I. Tetralogy of Fallot
TOF is the most common form of cyanotic preconditioning in clinical practice, accounting for 12% to 14% of the total preconditioning and more than 50% of cyanotic preconditioning. It is caused by the anterior displacement of the conical septum of the right ventricular outflow tract during embryonic development. The pathological and anatomical features include pulmonary stenosis, ventricular septal defect, aortic riding span and right ventricular hypertrophy.
Key points of echocardiographic examination: ①Detection of right ventricular outflow tract and pulmonary artery stenosis, measurement of the size of the pulmonary artery and its branches, and assessment of the degree of pulmonary artery development. ②Define the location and size of the ventricular defect. ③To determine the degree of aortic riding. ④Detection of coronary artery malformation.
1.Assessment of pulmonary artery stenosis
The subxiphoid right ventricular outflow tract view, the short-axis view of the root of the parasternal aorta, and the long-axis view of the parasternal right ventricular outflow tract can show the conical septum displaced to the left and forward, and clarify the right ventricular outflow tract stenosis. Parasternal and high parasternal long-axis views of the pulmonary artery can show the common pulmonary artery trunk and pulmonary artery branches, but there is some degree of underestimation of the pulmonary artery branches. Long-axis views of the right pulmonary artery in the superior sternal fossa can show the right pulmonary artery and its branches more clearly. Because the left pulmonary artery travels posteriorly, it is often difficult to show; after the long axis of the right pulmonary artery is shown in the superior sternal fossa view, the probe can be tilted slightly forward and to the left to show the long axis of the left pulmonary artery, which can also be shown in the long axis view of the right ventricular outflow tract under the saber and in the high parasternal short axis view. The internal diameter of the pulmonary artery measured in this view correlates best with the cardiovascular imaging values and is the best view for assessing the degree of pulmonary artery development. The sum of the diameters of the pulmonary arteries before the first branch vessel emanating from the right and left pulmonary arteries divided by the diameter of the descending aorta at the level of the transverse septum is called the McGoon ratio; if the ratio is ≥2,0, the pulmonary artery is considered free of stenosis; if the ratio is ≥1,2-1,3, radical surgery can be performed.
In cases of tetralogy of Fallot combined with pulmonary valve defect, the stenosis is mostly located at the pulmonary valve annulus, and subxiphoid and parasternal right ventricular outflow tract views can show the development of the outflow tract and annulus. The main pulmonary artery trunk is short, and the left and right branches are significantly dilated. The dilated branches may compress the trachea causing respiratory distress. The child’s head should not be tilted back excessively during the suprasternal fossa examination, and the probe should not compress the suprasternal fossa to avoid aggravating tracheal stenosis and causing asphyxia.
Color Doppler ultrasound shows a colorful mosaic of blood flow at the stenosis. Spectral Doppler ultrasound can be used to measure the velocity of pulmonary artery blood flow, and the magnitude of the differential pressure at the obstruction can be calculated according to the simplified Bernoulli equation to determine the severity of the stenosis. However, it should be noted that in severe pulmonary artery stenosis tending to atresia, the high velocity flow in the pulmonary artery may not be measured due to the low flow signal, and the assessment of pulmonary artery stenosis based on pressure difference alone may result in underestimation.
The development of the pulmonary artery should be evaluated in conjunction with the diameter of the common trunk and branches of the pulmonary artery.
2. Detection of ventricular septal defect
The distance from the septal stump to the root of the anterior aortic wall is the size of the ventricular defect, and the type of ventricular defect can be determined by combining the short-axis view of the parasternal aorta with the apical five-chamber view. The conical septal defect is a double subarterial ventricular defect, which can be shown in the long-axis view of the left ventricle, the short-axis view of the parasternal aorta, and the long-axis view of the parasternal right ventricular outflow tract.
The subxiphoid and apical four-chamber views can show the location of the ventricular defect, the degree of differentiation of the common atrioventricular valve anterior bridging valve, and the location of the anterior bridging valve tendon attachment, etc. In the case of a small myocardial ventricular septal defect, the majority is a type C atrioventricular septal defect, but it can also be type B. Type A is rare.
In combination with small myocardial ventricular septal defect, the two-dimensional section is often difficult to display due to the roughness of the right ventricular surface myocardial trabeculae; color Doppler ultrasound imaging is difficult due to the similarity of the left and right ventricular pressure and low shunt velocity; it is easy to miss the diagnosis. At this time, the integrity of the ventricular septum should be carefully observed in multiple sections, and the color Doppler ultrasound imaging speed should be reduced to carefully observe whether there is blood flow through the septum; the sampling volume should be placed on the right ventricular side of the ventricular defect, and the two-way low velocity shunt spectrum can be recorded.
3. Assessment of the degree of aortic riding
The parasternal left ventricular long-axis view is the standard view for the diagnosis of tetralogy of Fallot, which can clarify the degree of aortic riding, but attention should be paid to the position of the probe; a high parasternal view may overestimate the degree of aortic riding, and an apical left ventricular long-axis view may underestimate the degree of aortic riding. The degree of caval span can be expressed as the caval span rate: caval span rate = (vertical distance from the anterior aortic wall to the ventricular septum / distance from the anterior to the posterior aortic wall) x 100%. If the span rate is <25%, it is mild span; between 25% and 50%, it is moderate span; and >50%, it is severe span. The long-axis view of the left ventricle next to the sternum can show the connection between the posterior wall of the aorta and the mitral valve, and combined with the subxiphoid view, determine whether there is a conical structure under the aortic valve; if there is a fibrous connection between the aortic valve and the mitral valve, the diagnosis is TOF; if there is a muscular connection between the aortic valve and the mitral valve, the diagnosis is right ventricular double outlet.
4.Detection of coronary artery malformation
Patients with tetralogy of Fallot are often combined with coronary artery malformation, commonly the left anterior descending branch of coronary artery originates from the right coronary artery and single coronary artery. Using high-frequency probe, high parasternal short-axis views of the aorta can show the origin and course of the left and right coronary arteries, observe whether there is a coronary artery traveling on the surface of the right ventricular outflow tract, and observe whether the left anterior descending branch originates from the right coronary artery and whether it is a single coronary artery malformation. It is difficult to diagnose coronary artery malformation by ultrasound due to the resolution. High vigilance should be exercised in the following cases: ① The long-axis view of the left ventricle next to the sternum shows thickening of the right coronary artery, and attention should be paid to whether the left coronary artery trunk or branch originates from the right coronary artery. (ii) The coronary artery crosses the right ventricular outflow tract. ③There is only one coronary artery opening at the root of the aorta, and three branches from a single thickened left or right coronary artery are seen.
II. Pulmonary artery atresia with ventricular septal defect
PA/VSD is a relatively rare type of cyanotic preconditioning, accounting for 0.20% of the total preconditioning, and used to be considered the most severe type of tetralogy of Fallot, also known as TOF/PA, with similar hemodynamics and clinical manifestations to tetralogy of Fallot, and the ultrasound examination method is basically the same as that of tetralogy of Fallot.
The main pathological feature of PA/VSD is that there is no anatomical connection between the right ventricle and the pulmonary artery, and the blood supply to the pulmonary artery mainly comes from the ductus arteriosus and the collateral vessels, so clinically cyanosis can appear after birth. If a high velocity antegrade flow signal is detected, it is TOF; if there is no significant antegrade flow signal, it is PA/VSD. The majority of TOFs are combined with obtuse ductus arteriosus, and only very few severe TOFs are combined with vertical ductus arteriosus.
Functional pulmonary valve atresia: It refers to the presence of pulmonary valve leaflet structures, but the opening activity is not obvious, and there is no obvious transvalvular flow. The blood flow entering the common pulmonary artery trunk through the arterial duct folds back at the level of the atretic pulmonary valve, which is easily confused with the antegrade flow, which should be a high-speed flow and can be distinguished.
III. Double right ventricular outlet
DORV is a relatively rare type of cyanotic preconditioning, accounting for 0.48% to 1.67% of the total preconditioning. It is a group of lesions in which the inferior cones of the great arteries fail to absorb normally and rotate insufficiently during embryonic development, resulting in two great vessels connected to the right ventricle together.
The definition of right ventricular double outlet is more controversial in terms of the majority of large arteries originating from the right ventricle. Some scholars have proposed the 50% rule, that is, one large artery originates completely from the anatomic right ventricle, and the other large artery originates more than 50% from the right ventricle; some scholars have also proposed the 90% rule, that is, one large artery originates completely from the anatomic right ventricle, and the other large artery originates more than 90% from the right ventricle; the discontinuity between the semilunar valve of the two large arteries and the atrioventricular valve was also used as a diagnostic criterion for double outlet of the right ventricle. The 50% rule is now more commonly accepted, and discontinuity between the semilunar and atrioventricular valves is present in only about 86% of patients.
In 1972, Lev et al. classified right ventricular double outlet according to the presence or absence of combined pulmonary stenosis, the location of the ventricular septal defect, and the interrelationship between the aorta and the pulmonary artery: (i) according to the presence or absence of pulmonary stenosis, right ventricular double outlet was classified as: type I: right ventricular double outlet without pulmonary stenosis; type II: right ventricular double outlet with pulmonary stenosis. The right ventricular double outlet is classified according to the location of the ventricular septal defect: type A: the VSD is located under the aortic valve, the aorta rides over the ventricular septum, and there is a muscular connection between the aorta and the mitral valve; this type is the most common, accounting for about 61%. type B: the VSD is far from the two aortic openings, and there are tissues such as papillary muscle, tendon cords and tricuspid valve between the ventricular defect and the aortic valve orifice, and most of them are muscular trabecular or atrioventricular access type ventricular defects. Type C: VSD is located under the pulmonary valve and the pulmonary artery rides over the ventricular septum, also known as Taussig-Bing malformation, accounting for about 30% of cases. type D: VSD is located under both great arteries and the upper edge of the defect is the connecting part of the aortic and pulmonary valve annulus due to conical septal agenesis or hypoplasia; this type is the least common, accounting for about 4% of cases.
In 2000, two major databases of the International Association of Thoracic Surgeons and the European Association of Thoracic Surgery classified right ventricular double outlet as follows: (1) ventricular septal defect type (subaortic defect, double subarterial defect); (2) tetralogy of Fallot type; (3) transposition of the great arteries type (subpulmonary artery defect with or without pulmonary artery stenosis); (4) ventricular septal defect away from the great arteries type (4 subtypes according to whether it is a complete atrial septal defect, with or without pulmonary artery (divided into 4 subtypes according to whether the defect is complete or not, with or without pulmonary stenosis); ⑤ intact ventricular septum type.
The main points of echocardiographic diagnosis: ① clarify the origin, arrangement and course of the two great arteries. (2) Determination of the anatomic relationship between the atrioventricular valve and the semilunar valve. ③Detection of ventricular septal defect. ④Whether pulmonary artery stenosis is combined.
1.The two great arteries start from the right ventricle
The long axis and four-chamber view of the left ventricle next to the sternum: all or most of the aorta and pulmonary artery originate from the right ventricle, and the two sets of semilunar valves are arranged side by side at the same level, with the aortic valve on the right and the pulmonary valve on the left. If the subaortic cone is well developed, the aortic valve may be pushed to the right anterior or left anterior to the pulmonary valve. The aorta is anterior, the posterior wall of the aorta is close to the ventricular septum, and the aorta rides over the ventricular septum, or the aorta may originate entirely from the right ventricle. If the aorta originates entirely from the right ventricle and the pulmonary artery rides over the ventricular defect, it is called Taussing-Bing malformation.
Subxiphoid four-chamber view: an anterior-posterior sweep can clarify the origin and interrelationship of the two great arteries and determine whether there is a combined aortic or subvalvular pulmonary stenosis. Both great arteries can be found to originate from the right ventricle or one originates from the right ventricle and the other rides over the ventricular septum, mostly from the right ventricle. The aortic and pulmonary valves are usually at the same level due to the presence of conical structures under both great arteries.
Short-axis view of the great vessels: It can show the cross-section of the aortic and pulmonary artery roots, and then determine the spatial location of the relationship between them. Most of the aorta and pulmonary artery are lateralized, with the aorta on the right and the pulmonary artery on the left (50% to 65%); or the aorta on the right anterior and the pulmonary artery on the left posterior (26%); the aorta on the left posterior is rare (7%); occasionally, the relationship between the aorta and pulmonary artery is normal (3%). The size of the aorta and pulmonary artery should also be carefully measured in the above-mentioned views to determine whether transposition of the great arteries can be performed.
2.The relationship between the semilunar valve and atrioventricular valve connection
Under normal circumstances, most of the subaortic cones are absorbed, and the left coronary valve and noncoronary valve of the aorta are directly connected to the mitral valve; a small portion of the pulmonary cone is absorbed and shortened, and the intact cone structure is still retained. When the subaortic cone is not sufficiently absorbed, two large vessels are connected to the right ventricle to form the right ventricular double outlet. The relationship between the aortic and pulmonary valves depends on the development of the two sets of subsemilunar cones. In most cases, the presence of cone structures under both great vessels is referred to as a bilateral cone, so that the semilunar valve is separated from the atrioventricular valve by a myocardial cone without fibrous connections. Parasternal long-axis views of the left ventricle can reveal the semilunar and mitral valves. If there is a dense strip of strong echogenic shadow between the posterior wall of the great arteries and the anterior mitral valve, this is a subhemispheric cone structure.
The tetralogy of Fallot type with double right ventricular outlet has a clinical presentation similar to that of tetralogy of Fallot. The long-axis view of the left ventricle next to the sternum can show the connection between the posterior wall of the aorta and the mitral valve. If there is a fibrous connection between the aortic valve and the mitral valve, the diagnosis is tetralogy of Fallot, and most of them are large in the right atrium and right ventricle; if there is a muscular connection between the aortic valve and the mitral valve, the diagnosis is double outlet of the right ventricle, and most of them are large in the left atrium and left ventricle.
3.Determine the location, size and number of ventricular septal defects
Ventricular septal defect is most often located under the aorta, when the aorta starts to span the ventricular septum. When the ventricular defect is located under the pulmonary artery, the pulmonary artery starts to straddle the ventricular septum. The atrioventricular access ventricular defect and the myocardial trabecular ventricular defect, in which the opening of the defect is far from the opening of the two aorta, are called distant from the aorta ventricular defects. Because the relationship between the ventricular defect and the location of the great arteries is complicated, it should be combined with subxiphoid, apical, parasternal views and long-axis views of the left ventricle to make a comprehensive judgment.
4.Detection of pulmonary artery stenosis
Pulmonary artery stenosis is found in more than 50% of right ventricular double outlets, and is more common when the ventricular defect is located under the aorta or under both arteries. The subxiphoid and parasternal views can show the narrowed pulmonary artery and measure the internal diameter of the common trunk and branches of the pulmonary artery. Color Doppler ultrasound can show colorful turbulent flow through the stenosis, and spectral Doppler ultrasound can measure the high velocity flow in the pulmonary artery and assess the severity of pulmonary stenosis based on the pressure difference estimated by the simplified Bernoulli equation.
IV. Complete transposition of the great arteries
D-TGA is a common form of cyanotic preconditioning, accounting for about 5% of preconditioning and ranking second in cyanotic preconditioning, with a male to female ratio of 2 to 4:1. The incidence in diabetic mothers is 11 or 4 times higher than in normal mothers, and the incidence is higher in pregnant women who have used hormones and anticonvulsant drugs in early pregnancy. If left untreated, approximately 90% of patients die within 1 year of age.
Under normal conditions, the subvalvular cone of the pulmonary artery develops and the pulmonary artery is located in the anterior superior left; the subvalvular cone of the aorta atrophies and the aorta is located in the posterior inferior right. In transposition of the aorta, the subaortic cone is developed and not absorbed, and the aorta is located anteriorly and superiorly to the right; the pulmonary artery is located posteriorly and inferiorly to the left due to atrophy of the subaortic cone; this allows the pulmonary artery to connect posteriorly to the left ventricle and the aorta to connect anteriorly to the right ventricle; there is a muscular connection between the subaortic valve and the tricuspid valve due to the presence of the cone; there is no cone structure present under the pulmonary valve and there is a fibrous connection with the mitral valve. The pathology is characterized by a consistent connection between the atria and the ventricles, but not between the ventricles and the aorta; the aorta begins in the right ventricle and the pulmonary artery begins in the left ventricle.
Key points of echocardiographic diagnosis: ①judge the position of atria and ventricles, clarify the connection between ventricles and aorta, and establish the diagnosis. ②Evaluate the type, location and size of intracardiac shunt. ③Detection of left ventricular outflow tract obstruction. ④Define the origin and course of the coronary arteries, except for coronary artery malformation.
1. Determination of the origin and location of large vessels
After displaying the four-chamber section under the subxiphoid process, the probe is tilted forward and two large arteries are seen in a parallel relationship, which is different from the mutual crossover in normal people. The aorta is in front, originating from the right ventricle, and travels upward to continue with the aortic arch; there is no bifurcation before issuing the innominate artery; the left and right coronary arteries are issued at the aortic sinus (Valsalva sinus). The pulmonary artery is posterior and arises from the left ventricle with a short trunk, dividing into left and right pulmonary artery branches that travel toward the pulmonary hilum. In normal subjects, the main and pulmonary arteries cross in the long-axis view of the parasternal left ventricle, and one view cannot simultaneously show the long-axis images of both great vessels; when the great arteries are transposed, the two great vessels are seen to be parallel anteriorly and posteriorly, with the aorta located anteriorly on the right, continuing with the right ventricular outflow tract; the pulmonary artery is located posteriorly on the left, originating from the left ventricular outflow tract. A short-axis view of the parasternal aorta can be seen in cross-section of the aorta and pulmonary artery, and the relationship is mostly right anterior/left posterior. The aorta is located in the right anterior, and the anterior tilt of the probe can show its continuity with the aortic arch; the pulmonary artery is located in the left posterior, and the probe is tilted slightly downward, and the distal end of the common pulmonary trunk can be seen to continue with the left and right pulmonary artery branches, and the proximal end is continuous with the left ventricular outflow tract.
2.Type, location and size of intracardiac shunts
In more than 50% of patients with transposition of the great arteries combined with foramen ovale or atrial septal defect, the direction of the acoustic beam in the subxiphoid four-chamber and biventricular heart section is perpendicular to the atrial septum, which is less likely to produce echogenic loss resulting in misdiagnosis, and can clearly show the dissection end of atrial defect and the membrane-like tissue of foramen ovale. In combination with color and spectral Doppler ultrasound, the size of the defect can be accurately measured, the direction of the shunt can be determined, and the shunt flow at the atrial level can be calculated.
Patients with transposition of the great arteries are often combined with ductus arteriosus. Because the two great arteries are parallel and do not cross each other, the size of the ductus arteriosus and the direction of the shunt are more easily revealed in the superior sternal fossa view than in normal subjects. Pulmonary artery pressure can be calculated according to the simplified Bernoulli equation (ΔP=4V2) to assess the degree of pulmonary hypertension.
Ventricular septal defects are combined in approximately 33% of patients, with outflow tract (subpulmonary artery) and perimembranous inflow tract ventricular defects being more common. Due to rotation and dysplasia of the conus septum, the pulmonary artery often rides over the septum, forming a malaligned outflow tract ventricular defect. A parasternal long-axis view of the left ventricle can show an anteriorly displaced conus septum and a subpulmonary artery ventricular defect, but should be differentiated from a Taussig-Bing malformation. In patients with complete transposition of the great arteries, the aorta is located anteriorly on the right and arises from the right ventricle; the pulmonary artery is located posteriorly on the left, most of which (more than 50%) arises from the left ventricle, and the pulmonary artery is fibrously connected to the anterior mitral valve leaflet. The pulmonary artery is connected to the anterior mitral leaflet in a muscular fashion. The subaortic ventricle is missing in the outflow tract ventricular defect, and the short axis of the parasternal aorta is found to be more common when the aorta is located anteriorly on the left and the pulmonary artery is located posteriorly on the right.
3.Detection of left ventricular outflow tract obstruction
Left ventricular outflow tract stenosis is a common complication of D-TGA. When the ventricular septum is intact, the septum protrudes toward the left ventricular surface due to a decrease in left ventricular pressure, forming a power obstruction. Due to the increased blood velocity in the LV outflow tract, the Venturi effect can cause the mitral valve to move forward in systole and worsen the stenosis of the LV outflow tract. In contrast, the subpulmonary artery fibrous annulus or fibrous crest can cause organic stenosis of the LV outflow tract. In D-TGA combined with ventricular septal defect, the following conditions can cause LV outflow tract obstruction: (1) subpulmonary fibrous crest or annulus; (2) hypertrophic conical tissue protruding into the LV outflow tract; (3) pulmonary valve stenosis (4) membrane or tricuspid valve involvement protruding across the ventricular septum into the LV outflow tract; (5) mitral valve involvement. The subxiphoid view and parasternal long-axis view can show the site and type of stenosis; color Doppler ultrasound can show the colorful turbulent flow at the obstruction; spectral Doppler ultrasound can measure the high-speed blood flow at the stenosis; the pressure difference at the stenosis can be calculated according to the simplified Bernoulli equation to assess the severity of the obstruction.
4.Probing of coronary artery origin and its course
Using a high-frequency probe, a subxiphoid long-axis or short-axis view and a short-axis view of the parasternal aorta, the aortic root is observed and carefully searched for the origin of the left and right coronary arteries whether they originate from the left or right coronary sinus, and then the relationship between the left anterior descending branch and the left gyral branch and the coronary artery trunk is distinguished. The common coronary artery anomalies are gyral branch originating from the right coronary artery and single right coronary artery, while other coronary artery anomalies are rare.
V. Permanent arterial trunk
PTA refers to a single large arterial trunk emanating from the base of the heart, with only one set of semilunar valves under this trunk, from which the aorta, pulmonary artery and coronary arteries emanate. It is a rare congenital cardiovascular malformation, accounting for about 1% to 4% of congenital heart disease, and there is no significant difference between men and women. The prognosis is poor if left untreated, with a mortality rate of 90% within 1 year of age.
Most of the embryologic mechanisms of PTA are thought to be due to the failure to separate the arterial trunk, including the distal conus, proximal arterial trunk, and distal arterial trunk (i.e., the aortic sac), so the permanent arterial trunk manifests as a group of malformations including aortopulmonary septal defect, ventricular septal defect, and semilunar valve hypoplasia.
According to the combination of ventricular septal defect or not, Vanpragh et al. classified the permanent arterial trunk into two types as follows: ① Type A: with ventricular septal defect, accounting for about 96.5%. According to the location of origin of the pulmonary artery branches, there are four types: A1 ventricular septal defect + pulmonary artery trunk from common artery trunk; A2 ventricular septal defect + left and right pulmonary arteries directly from common artery trunk; A3 ventricular septal defect + left or right pulmonary artery agenesis, the blood of pulmonary circulation on that side is provided by collateral circulation; A4
ventricular septal defect + hypoplasia, stenosis, atresia or complete interruption of the aortic arch with a large unclosed ductus arteriosus. Type B: without ventricular septal defect, very rare. B1 to B4 have the same origin of pulmonary artery branches as type A.
The purpose of ultrasound examination: to clarify the ventricular origin of the common trunk and the form of branching, the type of ventricular septal defect, to observe whether there is stenosis at the beginning of the pulmonary artery, to clarify the morphology of the common trunk valve and whether there are functional abnormalities, the presence of abnormalities in the aortic arch and other combined malformations.
In the long-axis view of the left ventricle next to the sternum, a thick common arterial trunk was seen riding on the ventricular septum, and the continuity between the septum and the anterior wall of the common trunk was lost. In the left posterior aspect of the common arterial trunk, closer to the common trunk valve, the common pulmonary artery trunk can be seen emanating. Sometimes the pulmonary artery can be observed in a standard long-axis view, and sometimes it can be observed by tilting the probe slightly from right to left. The fibrous continuity between the common trunk valve and the mitral valve can also be observed in this view.
The parasternal short-axis view is the best view of the coaptation valve, septal defect, and pulmonary artery branch emanations. The leaflets and morphology of the common stem valve can be clearly demonstrated. The type of ventricular septal defect can also be clearly identified. In most cases, the septal defect is located above the supraventricular ridge with the membrane intact, and in rare cases, the membrane septum is also defective. Only one group of semilunar valves is seen, a common trunk valve, while continuity between the right ventricle and the pulmonary artery is interrupted and the pulmonary valve is absent, with the pulmonary artery originating directly from the common trunk.
Subsagittal coronal and sagittal views may also show the morphology of the septal defect, common trunk ride, and common trunk valves. These views are also often used to show pulmonary artery branches. The right pulmonary artery emanates from the common trunk or directly from the common trunk and travels posteriorly to the common trunk, and a long-axis view of the subxiphoid left ventricular outflow tract on a posterior scan will show that it is located posterior to the common trunk, whereas the left pulmonary artery extends directly posteriorly to the left, and a sagittal view will show that it is bowed and located above the left atrium.
A sagittal view of the superior sternal fossa shows whether there is a combined ductus arteriosus and shows the location and morphology of the aortic arch. The right aortic arch is more common. Sagittal views may show interruption of the aortic arch with aortic constriction, commonly in the presence of common trunk valve stenosis or regurgitation. The pulmonary artery can also be visualized, and sweeps along the pulmonary branches can be traced to their origin in the common arterial trunk.
Apical 4-chamber views and parasternal 4-chamber views can also show septal defects, common trunk valve ride, and valve morphology, as well as the size and degree of hypertrophy of both ventricles. Compared with tetralogy of Fallot, the left atrium and left ventricle of the permanent arterial trunk are more enlarged, especially in those with combined common trunk regurgitation and mainly into the left ventricle.
The purpose of Doppler examination is to observe the function of the common trunk valve and to detect the presence of stenosis at the origin of the pulmonary artery. Color Doppler can show the turbulent signal of regurgitation and stenosis in views that clearly show the common trunk valve, such as subxiphoid left ventricular outflow tract view, apical five-chamber view, and left ventricular long-axis view. Due to common trunk riding, the regurgitation sometimes flows back into both ventricles, and sometimes predominantly into one ventricle. The presence of stenosis at the beginning of the pulmonary artery can be observed in sections where the pulmonary artery branches can be clearly displayed, such as parasternal or suprasternal fossa views, and if there is stenosis, turbulent flow signals can be seen and high-speed blood flow can be recorded.
The application of echocardiography in the diagnosis of the permanent arterial trunk is easily confused with the following diseases and should be differentiated. The continuity between the right ventricular outflow tract and the pulmonary artery and the presence of a pulmonary valve are the key to differentiation. The arteries are poorly developed and are supplied by arterial ducts or large collateral branches of the aorta-pulmonary artery, and the arterial ducts are mostly vertical. One pulmonary artery of the semi-permanent arterial trunk originated from the aorta, while one pulmonary artery still originated normally from the right ventricle, and both the right ventricular outflow tract and the pulmonary valve structure and its continuity were present. The right ventricular outflow tract and pulmonary valve structure and its continuity are present in the main pulmonary artery window, and the pulmonary arteries are mostly thick and often combined with severe pulmonary hypertension.