Fetal Echocardiographic Diagnosis of Vascular Rings

Case Series Fetal Echocardiographic Diagnosis of Vascular Rings Chandrakant R. Patel, MBBS, John R. Lane, MD, Michael L. Spector, MD, Philip C. Smith, MD Objective. The purpose of this series is to describe the prenatal echocardiographic findings of vascular rings. Methods. The 3-vessel and trachea view consists of the axial view of the upper mediastinum. The normal left aortic arch appears as a V-shaped confluence of the ductus arteriosus and aortic arch, with the trachea situated posterior and to the right. No vessel should encircle the trachea. The diagnoses of vascular rings were made prenatally and were confirmed in all patients postnatally. Results. Six fetuses had diagnoses of vascular rings. The mean gestational age at diagnosis was 23.3 weeks (range, 18 31 weeks). The indications for fetal echocardiography were family history of congenital heart disease, echogenic focus in the left ventricle, and abnormal 4-chamber view. There were 2 fetuses with a double aortic arch; 3 fetuses with a right aortic arch, an aberrant left subclavian artery, and a left ductus arteriosus; and 1 with a right circumflex aortic arch with a left ductus arteriosus and an aberrant left subclavian artery. Two fetuses had associated structural cardiac defects, 1 with an unbalanced atrioventricular septal defect and trisomy 21 and the other with a double-outlet right ventricle, pulmonary atresia, and multiple other congenital anomalies. Conclusions. Vascular rings can be accurately diagnosed prenatally with recognition of a vascular structure that courses around the trachea and absence of the usual V-shaped relationship of the aortic and ductal arches. The color Doppler findings and the presence of a ductus arteriosus aid in identifying various components of the vascular ring. Key words: fetal echocardiography; prenatal diagnosis; vascular ring. Received August 16, 2005, from the Department of Pediatrics, Division of Pediatric Cardiology (C.R.P., J.R.L.), and Department of Cardiothoracic Surgery (M.L.S., P.C.S.). Children s Hospital Medical Center of Akron, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio, USA. Revision requested September 14, 2005. Revised manuscript accepted for publication October 18, 2005. Address correspondence to Chandrakant R. Patel, MBBS, The Heart Center, Children s Hospital Medical Center of Akron, 2 Perkins Sq, Akron, OH 44308-1062 USA. E-mail: cpatel@chmca.org Vascular rings are formed when 1 or more aortic arch abnormalities, with or without a patent ductus arteriosus or ligamentum, produce a ring that completely encircles the trachea and esophagus. Aortic arch anomalies are often associated with other congenital cardiac defects or chromosomal anomalies, such as microdeletion of chromosome 22q11. There are very few reports of prenatal diagnosis of vascular rings. 1 4 The typical presentation in postnatal life is stridor. Many times, parents notice noisy breathing from birth that is aggravated by intercurrent upper respiratory infections. In older children, there may be difficulty swallowing and choking on food. Modalities used to diagnose vascular rings postnatally include chest radiography, barium esophagography, transthoracic echocardiography, computed tomography, magnetic resonance imaging, and angiography. The aortic arch laterality can be defined in the transverse view of the upper mediastinum. It is possible to visualize the relationship of the aortic arch to the fetal tra- 2006 by the American Institute of Ultrasound in Medicine J Ultrasound Med 2006; 25:251 257 0278-4297/06/$3.50

Fetal Echocardiographic Diagnosis of Vascular Rings chea because it is filled with fluid. The normal left aortic arch can be defined by showing a V-shaped appearance of the great vessels. The left arm of the V represents the pulmonary trunk and its continuation into the ductus arteriosus, and the right arm represents the aortic arch. The trachea should be located posterior and lateral to vessel junction. This view is called the 3-vessel and trachea view (Figure 1). Normally, there should not be any vessel crossing posterior to the trachea. The presence of any vessel coursing behind the trachea with formation of a U-, 6-, or 9-shaped structure around the trachea helps in making the prenatal diagnosis of a vascular ring. Here we describe prenatal echocardiographic clues and different types of vascular rings in 6 fetuses. Details of gestational age at diagnosis, indications for fetal echocardiographic examination, types of vascular rings, associated chromosomal or noncardiac anomalies, and outcome are shown in Table 1. The diagnoses were confirmed in all patients postnatally by echocardiography, cardiac catheterization, or magnetic resonance imaging or at surgery. Figure 1. Cross-sectional view of the upper mediastinum in a healthy fetus showing an aortic and ductal arch forming a V- shaped confluence at the level of the descending aorta. The trachea is situated to the right of the confluence. ANT indicates anterior; AO, aorta; LT, left; POST, posterior; PT, pulmonary trunk; RT, right; SP, spine; SVC, superior vena cava; and T, trachea. Case Descriptions Case 1 A 35-year-old woman was referred for fetal echocardiographic evaluation because of an echogenic focus seen in the left ventricle on routine sonographic evaluation. Fetal echocardiography at 31 weeks gestation revealed a right aortic arch, an aberrant left subclavian artery, and a left ductus arteriosus. The thymus was present. A full-term neonate was born at 38 weeks gestation with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. The diagnosis of a vascular ring was confirmed on postnatal echocardiography. He was asymptomatic and was doing well at 6 years of age. Case 2 A 32-year-old woman, gravida 3, para 2, was because of 2 previous siblings with muscular ventricular septal defects. Fetal echocardiography at 20 weeks gestation revealed a right aortic arch, an aberrant left subclavian artery, and a left ductus arteriosus. There was also a retroaortic left brachiocephalic vein coursing under the ductus arteriosus to join the right superior vena cava. The intracardiac anatomy was normal. The thymus was present. The parents refused amniocentesis. Follow-up fetal echocardiography was performed at 26 weeks gestation. A fullterm neonate was born at 39 weeks gestation with a birth weight of 3.2 kg and with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. The diagnosis was confirmed on postnatal echocardiography. Stridor developed after an upper respiratory tract infection at 6 months of age. Because of the underlying cardiac diagnosis of the vascular ring, he underwent division of the left ligament at 8 months of age. He was doing well at 2 years old. Case 3 A 16-year-old woman, gravida 1, para 0, was because of an abnormal 4-chamber view with other noncardiac abnormalities consisting of hydrocephalus, occipital encephalocele, and an echogenic left lung. Fetal echocardiography at 23 weeks gestation revealed a double-outlet right ventricle, normally related great arteries, a subaortic ventricular septal defect, mild hypoplasia of the mitral valve and left ventric- 252 J Ultrasound Med 2006; 25:251 257

Patel et al Table 1. Fetal Echocardiographic Findings and Outcome GA at Case Echo, wk Indication Prenatal Diagnosis Associated Anomalies Outcome 1 31 Echogenic focus in LV Right aortic arch, left PDA, None Asymptomatic at 6 y aberrant left subclavian artery 2 20 Previous 2 children with Right aortic arch, left PDA, None Surgery VSDs aberrant left subclavian artery 3 23 Abnormal 4-chamber view, Right aortic arch, left PDA, DORV, subaortic VSD, normally Compassionate care, noncardiac anomalies aberrant left subclavian artery related great arteries, PA, died at 2 mo hydrocephalus, encephalocele, CCAM left lung 4 29 Abnormal 4-chamber view Double aortic arch, right dominant, Complete AVSD with mild Compassionate care, left PDA hypoplasia of LV and AAO, died at 3 mo trisomy 21 5 25 Echogenic focus in LV, Double aortic arch, left PDA, None Surgery previous child with PS right DAO 6 18 Previous child died with Right circumflex aortic arch, Ellis-Van Creveld syndrome Surgery CHD left PDA, aberrant left subclavian artery AAO indicates ascending aorta; AVSD, atrioventricular septal defect; CCAM, congenital cystic adenomatoid malformation; CHD, congenital heart disease; DAO, descending aorta; DORV, double-outlet right ventricle; Echo, echocardiography; GA, gestational age; LV, left ventricle; PA, pulmonary atresia; PDA, patent ductus arteriosus; PS, pulmonary stenosis; and VSD, ventricular septal defect. ular cavity, pulmonary atresia, a right aortic arch, an aberrant left subclavian artery, and a left ductus arteriosus (Figure 2, A C). The left ductus arteriosus with retrograde flow was the source of pulmonary blood flow. The thymus was present. Follow-up fetal echocardiography was performed every 4 to 6 weeks during the remainder of the pregnancy. A full-term male neonate was born by cesarean delivery at 39 weeks gestation. The Apgar scores were 7 and 8 at 1 and 5 minutes, respectively; birth weight was 3.3 kg. Postnatal echocardiography confirmed the prenatal diagnosis of the intracardiac anatomy with the vascular ring. He received prostaglandin E1. Postnatal neurologic evaluation of the head with magnetic resonance imaging revealed substantial hydrocephalus, absence of the corpus callosum, and occipital encephalocele. A poor neurologic prognosis was explained to the parents. Because of associated neurologic abnormalities, compassionate care was chosen, and he died at 2 months of age at home. Case 4 A 30-year-old woman, gravida 2, para 0, was because of an abnormal 4-chamber view. Fetal echocardiography at 29 weeks gestation revealed an unbalanced atrioventricular septal defect with mild hypoplasia of the left ventricular cavity, a primum atrial septal defect, and a common atrioventricular valve without atrioventricular valve regurgitation. There was a double aortic arch with a right dominant arch and a left ductus arteriosus. Subsequently, amniocentesis revealed trisomy 21. She went into spontaneous labor at 37 weeks gestation. A female neonate was born with Apgar scores of 7 and 8 at 1 and 5 minutes, respectively, and a birth weight of 2.1 kg. The diagnosis of a double aortic arch was confirmed on postnatal echocardiography; there was also an unbalanced atrioventricular septal defect with mild hypoplasia of the left ventricle. At 3 months of age, she underwent cardiac catheterization, and the diagnosis of the double aortic arch was confirmed. Because of the combination of Down syndrome, the complex intracardiac anatomy, the future likelihood of mitral stenosis, and the need for multiple surgical interventions, the parents chose compassionate care. The neonate died after a few days at home. Case 5 A 27-year-old woman, gravida 2, para 1, was referred for fetal echocardiography because of an echogenic focus in the left ventricle and a previous child with valvar pulmonary stenosis. A fetal echocardiogram at 25 weeks gestation revealed a double aortic arch with a right dominant arch, J Ultrasound Med 2006; 25:251 257 253

Fetal Echocardiographic Diagnosis of Vascular Rings a right descending aorta, and a left ductus arteriosus. The left arch gave rise to the left common carotid artery and left subclavian artery, and the right aortic arch gave rise to the right common carotid artery and right subclavian artery (Figure 3, A C). The intracardiac anatomy was normal. She underwent elective cesarean delivery at 38 weeks for a previous cesarean delivery. A female neonate was born with Apgar scores of 9 and 9 at 1 and 5 minutes, respectively, and birth weight was 3.5 kg. The diagnosis of the double aortic arch with a dominant right aortic arch was confirmed on postnatal echocardiography. Stridor developed after an upper respiratory tact infection at 5 months of age. She underwent surgery at 6 months of age. Case 6 A 34-year-old woman, gravida 3, para 1, was because a previous child had Ellis-Van Creveld syndrome associated with a primum atrial septal defect, coarctation of the aorta, and mitral stenosis. Routine sonography performed at 18 weeks gestation revealed postaxial polydactyly of the hands and feet. The fetal echocardiogram showed a right circumflex aortic arch coursing behind the trachea and esophagus toward the left descending aorta. There was also a left-sided A Figure 2. Right aortic arch with aberrant left subclavian artery and left ductus arteriosus. A, Transverse view of the upper mediastinum in gray scale showing the aorta to the right of the trachea, descending on the right side, with a left ductus arteriosus forming a U-shaped vascular loop around the trachea. B, Color flow Doppler image showing retrograde flow in the ductus arteriosus due to valvar pulmonary atresia in this fetus. C, Color flow Doppler image in the aberrant left subclavian artery originating from the descending aorta coursing behind the trachea. LSCA indicates left subclavian artery; LT DUCT, left ductus arteriosus; RSVC, right superior vena cava; and RT ARCH, right aortic arch; other abbreviations are as in Figure 1. B C 254 J Ultrasound Med 2006; 25:251 257

Patel et al arterial duct from the pulmonary trunk joining the descending aorta on the left side, thus forming a complete vascular ring. An aberrant left subclavian artery was noted to originate from the descending aorta. The 4-chamber view showed a discrepancy in the size of the ventricles, the right being larger than the left. Fetal echocardiography was performed every 4 weeks during the pregnancy, and labor was induced at 35 weeks gestation because of the development of maternal preeclampsia. A male neonate was born weighing 2.3 kg with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. A postnatal echocardiogram and magnetic resonance imaging confirmed the vascular ring anatomy. At 8 months of age, stridor developed, and he underwent surgery to divide the vascular ring. He was doing well at 5 years of age. Discussion The 4-chamber view is used in the fetal sonographic screening examination for detection of congenital heart disease. However, the sensitivity for detection of congenital heart diseases varies from 48% to 63% in some series. 5,6 This is because of the inherent limitations in the 4-chamber view in detecting anomalies of the outflow tract and great arteries. To improve the antenatal detection A Figure 3. Double aortic arch with left ductus arteriosus and right descending aorta. A, Transverse view of the aortic arch showing the ascending aorta dividing into 2 aortic arches, right and left, encircling the trachea. Note that the right aortic arch is the dominant arch. B, Color flow Doppler image showing the same anatomy as shown with gray scale imaging. There is a left ductus arteriosus. C, Coronal section posteriorly at the level of the descending aorta where both aortic arches are converging in the descending aorta. The common carotid artery and the subclavian artery were originating from their respective aortic arches. AAO indicates ascending aorta; LCCA, left common carotid artery; LT ARCH, left aortic arch; PDA, patent ductus arteriosus; RCCA, right common carotid artery; and RSCA, right subclavian artery; other abbreviations are as in Figures 1 and 2. B C J Ultrasound Med 2006; 25:251 257 255

Fetal Echocardiographic Diagnosis of Vascular Rings of congenital heart disease involving the outflow tract and great arteries, Yoo et al 7 proposed the 3- vessel view, an axial view of the fetal upper mediastinum. It can be easily obtained by moving the transducer from the 4-chamber view in a cranial direction. Achiron et al 2 showed that the location of the aortic arch in relation to the trachea can be easily visualized because the fetal airway is normally filled with fluid, allowing sonographic visualization. Yagel et al 8 reported application of the 3-vessel and trachea view, which is transverse in the upper mediastinum slightly cranial to the 3-vessel view described by Yoo et al. 7 Integration of the 3-vessel view has been proposed in sequential segmental analysis to diagnose congenital heart disease. Bronshtein et al 1 first reported the sonographic diagnosis of a fetal vascular ring in early pregnancy. They reported 6 fetuses with vascular rings; 5 of these had a right aortic arch. All cases were in patients with low-risk pregnancies. No other structural anomalies were noted in these fetuses. Four patients were delivered, and the diagnosis of the vascular ring was confirmed in the neonates, all of whom were asymptomatic. In the right aortic arch with mirror image branching, usually there is a left ductus arteriosus originating from the base of the left subclavian artery. Rarely there can be a right ductus arteriosus originating from the undersurface of the right aortic arch. This does not form a vascular ring. A vascular ring is formed if there is an aberrant left subclavian artery originating from the descending aorta coursing behind the trachea and esophagus with a left ductus arteriosus originating from the base of the left subclavian artery and joining the left pulmonary artery in front. On a transverse view of the upper mediastinum, the right aortic arch, proximal part of the aberrant left subclavian artery, left-sided ductus arteriosus, and pulmonary artery form a U-shaped vascular loop around the trachea and esophagus. The proximal portion of the left subclavian artery remains dilated, which is known as a diverticulum of Kommerell. However, in a fetus with a right aortic arch, an aberrant left subclavian artery, a left ductus arteriosus, and an associated double-outlet right ventricle, subaortic ventricular septal defect, and pulmonary atresia, there was retrograde flow in the left ductus arteriosus documented by pulsed and color flow Doppler sonography prenatally (case 3). A double aortic arch is one the most common types of vascular ring seen postnatally. It is likely to be symptomatic in the neonatal period. It represents persistence of both embryonic aortic arches. Usually there is persistence of the left ductus arteriosus. The presence of a ductus arteriosus is not required to form a vascular ring. The aortic arches may be asymmetrical, and, in fact, one arch is usually larger than other. The right arch is larger and higher in approximately 75% of cases. As a rule, the descending aorta is contralateral to the side of the dominant arch. A double aortic arch is associated with congenital heart disease in approximately 20% of cases. Rarely there can be atresia of the segment of the aortic arch, which can be difficult to differentiate from other aortic arch anomalies. On an axial view of the upper mediastinum, a double aortic arch can be seen to encircle the fluid-filled trachea. It is necessary to tilt the transducer to one or the other side if the aortic arches are not at the same level. If the ductus arteriosus and aortic arches can be imaged in the same plane, a figure 6 or 9 is formed, depending on the position of the fetus. Sometimes color Doppler sonography helps in delineating the components of the vascular ring. A right circumflex retroesophageal aortic arch is a rare form of vascular ring. The aortic arch ascends over the right main stem bronchus, courses to the right of the trachea, turns to the left behind the trachea and esophagus, and descends on the left side. The ring is completed by a left-sided persistent ductus arteriosus or a ligamentum. The aberrant left subclavian artery originates from the descending aorta. The association of congenital heart disease is not uncommon. On a transverse view of upper mediastinum, the aortic arch forms a D-shaped structure around the trachea, with the ductus arteriosus on the opposite side completing the vascular ring. In summary, the 3-vessel and trachea view in the upper mediastinum is very crucial in detecting abnormalities of the aortic arch. The fluidfilled trachea can be easily seen on a fetal sonogram. Absence of a V-shaped confluence of the ductus arteriosus and aortic arch, a space between the aorta and main pulmonary trunk, an abnormal location of the descending aorta on a 4- chamber view, and the presence of any vessel coursing behind the trachea with formation of U-, 6-, or 9-shaped structures around the trachea help in making prenatal diagnosis of a vascular ring. Color Doppler findings and the presence of a ductus arteriosus aid in identifying various components of the vascular ring. 256 J Ultrasound Med 2006; 25:251 257

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