Case of the Week # 521

Case of the Week # 521

Javier Cortejoso
 on 02/28/2023
 on Tuesday, February 28th, 2023
The images demonstrate the following:
• Images 1 and 2 at 11 weeks of pregnancy: In the 4-chamber view, two stripes are visualized, which represent normal filling of the cardiac chambers during diastole, although there could be some defect of the interventricular septum. At the level of the 3-vessel and tracheal view, a singular arm of the V sign is shown.
• Video 1 at 21 weeks of pregnancy: situs solitus is evident with the heart on the same side as the gastric chamber. In the 4-chamber view, there is a small left ventricle and a ventricular septal defect in the upper part of the interventricular septum. The two great arteries arise in parallel from the same ventricle (the right): aorta located to the right and anterior to the pulmonary artery. It appears that the first blood vessel to emerge must be the pulmonary artery, since it divides rapidly into two branches and its diameter is smaller than that of the other vessel, the aorta. The aorta, larger than the pulmonary artery, suggests that the ventricular defect could be subaortic. At the level of the 3-vessel and tracheal view, only one of the great vessels is seen: the aorta. In addition to the superior vena cava in its usual position, there is persistence of the left superior vena cava on the contralateral side.

Among several authors, Wiechec et al. describe the most common abnormal patterns of flow at the levels of the 4-chamber, 3-vessel and tracheal views in the late first trimester in different congenital heart defects. The 3-vessel and tracheal view is sensitive for identifying conotruncal abnormalities when only one oblique arm of the V sign is observed. However, it cannot be used for a conclusive diagnosis. The authors suggest adding the axial levels between the 4-chamber, 3-vessel, and tracheal views to further clarify the diagnosis.

Double-outlet right ventricle (DORV) refers to a group of complex cardiac anomalies in which either both the great arteries arise from the right ventricle, or at least one complete arterial trunk and half of the other arterial trunk arise from the right ventricle. The left ventricle has no direct outlet to either great artery and most commonly ejects through a ventricular septal defect (VSD) into the right ventricle. The first description of DORV was provided in 1703 by Mery, but the term "double outlet right ventricle" was coined by Witham in 1957. DORV accounts for 4% to 8% of prenatal congenital heart diseases, but their high association with cardiac, extracardiac, and chromosomal anomalies is responsible for its lower postnatal incidence (1% to 3%). It is associated with chromosomal abnormalities including trisomies 18, 13, and 21 and 22q11 microdeletion, as well as non-chromosomal conditions such as Adams-Oliver, Ellis-van Creveld, Gardner-Silengo-Wachtel, Kabuki, Kalmann, Melnick-Needles, Noonan, Opitz, Ritscher-Schinzel, and Robinow. Mutations in the CFC1 and CSX genes are the most commonly reported monogenic loci associated with DORV in humans. An increase in incidence of DORV has been reported in children of diabetic mothers. Regarding its etiopathogenesis, the primitive right ventricle is in fact a DORV, containing the conotruncus. If migration of the aortic side of the conotruncus toward the mitral valve is incomplete, the DORV anatomy persists.

DORV is a complex cardiopathy with different anatomic presentations depending on the location of the VSD, and the spatial relationship between the two arteries and with the VSD. The defect can be subpulmonary, subaortic, doubly committed (both subaortic and subpulmonary), and noncommitted (also known as remote type in which the VSD is not related to either artery). Four types of great artery relationships at the level of the semilunar valves have been described:
1. Normal: the aorta located to the right and posterior to the pulmonary artery
2. Side by side: the aorta located to the right and lateral to the pulmonary artery
3. Dextromalposition: the aorta located to the right and anterior to the pulmonary artery
4. Levomalposition: the aorta located to the left and anterior to the pulmonary artery

The association of the VSD and its flow to one particular vessel suggests that the other great vessel will have an element of obstruction. In postnatal series, the most common types are subaortic VSD (50%) and subpulmonary VSD (30%). Subaortic VSD is usually associated with a normal orientation of the great arteries, with some degree of pulmonary obstruction. Physiologically, this form resembles tetralogy of Fallot. In cases with subpulmonary VSD, the great arteries are usually malpositioned, and the defect resembles transposition of the great arteries with VSD. This variant of DORV is called Taussig-Bing malformation and is frequently associated with aortic obstruction. Doubly committed VSD is characterized by complete absence of the outflow muscular septum. When there is concomitant pulmonary stenosis, the defect resembles tetralogy of Fallot. Noncommitted VSD is the most complex variant of DORV, mostly in hearts with atrioventricular septal defect.

Several international associations (Society of Thoracic Surgeons and the European Association of Cardiothoracic Surgery) define four types of DORV on the basis of clinical presentation and treatment:
1. VSD type: DORV with subaortic VSD
2. Fallot type: subaortic or double committed VSD with pulmonary outflow stenosis
3. Transposition of the Great Arteries type or Taussig-Bing malformation: DORV with a subpulmonary VSD
4. Non-committed VSD type: DORV with a remote VSD
In 1949, Helen Taussig and Richard Bing described the clinical and pathological characteristics of a complex congenital malformation that has become classified as a subset of DORV. According to Van Praagh, the distinctive features of the Taussig-Bing malformation are a true DORV, semilunar valves side-by-side and approximately at the same height, a bilateral conus with equally well-developed muscular subaortic and subpulmonary conal free walls, and a large subpulmonary VSD. The great arteries in Taussig-Bing anomaly are situated in a parallel fashion. The aorta is positioned to the right and can be placed anteriorly or forming a side-by-side arrangement. It can potentially be complicated by additional anomalies, such as coarctation of the aorta, coronary artery malposition, atrioventricular septal defect, and subaortic stenosis.

The echocardiographic views most amenable to making the diagnosis of DORV are the long-axis views of the aorta and pulmonary artery. The four-chamber view will usually appear normal, as the size of the chambers may not be altered, and the VSD is usually anterior and easier to appreciate in the long-axis views. Once it is determined that both great vessels arise predominantly from the right ventricle, the orientation of these vessels should be investigated. The most common relationship of the great vessels is side-by-side, with the aorta located to the right and lateral to the pulmonary artery. When this occurs, the normal perpendicular course of the great vessels is lost. In the long-axis view, they appear to travel in a parallel course. Once orientation of the great vessels is determined, the location of the VSD should be evaluated. Most commonly, it will occur in a subaortic location. The spatial relationship between the great vessels and the VSD is an important surgical consideration, but unfortunately, the exact location may be very difficult to determine in the fetus.

In a significant number of cases, other major associated cardiac defects are present including venous anomalies such as total or partial anomalous pulmonary venous return and left superior vena cava, endocardial cushion defects including complete atrioventricular septal defect, ventricular hypoplasia, pulmonary stenosis, aortic hypoplasia / coarctation of the aorta, and coronary artery anomalies. DORV is common in heterotaxy conditions.

Because DORV is a complex conotruncal abnormality with considerable anatomic variation, it can be difficult to distinguish from other conotruncal abnormalities. The differential diagnosis includes tetralogy of Fallot if the VSD is subaortic, or transposition of the great arteries with a VSD if the VSD is subpulmonary. In DORV, both vessels originate from the right ventricle, while in complete transposition of the great arteries the aorta arises from the right ventricle and the pulmonary arises from the left ventricle. Tetralogy of Fallot may also appear similar to DORV if considerable override of the aorta is present. However, in tetralogy of Fallot the aorta should still arise predominantly from the left ventricle.

Suggested readings:

1. Abuhamad A and Chaoui R. Double outlet right ventricle. In: A practical guide to fetal echocardiography. Normal and abnormal hearts, third edition. Wolters Kluvers, Philadelphia, PA, USA, 2016; pg 435-446.
2. Bennasar M, Gómez O y Bartrons J. Ventrículo derecho de doble salida. En: Galindo A, Gratacós E y Martínez JM, ed. Cardiología fetal. Marbán, Madrid, España, 2015; pg 372-382.
3. Bennasar M and Martinez JM. Double-Outlet Right Ventricle. In: Copel JA, ed. Obstetric Imaging. Elsevier Saunders, Philadelphia, PA, USA, 2012; pg 443-445.
4. Drose, JA. Double-Outlet Right Ventricle and Double-Outlet Left Ventricle. In: Fetal Echocardiography, second edition. Saunders Elsevier, St. Louis, MO, USA, 2010; pg 256-267.
5. Gottschalk I, Abel JS, Menzel T, et al. Prenatal diagnosis, associated findings and postnatal outcome of fetuses with double outlet right ventricle (DORV) in a single center. J Perinat Med. 2019;47(3):354-364.
6. Hartge DR, Hoffmann U, Scheewe J, et al. Prenatal detection and perinatal management of Taussig-Bing anomaly with coarctation of the aorta and singular coronary artery: a case report. Arch Gynecol Obstet. 2011;284(6):1417-1421.
7. Hartge DR, Niemeyer L, Axt-Fliedner R, et al. Prenatal detection and postnatal management of double outlet right ventricle (DORV) in 21 singleton pregnancies. J Matern Fetal Neonatal Med. 2012;25(1):58-63.
8. Obler D, Juraszek AL, Smoot LB, et al. Double outlet right ventricle: aetiologies and associations. J Med Genet. 2008;45(8):481-497.
9. Quartermain MD. Double-Outlet Right Ventricle. In: Rychik J and Tian Z, ed. Fetal cardiovascular imaging. A disease-based approach. Elsevier Saunders, Philadelphia, PA, USA, 2012; pg 175-183.
10. Smith RS, Comstock CH, Kirk JS, et al. Double-outlet right ventricle: an antenatal diagnostic dilemma. Ultrasound Obstet Gynecol. 1999;14(5):315-319.
11. Tongsong T, Chanprapaph P, Sittiwangkul R, et al. Antenatal diagnosis of double outlet of right ventricle without extracardiac anomaly: a report of 4 cases. J Clin Ultrasound. 2007;35(4):221-225.
12. Van Praagh R. What is the Taussig-Bing malformation?. Circulation. 1968;38(3):445-449.
13. Wiechec M, Knafel A, Nocun A. Prenatal detection of congenital heart defects at the 11- to 13-week scan using a simple color Doppler protocol including the 4-chamber and 3-vessel and trachea views. J Ultrasound Med. 2015;34(4):585-594.
14. Witham AC. Double outlet right ventricle; a partial transposition complex. Am Heart J. 1957;53(6):928-939.

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