Study on the views and methods of ultrasonic screening and diagnosis for abnormal aortic arch in infants

Background

Aortic arch anomalies are common congenital heartmalformations, and ultrasonic diagnosis of such malformations is challenging. Failure to detect these diseases intime is the main cause of morbidity and mortality in severe cases of infants [1]. The three-vessel and trachealview is one of the internationally recognized importantviews for prenatal ultrasonic diagnosis of fetal congenitalheart diseases [2,3]. This view was applied to infants inthis study for the first time, combining with series ofviews of aortic arch to diagnose and analyse aortic archanomalies in infants. The objective of this study is to explore appropriate echocardiographic views and methodsof aortic arch anomalies in infants and to improve thescreening sensitivity and diagnostic accuracy.

Methods

Object

140 children with abnormal aortic arch diagnosed byultrasound in Children’s Hospital of Hebei Provincefrom January 2014 to December 2019 were collected forretrospective analysis. All were proved by surgery or/andcomputerized tomography angiography (CTA). Eightytwo cases were male, and 58 cases were female. Theirages ranged from 7 h to 12 months. The median age was72 days and the mean age was 117 days. One hundredtwenty-six cases were accompanied with other cardiacmalformations, including 4 with tetralogy of Fallot, 1with single ventricle, 1 with pulmonary atresia, 1 withBerry syndrome, 1 with aortopulmonary septal defect.Other malformations were mainly atrial septal defect,ventricular septal defect and patent ductus arteriosus.

Inclusion criteria

Available aortic arch views should be obtained by ultrasound among the infants who were diagnosed with aortic arch anomalies and all were proved by surgery or/and CTA.

Exclusion criteria

Infants who could not obtain the available views of aortic arch or cases who were not determined by surgeryor/and CTA should be excluded.

Equipment

Philips IE 33 with probe S5–1 and S8–3.

Methods of examination

The children took supine position or left-lateral position.When examining the suprasternal fossa, raise the shoulder and tilt the head and neck back. Appropriate sedation should be given to children if they did notcooperate. Firstly, follow the“cardiac segmental diagnostic method”for systematic ultrasonic examination, thena series of views for the aortic arch were performed (thethree-vessel and tracheal view, aortic arch short axisview, left aortic arch long axis view and aortic arch longaxis continuous scan views). The position of the tracheawhich is in front of esophagus was determined byesophageal imaging on the three-vessel and tracheal viewby means of drinking water or moving nasogastric feeding tube. Then the type of vascular ring was diagnoseddefinitely according to the relationship between vesselsand trachea.

The three-vessel and tracheal view: firstly, we obtainedthe parasternal great vessels level short-axis high position view (similarly to fetal three-vessel view). On thisbasis, we made the acoustic beam skew toward the headand obtained the view which was similar to the fetalthree-vessel and tracheal view. Then we could observethe position, number, morphological proportion. Theposition of the aortic arch is relative to the trachea. Theaortic arch on the left side of the trachea is the left aorticarch (LAA), and aortic arch on the right side of the trachea is the right aortic arch (RAA). If the left and rightsides of the trachea both have aortic arches, it is doubleaortic arch (DAA). Under normal circumstances, theaortic arch is located on the left side of the trachea, andsends out the brachiocephalic trunk, left common carotid artery, and left subclavian artery successively. Theinner diameter of the infants’aortic arch is similar tothat of the pulmonary artery (close to 1:1), which appears as a nearly symmetrical V-shape on the threevessel trachea view (Fig.1).

The aortic arch short axis view: get the transverse scanof suprasternal fossa with probe maker pointing to theleft, then we could observe the number, inner diameter,and first branch of the aortic arch (Fig.2).

The left aortic arch long axis view: Try to make acoustic beam parallel with sternum of the infant with theprobe marker pointing to the infant’s left shoulder, thenwe could observe the shape, inner diameter and continuity of aortic arch (Fig.3).

The aortic arch long axis continuous scan views:firstly, contrarotated the probe until the probe markerpointed to infant’s right shoulder on the basis of left aortic arch long axis view, and tried to make acoustic beamparallel with sternum of an infant. Then we could obtaina series of sagittal views of aortic arch. We made theacoustic beam tilt gradually toward the head on the basisof aortic arch short axis view, and we could get a seriesof coronal views of aortic arch. Comprehensively judgethe position, number, shape, branch and continuity ofaortic arch by observing all images obtained during this operation.

We summarized the echocardiographic features of different types of aortic arch anomalies in each view, andcompared ultrasonic diagnosis results with CTA or/and

surgery. The screening sensitivity, diagnostic coincidencerate, advantages and disadvantages of different views ofaortic arch anomalies were analyzed in order to acquirea reliable method of screening and diagnosis.

Results

Diagnostic results of different types of aortic archanomalies on different views by echocardiographyOne hundred forty infants with aortic arch anomalieswere verified by CTA or/and surgery. RAA were 21cases (6/21 were accompanied by mirror branch and 15/21 were with aberrant left subclavian artery (U - shapedvascular ring), and LAA with right aberrant subclavianartery (C - shaped vascular ring) were 2 cases. DAA withboth arches open (O - shaped vascular ring) were 20cases, and DAA with left arch atresia (similar O - shapedvascular ring) were 2 cases. Atresia of the proximal aortawith aortic arch dysplasia was 1 case. Sixty-seven caseswere coarctation of the aorta (COA) and 27 cases werethe interrution of the aortic arch (IAA). All the patients

were correctly diagnosed except that 2 infants withinterruption of aortic arch were incorrectly diagnosed asCOA, and 1 infant with COA was misdiagnosed asinterruption of aortic arch by echo. The screening sensitivities of three-vessel and tracheal view, aortic archshort axis view, left aortic arch long axis view, aorticarch continuous scan views and four-view combinationfor abnormal aortic arch were 99.3, 73.6, 87.1, 99.3, and100% respectively; the diagnostic coincidence rates were85.7, 27.1,66.4, 95.0%, and 97.9% respectively. Detaileddiagnosis of various types of aortic arch anomalies ondifferent views were shown in Tables1,2.

(1) The three-vessel and tracheal view: the sensitivity ofthis view was high and the position, number, internal diameter ratio and continuity of aortic archcould be observed. Typical types of aortic archanomalies in our group had characteristic imageson this view (detailed descriptions were in paragraph 2 of this section). This view is easy to

operate, and its advantage of visually showing therelationship between the vascular ring and the trachea is irreplaceable. However, this view had somelimitations in showing the branches of the brachiocephalic artery.

(2) The aortic arch short axis view: compared with thetraditional left aortic arch long axis view, the shortaxis of the aortic arch increases the display of theDAA. According to the branch of the firstbrachiocephalic artery, we can infer the position ofaortic arch, and whether there is aberrantsubclavian artery. Speculative diagnosis were madecorrectly in cases with DAA, RAA and aberrantsubclavian artery by this view. But abnormitiescould no be found easily on this view in some casesof COA of which the proximal aortic arch near thefirst branch were well developed.

(3) The left aortic arch long axis view: The shape,internal diameter and continuity of the LAA can beshown clearly on this view, but DAA and RAAcould not be observed directly because of scanningangle limitation.

(4) The aortic arch long axis continuous scan views:these views compensated deficiencies of the leftaortic arch long axis view on observation of DAAand RAA, and increased the detection rate of theaberrant subclavian artery significantly.

Echocardiographic features of various aortic archanomalies on the three-vessel and tracheal view

(1) Normal three-vessel view: superior vena cava, aorta,pulmonary artery (arranged from right to left).

(2) Normal three-vessel-tracheal view: the vena cava islocated on the right side of the trachea. The pulmonary artery is connected to the descending aortathrough the ductus arteriosus or ductal ligament,forming a symmetrical“V”sign with the aorta (theinner diameter of the aorta and the pulmonary artery is similar), both of which are located on the leftside of the trachea.

(3) RAA: the distance between the aortic arch and thepulmonary artery increased. The aortic arch islocated on the right side of the trachea, and thepulmonary artery is located on the left side of thetrachea. The pulmonary artery is connected to thedescending aorta via the arterial duct or ductligament, forming a“U”-shaped vascular ring withthe aorta. In some patients with the aberrant leftsubclavian artery, it could see that left subclavianartery (LSCA) originated from the descending aortaand ran to the left .

(4) LAA with aberrant right subclavian artery: Theaortic arch and pulmonary artery are both located on the left side of the trachea. The pulmonaryartery is connected to the descending aorta throughthe ductus arteriosus or ductal ligament, forming asymmetrical“V”sign with the aorta. And it couldsee that aberrant right subclavian artery originatedfrom the descending aorta and ran to the rightalong posterior of trachea, forming a“C”-shapedvascular ring.

(5) DAA with both arches open: the left and rightaortic arch on both sides of the trachea ranbackward and downward and connected with thedescending aorta, enclosing the trachea andesophagus to form an“O”-shaped vascular ring(Fig.4).

(6) DAA with left arch atresia: The left and right aorticarch on both sides of the trachea ran backward anddownward. The RAA connected with thedescending aorta, and the LAA was interrupted. Adiverticulum-like structure originated from the descending aorta with its tip pointing to the left,forming a similar“O”-shaped vascular ring. Thelong axis of the left aortic arch showed that thecontinuity of the distal LAA was interrupted aftersending out the left common carotid artery (LCCA)and LSCA in turn, and the LSCA was twisted backward and downward, showing the sign of pulling bythe tethered system (Fig.5).

(7) Proximal aortic atresia: It showed an asymmetric“V”sign. Hypoplasia of aortic arch and retrogradeflow of ductus arteriosus from the pulmonary arteryinto the aorta could be detected (Fig.6).

(8) COA: it showed the proportion of aortic andpulmonary artery was imbalanced and the internaldiameter of aorta was reduced, showing anasymmetric“V”sign (Fig.7).

(9) IAA: it showed the proportion of aortic andpulmonary artery was imbalanced, and the internaldiameter of aorta was reduced. The continuitybetween aorta and descending aorta interrupted.The V-shaped structure disappeared and an“0I”shape showed (Fig.8)

Discussion

A total of 6 pairs of arch arteries appeared during human embryonic development. At the 6th–8th week ofthe embryo, the arch arteries evolved into the basicstructure of the systemic arteries. Abnormalities occurring during this period could result in a variety of aorticarch anomalies, including anomalies of size, continuityand combination of aortic arch [4].

The types of aortic arch anomalies are complex andchangeable. The ultrasonic diagnosis is difficult and themisdiagnosis rate is high. Failure to detect these diseasesin time is the main cause of morbidity and mortality in

severe cases of infants [1]. At present, there is lack of researches on the methodology of ultrasonic screening anddiagnosis of these diseases in children. This paper putsforward the views and methods of echocardiographicscreening and diagnosis of these diseases after birth forthe first time, which is summarized as follows:

Views and methods of echocardiographic screening anddiagnosis of aortic arch anomalies

The views researched in this study include the threevessel and tracheal view, aortic arch short axis view, leftaortic arch long axis view and aortic arch long axis continuous scan views. We found that the screening sensitivity (73.6%) and diagnostic coincidence rate (27.1%) ofshort axis view of aortic arch were the lowest. No abnormalities were found in 37 (37/67) cases with COA whichwere well developed at the proximal transverse arch nearthe first branch. However, compared with the traditionalleft aortic arch axis view, the short axis of the aortic arch increases the display of the DAA. According to thebranch of the first brachiocephalic artery, we can inferthe position of aortic arch, and whether there is aberrantsubclavian artery. On the short axis view, the normalaortic arch shows that the first branch points to the rightanterior, and the proximal bifurcation can be seen (theright brachiocephalic trunk artery sends out the rightcommon carotid artery and right subclavian artery).When the first branch points to the right anterior andthere is no bifurcation (considered as right common carotid artery), we should take LAA with the aberrant rightsubclavian artery into consideration. When the firstbranch points to the left anterior and the proximal bifurcation is visible (the left brachiocephalic trunk sends outLCCA and LSCA), it should be considered as RAA withmirror branch. When the first branch points to the leftanterior and there is no bifurcation (considered asLCCA), we should take RAA with the aberrant left subclavian artery as consideration. When the short axis of

the aortic arch shows a“dumbbell sign”, it indicatesDAA. The screening sensitivity and diagnostic coincidence rate of left aortic arch long axis were 87.1 and66.4% respectively, and the shape, inner diameter andcontinuity of LAA could be observed on this view.However, due to the limitation of angle, it is impossibleto observe RAA or DAA completely. Especially whenneglecting the observation of the brachiocephalicbranches of aortic arch, it is inclined to misdiagnose thecase of DAA. Seventeen cases of (17/20) DAA weremissed by using this view alone, and the other 3 cases(3/20) were abnormal on this view because of dysplasiaof LAA. We are used to concerning the observation ofone side arch or dominant arch and neglecting the detection of contralateral arch and brachiocephalic arterybranches. It is also one of the common causes of misseddiagnosis of aortic arch anomalies, so we should payattention in our work. The aortic arch long axis continuous scan views are modified views based on the traditional left aortic arch long axis view. It can make up forthe display of RAA and DAA and improve the reveal ofthe aberrant subclavian artery. The screening sensitivityand diagnostic coincidence rate of aortic arch anomalieswere increased to 99.3 and 95.0% respectively. Theseviews are a series of views of aortic arch long axis sagittal and coronary dynamic scanning, which have a largeamount of information, and The screening sensitivityand diagnostic coincidence rate can be significantly improved. But it demands higher requirements for the operation and observation ability of doctors. There are stillsome shortcomings of these views: for example, they cannot directly show the spatial relationship between theaortic arch and the esophagus and trachea, so RAA andDAA could only be speculatively diagnosed. DAA withLSCA atresia is easy to be confused with mirror right arch, and all these cases need to be combined with threevessels-trachea view to complete the diagnosis.

The three vessel and tracheal view is one of the internationally recognized important views in the echocardiographic screening of fetal congenital heart diseases [2,3].In this study, this view was applied to the screening anddiagnosis of aortic arch anomalies in infants for the firsttime. The chest wall of the infant is thin. The thymus inthis period has not degenerated and its volume is large,which helps to reduce the interference of air in lung andeasily obtain a satisfactory three-vessel and tracheal view.During this study, except for a few cases of severe pneumonia, pneumothorax and severe thoracic deformity, thevast majority of children successfully obtained this view.The results of this study showed the screening sensitivityand diagnostic coincidence rate of this view were 99.3and 85.7% respectively, and it had distinct advantage inthe diagnosis of congenital vascular ring. In 2 cases ofsuspected DAA with LSCA distal atresia, although theatresia segment could not be directly displayed onultrasound, the diagnosis of this disease was suggestedaccording to the abnormal structural features in ultrasound (Fig.3) consistent with those reported in the literature [5–8]. CTA and bronchoscopy were performedin the 2 cases, which confirmed the existence of trachealcompression stenosis and further supported the ultrasonic diagnosis. One case was also proved by operation.This view could easily diagnose RAA. However, becauseaberrant subclavian artery was located in the far soundfield and had a large angle with the sound beam, it waseasy to be affected by air, which could cause misseddiagnosis easily. In only 2 cases with the C-shaped vascular ring of this study, 1(1/2) was missed diagnosis. Annotation: The coronal view of the descending part ofaorta arch long axis with blood flow guidance can improve the display of the aberrant subclavian artery.For the patients with difficulty in directly displayingthe aberrant subclavian artery, the identification ofthe first branch on the short axis of the aorta archview could play an important role in speculation anddiagnosis. In this group of patients with interruption,coarctation and dysplasia of aortic arch, the threevessel and tracheal view had characteristic images.The IAA showed an”0 l”shape. Coarctation anddysplasia of aortic arch showed an asymmetric“V”sign. This view could provide important diagnosticclues of aortic arch anomalies, combining with thelong axis view of aortic arch in suprasternal fossa tomake an accurate diagnosis. Because of the idealangle of this view, it can help the long-axis view ofthe aortic arch to distinguish the interruption orsevere COA. Diagnostic skills: we first obtain thethree-vessel view which can define the position of theroot of the aorta and the descending aorta, then tiltthe probe to the side of the head to get the threevessel and tracheal view. During the process, the continuity of the aortic arch and the descending aorta isobserved to determine whether there is any interruption or coarctation. In this study, a number of caseswith controversy in the long axis of the aortic archview were differentiated by this method, and a correctmodified diagnosis was obtained. However, in the caseof mild COA with a reasonable development of aorticarch, the imbalance of the aortic and pulmonary arteries in this view is inconspicuous and false negativesare prone to occur. The coarctation of the descendingaorta in the lower position also can not be directlyshowed on this view. Therefore, we should combinethis view with other views for diagnosis. This studyshows that the sensitivity of screening for aortic archabnormalities combined with four views can be increased to 100%, and the diagnostic coincidence ratecan be increased to 97.9%.

Analysis of missed and incorrectly diagnosed cases

IAA and severe COA are sometimes difficult to distinguish. In this group, 2 cases of IAA (isthmus atresia)were incorrectly diagnosed as COA and 1 case of severeCOA was incorrectly diagnosed as IAA. As to these 2cases of aortic isthmic atresia, the wall of the aortic isthmus was continuous with the descending aorta, but thelumen was atresia. The long axis of the aortic archshowed that the wall was continuous, and the tissue ofthe atresia segment was extremely low in echo, whichwas hollow lumen-like echo in two-dimensional view.The atresia segment was very short, and the false imageof aortic coarctation was caused by color spillover. Thethree-vessel and tracheal view showed that the aorticarch was continuous with the wall of the descending aorta. The tissue of the atresia segment was very low inecho, and the two-dimensional view showed hollowlumen-like echo, presenting an asymmetric“V”sign inthree-vessel and tracheal view. One case was misdiagnosed due to the identification of unopened blood flowpattern, and the other was incorrectly diagnosed by mistaking the collateral vessels for a continuous aortic arch.Encountering similar cases, especially the suspiciouscases of short segment coarctation without obviousblood flow acceleration found on the long axis of theaortic arch, we can make a diagnosis by simultaneousobservation on multiple views, multiple angles, twodimension and color [9]. As the case of severe COAincorrectly diagnosed as IAA, the reason for missingdiagnosis was that the coarctation segment of the aortawas lower, tortuous and slender, leading uneasily to beobserved on aortic arch long axis view. Its flow wasoverlapped with the crassi ductus arteriosus whichcovered it. Due to the small diameter, tortuosity, lowposition of the coarctation segment and dysplasia of theaortic arch, the continuity between the aortic arch andthe descending aorta was not showed on the three-vesseland tracheal view, presenting a“ol”sign, and resulted inmissing diagnosis. Some IAA (atresia) were consideredto be the anomaly of the most serious aortic coarctation[10]. The author ever found a case of severe coarctationof isthmus in neonatal period and developed aortic atresia 2 days later. When it is difficult to diagnose aorticarch anomalies by ultrasound or to determine the compression of vascular ring on trachea and esophagus, wecan make a definite diagnosis by CTA, radiography,bronchoscopy and so on [11].

LimitationsIn

this study we selected positive infant cases with aorticarch anomalies diagnosed by ultrasound and determinedby CTA or/and surgery. The positive cases that couldnot be detected by ultrasound, the cases of loss offollow-up and the older cases with poor images were notincluded in this study. Incorrect diagnosis may occur incases of mild coarctation of the distal aorta with well developed proximal aorta. The number of cases in thisstudy was small and didn’t include all types of aorticarch anomalies. Because infant cases with aberrant subclavian artery rarely had clinical symptoms, so it was difficult to be confirmed by follow-up. In practical work,some children with congenital heart disease like this areprone to complications such as heart failure, severepneumonia, even pneumothorax and thoracic deformities [12], which affect the clarity of the images. Prospective research needs to be carried out in the future,and the sample size should be expanded for furtheranalysis.

Conclusions

In general, the three-vessel and tracheal view which hashigh sensitivity is liable to be obtained and mastered. Itcan be widely applied in the ultrasonic screening anddiagnosis of aortic arch anomalies in infants, and has remarkable advantages in the diagnosis of vascular ring.The combination of four views is conducive to furtherimprove the screening sensitivity and diagnostic coincidence rate of aortic arch abnormalities.

Abbreviations

CTA:Computerized tomography angiography; COA: Coarctation of the aorticarch; IAA: Interruption of the aortic arch; DAA: Double aortic arch; RAA: Rightaortic arch; LAA: Left aortic arch; LCCA: Left common carotid artery;LSCA: Left subclavian artery

Acknowledgements

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Authors’contributions

XH: Concept/design, Drafting article, Criticle revision of article. JC: Datecollection. GL: Interpretation. The author(s) read and approved the final manuscript.

Authors’information

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Funding

Key research and development project of Heibei Province (item number:192777100D).

Availability of data and materials

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Ethics approval and consent to participate

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Consent for publication

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Competing interests

The authors declare that they have no competing interests.

Received: 29 April 2020 Accepted: 1 January 2021