Truncus arteriosis communis is the name given to a very rare heart defect in newborns caused by incomplete separation of the pulmonary arterial trunk from the arterial trunk of the systemic circulation. The aorta and pulmonary artery arise in a common trunk, resulting in mixing of the oxygen-depleted arterial blood of the pulmonary circulation with the oxygen-rich arterial blood of the systemic circulation. Almost always, TAC is associated with a septal defect just below the common arterial trunk and requires early postnatal surgical management.
What is truncus arteriosis communis?
The main feature of the very rare heart defect known as truncus arteriosus communis (TAC) is the common origin of the coronary artery (aorta) and the pulmonary artery (arteria pulmonalis) from both ventricles of the heart. At the same time, there is always a septal defect between the left and right ventricles (ventricular septal defect, VSD) located just below the confluence of the TAC. De facto, the oxygen-poor arterial blood of the pulmonary circulation mixes with the oxygen-rich arterial blood of the systemic circulation. Depending on the outflow of the pulmonary artery from the common trunk with the aorta, a distinction is made between types I to IV of a TAC. Common to all four categories is that there is only one common heart valve, the aortic valve converted to a truncus valve. However, it usually shows stenosis or is not adapted in size to the conditions, so that there is a limited functional capacity from the outset.
Causes
During the embryonic and fetal stages until birth, the pulmonary circulation or small body circulation is short-circuited via the junction of the ductus arteriosus with the aorta, the main artery of the body. During and after birth, the ductus arteriosus closes, separating the two circulations. Oxygen and nutrients are supplied prenatally through the mother’s circulation. The anlage for the possible later separation of the great circulation from the pulmonary circulation already occurs between the 32nd and 36th day of gestation. The originally single and common arterial trunk, the truncus arteriosus, in the even earlier stage of development divides into the aorta and the truncus pulmonalis. The septum, the dividing wall between the right and left ventricles, forms between the two arterial trunks. In rare cases, the separation of the two arterial trunks fails to occur, and similarly, the septum does not extend to the orifice of the two arterial trunks, so that the separation between the two circulations cannot occur postnatally-even after proper closure of the ductus arteriosus. Approximately 40 percent of newborns affected by TAC show a gene defect on the long arm of chromosome 22 at locus 22q11.2, which is thought to be causally related to TAC. For the remaining affected individuals, the reasons leading to the abnormality in the heart have not yet been adequately elucidated.
Symptoms, complaints, and signs
Symptoms and complaints caused by a TAC only become apparent postnatally because the two blood circuits are shorted prenatally, even in a healthy fetus. In some cases, the malformation of the heart is already conspicuous prenatally on ultrasound examinations, so that further targeted examinations provide clarity about the extent and category of the TAC. In the remaining affected newborns, a series of nonspecific symptoms resembling those of hypoxia with other causation present soon after birth. The newborns show increasing tendency to blue discoloration (cyanosis), and pulmonary hypertension is usually seen. The newborns usually suffer from weakness in drinking, and their respiratory rate is markedly increased. If left untreated, heart failure soon sets in. There may also be rapid development of hepatomegaly, an enlarged liver. The overall development of the newborn is impaired.
Diagnosis and course of the disease
If the diagnosis has not been made prenatally, routine auscultation of heart murmurs provides initial evidence of the presence of an abnormality in the cardiac anlage. Targeted echocardiography can provide clarity as to whether, for example, a septal defect is present and whether there is only a single common arterial outlet from the heart-usually just above the septal defect.In addition to magnetic resonance imaging (MRI), further diagnostic measures include angiocardiography, a radiological examination of vessels close to the heart and the heart itself as part of a cardiac catheterization. ECG also provides evidence of certain abnormalities. The course of TAC is severe.
Complications
Usually, the symptoms of truncus arteriosus communis occur immediately after the infants are born. This primarily results in a severe undersupply of oxygen, causing the infants to die without treatment. The skin turns blue and the brain and internal organs are damaged. The children are dependent on rapid treatment. Likewise, the children suffer from a strong drinking weakness, so that dehydration and also strong deficiency symptoms occur. Furthermore, truncus arteriosus communis leads to renal insufficiency if left untreated. The liver is also significantly enlarged in the disease, which can lead to pain. Child development is significantly limited by the disease. Likewise, heart failure can occur. Parents and relatives also often suffer from psychological discomfort or severe depression in cases of truncus arteriosus communis. The treatment of truncus arteriosus communis is carried out by various surgical interventions. It cannot be universally predicted whether complications will occur. However, the life expectancy of children is significantly reduced by the disease.
When should you see a doctor?
In cases of truncus arteriosus communis, the patient is dependent on medical examination and treatment. This is the only way to prevent further complications or further worsening of symptoms. If the disease is not treated, in the worst case, death of the affected person may occur. Therefore, in the case of truncus arteriosus communis, an early diagnosis with subsequent treatment must be made in any case. A doctor should be consulted for this condition when ultrasound examination shows that the arteries to the fetus are closed. Most often this is detected directly by the gynecologist or in a hospital. In many cases, the child also exhibits weakness in drinking or suffers from severe heart problems. If these symptoms occur, a doctor must be contacted in any case. Delayed development of the child may also indicate truncus arteriosus communis and should also be checked by a physician. A general practitioner or a pediatrician can be consulted for this condition. Further treatment is then carried out by a specialist. It is not generally possible to predict the further course.
Treatment and therapy
The truncus arteriosis communis involves a serious malformation of the heart, which is due to a maldevelopment already during the embryonic stage. Drug treatment cannot bring lasting success, so that only a “mechanical” correction of the malposition in an open-heart operation remains as the means of choice. The operation is performed as soon as possible in early infancy. Due to the individual differences in the degree of malposition, the corrective measures performed during surgery on the “arrested” heart are also very individual. The main goal of the operation is to achieve an effective separation between the pulmonary and the great systemic circulation. To achieve this, it is necessary to first correct the ventricular septal defect. The missing piece of septum or the hole within the septum is closed with a special plastic patch. In addition, the two pulmonary arteries are connected with a vascular prosthesis, which can be made from animal material or from a human donor. The other end of the vascular prosthesis is connected to the right ventricle. This is done to separate the two circulations and make the blood circulation comparable to that of a healthy person.
Prevention
Direct preventive measures to prevent TAC are not known. Because the basis for the malformation occurs during the embryonic stage between the 32nd and 36th day of pregnancy, it seems prudent for women to consciously stay away from potentially toxic substances such as environmental toxins, alcohol, and nicotine during the early stages of pregnancy to minimize the risk of malformations triggered by them.
Aftercare
Because the mortality rate of infants suffering from the common truncus arteriosus is very high during the first six months, surgery must be performed, which in turn requires consistent follow-up care. Thus, follow-up examinations should take place at regular intervals, because problems such as valve weakness as well as the risk of short-circuit connections that do not grow along with the patient still exist after the surgical intervention. In some cases, additional surgical treatments may also be necessary. The mortality rate after surgery of the common truncus arteriosus is about ten percent. There is a survival rate of ten years in approximately 80 percent of babies operated on. Among the indispensable follow-up measures are cardiological progress controls. They must take place throughout the baby’s life. During these examinations, doctors pay particular attention to possible calcifications, narrowing (stenoses) and insufficiencies. Pulmonary hypertension and ventricular arrhythmias are also of interest. Sometimes there is an increase in truncal valve insufficiency requiring treatment as the disease progresses. Prophylaxis against endocarditis (inflammation of the inner lining of the heart) is also necessary throughout the patient’s life. In order to check the functions of the conduits (artificial tubes), echocardiograms and regular magnetic resonance imaging are performed. Furthermore, the truncus valve, the aorta (main artery) and the aortic arch are checked. Frequently, the conduits have to be replaced after a few years. In more than 50 percent of all patients, replacement takes place after five years.
Here’s what you can do yourself
Truncus arteriosus communis is a rare condition that requires primarily surgical and drug treatment. Regular intake of prescribed medications is an important self-help measure that patients must strictly adhere to. In addition, lifelong control examinations by the physician are necessary. The parents and later the patient himself must ensure that the appointments are kept. Comprehensive endocarditis prophylaxis is also necessary. In addition to taking antibiotics, prevention of inflammation succeeds through a gentle lifestyle. Infections and cardiovascular diseases must be avoided at all costs. Otherwise, life-threatening endocarditis may occur. Should a febrile illness nevertheless occur, the doctor must be consulted. From then on, a strong antibiotic must be taken to cure the inflammation as quickly as possible. Usually the treatment takes place in a specialized clinic. The cardiologist in charge will suggest suitable self-help measures to accompany the therapy of the truncus arteriosus communis. The supportive measures are based on the course of the disease and the chosen therapy. They should be discussed closely with the physician so that rapid action can be taken in the event of adverse events.
