What is Truncus Arteriosus?
During normal fetal development both of the great vessels of the heart (aorta and main pulmonary artery) arise from division of a single primitive arterial trunk (trunk arteriosus). The aorta supplies blood to the head and the body, the pulmonary artery supplies blood to the lungs. During fetal development in a child with persistent truncus arteriosus, the embryological division, or separation, these infants are born essentially with one great vessel originating from the heart instead of two. This vessel supplies blood to the head and body, as well as the lungs. In addition to the persistent truncal artery, infants are usually born with a ventricular septal defect, or hole between the two pumping chambers of the heart.
There are four types of truncal defects (Collett and Edwards classification):
Truncus I: In this type of truncus there is a main truncal vessel which gives rise to the aorta, and a short main pulmonary artery distal to the truncal valve. The right and left pulmonary arteries arise from the short main pulmonary artery.
Truncus II: In this type of truncus there is no main pulmonary artery trunk. The right and left pulmonary arteries arise from separate holes on the truncal artery, but next to one another.
Truncus III: In this type of truncus there is not a distinguishable main pulmonary artery. Instead the right and left pulmonary arteries arise from different areas on the truncal artery distal to the truncal valve.
Truncus IV: In this type of truncus the right and left pulmonary arteries arise from the descending aorta. Blood is supplied to the arteries through collateral vessels from the aorta.
In a high percentage of Truncus Arteriosus the valve of the truncal vessel is abnormal. In most cases the valve has 3 leaflets, but may have 2, 4 or even 5 leaflets. Because of this, the valve may leak and may never function 100%. In addition to the above, the coronary arteries may be abnormal.
What happens when a child is born with persistent Truncus Arteriosus?
In Truncus Arteriosus, there is abnormal flow of blood out of the heart. Because of the large ventricular septal defect, blood returning to the right side of the heart from the body (unoxygenated and blue), mixes with the blood returning to the left side of the heart from the lungs (oxygenated and red), and is ejected together out the truncal valve and artery. Blood flow coming out of the heart through the truncal vessel flows to the lungs and the body. Because the lungs normally have a lower pressure and resistance than the body, blood flows preferentially to the lungs causing the lungs to become congested. The mixing of red and blue blood might make the child cyanotic (blue), although it may not be noticeable at birth. Babies with too much pulmonary blood flow usually breathe very rapidly, and do not feed well; subsequently they do not grow normally. Eventually, if left untreated, patients will have complications from too much blood flow to the lungs which will ultimately lead to the child’s death.
How is Truncus Arteriosus diagnosed?
Diagnosis of this congenital heart defect is usually made shortly after birth by echocardiography. A murmur or abnormal heart sound may be noted on exam, and or an abnormal chest x-ray may reveal an enlarged heart. As stated earlier, some infants may exhibit a bluish color to their lips, fingers, and toes (cyanosis), but this may not always be noticeable. The diagnosis of Truncus Arteriosus has been made with the use of prenatal sonography. This may prove beneficial to the infant as treatment for congestive heart failure could be started as soon as the infant was born.
How is Truncus Arteriosus treated?
Surgical treatment for this congenital heart defect usually takes place when the child is a neonate. Most babies will be transported, once the diagnosis has bee made, to a facility with trained personnel. The baby may or may not be placed on a breathing machine to stabilize the breathing. Diagnosis will be confirmed with an echocardiogram, and possibly a cardiac catheterization.
The surgical operation to repair Truncus Arteriosus involves separating the pulmonary circulation from the main truncal artery, and closing the Ventricular Septal Defect. The truncal artery and valve are committed to the left side of the heart. The pulmonary arteries are connected to the right ventricle with a cadaver tube graft (homograft) that contains a valve. Because the homograft is cadaver (dead) tissue, it will not grow with the patient. The baby will have to undergo at least one or more open heart procedures to replace the homograft before he/ she reaches adulthood.
Are there other congenital heart defects or genetic defects that are specifically related to Truncus Arteriosus?
A Syndrome known as Digeorge syndrome has been linked to a significant number of patients diagnosed with Truncus Arteriosus. Because of this link most infants diagnosed with a truncal defect will also have a genetics doctor see them while he/ she is in the hospital.
Another lesion associated with Truncus Arteriosus is and interrupted Aortic Arch. This defect is repaired at the same time as the truncus. The two ends of the interrupted aorta are sewn together. This associated lesion creates an additional challenge and risk when repairing the heart with Truncus Arteriosus.
Will my baby have a normal heart after the surgical repair for Truncus Arteriosus?
As far as the normal pathway of blood flow goes a repaired Truncus Arteriosus functions as a “normal heart”. This is evidenced by “blue” blood passing from the right side of the heart through the pulmonary arteries to the lungs, and the “red” blood returning to the left side of the heart from the lungs and being pumped out of the truncal artery to the body. The ventricular septum is intact so that no mixing of the red and blue blood occurs. Although the blood flow in the heart of a repaired truncus is “normal”, the infant still has a tube graft connecting the right ventricle to the right and left pulmonary arteries. This homograft will have to be replaced at least 1-2 times before the patient is an adult. Each time the homograft is replaced the surgery carries a risk for the patient.
What are some of the risks associated with the surgical repair of Truncus Arteriosus?
Complications that can be associated with cardiopulmonary bypass and open heart surgery in general:
- Infections
- Bleeding
- Blood Transfusion
- Stroke
- Death
The repair of Truncus Arteriosus usually includes closure of the Ventricular Septal Defect. There is a risk of injury to the conduction (electrical) system of the heart. This may result in the need for insertion of a permanent pacemaker. There is always a risk of future surgeries for homograft stenosis, calcification, or valve leakage.
Contact Information:
John Mark Morales MD, FACS, FAAP
Chief of Cardiothoracic, Director of Perfusion Services
Certified by the American Board of Surgery, American Board of Thoracic SurgeryMark Bielefeld, MD
Driscoll Children's Hospital Chief of Staff
Certified by the American Board of Surgery, American Board of Thoracic SurgeryThoracic surgeons are available for questions and consultations: (361) 854-0201. For appointments, assistance, and physician references in Corpus Christi call:
(361) 854-0201 or (800) DCH-LOVE
Fax : 361-855-7572
E-MAILS : Mark Morales, MD
Mark Bielefeld, MD
For further information on any surgical procedures you can contact Carol Kaplan, RN, Surgical Nurse Liaison at (361) 694-5150. Consultation and surgery for inpatients is provided in concert with neonatology and pediatric cardiology departments. Complete evaluation and management for infants, children, adolescents and adults with congenital or acquired cardiac, vascular or thoracic anomalies.
Cardiothoracic Associates
3533 S. Alameda, Suite 202
Corpus Christi, Texas 78411
Office: (361) 854-0201 or (361) 694-5150
Fax: (361) 855-7572
Hours: 9am to 6pm
Fri 9am to 5pm
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Copyright © Driscoll Children's Hospital 2008
Corpus Christi, Texas
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