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Persistent Truncus Arteriosus

By

Lee B. Beerman

, MD, Childrens Hospital of Pittsburgh of UPMC, University of Pittsburgh School of Medicine

Last full review/revision Dec 2020| Content last modified Dec 2020
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Persistent truncus arteriosus occurs when, during fetal development, the primitive truncus does not divide into the pulmonary artery and aorta, resulting in a single, large, arterial trunk that overlies a large, malalignment type ventricular septal defect. Consequently, a mixture of oxygenated and deoxygenated blood enters systemic, pulmonary, and coronary circulations. Symptoms include cyanosis and heart failure, with poor feeding, diaphoresis, and tachypnea. A normal 1st heart sound (S1) and a loud, single 2nd heart sound (S2) are common; murmurs may vary. Before profound heart failure develops, peripheral pulses will be bounding because of the large run off from the proximal aorta to the pulmonary arteries. Diagnosis is by echocardiography or cardiac catheterization. Medical treatment for heart failure is typically followed by early surgical repair.

Persistent truncus arteriosus (see figure Truncus arteriosus Truncus arteriosus Persistent truncus arteriosus occurs when, during fetal development, the primitive truncus does not divide into the pulmonary artery and aorta, resulting in a single, large, arterial trunk that... read more ) accounts for about 1% of congenital heart anomalies and 4% of critical congenital heart defects. About 35% of patients have 22q11 deletion syndrome, which includes DiGeorge syndrome DiGeorge Syndrome DiGeorge syndrome is thymic and parathyroid hypoplasia or aplasia leading to T-cell immunodeficiency and hypoparathyroidism. Infants with DiGeorge syndrome have low-set ears, midline facial... read more and velocardiofacial syndromes. A severe form of truncus arteriosus is one associated with an interrupted aortic arch.

Truncus arteriosus

The primitive truncus does not divide into the pulmonary artery and aorta, resulting in a single large arterial trunk that overlies a large ventricular septal defect.

Truncus arteriosus

IVC = inferior vena cava; LA = left atrium; LV = left ventricle; PA = pulmonary artery; PV = pulmonary veins; RA =right atrium; RV = right ventricle; SVC = superior vena cava.

Classification

There are several classification systems in use.

An earlier classification, by Collett and Edwards, is

An updated classification by Van Praagh consists of type A (truncus arteriosus withventricular septal defect Ventricular Septal Defect (VSD) A ventricular septal defect (VSD) is an opening in the interventricular septum, causing a shunt between ventricles. Large defects result in a significant left-to-right shunt and cause dyspnea... read more Ventricular Septal Defect (VSD) [VSD]) and the very rare type B (truncus arteriosus without VSD). Type A is subdivided into 4 types:

  • Type A1: The main pulmonary artery arises from the truncus and then divides into right and left pulmonary arteries.

  • Type A2: The right and left pulmonary arteries arise separately from the posterior aspect of the truncus.

  • Type A3: One lung is supplied by a pulmonary artery branch that arises from the truncus and the other lung (usually the left) is supplied by a ductus-like collateral artery

  • Type A4: The truncus is a large pulmonary artery and the aortic arch is interrupted or coarctation is present.

The truncal valve may be quite abnormal and manifest with stenosis, regurgitation, or both. The valve is tricuspid in 69%, quadricuspid in 22%, and bicuspid in 9%. Other anomalies (eg, right aortic arch, interrupted aortic arch, coronary artery anomalies) may be present and may contribute to the high surgical mortality rate. A patent ductus arteriosus Patent Ductus Arteriosus (PDA) Patent ductus arteriosus (PDA) is a persistence of the fetal connection (ductus arteriosus) between the aorta and pulmonary artery after birth. In the absence of other structural heart abnormalities... read more Patent Ductus Arteriosus (PDA) is exceedingly rare in Collett and Edwards types I, II, and III defects or in Van Praagh types A1 and A2 but is present in about half of patients with truncus arteriosus, most notably those with types A3 and A4 defects.

Symptoms and Signs of Persistent Truncus Arteriosus

Infants usually present with mild cyanosis and symptoms and signs of heart failure (eg, tachypnea, poor feeding, diaphoresis) in the first few weeks of life. Physical examination may detect a hyperdynamic precordium, increased pulse pressure with bounding pulses, a loud and single 2nd heart sound (S2), and an ejection click. A grade 2 to 4/6 systolic murmur is audible along the left sternal border (see table Heart Murmur Intensity Heart Murmur Intensity Auscultation of the heart requires excellent hearing and the ability to distinguish subtle differences in pitch and timing. Hearing-impaired health care practitioners can use amplified stethoscopes... read more ). A mid-diastolic mitral flow murmur may be audible at the apex when pulmonary blood flow is increased. With truncal valve insufficiency, a high-pitched diastolic decrescendo murmur is audible over the mid left sternal border.

Diagnosis of Persistent Truncus Arteriosus

  • Chest x-ray and ECG

  • Echocardiography

  • Occasionally cardiac catheterization, cardiac MRI, or CT angiography

Diagnosis is suspected clinically, supported by chest x-ray and ECG, and established by 2-dimensional echocardiography with color flow and Doppler studies. Cardiac catheterization is occasionally necessary to delineate associated anomalies before surgery, but cardiac MRI or CT angiography may supplant the need for catheterization.

Chest x-ray shows varying degrees of cardiomegaly with increased pulmonary vascular markings, right aortic arch (in about 30%), and relatively high position of pulmonary arteries.

ECG commonly shows combined ventricular hypertrophy. Substantial pulmonary overcirculation may produce evidence of left atrial enlargement.

Treatment of Persistent Truncus Arteriosus

  • Medical treatment of heart failure (eg, diuretics, digoxin, angiotensin-converting enzyme inhibitors) before surgery

  • Surgical repair

Heart failure Heart failure in older infants and children Congenital heart disease is the most common congenital anomaly, occurring in almost 1% of live births (1). Among birth defects, congenital heart disease is the leading cause of infant mortality... read more Heart failure in older infants and children is treated vigorously with diuretics, digoxin, and angiotensin-converting enzyme (ACE) inhibitors, followed by early surgical repair. Prostaglandin infusion is beneficial to maintain ductal patency when there is interruption or coarctation of the aortic arch, in which case right-to-left shunt through the ductus provides systemic blood flow.

Surgical management consists of repair during the neonatal period. The ventricular septal defect is closed so that the left ventricle ejects into the truncal root. Usually, continuity between the right ventricle and the confluence of the pulmonary arteries is achieved using a conduit with or without a valve. Some centers have reported good success using a non conduit approach, in which the left atrial appendage is used as the posterior wall of the pulmonary outflow and a patch is used as the anterior wall, with or without the insertion of a monocusp valve.

When a conduit is placed during early infancy, its size becomes inadequate as children grow, and the conduit must be revised during childhood. When the patient's own tissue is used for part of this outflow tract, there is the potential for growth of the conduit as the child grows.

Branch pulmonary artery stenosis is a common sequela. Surgical mortality rates have decreased to as low as 10% in recent years.

Endocarditis prophylaxis Prevention Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more Prevention is recommended preoperatively but is required only for the first 6 months after repair unless there is a residual defect adjacent to a surgical patch or prosthetic material.

Key Points

  • In persistent truncus arteriosus, the primitive truncus does not divide into the pulmonary artery and aorta, resulting in a single large arterial trunk that overlies a large ventricular septal defect (VSD).

  • Different types are distinguished based on the origin of the pulmonary arteries and associated defects.

  • Patients present with mild cyanosis, significant pulmonary overcirculation, and heart failure; a grade 2 to 4/6 systolic murmur is audible along the left sternal border and a mid-diastolic mitral flow murmur may be audible at the apex.

  • Treat heart failure with diuretics, digoxin, and ACE inhibitors; prostaglandin infusion is beneficial to maintain duct patency only in patients with type A4 truncus with interrupted aortic arch or coarctation.

  • Do surgical repair early; one or more revisions are usually needed as children grow.

More Information

The following are some English-language resources that may be useful. Please note that The Manual is not responsible for the content of these resources.

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