus. Structure ...

. Ao.

Truncus arteriosus The truncus arteriosus is a structure that is present during embryonic development. It is an arterial trunk that originates from both ventricles of the heart that later divides into the aorta and the pulmonary trunk. Structure The truncus arterio ...

. Au.

Atrium Atrium may refer to: Anatomy * Atrium (heart), an anatomical structure of the heart * Atrium, the genital structure next to the genital aperture in the reproductive system of gastropods * Atrium of the ventricular system of the brain * Pulmona ...

. B.

Bulbus cordis The bulbus cordis (the bulb of the heart) is a part of the developing heart that lies ventral to the primitive ventricle after the heart assumes its S-shaped form. The superior end of the bulbus cordis is also called the conotruncus. Structure ...

. RV.

Right ventricle A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...

. LV.

Left ventricle A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...

. P.

Pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and t ...

References

External links

A.D.A.M. Medical Encyclopedia
from NCBI site.
Truncus arteriosus
{{DEFAULTSORT:Persistent Truncus Arteriosus Congenital heart defects Rare diseases