Double-outlet right ventricle (DORV) is a “disease” that includes a family of anatomically related complex congenital heart lesions involving the right ventricular outflow tract (RVOT). There are several variations within the DORV diagnostic category that give rise to a wide spectrum of physiology ranging from tetralogy of Fallot to transposition of the great arteries (TGA) to true single-ventricle physiology. It therefore encompasses virtually the entire spectrum of cardiac physiology.
Determining treatment requires an understanding of the specific relationship of the ventricular septal defect (VSD) to the great vessels, the size of the VSD, the size of the great vessels, the ventricular size, and the status of the atrioventricular (AV) valves. Understanding these components and their relationships allows one to predict the physiology and therefore consider appropriate treatment algorithms. Repair may consist of one-stage biventricular repair, biventricular repair with a conduit, or staged palliative single-ventricle surgery ( Table 54.1 ).
| Location of VSD | Associated Lesions | Physiology (like) | Intervention |
|---|---|---|---|
| Subaortic | — | VSD | Tunnel repair |
| Subpulmonary stenosis | Tetralogy of Fallot | Tetralogy of Fallot–type repair | |
| Subpulmonary | — | Transposition | Arterial switch procedure |
| CoA | Transposition and CoA | Arterial switch with repair of aortic arch | |
| Doubly committed | — | VSD | Tunnel repair |
| — | — | Arterial switch (see text) | |
| Remote | — | VSD | Fontan route or occasionally biventricular repair |
Definition
A consensus definition derived from the Congenital Heart Surgery Nomenclature and Database Project states that “DORV is a type of ventriculoarterial connection in which both great vessels arise either entirely or predominantly from the right ventricle.” This definition implies that more than 50% of each of the great vessels arises from the morphologic right ventricle (RV), which is known as “the 50% rule.” This definition may not be sufficient in cases of tetralogy of Fallot with extreme aortic override or transposition with extreme pulmonary override. An additional morphologic criterion that could differentiate between these conditions and DORV is the aortic-mitral fibrous continuity (in patients with tetralogy of Fallot) and pulmonary-mitral continuity (in patients with transposition). Some suggest that the absence of the fibrous continuity between the arterial and AV valves is a feature of DORV. Hearts with DORV, remote VSD, and both great vessels arising entirely from the RV constitute a complete DORV known as the “200% DORV.”
History
The earliest description of DORV probably dates to 1703 in a report by Mery. In 1793 Abernathy described a heart with the origin of both great arteries from the RV. In 1893 a similar description was reported by Birmingham. The designation of “double-outlet ventricle” was probably first reported by Braun and associates in 1952. The specimen had both great vessels arising from the RV. Another “double-outlet right ventricle” designation is found in a report by Witham in 1957. A form of DORV in which the VSD was associated with the pulmonary artery (PA), was described by Taussig and Bing in 1949, but was initially classified as TGA. Lev and coworkers subsequently clarified what became known as the Taussig-Bing heart to be part of the spectrum of DORV. DORV was first repaired at the Mayo Clinic in 1957 by John Kirklin.
Embryology
Embryologic development of the heart includes a phase in which a common arterial trunk arises from the RV. The common trunk separates into the two great vessels, both arising from the RV for a period of time. Regression of muscle between the aorta and the mitral valve results in the aorta arising from the left ventricle in fibrous continuity with the mitral valve. In some situations the muscle between the mitral and aortic valve does not regress, resulting in what is known as a persistent left ventriculoinfundibular fold (VIF). An alternative term is persistent left-sided conus. A persistent left VIF can be, but is not necessarily, associated with DORV.
Epidemiology
DORV may exist as an isolated condition or in association with cardiac or extracardiac anomalies. The reported incidence ranges from 0.03 to 0.14 per 1000 live births. It occurs in about 1% of all congenital heart disease. There may be associated aortic coarctation, aortic arch hypoplasia, or interrupted aortic arch, particularly at the transposition end of the spectrum. Additionally, in hearts with right atrial isomerism, DORV is a frequent finding. Several chromosomal abnormalities have been associated with DORV, including trisomy 13, trisomy 18, and chromosome 22q11 deletion.
Classification
The traditional classification of DORV is based on the position of the VSD relative to the great vessels. Lev and associates classified the VSD associated with DORV as subaortic, subpulmonary, doubly committed, and noncommitted (remote). This classification system has the advantage of relative simplicity and provides a means by which DORV outcomes can be examined. However, this classification system alone is not adequate to determine the management algorithm. In addition, in rare cases of the DORV, the ventricular septum may be intact. From a practical standpoint, it is the specific location of the VSD in combination with associated lesions and the resultant pathophysiology that allows one to determine management strategy.
DORV can also be classified based on clinical presentation: a VSD type (with subaortic or doubly committed VSD), a tetralogy of Fallot type (VSD with infundibular deviation), a TGA type (Taussig-Bing with subpulmonary VSD), and a single-ventricle type (noncommitted VSD). This clinical classification system has the advantage of predicting the natural and modified history of DORV. Specifically, a VSD-type DORV will have a presentation, surgical options, and outcomes similar to VSD, and a Fallot-type DORV will have a presentation, surgical options, and outcomes similar to tetralogy of Fallot.
The VSD of DORV is typically large and unrestrictive. Occasionally it can be shallow and restrictive or potentially restrictive. In DORV with a subaortic or subpulmonary VSD, the VSD sits between the two limbs of the trabeculae septomarginalis (TSM) ( Fig. 54.1A and B). The TSM is a Y -shaped muscle bar in which the two limbs of the Y are the muscular rim of the VSD. The respective limbs of the Y are known as the anterior and posterior limbs of the TSM. The attachment of the infundibular septum to the anterior or posterior limb predicts which great vessel is related to the VSD. Attachment of the infundibular septum to the anterior limb of the TSM leaves the VSD in the subaortic position (see Fig. 54.1A ). Attachment of the septum to the posterior limb of the TSM leaves the VSD in the subpulmonary position (see Fig. 54.1B ). Absence of the infundibular septum leaves a doubly committed VSD (committed to both great arteries) (see Fig. 54.1C ).
Pathophysiology and Presentation
Subaortic Ventricular Septal Defect
DORV with subaortic VSD (see Fig. 54.1A ) is the most common type of DORV occurring in about 50% of the cases. The resultant pathophysiology depends on the degree of anterior deviation of the infundibular septum toward the PA. In the presence of anterior deviation, there is associated RVOT obstruction with stenosis in the subvalvular or valvular region. Pulmonary blood flow is decreased. The degree of cyanosis is variable, as is seen with tetralogy of Fallot. In the absence of anterior deviation of the infundibular septum (ie, no RVOT obstruction), the pulmonary blood flow is increased, and heart failure is usually the presenting symptom. In the latter situation, the pathophysiology is similar to that of a very large VSD.
Subpulmonary Ventricular Septal Defect
The subpulmonary position VSD with DORV (see Fig. 54.1B ) occurs in about 30% of the cases. In this anatomic configuration there is unfavorable streaming of cyanotic blood to the aorta and saturated blood to the PA (transposition-type physiology). This occurs because the VSD is closely associated with the PA. The PA preferentially receives left ventricular oxygenated blood, whereas the desaturated blood from the RV streams to the aorta. The Taussig-Bing anomaly is the classic example for this morphology. Associated coarctation or arch hypoplasia may occur in up to 50% of neonates presenting with DORV and subpulmonary VSD. There is usually a small outlet to the RV with a substantial size mismatch between the aortic and pulmonary trunks. Clinical presentation is similar to that of transposition with associated severe cyanosis and increased pulmonary blood flow.
Doubly Committed Ventricular Septal Defect
In a doubly committed–type DORV (see Fig. 54.1C ) both semilunar valves (aortic and pulmonary) are related to the VSD. There is no infundibular septum separating the aortic and pulmonary valves. The lesion is an uncommon variant (perhaps 5%). It may have streaming, which can be favorable or unfavorable. Pulmonary stenosis may be associated. Therefore, the clinical picture is similar to that of VSD with or without pulmonary stenosis.
Remote (Noncommitted) Ventricular Septal Defect
A remote VSD may be an inlet VSD (see Fig. 54.1D ) or a trabecular muscular VSD. Either type of VSD could be unrelated to either great vessel. Saturations typically would be that of complete mixing. These children behave physiologically as patients with a single ventricle. There may be too much, too little, or appropriate pulmonary blood flow for a single ventricle.
Other Considerations
Position of the Aorta
The position of the aorta in DORV is variable. In most cases the relationship to the PA is posterior and slightly rightward (usual spiraling pattern). Completely normal relationships may occur. In the absence of spiraling (ie, parallel configuration), the aorta could be side by side and to the right of the PA ( d -malposition—most common) or side by side and to the left of the PA ( l -malposition—rare). Occasionally, the aorta is parallel and anterior to the PA.
Conduction Tissue
AV node and bundle of His pathways follow the normal pathways for specific AV connections. The VSD in DORV is frequently in the perimembranous position and is thereby in jeopardy at the time of surgical repair at the margin of the tricuspid annulus and VSD closest to the crux of the heart. DORV associated with AV discordance has conduction pathways that match the AV discordance, that is, anterior to the typical VSD, where it is associated with the PA.
Other Anatomic Characteristics
Other intracardiac components may be abnormal and may impact physiology and management options. AV valve tissue may be attached to the infundibular septum. The AV valve apparatus from either AV valve may straddle the VSD. DORV can occur with a hypoplastic ventricle, thereby acting as a functional single ventricle. Unusual relationships can be superoinferior ventricles with twisted (or criss-cross) AV connections.
DORV may also occur with AV discordance, in which both great arteries arise from the left-sided systemic morphologic RV ( Fig. 54.2 ). It may also occur with pulmonary atresia or other complex lesions such as right atrial isomerism and total anomalous pulmonary venous return. Most cases of right atrial isomerism and DORV are palliated with staged single-ventricle surgery. Occasionally, DORV presents as an isolated associated anomaly of an AV septal defect. A biventricular repair in this circumstance is possible, but challenging.
Indications for Repair and Preoperative Evaluation
The pathophysiologic spectrum of DORV is wide, thus making the natural history variable. Generalization can be applied based on natural history studies obtained from pathophysiologies that are similar. A DORV with subaortic VSD and no pulmonary stenosis will have a natural history similar to that of a large VSD. There is congestive heart failure and risk of pulmonary vascular obstructive disease. Similarly, at the tetralogy of Fallot or transposition ends of the spectrum, the natural history may resemble those conditions.
Spontaneous closure of the VSD is rare, and when it occurs, it is fatal. The diagnosis of DORV is sufficient indication for surgical repair. Preoperative evaluation includes a thorough echocardiographic examination that provides information regarding the AV valves, ventricular size and function, location and size of the VSD, relationship of the great vessels, status of the semilunar valves, associated lesions (eg, coarctation), and coronary anatomy. Cardiac catheterization may be necessary for therapeutic reasons (at the transposition end of the spectrum to perform balloon atrial septostomy) or for diagnostic reasons (in late presentation when pulmonary vascular disease is in question or if the anatomy is unclear by echocardiography or magnetic resonance imaging [MRI]). Three-dimensional (3D) echocardiography and cardiac MRI (CMR) are now approaching a level of functionality in which their use may assist in decision making with regard to repair strategy. 3D printing is also emerging as a potentially interesting tool for preoperative preparation. Using data derived from MRI and computed tomography scans, life-size heart models are generated that help in visualizing the planned location and dimension of the potential baffle, and hence the “routability” of the left ventricle to the aorta ( Box 54.1 ).
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Transthoracic echocardiography is invaluable in the assessment of DORV. It will detail most of the anatomic and physiologic variables shown in Table 54.1 .
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Transesophageal echocardiography can provide clearer information of complex atrioventricular arrangements such as straddle or override.
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When cyanosis is present, further imaging may be needed to ascertain whether it is because of:
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Decreased pulmonary blood flow
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Eisenmenger complex (see Chapter 52 )
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Impaired ventricular function
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Magnetic resonance imaging provides complementary and important information on:
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Intracardiac anatomy
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Aortic arch
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Morphology of the pulmonary arteries
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Three-dimensional relationship of the chambers and great vessels
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Right and left ventricular function
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Cardiac catheterization may be performed to:
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Determine the hemodynamics
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Exclude pulmonary vascular disease
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Assess the course of the coronary arteries
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