Arterial trunk. Congenital anomaly of the great vessels at the base of the heart characterized by the existence of a single arterial trunk, due to the persistence of the common embryonic arterial trunk (absence of partitioning of the arterial bulb). This trunk, born on horseback over the two ventricles , above a ventricular septal defect, gives rise to the branches of the aorta and the right and left pulmonary arteries.
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- 1 Pathological anatomy
- 2 Hemodynamics
- 3 Clinical signs
- 4 Diagnosis
- 5 Forecast
- 6 Treatment
- 7 Sources
In the arterial trunk, the aorta and the pulmonary artery converge to form a trunk. The caliber and origin of the pulmonary arteries stemming from the single trunk vary considerably, but are rarely entirely absent. There is always a defect of the ventricular septum and not infrequently a single ventricle . The trunk valve is frequently deformed and incompetent.
Each ventricle pumps blood through a common trunk. There is excessive blood flow to the lungs, and if pulmonary vascular resistance decreases rapidly, there may be left ventricular heart failure in the neonatal period . The degree of arterial oxygen delivery is variable, and when there is considerable mixing through a large ventricular defect, there may be only minimal cyanosis .
In this anomaly, a heart murmur is almost always discovered while the newborn is still in the childcare room. Cyanosis is generally not observed during this period, except when the pulmonary arteries are hypoplastic. A harsh, loud murmur is heard that does not differ from that seen in interventricular septal defects.
A continuous murmur can be heard and it is not uncommon to palpate a systolic thrill and full peripheral pulses. Transient tachypnea is often seen from birth. These children take food poorly and generally experience developmental arrest. Signs of heart failure may occur during the first month of life.
The x – ray heart shows little or no cardiomegaly during the first few days, although it may occur after the first month of life a progressive increase in heart size. In some cases the absence of the pulmonary trunk forms an acute angle between the supracardiac shadow and the main mass of the heart. Taussig indicated that the width of the supracardiac shadow remains unchanged in oblique projections.
Unfortunately, the cardiac zone of the great vessels is often hidden in the newborn by the thymus , which is why these signs are less useful during this period of life. An increase in pulmonary vascularization is commonly observed, except in cases of hypoplasia of the pulmonary arteries. The electrocardiogram is variable and can show a plot of left, right, or combined ventricular hypertrophy.
It is usually not possible to accurately establish the clinical diagnosis of truncus arteriosus in the newborn . Most of these children do not present cyanosis during the neonatal period and the systolic murmur does not differ from the auscultated murmur in left-to-right shunt defects and the single ventricle. The most indicative sign is the presence of a continuous murmur that was found in half of Nadas’ cases.
If the arterial trunk is combined with thick pulmonary arteries, heart failure may develop early. These patients resemble cases with circulating pulmonary hypervolemia, caused by a ventricular septal defect and persistent ductus arteriosus .
When the truncus arteriosus is combined with hypoplasia or absence of the pulmonary arteries, cyanosis occurs from birth. These children must be distinguished from cases with severe Tetralogy of Fallot and tricuspid atresia and other abnormalities with cyanosis and decreased pulmonary blood flow.
Angiocardiography will confirm the diagnosis. The common trunk is filled with contrast and can be seen as it leaves the base of the heart.
The truncus arteriosus is a serious abnormality. Although death rarely occurs in the first month of life, survival of more than one year is uncommon, and death occurs from severe anoxia or congestive heart failure.
The surgery has successfully been initiated by the group at the Mayo Clinic and the percentage of survival constantly improving (Mair et al.). Although the optimal age for surgery is four years, corrective surgery can be performed on one-year-old children. The real problem is the very young infant who does not respond to decongestant treatment. Pulmonary artery bandaging is recommended for these infants, although palliative bandaging may not be effective due to trunk valve incompetence (Gelband et al.).