|Year : 2022 | Volume
| Issue : 3 | Page : 209-215
Echocardiography in Planning Aortic Arch Interventions
Neeraj Awasthy, Aditya Bhatt, Gaurav Kumar
Department of Pediatric and Congenital Heart Disease, Max Hospital, Saket, Delhi, India
|Date of Submission||18-Apr-2022|
|Date of Decision||02-Jun-2022|
|Date of Acceptance||05-Jun-2022|
|Date of Web Publication||12-Nov-2022|
Dr. Neeraj Awasthy
Department of Pediatric and Congenital Heart Disease, Max Hospital, Saket, Delhi
Source of Support: None, Conflict of Interest: None
Aortic arch anomalies are suspected on echocardiography, though the final diagnosis may need additional investigative modalities such as cardiac catheterization, computed tomography angiography or rarely magnetic resonance imaging. Most of the interevntions are however planned on the basis of echocardiography. Suprasternal and subcoastal views are particularly important for evaluation, although other indirect parameters such as pressure effects (ventricular hypertrophy) and ventricular dysfunction etc. may serve as indirect markers of the arch lesion. This review provides an overview of the role of echocardiography in planning aortic arch interventions.
Keywords: Arch anomalies, arch interruption, coarctation, echocardiography
|How to cite this article:|
Awasthy N, Bhatt A, Kumar G. Echocardiography in Planning Aortic Arch Interventions. J Indian Acad Echocardiogr Cardiovasc Imaging 2022;6:209-15
|How to cite this URL:|
Awasthy N, Bhatt A, Kumar G. Echocardiography in Planning Aortic Arch Interventions. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2022 [cited 2023 Feb 4];6:209-15. Available from: https://jiaecho.org/text.asp?2022/6/3/209/361058
Echocardiography is the diagnostic modality of choice in the initial evaluation and planning for the management of aortic arch anomalies. Clinical assessment with echocardiographic evaluation is the most accessible initial tool to suspect aortic arch anomaly. Anomalies of the aortic arch may be classified based on the following:
- Abnormal formation of aortic arch
- Coarctation of the aorta and its severest form, i.e., interrupted aortic arch
- Aortic aneurysms.
Echocardiography is particularly diagnostic in the pediatric population, for the most frequently encountered arch disease – coarctation of the aorta. Less frequently seen is an extreme variant of the above pathology, with luminal discontinuity manifesting as an interrupted aortic arch.
In the grown-up population with limited suprasternal windows, the arch anomalies may be suspected by indirect evidence but generally need additional imaging modalities, such as computed tomography (CT) scan, magnetic resonance imaging (MRI), or conventional angiogram, to profile the lesion.
| Echocardiographic Clues in Aortic Arch Evaluation|| |
For the diagnosis of aortic arch anomalies, the most important echocardiography view is the suprasternal view [Figure 1]. In neonates and infants, subcostal, high parasternal, and even apical views can also provide imaging of the aortic arch. However, these echocardiography views permit imaging only up to the origin of the first branch and these windows are inadequate in older children and adults. Hence, the grown-up population with limited echocardiography windows may need additional imaging modalities. Only proximal aorta can be images in the parasternal long-axis and short-axis views, and hence, these have limited importance.
|Figure 1: Two-dimensional echocardiography with color compare in suprasternal long-axis view showing severe discrete coarctation of the aorta after the origin of the left subclavian artery (marked in a). (b) Image showing color flow across the same demonstrating severe narrowing|
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Evaluation of suspected aortic arch disease begins with looking for subtle clues to its presence. Blunted descending aortic Doppler in subcostal imaging and lack of vigorous pulsatile flow in the descending aorta in the subcostal bicaval view are important initial pointers to the presence of coarctation [Figure 2]. Markers of significant arch obstruction include features such as left ventricular (LV) dysfunction and LV hypertrophy. Additional suspicion comes from findings commonly associated intracardiac pathologies such as left-sided obstructive lesions, Shone complex, double-outlet LV with subpulmonary ventricular septal defect (VSD) (Taussig Bing anomaly), and muscular VSDs. Additional clues may be important in the grown-up population to suspect the lesion. In the neonatal period, unlike other age groups, there is a significant presence of enlargement of right-sided structures such as right atrium, right ventricle (RV), and pulmonary hypertension with or without LV dysfunction.
|Figure 2: (a) Image demonstrating the Doppler signal in the descending aorta secondary to severe proximal coarctation of the aorta. (b) Image showing the normal flow across the descending aorta (for comparison). Flow as in (b) may be seen when the patent ductus arteriosus supplies the descending aorta|
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Suprasternal view is formed when transducer is placed in suprasternal notch and aligned closely and parallel to the sternum. To gain access to the suprasternal notch, the patient is positioned supine with a pillow beneath the shoulders to extend the neck without producing tension on the sternocleidomastoid muscles. The patient's head is turned to the right or left side so that the chin does not prevent adequate placement of the transducer in the suprasternal notch.
| Abnormal Formation of Arch|| |
The subgroup of aortic arch abnormities resulting from abnormal formation of aortic arch includes (a) mirror image right-sided aortic arch, (b) vascular rings, and (c) cervical aortic arch.
Right aortic arch
Aortic arch (which in most cases is the left arch) is viewed in suprasternal long axis with the plane of ultrasound beam that is directed between the right nipple and the left scapular tip with the first vessel originating being the right innominate artery which bifurcates into the right subclavian and right carotid artery. Right-sided arch is demonstrated by rotating the transducer counterclockwise between the left nipple and the right scapular tip to visualize the arch. Tilting the transducer anteriorly and posteriorly from suprasternal long-axis view images the relation of transverse aorta with the tracheal rings and tracheal air column, e.g., in the right aortic arch, the transverse aortic arch is seen to the right of the trachea. Right-sided aortic arch is further confirmed if the first vessel courses leftward and bifurcates which is seen in the suprasternal short-axis view. If the first arch vessel courses to left but does not bifurcate, then there are chances of more complex malformation as aberrant left subclavian artery and chances of vascular ring formation. The presence of right arch may be a pointer to other associated intracardiac pathologies such as VSD with pulmonary stenosis.
Vascular rings are formed when an aortic arch abnormality forms a ring of tissue encircling the trachea and esophagus. There is a high probability of its presence if the suprasternal views demonstrate arch anatomy other than a left arch with a normal right innominate artery or a right arch with mirror image branching. The common type of vascular ring anomalies includes left aortic arch with aberrant right subclavian artery and right duct or ligament, right aortic arch with aberrant left subclavian artery and left duct or ductus ligament, right aortic arch with retroesophageal segment and left descending aorta, and double aortic arch. On echocardiography, diagnosis of the left aortic arch with aberrant right subclavian or right aortic arch with aberrant left subclavian is possible if there is failure to demonstrate bifurcation of the first arch vessel. Demonstration of origin of the fourth arch vessel, i.e., aberrant subclavian, is difficult by echocardiography, and definition of detailed anatomy requires spiral CT or MRI. Double aortic arch can be directly visualized by performing a standard long-axis view and rotating the transducer 30°–45° counterclockwise. In suprasternal short-axis view, evidence of double circle with tracheal ring at the center is suggestive of double aortic arch. In some cases, even subcostal view may demonstrate bifurcating aorta into two arches few centimeters above the aortic valve. Demonstration of both arches requires the use of views for left and right aortic arch. Usually, one arch is dominating, and the other is hypoplastic or atretic. Origin of the arch vessels should be defined from suprasternal views. The demonstration of the same is important when undertaking procedures such as patent ductus arteriosus (PDA) device closure where doing the procedure may be contraindicated with its presence. The anomalies are best delineated on advanced imaging such as CT scan [Figure 3].
|Figure 3: Computed tomography angiogram of the chest in sagittal view showing the two components of the double aortic arch (marked by arrow). Also, note the right arch with the right descending aorta and mild kinking of the descending aorta with no constriction|
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Cervical aortic arch
Cervical aortic arch presents as a pulsatile mass and may be identified from the suprasternal long-axis view. It requires moving the transducer onto the neck over the pulsatile mass and suprasternal long-axis view shows the long ascending aorta.
| Coarctation of the Aorta|| |
Aortic coarctation denotes anatomical narrowing of the aorta. Congenital form which is the most common is seen at the isthmic region. It can be associated with varying degrees of hypoplasia of the arch as well. Coarctation classification has evolved from oversimplified pre- and post-ductal variants to Van Praagh's juxtaductal coarctation in relation to position of the most narrowed aortic segment near ductus arteriosus. Amanto's surgical classification (detailed below) is widely acceptable.
- Type I: Primary coarctation of the aorta. Discrete coarctation of the aorta, all aortic arch segments are normal in size
- Type II: Coarctation of the aorta with isthmus hypoplasia (hypoplasia of the aortic arch between the left subclavian artery and the arterial duct)
- Type III: Coarctation of the aorta with tubular hypoplasia (hypoplasia of the aortic isthmus, between the left subclavian artery and arterial duct, and the distal transverse arch, the aortic arch segment from the left carotid artery to the left subclavian artery)
- Subtype A: VSD is present in addition to the above aortic arch anatomy
- Subtype B: Other cardiac lesion is present in addition to the above aortic arch anatomy.
Clinical presentation in coarctation of the aorta is influenced by the age of presentation. It can vary from a neonate with dysfunctional ventricle and profound pulseless shock to an adolescent with incidentally detected hypertension and LV hypertrophy. However, two-dimensional (2D) echocardiography correlates in the assessment of aortic arch tend to be similar, albeit with varying complexities in imaging. Overall, there is narrowing of the aortic lumen secondary to intimal thickening, varying degrees of hypoplasia, and angular tortuosity between isthmus and the transverse arch. Narrowed segment can range from 2 to 3 mm or discrete coarctation to a much-extended long-segment one. Intimal and medial tissue proliferation manifests in early neonatal and infantile age as a prominent “shelf,” which although circumferential is most pronounced in the posterior arch planes and correlates with the site of flow acceleration on Doppler evaluation. In addition, one can profile a distinctive poststenotic dilatation in the descending aorta immediately below the coarctation segment. The presence of posterior shelf in the presence of PDA should alert a clinician to reevaluate the lesion as they are known to progress to severe coarctation as the ductus closes.
| Goals of Imaging in Suspected Arch Disease|| |
The primary goals of good imaging are to identify the anomaly, to access its severity, and to plan interventions based on these characteristics. There can be no substitute for segmental analysis as is true for any congenital heart disease. Salient features for the arch lesions are elaborated as under:
Identification of disease
- Begin with the identification of cardiac situs and segmental anatomy, to better delineate arch sidedness
- Identify arch-sidedness and delineate arch branches, including aberrant subclavian artery which will impact surgical planning
- Locate the site of maximal narrowing and measure it in systole, measure arch components reporting them in z scores that are adjusted as per body surface area. Utilizing z scores helps in defining arch hypoplasia (arch z score less than − 2) and aiding further management planning
- Define arch segments as per predefined conventions of Lopez et al. as follows:
Proximal transverse arch (segment of the aortic arch between the innominate artery and the left common carotid artery), distal transverse arch (arch between the left common carotid artery and the left subclavian artery), and aortic isthmus (narrowest aortic arch segment distal to the left subclavian artery) [Figure 4]
|Figure 4: Image showing measurements of the ascending aorta, transverse arch, isthmic region, and the descending aorta in a case of coarctation of the aorta. Note the descending aortic measurement is made at the level of the diaphragm|
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- Evaluate LV inflow and outflow for associated anomalies, especially Shone complex]
- Identify the degree of LV hypertrophy and dysfunction if any
- Identify flow across PDA in neonatal setting, its location with respect to the coarctation and shunting across it.
- Identify the degree of pulmonary hypertension in younger subset
- Rule out associations, seen in up to 50% of all patients including bicuspid aortic valve, VSD, subaortic and valvar aortic stenosis, common atrioventricular canal, transposition of the great arteries, double-outlet RV, secundum atrial septal defect, and single ventricle, especially tricuspid atresia with transposition of the great arteries.
Identification of disease severity
- Doppler evaluation is helpful in the identification and quantification of coarctation severity. Peak arch gradient greater than 20 mm in color continuous-wave (CW) Doppler suggests hemodynamically significant and severe coarctation of the aorta. Doppler gradients may be falsely low in the presence of severe ventricular dysfunction or a large PDA [Figure 5]
- CW Doppler flows across arch can aid in diagnosis even when 2D imaging is not very convincing, with the presence of high-velocity systolic amplitude with continuous antegrade flow throughout diastole manifesting as a “diastolic tailing” or diastolic spill. Presence of diastolic spill signifies severe coarctation with gradient differences persisting across cardiac cycle [Figure 6]
- Additional markers of disease severity include presence of blunted abdominal aortic Doppler flows and presence of significant LV hypertrophy. Abdominal descending aorta (DAO) Doppler in subcostal imaging may show a normal Doppler trace in the presence of large ductus and RV aided pulsatility; however, for most parts, blunted signals showing low-velocity systolic–diastolic flow with minimal phasic variations are seen
- Presence of LV hypertrophy is an important marker and correlates with the severity of outflow obstruction. Posterior wall thickness and the interventricular septal thickness should always be measured in any case of LV outflow or arch obstruction
- Objective measurement of LV function should be documented in all such cases, and the presence of ventricular dysfunction is an ominous sign signifying severe obstruction irrespective of the gradient across the aortic arch.
|Figure 5: Continuous-wave Doppler evaluation in suprasternal long-axis view in a case of neonatal coarctation with systolic acceleration; however, the patent ductus arteriosus flow tends to mask the underlying severity|
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|Figure 6: Infantile coarctation with severe narrowing as evidenced by serrated peak systolic acceleration and diastolic tailing|
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Planning management based on echocardiography
The indications for need for interventions and role of percutaneous versus primary surgical modality have been previously elucidated in multiple guidelines. Hemodynamically significant coarctation with arch gradient greater than 20 mmHg constitutes a class I indication for intervention. In the absence of such significant gradient, the presence of severe ventricular dysfunction acts as a marker of disease severity. As a rule, in any patient with ventricular dysfunction, arch obstruction should always be ruled out.
Echocardiographic evaluation in neonatal/infantile coarctation is often difficult due to many confounders. Arch can be difficult to visualize due to short neck or lack of age-appropriate probes. Doppler gradients may be falsely low due to ventricular dysfunction or the presence of PDA, which can give a signal overlap as well. One must rely on appropriate 2D images and look for hypoplasia as well as posterior arch shelf.
Presence of significant long-segment coarctation in this age group or presence of significant arch hypoplasia would render patients unsuitable for primary percutaneous intervention, unless used as a salvage procedure. Surgical repair of coarctation in this subset offers good results, and surgical decisions are guided by the degree of arch hypoplasia [Figure 7] and presence or absence of associated lesions.
|Figure 7: Suprasternal long-axis view with color compare demonstrating severe coarctation (arrow) of the aorta with transverse arch hypoplasia. Such candidates are likely to have suboptimal results or recurrent coarctation when subjected to interventional approach.TA: Transverse arch|
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While planning balloon dilatation of coarctation of the aorta, echocardiographic images are used to select the appropriate-sized balloons. Although surgical intervention is the treatment of choice in selected subgroup of patients unfit for surgery, low-pressure balloons such as coronary balloons, Tyshak Mini, or Tyshak II may be used. In older infants and children, balloon dilatation is the treatment of choice and generally involves the usage of balloons such as Tyshak II. By convention, the largest balloon used is limited to the size of the undilated adjacent aorta or DAO at the diaphragmatic level or upto three times the minimal lumen diameter of the aorta coarctation site [Figure 4] and [Figure 8]. These dimensions are readily available from the echocardiographic images. The need of using appropriate-sized balloons arises from the anticipated acute vascular complications of dilatation seen in up to 11% of primary dilatations.
|Figure 8: Neonatal coarctation with descending aortic measurement in the subcostal long-axis view. The largest systolic edge-to-edge aortic dimensions guide maximal balloon size to be used for coarctation dilatation. In this neonate, with 4-mm descending aorta measurement, a 4-mm coronary balloon was used successfully|
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In certain situations such as in the absence of availability of fluoroscopic equipment or when the patient condition does not allow shifting to the catheterization laboratory (e.g., high ventilator dependent newborn), balloon valvoplasty may be done under echocardiography guidance assisted by visualization of the inflated balloon on echocardiography.
Postprocedure reduction in pullback gradient during interventions correlates with reduction in arch gradient by echo Doppler estimation.
Interruption of aorta
Arch interruption represents the most severe form of coarctation. It is mostly demonstrated in suprasternal views. Interruption of the aorta is generally associated with other complex intracardiac congenital heart diseases such as atrioventricular canal defect, d-transposition of great arteries with or without tricuspid atresia, Taussig Bing anomaly, and congenitally corrected transposition apart from VSD, subaortic stenosis, and bicuspid aortic valve and mitral stenosis. The interruption of the aorta may involve only a short segment or a long segment with a marked distance between the proximal and distal segments of the aorta.
The interruption of aortic arch is classified as [Figure 9]:
|Figure 9: Image showing various types of interrupted aortic arches/all the imaging is in suprasternal view. (a) Type A interruption. (b) Two-dimensional imaging with color compare in a case of Type B interruption. (c) Type C interruption|
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- Type A: Interruption is distal to the left subclavian artery; all three arch branches arise proximal to the interrupted segment
- Type B: Interruption is between the second and third arch branches, i.e., carotid and subclavian arteries
- Type C: Interruption is between the carotid arteries, only the first branch (innominate artery) arises proximal to the interruption.
Type B arch interruption is the most common form and is usually associated with conotruncal anomalies with normally aligned great arteries in which there is a large malalignment type of VSD associated with posterior displacement of the infundibular septum and subaortic obstruction. DiGeorge's syndrome is commonly associated with type B interruption. Type A interruption has association with aortopulmonary septal defect and transposition of great arteries.
On 2D echocardiography, suprasternal views show ascending aorta continuing to at least one of the arch vessel. In type A arch interruption, all the three branches are seen proximal to the interruption; in type B interruption, first and second branches are seen proximal to the interruption; and in type C interruption, only the first branch, i.e., innominate artery, arises proximal to the interruption. Descending aorta is generally relatively dilated with ductal continuation to descending aorta. This is well profiled in suprasternal long-axis or/and high parasternal short-axis views. Caution should be taken that duct arteriosus connecting the main pulmonary artery to descending aorta (ductal arch) should not be confused as true arch. Color flow mapping confirms the findings, and as systemic flow is duct dependent, patency as well as any restriction of the duct should be defined by color flow mapping. Gradient across the ductus is profiled using pulsed-wave Doppler evaluation. Sometimes, restricted ductus arteriosus can mimic coarctation of the aorta and needs to be defined in various views.
| Aortic Aneurysm|| |
The third important subgroup of aortic arch anomalies includes aneurysm of the aorta. It is defined as a dilated segment which is more than 50% in diameter as compared to the preceding segment. In pediatric age group (in contrast to adults), aneurysm of the ascending aorta is more common than of the descending aorta. Annulo-aortic ectasia is defined as aneurysmal involvement of the annulus and aortic root, in addition to ascending aorta. In children, aneurysmal dilatation of proximal aorta is mostly caused by conditions associated with medial degeneration such as Marfan's syndrome, Turner syndrome, Ehler-Donlos syndrome, bicuspid aortic valve, or may be idiopathic; however, some types of infectious diseases as bacterial endocarditis can also result in aneurysm formation. Aneurysm of the proximal aorta is usually easily recognized from the parasternal long-axis view, parasternal short-axis view, subcostal coronal view, and the suprasternal long-axis view. Aneurysmal involvement of the descending aorta usually occurs secondary to previous surgical or catheter intervention, such as surgical repair of coarctation of the aorta or balloon dilatation of coarctation. Chances of aneurysmal formation are much less after stent deployment for coarctation of the aorta. Descending aorta aneurysm can be defined from suprasternal long-axis, the suprasternal short-axis (aneurysm from lateral wall), and subcostal sagittal views. The echocardiographic measurements help diagnose and assess the progression of the disease. Echocardiography shows the aneurysm itself and its complications, viz., compression of adjacent structures and fistula formation.
Tips to improve arch evaluation
- Aortic arch, isthmus, arterial duct, and descending aorta are adequately imaged from the suprasternal notch and the right and left infraclavicular windows
- Slight neck extension by placing a rolled towel under the shoulders facilitates appropriate imaging
- In infants, using high-frequency echocardiography probes of 8–12 MHz aids in diagnosis due to smaller footprint of the probe, lesser requirement of deep penetration of ultrasound beams, and high-resolution imagery
- Echocardiography evaluation of the arch best begins at 3 o'clock transducer plane, in transverse field providing short-axis view of the ascending aorta., With a cranial sweep, it allows delineation of the entire ascending arch of the aorta and initial branching pattern. This view demonstrates arch continuity, sidedness, and the branching patterns. Further, in an oblique sagittal plane, a long-axis “candy cane” equivalent view can be obtained to profile the arch in its entirety
- In coarctation, narrowing is visible in 2D images at isthmus (area distal to the left subclavian origin) in a juxtaductal location. Placing sample volume in this zone allows perfectly parallel alignment of the CW Doppler beam with the blood flow and yields an excellent spectral Doppler trace that can be used for quantifying the coarctation severity
- Double envelope sign, serrated systolic trace, and diastolic tailing are Doppler findings that are specific to severe coarctation.
- Isthmic area is measured in an edge-to-edge manner, taking the minimal dimensions and calculating z score appropriated to body surface area. Normative charts are readily available and aid in the identification of arch hypoplasia
- In neonates with short necks, airway issues, or those on assisted ventilation, the modified right infraclavicular view can give a good sagittal plane of the entire arch
- In the left high parasternal or ductal view, PDA as well as aortic isthmus can be well profiled. Presence of a large PDA interferes with Doppler evaluation, and one must rely on 2D images in these patients
- CT scan may be used to delineate the anatomy, especially in the grown-up patients [Figure 10].
|Figure 10: Computed tomography angiogram with three-dimensional reconstruction showing severe coarctation of aorta|
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In summary, echocardiography, along with the clinical background, allows a comprehensive evaluation of the aortic arch. It not only helps in confirming the diagnosis and in planning the appropriate intervention, but may also serve as a valuable tool for intra-procedure guidance and post-procedure follow-up. In some cases, especially the grown-up patients, additional imaging tools such as CT scan may be needed to better define the aortic arch anomalies.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]