Abstract
Anomalies of the aortic arch and the brachiocephalic vessels may occur in isolation or in association with congenital heart disease. Echocardiographic assessment of possible abnormalities in the position or branching of the aortic arch requires a systematic approach, based on the knowledge of the hypothetic bilateral aortic arch model according to Edwards. Identification of the brachiocephalic vessels and their connections is greatly enhanced by colour Doppler interrogation. Examination starts with the determination of the first brachiocephalic vessel and the position of the aorta from a high parasternal or suprasternal window. This approach allows to discriminate right, left and double aortic arch. In patients with double aortic arch, colour Doppler reveals patency or obstruction of either of the aortic arches. The presence of the thymus and the good imaging conditions in newborns and young infants allow to diagnose anomalies of the subclavian arteries and carotid arteries. These anomalies include aberrant origin of the subclavian artery from the descending aorta, isolation or cervical origin. Since determination of the laterality of the aortic arch and exclusion of pulmonary artery sling can be achieved quickly in infants, echocardiography represents an ideal screening method for detection of the majority of cardiovascular anomalies, which may cause obstructions of the upper airways in infancy.
23.1 Anatomy and Haemodynamics
Due to the close spatial relationship in the upper mediastinum, abnormalities in the position or branching of the aortic arch or pulmonary bifurcation may cause obstruction of the central airways and the oesophagus. This chapter is dedicated to the echocardiographic diagnosis of these abnormalities and its implication for the noninvasive diagnosis of vascular causes of upper airway obstruction.
23.1.1 Laterality of the Aortic Arch
Formation of the normal aortic arch and the brachiocephalic arteries as well as the development of aortic arch anomalies can be explained according to the hypothetical bilateral aortic arch model of J.E. Edwards (Edwards 1948; Moes 1997; Muster et al. 2001). According to this model, the embryonal ascending ventral aortae are connected to the dorsal aortae via bilateral arches encircling both the trachea and the oesophagus (Fig. 23.1). The right-sided and the left-sided arches give rise to the respective common carotid and subclavian arteries. Distal to the origin of the subclavian arteries, both arches are connected to the pulmonary artery via a right-sided and a left-sided ductus arteriosus (Fig. 23.2).
Scheme of the hypothetical double aortic arch model according to Edwards (Modified with kind permission according to (Moes and Freedom 1992)). The ventral and dorsal aortae are connected by pairs of aortic arches (a). The development of the normal aortic arch can be explained by persistence (dotted areas) or regression (clear areas) of parts of this double aortic arch. The cephalic extensions of the ventral aorta beyond the third arches become the external carotid arteries, while the third arches and the superior portions of the dorsal aortae form the internal carotid arteries (b). The right fourth arch becomes the base of the right subclavian artery, while the left fourth arch forms the aortic arch segment between the left carotid and left subclavian artery. The proximal parts of the sixth arches form parts of the right and left pulmonary artery, the distal parts of the sixth arches become a left or right ductus arteriosus (Modified with kind permission according to (Moes and Freedom 1992) RADAR/LDAR right/left dorsal aortic root)
The hypothetical plan of double aortic arches according to Edwards allows to define segments, which can be attributed to the different embryonal aortic arches. Anomalies of laterality of the arch and anatomy of the brachiocephalic arteries can be explained by persistent patency of segments that normally regress and regression of segments that normally remain patent. In the development of the normal left aortic arch, the right dorsal aortic root (RDAR), the right ductus arteriosus and the short segment between the right ductus arteriosus and the right subclavian artery (segments 1, 7 and 9) regress (b). The formation of right aortic arch with mirror image branching of the brachiocephalic arteries (c) is the result of regression of the left dorsal aortic root, the left ductus arteriosus and the segment between the left ductus arteriosus and the left subclavian artery (segments 2, 8 and 10). IA Innominate artery (Modified with kind permission according to (Moes and Freedom 1992))
Formation of the normal left aortic arch requires the involution of parts of this bilateral aortic arch system (Fig. 23.2). Normal development is characterized by involution of the right dorsal aortic root distal to the origin of the right subclavian artery. In addition there is complete involution of the right-sided ductus arteriosus. This results in an aortic arch passing the trachea anteriorly and to the left connecting to a left-sided descending aorta (Fig. 23.2). The innominate artery, giving rise to the right common carotid and right subclavian artery, represents the remnant of the former proximal right aortic arch.
Formation of right aortic arch with mirror image branching of the brachiocephalic vessels is explained embryologically by persistence of the right aortic arch and involution of the left dorsal aortic root distal to the origin of the left subclavian artery (Fig. 23.2). Right aortic arch as an isolated malformation is rare and has been reported with an incidence of 0.1 % (Muster et al. 2001). In the majority of cases right aortic arch with mirror image branching is associated with congenital heart defects. The incidence of right aortic arch may differ significantly among the various congenital cardiac malformations (Moes 1997). The highest incidence of right aortic arch has been reported among patients with conotruncal malformations like tetralogy of Fallot, pulmonary atresia and VSD, truncus arteriosus communis and double outlet right ventricle (Moes 1997). Right aortic arch is quite rare however in patients with complete transposition of the great arteries, congenitally corrected transposition and obstructive lesions of the left heart like aortic stenosis, coarctation of the aorta or hypoplastic left heart syndrome (Moes 1997).
23.1.2 Subclavian Artery Anomalies
Left aortic arch with aberrant right subclavian artery is the most frequent aortic arch anomaly with an incidence of 0.5 % (Moes 1997). However aberrant origin of the subclavian artery from the descending aorta represents only one out of four possible anomalies concerning subclavian artery origin. These anomalies include aberrant origin from the descending aorta, isolation, ductal origin and cervical origin of the subclavian artery (Kutsche and Van Mierop 1984). Subclavian artery anomalies can be explained embryologically by disturbances involving the development of the right fourth aortic arch (Kutsche and Van Mierop 1984).
Aberrant origin of the subclavian artery from the descending aorta is due to interruption of the aortic segment between the right common carotid and the right subclavian artery (right fourth aortic arch). Persistence of the right dorsal aortic root secures perfusion of the right subclavian artery from the descending aorta (Fig. 23.3). This anomaly results in absence of the right innominate artery, with the right common carotid artery originating as the first and the right subclavian artery as the last vessel from the aortic arch (Fig. 23.3). This anomaly is usually not associated with the presence of a vascular ring (Moes 1997). Although the subclavian artery takes a retroesophageal course to the right, causing an indentation, which can be visualized on a lateral esophagogram, clinical problems with swallowing are rare. An increased incidence of this anomaly has been reported recently among fetuses with Down syndrome (Chaoui et al. 2005; Chaoui et al. 2008).
Subclavian artery anomalies are related to developmental disturbance of the right fourth aortic arch, representing segment 3 in the bilateral aortic arch model (a). In aberrant origin from the descending aorta, the right subclavian artery (RSA) remains connected to the descending aorta via the right dorsal aortic root (RDAR). If the right dorsal aortic root involutes as well, the subclavian artery becomes isolated (c), receiving only retrograde perfusion from the right vertebral artery (RVA). If a right-sided ductus arteriosus (DA) persists, the right subclavian artery remains connected both to the right pulmonary and the right vertebral arteries (d) (Modified with kind permission according to (Moes and Freedom 1992))
Interruption of the proximal right aortic arch between the right common carotid and the right subclavian artery is present as well in isolation of the subclavian artery (Fig 23.3). However in these cases the subclavian artery retains no connection to the right dorsal aortic root (Hofbeck et al. 1991; Kutsche and Van Mierop 1984; McElhinney et al. 1998; Moes 1997). If the right ductus arteriosus closes as well, the right subclavian artery becomes isolated, receiving only retrograde perfusion from the right vertebral artery (Fig 23.3). If the ductus arteriosus remains open, the subclavian artery retains a connection both to the right pulmonary artery and to the vertebral artery. Since the right subclavian artery both in patients with isolation and with ductal origin is connected to the ipsilateral vertebral artery, patients with this anomaly are possible candidates for subclavian steal syndrome (Deeg et al. 1993; Hofbeck et al. 1991; Russell et al. 2000): retrograde flow to the right subclavian artery can be demonstrated by Doppler evaluation of the right vertebral artery (Deeg et al. 1993; Hofbeck et al. 1991). In patients with right aortic arch, isolation and ductal origin of the left subclavian artery has been reported in mirror image fashion (McElhinney et al. 1998; Russell et al. 2000). Actually this anomaly appears to be more common in patients with right aortic arch (Russell et al. 2000; Sun et al. 2005).
The last anomaly, originally described by Kutsche and van Mierop, is cervical origin of the right subclavian artery (Kutsche and Van Mierop 1984). Following disturbed development of the right fourth aortic arch, the right subclavian artery remains connected to the right dorsal aorta between the third and fourth arches (Fig. 23.4). This results in abnormal origin of the right subclavian artery from the right common carotid artery close to its bifurcation into internal and external carotid arteries (Kutsche and Van Mierop 1984; Rauch et al. 2002, 2005).
During normal embryonic development (a, b), the right fourth aortic arch (arrow) forms the base of the right subclavian artery. Disturbed development of the right fourth aortic may result in cervical origin of the right subclavian artery (c, d). In these cases the subclavian artery (RSA) retains its connection to the third aortic arch close to the bifurcation into internal and external carotid artery (ICA, ECA) (Modified with kind permission according to (Kutsche and Van Mierop 1984))
All these subclavian artery anomalies may also be encountered in mirror image fashion in patients with right aortic arch involving the left subclavian artery. Although these anomalies usually do not cause clinical symptoms (exceot for subclavian steal in isolation and ductal origin), they still may have significant clinical relevance for surgical procedures and perioperative monitoring: aberrant subclavian artery from the descending aorta may complicate the surgical repair of isthmic coarctation of the aorta or interruption of the aortic arch (see Chap. 21). In the majority of cases, the aberrant subclavian artery originates distal to the aortic arch obstruction, which has to be considered if the right subclavian artery is used for invasive monitoring of arterial blood pressure in the perioperative period. Isolation of the subclavian artery results in significantly decreased blood pressures on the respective arm, which makes the radial artery of the respective arm useless for invasive monitoring of blood pressure, a fact that has to considered again in the planning of perioperative monitoring. Furthermore reimplantation of an isolated subclavian artery should be considered during surgery of an associated cardiovascular malformation, to prevent subclavian steal in these patients during later life (Deeg et al. 1993; Russell et al. 2000).
Last but not least the above-mentioned anomalies of the subclavian arteries, which can be explained by disturbance of the development of the fourth aortic arch, are closely related to 22q11.2 deletion syndromes. Cardiovascular anomalies have been described in about 75–80 % of patients with monosomy 22q11.2, the majority of them belonging to the group of so-called conotruncal malformations (Goldmuntz et al. 1998; Momma 2010; Rauch et al. 2004). Among patients with conotruncal malformations (including interrupted aortic arch, pulmonary atresia and VSD as well as truncus arteriosus), the presence of subclavian artery anomalies is a very strong indicator for 22q11.2 deletion syndromes (Goldmuntz et al. 1998; Momma 2010; Rauch et al. 2004). This refers specifically to the cervical origin of the subclavian artery (Rauch et al. 2002). Since isolated anomalies of laterality or branching of the aortic arch are associated with 22q11.2 deletion in 24 % of cases, these findings should alert the clinician to consider genetic testing also in patients without conotruncal malformations (McElhinney et al. 2001).
23.1.3 Vascular Rings
Among the large variety of possible malformations of the aortic arch system, a specific group is characterized by the formation of a complete ring encircling the trachea and the oesophagus. The development of these vascular rings can be explained by the disturbed involution or abnormal persistence of segments of the hypothetical bilateral aortic arch model (Edwards 1948; Moes 1997; Moes and Freedom 1992). It has to be noted, however, that even complete rings may be asymptomatic or may become symptomatic only later in life (Moes 1997).
The most significant anomaly, which may result in severe airway obstruction of the neonate and young infant, is double aortic arch (Fig. 23.5). In this anomaly both the left and right aortic may persist as patent vessels encircling the trachea and oesophagus as a closed vascular ring. These patients have no innominate artery: instead the common carotid and the subclavian arteries originate as separate vessels from both aortic arches. In the majority of cases, the right aortic arch is larger than the left; only in rare cases both arches are of equal size (Moes 1997).
Patients with double aortic arch may present with two patent arches, characterized by bilateral separate origin of the carotid (RCA, LCA) and subclavian arteries (RSA, LSA) from the respective arches (a). Although either of the aortic arches may be partially atretic, atresia of the left arch is much more common (b). The most frequent variant is atresia distal to the left subclavian artery (LSA). Since the atretic parts cannot be visualized by echocardiography, the anatomy may resemble right aortic arch with mirror image branching of the brachiocephalic arteries (c) (Modified with kind permission according to (Moes and Freedom 1992))
Patients may present with variants of double aortic arch that contain segments that are atretic and represented by strands of fibrous tissue. Atresia of aortic arch segments in this context affects preferentially parts of the left aortic arch (Moes 1997; Moes and Freedom 1992). The atretic segment may be located between the left common carotid artery and the left subclavian artery, distal to left subclavian artery or between the left subclavian artery and the ductus arteriosus (Fig. 23.5). In the latter case, the ductus arteriosus connects an aortic diverticulum (diverticulum of Kommerell – representing the patent dorsal part of the left aortic arch) to the left pulmonary artery. If the left aortic arch distal to the subclavian artery is atretic, it may be difficult to differentiate this anomaly from the right aortic arch with mirror image branching (Fig. 23.5). However two distinct findings allow differentiation of these entities: since the fibrous strand of the atretic left aortic arch imposes some caudal tension on the left brachiocephalic artery, the subclavian artery in this situation frequently shows an inferior kink. Furthermore a diverticulum of Kommerell remains as an outpouching of the descending aorta representing the atretic distal left aortic arch (left dorsal aortic root) (Fig. 23.5).
Several further aortic arch anomalies result in the formation of a vascular ring or sling with possible compression of the trachea. The most frequent of these anomalies is right aortic arch with aberrant left subclavian artery (McElhinney et al. 2001; Moes 1997). This malformation presents with a patent right aortic arch, while the left aortic arch is interrupted between the left common carotid and left subclavian artery (Fig. 23.6). Due to this interruption, the left common carotid artery originates as the first brachiocephalic vessel from the aorta followed by the right common carotid and right subclavian artery. The left subclavian artery originates as the last brachiocephalic vessel and takes a retroesophageal course (Fig. 23.6). A vascular ring is formed if the aberrant subclavian artery originates from an outpouching of the descending aorta, a so-called diverticulum of Kommerell. In these cases, the ductus arteriosus connects the diverticulum of Kommerell to the left pulmonary artery. The ductus may remain patent; in the majority of cases, it is closed however and presents as a fibrous ligament.
In patients with right aortic arch and aberrant origin of the left subclavian artery, the developmental disturbance affects the left fourth aortic arch, representing the aortic segment 6 between the left carotid and left subclavian artery (a). The left subclavian artery (LSA) remains connected to the descending aorta via the left dorsal aortic root, which becomes the diverticulum of Kommerell (b). The vascular ring is completed by the ductus arteriosus or its ligament, connecting the diverticulum of Kommerell to the left pulmonary artery (Modified with kind permission according to (Moes and Freedom 1992))
The left circumflex aortic arch is a very rare anomaly, which is characterized by an initially normal left aortic arch passing the trachea in a normal fashion to the left (Moes 1997). Posterior to the oesophagus, the aortic arch takes a rightward course to continue as a right descending aorta. It may be associated either with normal branching of the brachiocephalic vessels or with aberrant origin of the right subclavian artery (Moes 1997). A complete ring exists in these patients, if a patent ductus arteriosus or a ductal ligament connects the descending aorta to the right pulmonary artery (Moes 1997).
Cervical aortic arch is a malformation characterized by malposition of the aortic arch, which extends further cranially above the level of the clavicles into the neck (Moes 1997; Snider 1996). Cervical aortic arch may present as right or left aortic arch and may be associated with anomalies of the brachiocephalic arteries or coarctation of the aorta. Anomalies of the brachiocephalic arteries may result in formation of a vascular ring with subsequent symptoms of tracheal compression. The diagnosis can be suspected clinically due to palpation of a pulsatile mass in the suprasternal notch and in the neck.
23.1.4 Pulmonary Artery Sling
Pulmonary artery sling is characterized by abnormal origin of the left pulmonary artery from the right pulmonary artery (1997). The left pulmonary artery originates to the right of the trachea, crosses over the right main bronchus and takes a course posterior to the trachea and anterior to the oesophagus to reach the hilum of the left lung (Fig. 23.7). Due to this abnormal course, the left pulmonary artery may compress the proximal right main bronchus as well as the distal trachea. About one-third of the patients has associated major cardiovascular anomalies (Dohlemann et al. 1995; Gikonyo et al. 1989). These include ventricular and atrial septal defects, ductus arteriosus, tetralogy of Fallot, univentricular heart and coarctation of the aorta (Gikonyo et al. 1989).
In pulmonary artery sling, the anomalous left pulmonary artery (LPA) originates from the right pulmonary artery (RPA) and crosses over the right main stem bronchus to pass between the trachea (T) and oesophagus (E) to the left (a). Possible compression of the trachea from the right and posterior becomes even more apparent in the diagram showing the anatomy from above (b). AO Ascending aorta, DAO Descending aorta
Pulmonary sling presents in two distinct anatomical subtypes, which have to be distinguished, since they require different therapeutical strategies (Wells et al. 1988). The first variant (type I according to the classification of Wells et al.) is associated with a normal trachea of normal length and normal number of tracheal cartilage rings (Wells et al. 1988). The second variant (type II according to the classification of Wells et al.) is associated with a so-called bridging bronchus. Bridging bronchus is characterized by origin of a common right middle and lower lobe bronchus from the left main bronchus crossing the midline (“bridging”) from left to right (Baden et al. 2008; Wells et al. 1988). While this common middle and lower lobe bronchus originates from a pseudocarina at a lower level than the normal carina, the right upper lobe bronchus may originate from the trachea at the level of the normal bifurcation (type IIA according to the classification of Wells et al.) or may be even absent (type IIB). In patients with type II, the pulmonary sling crosses over the bridging bronchus on its way to the left hilum. The identification of patients with pulmonary sling type II and bridging bronchus is important, since they frequently present complete cartilage rings with absence of the pars membranacea in the trachea and in the main bronchi, resulting in severe tracheal and left main bronchus stenoses (Baden et al. 2008; Berdon et al. 2012; Medina-Escobedo and Lopez-Corella 1992; Wells et al. 1988, 1990).
These additional tracheobronchial malformations result in significant aggravation of respiratory problems in patients with pulmonary sling type II. In these patients, airway obstruction cannot be abolished by surgical correction of pulmonary sling (e.g. by transection and reinsertion of the left pulmonary) as in patients with type I. Surgical repair in children with bridging bronchus requires relocation of the left pulmonary artery in combination with complex tracheal and bronchial reconstruction including slide tracheoplasty, tracheal autograft, tracheal resection or pericardial patch tracheoplasty (Backer et al. 2012; Beierlein and Elliott 2006; Berdon et al. 2012; Ziemer et al. 1992).
23.2 2D Echo and Colour Doppler Echocardiography
The introduction of three-dimensional imaging techniques like MRI and multislice CT has revolutionarized the diagnostic evaluation of children with upper airway obstruction due to vascular rings or slings, since it allows the visualization of the vessels, the surrounding structures and the airways (Baden et al. 2008; Hernanz-Schulman 2005; Kir et al. 2012). Nevertheless echocardiography remains a valuable diagnostic tool that allows detection of the vast majority of cardiovascular anomalies that may cause obstruction of the upper airways (Murdison 1996; Snider 1996). This is especially true in the neonatal period and early infancy, when echocardiographic imaging of the upper mediastinum is facilitated by the thymus gland. Furthermore echocardiography in neonates and infants allows the detection of abnormalities of the aortic arch and its brachiocephalic vessels, which are not associated with airway obstruction but which are relevant for other aspects of treatment (McElhinney et al. 1998; Rauch et al. 2004, 2005; Russell et al. 2000). Since identification of the brachiocephalic vessels and their connections is greatly enhanced by determination of their flow, echocardiographic examination almost always includes primary involvement of colour Doppler examination.
23.2.1 Assessment of Laterality of the Aortic Arch
Echocardiographic examination of the aortic arch and the brachiocephalic vessels for possible vascular rings or slings requires the application of a systematic approach (Huhta et al. 1984; Murdison 1996; Snider 1996). Even the diagnosis of right aortic arch with mirror image branching of the brachiocephalic arteries can be missed easily, without a careful examination. The examination is greatly facilitated by elevation of the patient’s shoulders. Frequently this requires sedation especially in older infants and young children.
We suggest to begin the examination either from the high parasternal or from the suprasternal window (Murdison 1996). Starting in the short-axis view with the ascending aorta displayed in cross section, the transducer is tilted cranially (Fig. 23.8). In patients with normal left aortic arch, the innominate artery originates as the first vessel from the aorta to the right (Huhta et al. 1984; Murdison 1996; Snider 1996) (Videos 23.1 and 23.2). Slight clockwise rotation of the transducer elongates the innominate artery and allows to verify branching of this vessel into right common carotid and right subclavian artery (Fig. 23.8, Video 23.3). Confirmation of normal branching of the right innominate artery excludes subclavian artery anomalies like anomalous origin from the descending aorta, isolation, ductal origin or cervical origin. Following that manoeuvre, the transducer is tilted back to the high parasternal or suprasternal short-axis view. Confirmation of the laterality of the aortic arch is obtained by rotation of the transducer starting with the aorta displayed in cross section: counterclockwise rotation together with some leftward tilt results in elongation of the arch presenting finally the long-axis view of a left aortic arch.
Evaluation of the laterality of the aortic arch starts in a high parasternal or suprasternal short-axis view (a), displaying the pulmonary artery bifurcation (PA) and the ascending aorta (AO) in cross section. Cranial tilt of the transducer (b) shows the transverse aortic arch (AO) and the superior vena cava (SVC). Further cranial tilt (c) displays the origin of the innominate artery (IA) from the aorta and the innominate vein (IV). Following clockwise rotation of the transducer combined with some more cranial tilt (d), the innominate artery is depicted in longitudinal section revealing its bifurcation into the right subclavian (RSA) and right carotid artery (RCA)
This high parasternal short-axis sweep shows evaluation of laterality in a patient with normal left aortic arch. It starts with the parasternal short-axis view of the pulmonary artery bifurcation, displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the transverse aortic arch, the superior vena cava in cross section and the innominate vein in longitudinal section. Further cranial tilt displays the origin of the innominate artery from the aorta to the right. Following clockwise rotation of the transducer combined with some more cranial tilt, the innominate artery is depicted in longitudinal section revealing its bifurcation into the right subclavian and right carotid artery (AVI 49571 kb)
Colour Doppler in this high parasternal short-axis sweep shows evaluation of laterality in a patient with normal left aortic arch in analogy to Video 23.2 (AVI 23211 kb)
Slight rotation of the transducer from the long-axis view of the innominate artery displays the branching into right subclavian and right common carotid artery (AVI 5470 kb)
In the presence of right aortic arch and mirror image branching of the brachiocephalic arteries, cranial tilt of the transducer starting from the high parasternal or suprasternal short-axis view reveals origin of the first brachiocephalic vessel to the left (Videos 23.4 and 23.5). The left innominate artery subsequently divides into the left common carotid and into the left subclavian artery (Fig. 23.9). Confirmation of right aortic arch is obtained by rotation of the transducer: starting from a parasternal short-axis view, the right aortic arch can be displayed in its long axis following clockwise rotation associated with some rightward tilt of the transducer (Videos 23.6 and 23.7).
The high parasternal short-axis view in a patient with right aortic arch shows origin of the first brachiocephalic artery to the left. Origin of the left subclavian (LSA) and left common carotid artery (LCA) characterizes this vessel as left innominate artery. The anatomy is confirmed by colour Doppler interrogation. IV Innominate vein, SVC Superior vena cava
The high parasternal short-axis view in a patient with right aortic arch shows origin of the first brachiocephalic artery to the left. Branching of the innominate artery into left subclavian and left common carotid artery characterizes this vessel as left innominate artery (AVI 5812 kb)
The anatomy is confirmed by colour Doppler interrogation displaying the innominate vein cranial to the aorta and the superior vena cava to the right of the aorta (AVI 5868 kb)
This high parasternal short-axis sweep shows evaluation of laterality in a patient with right aortic arch. It starts with the parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the superior vena cava in cross section and the innominate vein in longitudinal section. Further cranial tilt displays the origin of the innominate artery from the aorta to the left branching into the left subclavian and left common carotid artery (AVI 23620 kb)
Colour Doppler in this high parasternal short-axis sweep shows evaluation of laterality in a patient with right aortic arch. It starts with the parasternal short-axis view of the pulmonary artery bifurcation, displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the superior vena cava in cross section and the innominate vein in longitudinal section. Clockwise rotation and some rightward tilt of the transducer open the aortic arch and display the right descending aorta (AVI 22931 kb)
23.2.2 Double Aortic Arch
In patients with double aortic arch, we start echocardiographic examination in the high parasternal or suprasternal short-axis view displaying the ascending aorta in cross section (Fig. 23.10). Cranial tilt of the transducer reveals transition of the normal circular cross section of the aorta to the figure of a horizontal 8 (Fig. 23.10, Videos 23.8 and 23.9). In patients with two patent arches, further cranial tilt of the transducer displays both arches (encircling trachea and oesophagus) on their bilateral course to the descending aorta (Fig. 23.10, Video 23.10). Clockwise rotation of the transducer opens the right-sided aortic arch; counterclockwise rotation opens the left-sided aortic arch (Fig. 23.11). Both arches are characterized by separate origins of the common carotid and subclavian arteries (Fig. 23.11). A sagittal sweep of the transducer from the high parasternal or suprasternal window consecutively displays the long axis of both arches (Video23.11). Frequently the right-sided arch is significantly larger than the left (Moes 1997).
The high parasternal short-axis view in a patient with double aortic arch displays the ascending aorta (AO) in cross section (a). Cranial tilt of the transducer displays the innominate vein (IV) and shows origin of both aortic arches from the ascending aorta with transition of the circular shape of the aorta into the configuration of a horizontal 8 (b). Colour Doppler (c) reveals flow to the left-sided arch (LAA), which is confirmed by further cranial tilt of the transducer (d, e), displaying patency both of the right (RAA) and left (LAA) aortic arches (f)
The suprasternal long-axis view (a) of the left aortic arch (same patient as Fig. 23.10) shows separate origin of the left carotid (LCA) and left subclavian artery (LSA). Patency of the arch is confirmed by colour Doppler (b). Separate origin of the right carotid (RCA) and right subclavian artery (RSA) is displayed in the suprasternal long-axis view of the right aortic arch (c). Colour Doppler shows patency and unobstructed flow in the right aortic arch (d)
The colour Doppler sweep in a young infant with double aortic arch starts in the high parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt of the transducer displays the innominate vein and shows origin of both aortic arches from the ascending aorta with transition of the circular shape of the aorta into the configuration of a horizontal 8. Further cranial tilt shows separation of the right and left aortic arch. Colour Doppler reveals patency both of the right and left aortic arches (AVI 16269 kb)
The colour Doppler sweep in another infant with double aortic arch starts in the high parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt displays the innominate vein cranial to the aorta and shows separation of the aorta into a dominant right and a significantly smaller left aortic arch. Further cranial tilt of the transducer confirms patency of both aortic arches (AVI 29467 kb)
Colour Doppler in a cranial short-axis view (same patient as in Video 23.8) displays the complete vascular ring formed by a patent right and left aortic arch (AVI 2392 kb)
The colour Doppler sweep in a high parasternal long-axis view in a patient with double aortic arch starts with a long-axis view of the right aortic arch. Leftward tilt of the transducer shows the longitudinal view of the oesophagus; further leftward tilt of the transducer reveals the left aortic arch which reveals a smaller segment distal to the left carotid artery. Distal to the left subclavian artery, the aorta is larger due to the ampulla of the former ductus arteriosus. Finally, the transducer is tilted back towards the right displaying again the larger right aortic arch (AVI 40941 kb)
Patients with double aortic arch may present with partial atresia of one arch. In the vast majority of cases, atresia affects the left-sided arch, leaving only a patent right aortic arch (McElhinney et al. 2001). Echocardiographic appearance of these patients depends on the time of their presentation. Following prenatal detection of the aortic arch anomaly, an increasing number of these children is examined in the neonatal period (Tuo et al. 2009). Examination in the neonatal period may reveal a situation that is very similar to patients with bilaterally patent arches. Colour Doppler examination demonstrates antegrade perfusion of the patent arch. In the arch with the atretic segment, colour Doppler examination reveals antegrade perfusion up to the point of atresia (Fig. 23.12, Video 23.12). The distal part of the arch beyond the atretic segment (frequently the segment distal to the left subclavian artery) shows retrograde flow from the descending aorta via the distal left aortic arch (Fig. 23.12). If the examination is performed within the first few days of life, the ductus may be still patent. In the common situation of a patent right aortic arch with atresia of the left arch distal to the subclavian artery, the left-sided ductus arteriosus connects the distal aortic arch segment with the left pulmonary artery (Fig. 23.12, Video 23.13).
In a newborn with double aortic arch, the left aortic arch is displayed from a suprasternal window (a) revealing atresia distal to the origin of the left carotid (LCA) and left subclavian artery (LSA). Absence of antegrade flow across the aortic isthmus as well as retrograde filling (coded in red) of the right aortic arch is evident on colour Doppler examination (b) in the long-axis view of the arch and in the ductal view (c). Slight medial sweep of the transducer in the ductal view (d, e) shows a restrictive ductus arteriosus (DA) connecting the left descending aorta to the pulmonary artery (PA). At the end of the first day of life, the ductus has undergone almost complete spontaneous closure in this patient
In a newborn with double aortic arch, the left aortic arch is displayed from a suprasternal window revealing atresia distal to the origin of the left carotid and left subclavian artery. Absence of antegrade flow across the aortic isthmus as well as retrograde filling (coded in red) of the distal left descending aorta (diverticulum of Kommerell) from the right aortic arch is evident on colour Doppler examination (AVI 1866 kb)
This colour Doppler sweep in the high left parasternal sagittal view (ductal view) starts with a lateral plane displaying the main and left pulmonary artery (same patient as in Video 23.12). Leftward tilt of the transducer reveals a small and restrictive ductus arteriosus connecting to the MPA just proximal of the origin of the LPA. The ductus originates from the distal left descending aorta. Further rightward tilt displays the left aortic arch interrupted distal to the left subclavian artery, while the distal left aortic arch is filled retrogradely. Finally, the transducer is tilted again to the left (WMV 13225 kb)
In older children, the continuity of the arch segments adjacent to the atresia is no longer obvious. In the presence of a patent right aortic arch, the distal left descending aorta (left dorsal aortic root) regresses following closure of the ductus arteriosus to become a diverticulum of Kommerell. The proximal arch ends either distal to the carotid artery or distal to the subclavian artery (Fig. 23.13). The former situation resembles right aortic arch with aberrant origin of the left subclavian artery from the descending aorta. In patients with interruption distal to the subclavian artery, the echocardiographic appearance resembles right aortic arch with mirror image branching of the brachiocephalic vessels (Fig. 23.5). The presence of a double aortic arch with partial atresia of the left arch can be suspected, however, if the left subclavian artery shows a sharp downward bend, which is due to the traction of the fibrous ligament of the atretic left-sided arch (Fig. 23.13, Videos 23.14 and 23.15). Cardiac MRI and CT-thorax reveal the presence of a diverticulum of Kommerell representing the remnant of the left dorsal aortic root (Fig. 23.13).
The high left parasternal short-axis view (a) in a 4-month-old infant with apparently right aortic arch shows a left innominate artery dividing into left carotid (LCA) and left subclavian artery (LSA). The left subclavian artery shows an inferior bend (arrows), suggesting the correct diagnosis of double aortic arch with partial atresia of the left arch distal to the left subclavian artery (b). Flow in the innominate artery is demonstrated by colour Doppler (c). The anatomy is confirmed by 3D reconstruction of CT-thorax, showing the patent right aortic arch and the bend of the subclavian artery (arrow) in the anterior view (d). The posterior view (e) reveals a diverticulum of the descending aorta (DIV), which together with the inferior angulation of the left subclavian artery confirms the presence of an atretic left aortic arch, forming a complete vascular ring around the trachea, which is displayed in blue (3D reconstruction of the CT-thorax courtesy of Prof. Dr. J. Schaefer, Dpt. of Radiology, University Hospital Tuebingen, Germany)
The high left parasternal short-axis view in a 4-month-old infant shows a left innominate artery dividing into the left carotid and left subclavian artery suggesting a right aortic arch. However, the left subclavian artery shows an inferior angulation, indicating the correct diagnosis of double aortic arch with partial atresia of the left arch distal to the left subclavian artery (AVI 6111 kb)
Colour Doppler confirms regular flow in the innominate artery and branching into left common carotid and left subclavian artery (same patient as in Video 23.14) (AVI 1381 kb)
23.2.3 Right Aortic Arch and Aberrant Left Subclavian Artery
A frequent anomaly causing upper airway obstruction by a vascular ring is right aortic arch with aberrant origin of the left subclavian artery from the descending aorta via a diverticulum of Kommerell (McElhinney et al. 2001). Echocardiography in these patients reveals a right aortic arch (Fig. 23.14, Video 23.16). The first brachiocephalic vessel, originating from the aortic arch, is the left common carotid artery followed by the right common carotid and the right subclavian artery (Fig. 23.14, Video 23.17). In the first few days of life, the patent ductus arteriosus can be visualized in a high left parasternal long-axis view (“ductal view”), connecting the distal left descending aorta (represented by a diverticulum of Kommerell) with the left pulmonary artery (Fig. 23.14, Video 23.18). The left subclavian artery originates from this diverticulum as the last brachiocephalic vessel (Video 23.18).
The suprasternal long-axis view in a newborn (a) shows a right aortic arch, giving origin to the right carotid (RCA) and right subclavian artery (RSA). The oblique high left parasternal short-axis view in the same patient (b) displays the ascending aorta (AO) in cross section giving rise to the left carotid artery (LCA), originating as the first brachiocephalic vessel. The left subclavian artery (LSA) originates as the last brachiocephalic vessel from a diverticulum of Kommerell (DIV), representing the distal portion of the left aortic arch (c). Flow in the left carotid and left subclavian artery is apparent on the systolic frame (d). Caudal tilt of the transducer with some clockwise rotation (e) displays a patent ductus arteriosus (DA) originating from the diverticulum of Kommerell, connecting with the pulmonary artery bifurcation (f). RPA/LPA: Right/left pulmonary artery
The suprasternal long-axis view in a newborn shows a right aortic arch, giving origin to the right carotid and right subclavian artery. The view was obtained by clockwise rotation of the transducer from the suprasternal short-axis view (same patient as in Videos 23.17 and 23.18) (AVI 3016 kb)
The oblique high left parasternal short-axis view (same patient as in Videos 23.16 and 23.18) displays the ascending aorta in cross section giving rise to the left common carotid artery originating as the first brachiocephalic vessel. The left subclavian artery originates as the last brachiocephalic vessel from a diverticulum of Kommerell, which represents the distal portion of the left aortic arch. From the top of the diverticulum of Kommerell originates the left-sided ductus arteriosus which is further delineated in the sweep of Video 23.18 (AVI 1040 kb)
The colour Doppler sweep in this newborn reveals the diagnosis of RAA, aberrant left subclavian artery and left ductus arteriosus originating from a diverticulum of Kommerell (same patient as in Videos 23.16 and 23.17). It starts in the oblique high left parasternal short-axis view displaying aberrant origin of the left subclavian artery from a diverticulum of Kommerell. Clockwise rotation of the transducer and caudal shift reveal a tortuous ductus arteriosus originating from the top of the diverticulum of Kommerell connecting to the pulmonary bifurcation (AVI 19067 kb)
In the majority of these patients, the ductus arteriosus closes spontaneously in the neonatal period. The resulting ductal ligament no longer can be visualized by echocardiography. Beyond the neonatal period, echocardiography in these patients reveals a right aortic arch with a solitary left common carotid artery, originating as the first brachiocephalic vessel (Fig. 23.15). In young infants, it is frequently possible to visualize the aberrantly originating left subclavian artery by colour Doppler examination: it can be displayed in an oblique high left parasternal or suprasternal view running caudally and almost parallel to the left common carotid artery (Fig. 23.15, Videos 23.19 and 23.20). However with increasing age of the patient, visualization of the aberrant subclavian artery becomes more and more difficult and frequently requires imaging techniques like MRI or CT-thorax (Fig. 23.15).
The oblique suprasternal short-axis view in a 4-year-old patient (a) with right aortic arch shows the ascending aorta (AO) in cross section giving rise to the left carotid artery (LCA). The left subclavian artery (LSA) originates aberrantly from the descending aorta via a diverticulum of Kommerell (DIV). Separate origin of the left carotid and left subclavian artery is confirmed by colour Doppler (b). 3D reconstruction of the CT-thorax in the anterior view (c) shows the right aortic arch and anomalous origin of the left subclavian artery (LSA) from the descending aorta via a diverticulum of Kommerell (DIV). Origin of the left subclavian artery from the diverticulum of Kommerell is also well displayed in the posterior view (d). The vascular ring around the trachea is completed by a ductal ligament, connecting the top of the diverticulum to the left pulmonary, which is neither displayed by echocardiography nor by CT-thorax, since it is atretic (3D reconstruction of the CT-thorax courtesy of Prof. Dr. J. Schaefer Dpt. of Radiology, University Hospital Tuebingen, Germany)
The oblique suprasternal short-axis view in a 4-year-old patient with right aortic arch shows the ascending aorta in cross section giving rise to the left common carotid artery, which originates as the first brachiocephalic vessel (same patient as in Video 23.20). The left subclavian artery originates aberrantly from the descending aorta via a diverticulum of Kommerell (AVI 5371 kb)
Separate origin of the left carotid and left subclavian artery is confirmed by colour Doppler (same patient as in Video 23.19). Colour Doppler reveals no evidence for persistent patency of the ductus arteriosus (AVI 1824 kb)
23.2.4 Subclavian Artery Anomalies Without Vascular Ring
Systematic evaluation of the aortic arch and of the brachiocephalic vessels also reveals subclavian artery anomalies that are not associated with compression of the trachea and oesophagus by formation of a vascular ring (McElhinney et al. 1998; Rauch et al. 2005; Russell et al. 2000). The diagrams showing these anomalies refer to patients with left aortic arch. However all subclavian artery anomalies may be encountered in mirror image fashion in patients with right aortic arch, affecting the left subclavian artery (McElhinney et al. 1998).
In patients with left aortic arch and normal branching of the brachiocephalic arteries, cranial tilt of the transducer with clockwise rotation shows the first brachiocephalic vessel directed to the right. This right innominate artery is characterized by branching into right common carotid and right subclavian arteries (Fig. 23.8). Absence of normal branching of the first brachiocephalic artery definitely proves the presence of a subclavian artery anomaly and should prompt a careful search for the underlying pathology. While complete clarification of the anatomy is possible in the majority of neonates, evaluation becomes increasingly difficult in older children due to the deteriorating echocardiographic window. Although absence of normal branching can be ascertained easily in older patients, clarification of the underlying anatomy in this age group frequently requires cardiac MRI or CT-thorax.
The most frequent anomaly is aberrant origin of the subclavian artery from the descending aorta. In these patients the first brachiocephalic vessel originating from the ascending aorta represents the right common carotid artery (Fig. 23.16, Video 23.21). Starting with the longitudinal image of the right common carotid artery from a high right parasternal or suprasternal window, caudal tilt of the transducer reveals the aberrant subclavian artery running caudally and parallel to the carotid artery (Fig. 23.16, Video 23.22). Imaging of the aberrant subclavian artery is greatly facilitated by colour Doppler. Since the insonation angle of the subclavian artery is unfavourable for colour Doppler interrogation, colour Doppler velocity (prf-rate) should be reduced to 20–30 cm/s. From the suprasternal notch, the origin of the aberrant subclavian artery from the descending aorta can be displayed in a coronal plane with posterior orientation of the transducer (Video 23.23). To obtain adequate imaging of this posterior plane, elevation of the shoulders and reclination of the neck are mandatory.
The high parasternal short-axis view in a neonate (a) with left aortic arch shows the ascending aorta (AO) in cross section giving rise to the right carotid artery (RCA). Caudal tilt of the transducer (b) depicts the right subclavian artery (RSA), taking a parallel but inferior course, due to its aberrant origin from the descending aorta. The anatomy is confirmed by colour Doppler (c), showing also origin of the right vertebral artery (RVA) from the right subclavian artery (RSA)
The high right parasternal short-axis view in a neonate with left aortic arch shows the ascending aorta (AO) in cross section giving rise to a brachiocephalic vessel to the right. The rather small size of this first vessel suggests that it might not represent the right innominate artery but only the right common carotid artery (AVI 17226 kb)
Caudal tilt of the transducer in a similar patient depicts the right subclavian artery, taking a parallel but inferior course to the carotid artery, due to its aberrant origin from the descending aorta (AVI 3286 kb)
Caption (AVI 2620 kb)
The second most frequent subclavian artery anomaly is cervical origin (Kutsche and Van Mierop 1984; Rauch et al. 2002, 2004). In this anomaly branching of the first brachiocephalic artery does not occur in the normal position (Rauch et al. 2005). Longitudinal imaging of the distal innominate artery depicts cervical origin of the subclavian artery from the common carotid artery close to the bifurcation into internal and external carotid arteries (Fig. 23.17, Videos 23.24 and 23.25). From there the subclavian artery takes a retrograde caudal course back to the right arm, which is confirmed by colour Doppler (Fig. 23.17, Videos 23.26 and 23.27).
In an infant with pulmonary atresia, VSD and left aortic arch, the longitudinal section of the right neck (a) shows the right common carotid artery (RCA). Proximal to the bifurcation into internal (ICA) and external carotid artery (ECA), the right subclavian artery (RSA) is displayed taking a cervical origin. Caudally directed flow in the subclavian artery is confirmed by colour Doppler (b), while caudal shift of the transducer shows its inferior course to the right arm (c–e)
Colour Doppler in a posterior suprasternal short-axis plane of a newborn with left aortic arch shows origin of the aberrant right subclavian artery from the descending aorta. Note significant retrograde flow in the descending aorta in diastole, which is explained by the diagnosis of truncus arteriosus resulting in diastolic run-off to the pulmonary arteries (AVI 14408 kb)
In an infant with pulmonary atresia, VSD and left aortic arch, colour Doppler in the longitudinal view of the right neck shows the right common carotid artery. Proximal to the bifurcation into internal and external carotid artery, the right subclavian artery is displayed taking a cervical origin (same patient as in Videos 23.26 and 23.27 (AVI 2870 kb)
Caudal angulation of the transducer displaying the right brachiocephalic vessels in the lower region of the right neck shows the caudal course of the right subclavian artery parallel to the right common carotid artery (same patient as in Videos 23.25 and 23.27) (AVI 1901 kb)
Caudally directed flow in the subclavian artery as opposed to cranial flow in the common carotid artery is confirmed by colour Doppler (same patient as in Videos 23.25 and 23.26) (AVI 2681 kb)
The last anomaly, isolation of the subclavian artery, is characterized by solitary origin of the right common carotid artery as the first vessel of the aorta to the right. While isolation of the subclavian artery is rare in the setting of left aortic arch, it is more common in patients with right aortic arch, affecting the left subclavian artery in mirror image fashion (McElhinney et al. 1998; Sun et al. 2005). This anomaly can be suspected clinically, since blood pressure measurements of all four extremities reveal significantly reduced blood pressures on the arm of the affected subclavian artery. The respective subclavian artery may be completely isolated, receiving exclusively retrograde flow from the circulus arteriosus Willisii via the right vertebral artery (Fig. 23.3). Echocardiographic visualization of this rare anomaly although possible is certainly difficult even with colour Doppler, since there is only little flow in the subclavian artery. The position of the transducer from a high right parasternal window is similar to that required for demonstration of aberrant origin of the right subclavian artery from the descending aorta. In patients with right aortic arch, the same applies in mirror image fashion requiring positioning of the transducer either in the suprasternal notch or a high left parasternal window. Due to the absence of antegrade perfusion, colour Doppler reveals retrograde flow in the subclavian artery (Video 23.28).
The oblique suprasternal short-axis view in a newborn with right aortic arch shows the ascending aorta in cross section giving rise to the left common carotid artery, which originates as the first brachiocephalic vessel. In a more caudal position, a diverticulum of Kommerell is visualized with some distance to the ascending aorta. Colour Doppler fails to demonstrate antegrade flow from the diverticulum to the left subclavian artery. Instead colour Doppler reveals retrograde flow in the left subclavian artery suggesting perfusion from the left vertebral artery and confirming the rare diagnosis of isolation (AVI 1574 kb)
The subclavian artery may not be completely isolated but remain connected via a ductus arteriosus to the ipsilateral pulmonary artery (Hofbeck et al. 1991; McElhinney et al. 1998; Russell et al. 2000). In addition the subclavian artery remains connected via the vertebral artery to the circulus arteriosus Willisii (Fig. 23.18). In these cases blood pressure in the subclavian artery depends on the presence of associated cardiovascular anomalies and on the pressure in the pulmonary artery. If the pulmonary artery pressure is normal, the low pressure will also affect the subclavian artery pressure, resulting in a significantly reduced blood pressure on the right arm (Russell et al. 2000). In addition retrograde flow in the right vertebral artery occurs due to subclavian steal syndrome (Hofbeck et al. 1991). Diagnosis of isolation with ductal origin of the subclavian artery can be established in high parasternal short-axis views, demonstrating connection of the subclavian artery to the ipsilateral pulmonary artery (Fig. 23.18). Transfontanellar PW Doppler and colour Doppler interrogation of blood flow in the circulus arteriosus Willisii and in the vertebral arteries confirms retrograde flow in the corresponding vertebral artery (Hofbeck et al. 1991).
The high parasternal short-axis view in a newborn with transposition of the great arteries shows anteroposterior position of the great arteries (a). Colour Doppler reveals retrograde flow in the right subclavian artery (RSCA), which is connected to the right pulmonary artery (RPA) via a right-sided ductus arteriosus. Pulsed wave Doppler of the right subclavian artery confirms predominantly retrograde flow from the subclavian artery to the pulmonary artery (b). Retrograde flow to the right subclavian artery is provided by the right vertebral artery (RVA) via the circle of Willis. Colour Doppler in the posterior plane of the coronal section of the brain (transfontanellar sonography) shows retrograde flow coded blue in the right vertebral artery (RVA) due to subclavian steal syndrome (c). Retrograde flow in the right vertebral artery directed towards the right subclavian artery is confirmed by PW Doppler interrogation (d). The flow pattern is altered due to frequent premature supraventricular beats (arrows)
Cervical aortic arch is an aortic arch anomaly that is not necessarily associated with the formation of a vascular ring and clinical symptoms due to airway obstruction (Moes 1997; Snider 1996). Due to the cranial course of the aortic arch, the pulsation of the aorta can be palpated in the suprasternal notch. Echocardiography from the suprasternal window displays the cervical extension of aortic arch, which is displayed in close proximity to the transducer (Fig. 23.19, Video 23.29). Symptoms associated with cervical aortic arch are due to possible vascular ring formation in the presence of associated anomalies of the brachiocephalic vessels, especially the subclavian arteries.
Colour Doppler from a high right parasternal view in a newborn with left cervical aortic arch shows cranial extension of the aortic arch (a). Cranial extension and tortuous course of the aortic arch can also be appreciated from a right cervical window (b). AAO Ascending aorta, DAO Descending aorta
Colour Doppler from a right cervical window in a newborn with left cervical aortic arch shows cranial extension and tortuosity of the aortic arch (AVI 4140 kb)
23.2.5 Pulmonary Sling
Echocardiographic diagnosis of pulmonary sling is much more difficult than exclusion of this anomaly. Pulmonary sling is easily excluded by demonstration of the normal pulmonary bifurcation in the high parasternal short-axis view (Video 23.30). If a normal pulmonary artery bifurcation with origin of right and left pulmonary cannot be displayed in this view, the differential diagnosis includes pulmonary artery sling, origin of the left pulmonary artery from a left-sided ductus arteriosus and pulmonary artery origin from the ascending aorta. The latter diagnoses are unassociated however with upper airway obstruction. Echocardiographic confirmation of pulmonary sling usually requires elevation of the patient’s shoulders and reclination of his head. Echocardiography of the pulmonary artery bifurcation from the suprasternal notch or high parasternal window confirms absence of origin of the left pulmonary artery at its expected position (Fig. 23.20, Videos 23.31 and 23.32). The origin of the left pulmonary artery is displaced far to the right, taking a posterior and leftward course to the left hilum (Fig. 23.20). If left pulmonary artery sling is taken into consideration as a possible diagnosis, echocardiography has a very high probability to visualize this anomaly (Backer et al. 2012; Kir et al. 2012).
The suprasternal short-axis view (a) in a newborn with pulmonary artery sling shows the aorta in cross section (AO) and the right pulmonary artery in longitudinal section (RPA). The left pulmonary artery (LPA) takes a distal origin from the right pulmonary artery with a retrograde course to the left hilum. The diastolic frame (b) shows inflow into the main pulmonary artery from a small ductus arteriosus (DA) at the expected site of origin of the left pulmonary artery from the bifurcation. The ductal view (c) confirms patency of the small ductus connecting the descending aorta (AO) to the main pulmonary artery (MPA), while the left pulmonary artery cannot be visualized in this plane
Colour Doppler in the parasternal short-axis view of a normal newborn shows the pulmonary bifurcation with normal origin of right and left pulmonary artery (AVI 2697 kb)
The suprasternal short-axis view in a newborn with pulmonary artery sling shows the aorta in cross section and the right pulmonary artery in longitudinal section. The left pulmonary artery takes a distal origin from the right pulmonary artery with a retrograde course to the left hilum (same patient as in Video 23.32) (AVI 25625 kb)
Colour Doppler in the suprasternal short-axis view of this newborn (same patient as in Video 23.31) confirms distal origin of the left pulmonary artery. Colour Doppler reveals proximal diastolic inflow into the main pulmonary artery originating from a small ductus arteriosus at the expected site of origin of the left pulmonary artery from the bifurcation (AVI 6343 kb)
23.3 Pulsed Wave and Continuous Wave Doppler
PW Doppler is an important tool for confirmation and documentation of direction of flow in the different parts of the aortic arch system or in aberrant vessels. Double aortic arch may be associated with obstruction of the right or left aortic arch. In this case PW Doppler interrogation usually does not reveal increase in flow velocities at the site of obstruction: A significant pressure gradient across the stenosis is absent, since the patent contralateral aortic arch allows retrograde filling of the distal descending aorta. Bilateral stenosis of double aortic arch has been reported however. In these cases PW and CW Doppler interrogation reveals flow profiles with acceleration of systolic and diastolic flow velocities in both aortic arches according to bilateral coarctation.
In neonates and young infants, transfontanellar PW Doppler examination of the intracerebral vessels is helpful in the diagnosis of isolation of the subclavian artery or innominate artery. Examination of the circulus arteriosus Willisii and of the ipsilateral vertebral artery reveals retrograde flow due to subclavian steal from the affected subclavian artery (Deeg et al. 1993; Hofbeck et al. 1991). Subclavian steal may even result in hyperperfusion of the affected pulmonary artery (Russell et al. 2000).
Obstruction of the left pulmonary artery at its distal origin from the right pulmonary artery may be present in patients with pulmonary sling. PW and CW Doppler interrogation will confirm the obstruction by detection of acceleration of flow at the origin of the left pulmonary artery (see also Chap. 7).
References
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23.1 Electronic Supplementary Material
Video 23.1
This high parasternal short-axis sweep shows evaluation of laterality in a patient with normal left aortic arch. It starts with the parasternal short-axis view of the pulmonary artery bifurcation, displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the transverse aortic arch, the superior vena cava in cross section and the innominate vein in longitudinal section. Further cranial tilt displays the origin of the innominate artery from the aorta to the right. Following clockwise rotation of the transducer combined with some more cranial tilt, the innominate artery is depicted in longitudinal section revealing its bifurcation into the right subclavian and right carotid artery (AVI 49571 kb)
Video 23.2
Colour Doppler in this high parasternal short-axis sweep shows evaluation of laterality in a patient with normal left aortic arch in analogy to Video 23.2 (AVI 23211 kb)
Video 23.3
Slight rotation of the transducer from the long-axis view of the innominate artery displays the branching into right subclavian and right common carotid artery (AVI 5470 kb)
Video 23.4
The high parasternal short-axis view in a patient with right aortic arch shows origin of the first brachiocephalic artery to the left. Branching of the innominate artery into left subclavian and left common carotid artery characterizes this vessel as left innominate artery (AVI 5812 kb)
Video 23.5
The anatomy is confirmed by colour Doppler interrogation displaying the innominate vein cranial to the aorta and the superior vena cava to the right of the aorta (AVI 5868 kb)
Video 23.6
This high parasternal short-axis sweep shows evaluation of laterality in a patient with right aortic arch. It starts with the parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the superior vena cava in cross section and the innominate vein in longitudinal section. Further cranial tilt displays the origin of the innominate artery from the aorta to the left branching into the left subclavian and left common carotid artery (AVI 23620 kb)
Video 23.7
Colour Doppler in this high parasternal short-axis sweep shows evaluation of laterality in a patient with right aortic arch. It starts with the parasternal short-axis view of the pulmonary artery bifurcation, displaying the ascending aorta in cross section. Cranial tilt of the transducer shows the superior vena cava in cross section and the innominate vein in longitudinal section. Clockwise rotation and some rightward tilt of the transducer open the aortic arch and display the right descending aorta (AVI 22931 kb)
Video 23.8
The colour Doppler sweep in a young infant with double aortic arch starts in the high parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt of the transducer displays the innominate vein and shows origin of both aortic arches from the ascending aorta with transition of the circular shape of the aorta into the configuration of a horizontal 8. Further cranial tilt shows separation of the right and left aortic arch. Colour Doppler reveals patency both of the right and left aortic arches (AVI 16269 kb)
Video 23.9
The colour Doppler sweep in another infant with double aortic arch starts in the high parasternal short-axis view displaying the ascending aorta in cross section. Cranial tilt displays the innominate vein cranial to the aorta and shows separation of the aorta into a dominant right and a significantly smaller left aortic arch. Further cranial tilt of the transducer confirms patency of both aortic arches (AVI 29467 kb)
Video 23.10
Colour Doppler in a cranial short-axis view (same patient as in Video 23.8) displays the complete vascular ring formed by a patent right and left aortic arch (AVI 2392 kb)
Video 23.11
The colour Doppler sweep in a high parasternal long-axis view in a patient with double aortic arch starts with a long-axis view of the right aortic arch. Leftward tilt of the transducer shows the longitudinal view of the oesophagus; further leftward tilt of the transducer reveals the left aortic arch which reveals a smaller segment distal to the left carotid artery. Distal to the left subclavian artery, the aorta is larger due to the ampulla of the former ductus arteriosus. Finally, the transducer is tilted back towards the right displaying again the larger right aortic arch (AVI 40941 kb)
Video 23.12
In a newborn with double aortic arch, the left aortic arch is displayed from a suprasternal window revealing atresia distal to the origin of the left carotid and left subclavian artery. Absence of antegrade flow across the aortic isthmus as well as retrograde filling (coded in red) of the distal left descending aorta (diverticulum of Kommerell) from the right aortic arch is evident on colour Doppler examination (AVI 1866 kb)
Video 23.13
This colour Doppler sweep in the high left parasternal sagittal view (ductal view) starts with a lateral plane displaying the main and left pulmonary artery (same patient as in Video 23.12). Leftward tilt of the transducer reveals a small and restrictive ductus arteriosus connecting to the MPA just proximal of the origin of the LPA. The ductus originates from the distal left descending aorta. Further rightward tilt displays the left aortic arch interrupted distal to the left subclavian artery, while the distal left aortic arch is filled retrogradely. Finally, the transducer is tilted again to the left (WMV 13225 kb)
Video 23.14
The high left parasternal short-axis view in a 4-month-old infant shows a left innominate artery dividing into the left carotid and left subclavian artery suggesting a right aortic arch. However, the left subclavian artery shows an inferior angulation, indicating the correct diagnosis of double aortic arch with partial atresia of the left arch distal to the left subclavian artery (AVI 6111 kb)
Video 23.15
Colour Doppler confirms regular flow in the innominate artery and branching into left common carotid and left subclavian artery (same patient as in Video 23.14) (AVI 1381 kb)
Video 23.16
The suprasternal long-axis view in a newborn shows a right aortic arch, giving origin to the right carotid and right subclavian artery. The view was obtained by clockwise rotation of the transducer from the suprasternal short-axis view (same patient as in Videos 23.17 and 23.18) (AVI 3016 kb)
Video 23.17
The oblique high left parasternal short-axis view (same patient as in Videos 23.16 and 23.18) displays the ascending aorta in cross section giving rise to the left common carotid artery originating as the first brachiocephalic vessel. The left subclavian artery originates as the last brachiocephalic vessel from a diverticulum of Kommerell, which represents the distal portion of the left aortic arch. From the top of the diverticulum of Kommerell originates the left-sided ductus arteriosus which is further delineated in the sweep of Video 23.18 (AVI 1040 kb)
Video 23.18
The colour Doppler sweep in this newborn reveals the diagnosis of RAA, aberrant left subclavian artery and left ductus arteriosus originating from a diverticulum of Kommerell (same patient as in Videos 23.16 and 23.17). It starts in the oblique high left parasternal short-axis view displaying aberrant origin of the left subclavian artery from a diverticulum of Kommerell. Clockwise rotation of the transducer and caudal shift reveal a tortuous ductus arteriosus originating from the top of the diverticulum of Kommerell connecting to the pulmonary bifurcation (AVI 19067 kb)
Video 23.19
The oblique suprasternal short-axis view in a 4-year-old patient with right aortic arch shows the ascending aorta in cross section giving rise to the left common carotid artery, which originates as the first brachiocephalic vessel (same patient as in Video 23.20). The left subclavian artery originates aberrantly from the descending aorta via a diverticulum of Kommerell (AVI 5371 kb)
Video 23.20
Separate origin of the left carotid and left subclavian artery is confirmed by colour Doppler (same patient as in Video 23.19). Colour Doppler reveals no evidence for persistent patency of the ductus arteriosus (AVI 1824 kb)
Video 23.21
The high right parasternal short-axis view in a neonate with left aortic arch shows the ascending aorta (AO) in cross section giving rise to a brachiocephalic vessel to the right. The rather small size of this first vessel suggests that it might not represent the right innominate artery but only the right common carotid artery (AVI 17226 kb)
Video 23.22
Caudal tilt of the transducer in a similar patient depicts the right subclavian artery, taking a parallel but inferior course to the carotid artery, due to its aberrant origin from the descending aorta (AVI 3286 kb)
Video 23.23
Caption (AVI 2620 kb)
Video 23.24
Colour Doppler in a posterior suprasternal short-axis plane of a newborn with left aortic arch shows origin of the aberrant right subclavian artery from the descending aorta. Note significant retrograde flow in the descending aorta in diastole, which is explained by the diagnosis of truncus arteriosus resulting in diastolic run-off to the pulmonary arteries (AVI 14408 kb)
Video 23.25
In an infant with pulmonary atresia, VSD and left aortic arch, colour Doppler in the longitudinal view of the right neck shows the right common carotid artery. Proximal to the bifurcation into internal and external carotid artery, the right subclavian artery is displayed taking a cervical origin (same patient as in Videos 23.26 and 23.27 (AVI 2870 kb)
Video 23.26
Caudal angulation of the transducer displaying the right brachiocephalic vessels in the lower region of the right neck shows the caudal course of the right subclavian artery parallel to the right common carotid artery (same patient as in Videos 23.25 and 23.27) (AVI 1901 kb)
Video 23.27
Caudally directed flow in the subclavian artery as opposed to cranial flow in the common carotid artery is confirmed by colour Doppler (same patient as in Videos 23.25 and 23.26) (AVI 2681 kb)
Video 23.28
The oblique suprasternal short-axis view in a newborn with right aortic arch shows the ascending aorta in cross section giving rise to the left common carotid artery, which originates as the first brachiocephalic vessel. In a more caudal position, a diverticulum of Kommerell is visualized with some distance to the ascending aorta. Colour Doppler fails to demonstrate antegrade flow from the diverticulum to the left subclavian artery. Instead colour Doppler reveals retrograde flow in the left subclavian artery suggesting perfusion from the left vertebral artery and confirming the rare diagnosis of isolation (AVI 1574 kb)
Video 23.29
Colour Doppler from a right cervical window in a newborn with left cervical aortic arch shows cranial extension and tortuosity of the aortic arch (AVI 4140 kb)
Video 23.30
Colour Doppler in the parasternal short-axis view of a normal newborn shows the pulmonary bifurcation with normal origin of right and left pulmonary artery (AVI 2697 kb)
Video 23.31
The suprasternal short-axis view in a newborn with pulmonary artery sling shows the aorta in cross section and the right pulmonary artery in longitudinal section. The left pulmonary artery takes a distal origin from the right pulmonary artery with a retrograde course to the left hilum (same patient as in Video 23.32) (AVI 25625 kb)
Video 23.32
Colour Doppler in the suprasternal short-axis view of this newborn (same patient as in Video 23.31) confirms distal origin of the left pulmonary artery. Colour Doppler reveals proximal diastolic inflow into the main pulmonary artery originating from a small ductus arteriosus at the expected site of origin of the left pulmonary artery from the bifurcation (AVI 6343 kb)
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Hofbeck, M., Deeg, KH., Rupprecht, T. (2017). Vascular Rings and Anomalies of the Aortic Arch Vessels. In: Doppler Echocardiography in Infancy and Childhood. Springer, Cham. https://doi.org/10.1007/978-3-319-42919-9_23
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DOI: https://doi.org/10.1007/978-3-319-42919-9_23
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