eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology

Double Outlet Right Ventricle, Normally Related Great Arteries

Author: Rod Tarrago, MD, Pediatric Intensivist, Department of Pediatric Critical Care, Children's Hospitals and Clinics of Minnesota
Coauthor(s): Steven R Neish, MD, SM, Director of Pediatric Cardiology Fellowship Program, Associate Professor, Department of Pediatrics, Baylor College of Medicine
Contributor Information and Disclosures

Updated: Oct 6, 2008

Introduction

Background

Double outlet right ventricle (DORV) was first pathologically described in the late 19th century as partial transposition. In 1957, Witham first used the term double outlet right ventricle to describe a partial transposition of the great arteries.¹ He described 4 hearts with 2 varieties of "complete aortic transposition with the pulmonary artery in normal position."

Double outlet right ventricle is defined as a form of ventriculoarterial connection in which both great arteries arise completely or predominantly from the morphologic right ventricle. This definition is still controversial. For example, some researchers require that the aorta and the pulmonary artery arise entirely from the right ventricle. Others require that 90% of the great vessels arise from the morphologic right ventricle. Alternatively, the 50% rule states that more than one half of both arterial trunks must arise from the morphologic right ventricle. Some require only the presence of fibrous discontinuity between the mitral and semilunar valves. This is present in most specimens and is referred to as subpulmonic and subaortic conus.

Pathophysiology

Double outlet right ventricle, with a large variability in anatomy, represents a continuum of congenital heart defects (CHDs) that includes ventricular septal defect (VSD) with significant override of the aorta, origin of both great arteries from the right ventricle, and transposition of the great arteries with pulmonary override of the VSD. A common arterial trunk may also arise completely from the right ventricle. This is actually a type of truncus arteriosus.

Pathophysiologic description and classification is accomplished by relating the location of the VSD to the arrangement of the great vessels. Each combination results in a physiologic behavior similar to that of other CHDs. The VSD in double outlet right ventricle can be subaortic, subpulmonary, noncommitted, or doubly committed. Most VSDs are nonrestrictive, but as many as 17% of patients may require VSD enlargement during repair to allow unrestricted systemic blood flow.

The most common type of VSD found in double outlet right ventricle is a subaortic type. The aortic orifice is usually posterior and to the right of the pulmonary orifice, with a spiral arterial relationship. Because the great arteries are normally related, the left ventricular outflow is directed toward the aorta, resulting in aortic oxygen saturations that exceed pulmonary saturations. Associated pulmonary stenosis is present in as many as 50% of patients with double outlet right ventricle. The resulting physiology is similar to tetralogy of Fallot, in which the aorta completely overrides the right ventricle.

Systolic pressures are equal in both ventricles and in the aorta. In the absence of pulmonary stenosis, the physiology resembles that of a large isolated VSD, in which the ratio of pulmonary to systemic blood flow is determined by the pulmonary vascular resistance. Systemic and pulmonary saturations are also affected by the degree of mixing in the right ventricle. This anatomy may result in congestive heart failure (CHF) and pulmonary vascular disease.

In double outlet right ventricle with subpulmonary VSD (Taussig-Bing anomaly), the left ventricular outflow is directed toward the pulmonary artery. This preferential streaming results in pulmonary artery saturations greater than aortic saturations. The aortic and pulmonary orifices are usually positioned side by side but are described as transposed or malposed. The rare presence of pulmonary stenosis results in physiology similar to tetralogy of Fallot. However, in the absence of pulmonary obstruction or stenosis, patients with double outlet right ventricle and subpulmonary VSD have physiology similar to transposition of the great arteries and VSD. In this case, pulmonary vascular resistance (PVR) determines pulmonary blood flow. Early-onset pulmonary obstructive vascular disease commonly develops because of increased pulmonary blood flow and pressures, yet cyanosis may be absent with high pulmonary blood flow. This type of double outlet right ventricle is frequently associated with subaortic stenosis and arch obstruction.

Double outlet right ventricle with noncommitted or remote VSD has anatomy and physiology similar to that of an isolated VSD or atrioventricular canal defect. To meet the criteria for double outlet right ventricle with noncommitted VSD, some have suggested that the distance between the VSD and the aortic and pulmonary outflow tracts should be at least equal to the aortic valve diameter. Most commonly, the great arteries are normally related in this type of double outlet right ventricle. Pulmonary and systemic blood flow and saturations are determined by the ratio of pulmonary to systemic vascular resistance and by the degree of right ventricular mixing.

Finally, double outlet right ventricle with doubly committed VSD displays physiology in which the left ventricular outflow is equally shared by the aorta and pulmonary artery. The systemic and pulmonary vascular resistances determine the ratio of pulmonary-to-systemic blood flow. This is a relatively rare form of double outlet right ventricle that typically has normally related great arteries. Right ventricular mixing affects oxygen saturations.

Because double outlet right ventricle is the only defect in less than 50% of patients with double outlet right ventricle, classification and description may also take into consideration obstruction of the systemic circulation, ventricular anomalies, coronary artery anomalies, and conduction system abnormalities. Upon further investigation, findings of additional VSDs, anomalies of ventricular rotation, and anomalies of insertion of the subvalvar apparatus of atrioventricular valves are not uncommon.

Systemic circulation may be obstructed at the aortic valve or the obstruction may be subaortic; subaortic obstruction develops in approximately 10% of patients. Aortic valve anomalies are usually associated with mitral valve anomalies that may also be present in the form of a restrictive VSD. Coarctation of the aorta is the most common associated lesion, and interrupted aortic arch may also be present.

Patients with double outlet right ventricle can have coexisting ventricular anomalies. Left ventricular inflow anomalies are less frequent yet can be severe. Mitral stenosis or atresia is often associated with a hypoplastic left ventricle and intact ventricular septum. Left ventricular hypoplasia is present if decreased pulmonary venous return, restrictive VSD, and large atrial septal defect (ASD) are present. Misalignment of atrioventricular valves is also visible. This is very important for surgical correction and must be investigated. Finally, straddling of the atrioventricular valve annuli or straddling of the chordae may be present. Right ventricular abnormalities including tricuspid regurgitation, tricuspid stenosis, and Ebstein malformation may develop.

Coronary artery abnormalities are related to the relationship of the great arteries with several variations, including anomalous origin of the right coronary artery (RCA) from the left main coronary artery (LMCA), duplication of left anterior descending coronary artery (LAD), anomalous origin of LAD from RCA (associated with a subaortic VSD and pulmonary stenosis), anterior origin of LAD, RCA immediately beneath pulmonary annulus (seen with L-malposed aorta), and RCA from the posterior sinus of Valsalva/LMCA from the left sinus, which is seen with an anterior aorta and subpulmonary VSD and is similar to transposition of the great arteries.

Conduction system abnormalities develop because of alterations in anatomy. Anatomy of the atrioventricular node and His-Purkinje system is similar to that in an isolated perimembranous VSD. In subaortic, subpulmonary, and doubly committed VSD, conduction tissues are displaced from the superior margin of the VSD.

Other abnormalities and associations are rare and can include dextrocardia and atrioventricular discordance, superior and inferior ventricles, and single atrioventricular valve connection.

Frequency

United States

Double outlet right ventricle accounts for 1-1.5% of all CHDs, with an incidence of 1 per 10,000 live births.

International

Incidence is the same internationally as in the United States.

Mortality/Morbidity

One review found early in-hospital mortality after operation to be 4.8%.² The rate was significantly higher in patients with complex lesions. Late mortality was 3.2% with a mean follow-up time of 5.3 years. Overall 15-year survival ranged from 89.5-95.8%, with more complex lesions exhibiting higher mortality rates. Reoperation was required in 11.2% of surviving patients. This occurred a mean of 4.1 years after the original definitive repair. The most likely cause of reoperation was right ventricular outflow tract obstruction. Fifteen-year freedom from reoperation rates in surviving patients ranged from 72-100%. The reoperation rate was higher in patients with subpulmonary VSDs.

Race

No race predilection has been reported.

Sex

No sex predilection has been reported.

Age

Most cases of double outlet right ventricle are diagnosed in the first month of life.

Clinical

History

History of double outlet right ventricle (DORV) varies based on type of anatomy.

• Subaortic or subpulmonary ventricular septal defect (VSD) with pulmonary stenosis
  • These children present with histories similar to those of children with tetralogy of Fallot.
  • If pulmonary oligemia is present, severe cyanosis is seen in the newborn period, and the condition is recognized early.
  • Beyond the newborn period, cyanosis may be accompanied by hypercyanotic spells, polycythemia, and failure to thrive.
  • These children are less likely to develop pulmonary obstructive vascular disease due to limitation of blood flow and pressure by pulmonary stenosis.
• Subaortic VSD without pulmonary stenosis
  • These children present with histories similar to those of children with a large VSD and pulmonary hypertension.
  • Oxygenation is relatively normal, and patients usually present with congestive heart failure (CHF) and failure to thrive.
  • Referral usually occurs later unless associated left heart lesions are present.
  • These children may have associated chromosomal abnormalities such as trisomy 13 or 18.
  • These children are likely to acquire pulmonary obstructive vascular disease without surgical repair, especially if the VSD is large.
• Subpulmonary VSD without pulmonary stenosis
  • These children present with histories similar to those of children with transposition of the great arteries.
  • Cyanosis varies, with oxygen saturations ranging from 40-80%.
  • If associated coarctation or interruption of the aorta is present, earlier onset of CHF can be expected to result in earlier referral.

Physical

Physical examination findings vary with the anatomy.

• Subaortic or subpulmonary VSD with pulmonary stenosis: Physical examination reveals prominent right ventricular impulse, systolic thrill at left upper sternal border, harsh systolic murmur, and a single second heart sound.
• Subaortic VSD without pulmonary stenosis
  • Physical examination reveals hyperdynamic precordial impulse, a grade III-IV/VI holosystolic murmur, a loud pulmonary component of the second heart sound, an apical diastolic rumble, and, sometimes, a palpable thrill.
  • Once these children acquire pulmonary obstructive vascular disease, they exhibit decreased pulmonary blood flow with subsequent loss of the diastolic rumble and attenuation of systolic murmur. They may also develop a loud second heart sound and a diastolic decrescendo murmur of pulmonary insufficiency.
• Subpulmonary VSD without pulmonary stenosis
  • Physical examination reveals cyanosis, tachypnea, grunting, and signs of CHF.
  • Examination also reveals a loud pulmonary component of the second heart sound, a III/VI systolic murmur, and an apical diastolic rumble.
  • If coarctation of aorta is present, the examination also reveals diminished femoral pulses.

Causes

As with other conotruncal heart defects, the cause of double outlet right ventricle may be of neural crest origin.³ The neural crest is involved in the development of the cardiac septum. Studies indicate removal of the neural crest during development results in outflow tract malformations, and total removal of cardiac neural crest usually results in truncus arteriosus abnormality. Deletions of smaller parts of the cardiac neural crest result in malformations such as double outlet right ventricle, tetralogy of Fallot, and Eisenmenger complex. Interestingly, neural crest ablation rarely results in transposition of the great arteries. Most changes in heart morphology occur while the heart is still in the looped tube stage.

In addition to formation of cardiac structures, this area of neural crest cells participates in formation of the thymus and the thyroid and parathyroid glands, serving as the basis for association of congenital heart diseases (CHDs) with DiGeorge syndrome. The combination of velocardiofacial syndrome, DiGeorge syndrome (facial anomalies and parathyroid/thymus aplasia or hypoplasia), and a chromosome band 22q11 deletion is known as CATCH 22.^4,5,6

The most common types of CHD associated with the band 22q11 deletion include tetralogy of Fallot, truncus arteriosus, VSDs, and aortic arch abnormalities.^4,5,6 Research has shown that 22q11 deletions are rare in double outlet right ventricle. In one study, only 1 in 20 patients with double outlet right ventricle had the deletion; double outlet right ventricle was defined only by lack of fibrous continuity between mitral and aortic valves and an aorta that arises more than 50% above the right ventricle.⁶ However, because double outlet right ventricle encompasses such a large spectrum of anomalies, recommendations are to continue to test patients for the 22q11 deletion, especially when they display other features of velocardiofacial syndrome.

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