Double Outlet Right Ventricle

Peter Frommelt, MD, pediatric cardiologist

Double outlet right ventricle (DORV) is a rare congenital cardiac defect in which all of one great artery and at least half of the other great artery arise from the right ventricle.

This defect is found only in about 1.5 percent of all patients with congenital heart disease and frequently is associated with other congenital cardiac abnormalities. For example, since both great arteries arise from the right ventricle, a ventricular septal defect (VSD) almost always is present to allow egress of blood flow from the left ventricle (otherwise it would have no outlet to empty). The position of the great arteries relative to the VSD determines the physiology of each patient. The clinical presentation and surgical options can vary dramatically depending on the relationship of the great arteries with the VSD and whether there is obstruction to either great artery.

Anatomy and physiology
The three most common anatomic subtypes of double outlet right ventricle are:

1. The VSD sits below the aortic valve without pulmonary stenosis.
2. The VSD sits below the pulmonary artery without pulmonary stenosis.
3. The VSD sits below either great artery in association with pulmonary stenosis.

Subaortic VSD without pulmonary stenosis
In this situation, oxygenated blood from the left ventricle is directed appropriately into the aorta, so there is no systemic desaturation. Since pulmonary stenosis is not present, the majority of right ventricular output, as well as some of the left ventricular output that passes across the VSD, will shunt into the pulmonary arteries, similar to the patient with a large VSD. Because of this left to right shunt, these patients typically present with congestive heart failure, failure to thrive and normal oxygen saturations.

Subpulmonary VSD without pulmonary stenosis
In this anatomical subset, called the Taussig-Bing form of double outlet right ventricle, oxygenated blood from the left ventricle is directed back into the pulmonary artery, while deoxygenated blood that returns to the right ventricle is directed into the aorta. This physiology is identical to patients with complete transposition of the great arteries. Cyanosis generally is the first clinical sign of heart disease and usually is recognized early in the neonatal period. Some patients with a subpulmonary VSD also develop obstructive subaortic muscle and aortic outflow tract obstruction in combination with coarctation of the aorta. They can present with a shock-like state and poor lower extremity pulse and perfusion.

Subaortic VSD with pulmonary stenosis
In patients with DORV, an atrial septal defect occurs 25 percent of the time. Additional muscular ventricular septal defects and a patent ductus arteriosus occasionally are found. Mitral valve abnormalities, including mitral valve straddle, parachute mitral valve and cleft mitral valve also are seen. In addition, coronary artery anomalies frequently are associated with DORV. If there is pulmonary stenosis, the left anterior descending coronary artery arising from the right main coronary artery and crossing anteriorly across the outflow tract occasionally occurs. If the aorta is in an anterior position relative to the pulmonary artery, coronary anomalies similar to the ones found in D-transposition of the great arteries are common.

DORV generally occurs as an isolated entity, but it also is seen in association with other complex defects such as total anomalous pulmonary venous return, atrioventricular septal defect, mitral stenosis or atresia, juxtaposition of the right atrial appendage and a persistent left superior cava. These complex patients often also have situs anomalies, particularly heterotaxy syndromes (asplenia and polysplenia).

Surgical treatment
Subaortic VSD without pulmonary stenosis
Since their defect acts like a large VSD with significant congestive heart failure and puts these patients at risk for early pulmonary vascular obstructive disease, surgery generally is performed by age 1. This is the simplest DORV to repair, as the VSD already is situated in close proximity to the aortic valve. The VSD is closed to include the aortic valve as part of the left ventricle, creating a tunnel that excludes the right ventricle from the systemic circulation. Since this intraventricular tunnel is relatively simple to create, it is rare to find postoperative tunnel obstruction. Long-term prognosis is excellent, and no further surgery generally is required.

Subpulmonary VSD
Two surgical approaches are possible for these patients. If there is no pulmonary or aortic stenosis, the simplest repair is closure of the VSD, so the left (closer) ventricle ejects into the pulmonary artery, combined with an arterial switch repair. This operation generally is performed during the first one to two months of life, depending on the degree of cyanosis. This procedure carries the same risks as an arterial switch repair for transposition of the great arteries, although the positioning of the great arteries (generally side by side rather than anterior-posterior) can result in distortion of the branch pulmonary arteries after the arterial switch, with late development of branch pulmonary artery stenosis.

Figure 1 - DORV with side-by-side great arteries and pulmonary stenosis.

If the pulmonary outflow tract is obstructed (figure 1), the arterial switch repair is not an option. Under these circumstances, a Rastelli repair is performed, with creation of an intraventricular tunnel to baffle left ventricular blood to the aorta and placement of a right ventricular-to-pulmonary artery conduit (figure 2). Because the aorta sits farther away from the VSD in this anatomic subset, the creation of the tunnel is more complex and the incidence of tunnel obstruction or leakage is significantly higher than when the VSD is closely related to the aortic valve. A valved homograft generally is used to connect the right ventricle and pulmonary artery, so this procedure is often delayed until the child is at least 1. This step allows for placement of a larger homograft, by delaying homograft replacement until the child is school-age. If the patient has excessive cyanosis during the first year of life, a palliative Blalock-Taussig shunt is placed to augment pulmonary blood flow.

Figure 2 - DORV S/P Rastelli

Subaortic VSD with pulmonary stenosis
These patients are physiologically and anatomically similar to those with tetralogy of Fallot. VSD closure, to allow left ventricular ejection only into the aorta in association with patch augmentation of the right ventricular outflow tract to relieve the subvalvar and valvar pulmonary stenosis generally is performed at 6 to 12 months of age. Excessive cyanosis during early infancy again can be palliated by a Blalock-Taussig shunt prior to the definitive surgical operation. As with tetralogy of Fallot repair, the most common postoperative complication is poor right ventricular systolic and diastolic function, with low cardiac output and systemic venous congestion. Rarely, residual right ventricular outflow tract or branch pulmonary artery obstruction can complicate the postoperative course. More commonly, these patients have significant pulmonary insufficiency related to patch augmentation of the right ventricular outflow tract, and many require placement of a right ventricular-to-pulmonary artery homograft as older children or young adults when right ventricular dysfunction develops secondary to the chronic right ventricular volume overload.

Complex double outlet right ventricle
DORV with complex associated defects (atrioventricular valve anomalies, anomalous venous drainage, ventricular hypoplasia) frequently must be palliated as a functional single ventricle. If no pulmonary stenosis exists in these complex cases, pulmonary artery banding is performed early in life to control congestive heart failure and protect the pulmonary vascular bed. If pulmonary stenosis exists, then a Blalock-Taussig shunt is placed to augment pulmonary blood flow. As within any single ventricle patient, a bidirectional Glenn anastomosis is created between 6 and 12 months of age, and complete Fontan palliation usually is performed between ages 2 and 4.