Laboratory Studies
Routine laboratory studies are not required for the initial diagnosis and management in children with double outlet right ventricle (DORV). Assess hemoglobin and hematocrit if children are thought to have polycythemia. Monitor serum electrolyte levels after treating children with diuretics, glycosides, and afterload-reducing agents.
Imaging Studies
Chest radiography
Chest radiography findings usually correlate with clinical presentation, but do not differentiate double outlet right ventricle from other forms of congenital heart disease (CHD).
The presence or absence of pulmonary stenosis and pulmonary vascular resistance determines if cardiomegaly and increased pulmonary vascularity are present. Patients with subaortic ventricular septal defect (VSD) and severe pulmonary stenosis demonstrate diminished pulmonary vascularity and concave left heart border (similar to appearance associated with tetralogy of Fallot). If pulmonary obstructive vascular disease is present, peripheral pulmonary vascularity may be reduced and proximal pulmonary arteries may be dilated.
The appearance in patients with subpulmonary VSD is similar to that in patients with transposition of the great arteries, revealing increased pulmonary vascularity and cardiomegaly.
In patients in whom the aorta is anterior and to the left, radiography may reveal the leftward position of the aorta.
Echocardiography
Echocardiography is the imaging technique most often used to diagnose double outlet right ventricle. The principle diagnostic feature is appearance of both great arteries primarily committed to the right ventricle. Parasternal long-axis and short-axis views reveal the degree of commitment to the right ventricle. Subcostal and apical 4-chamber views reveal the separation between semilunar and atrioventricular valves (ventriculoinfundibular fold).
Use multiple views to determine the relationship between the ventricular septum and the outlet septum.
Features that must be established with echocardiography include the primary commitment of both great arteries to the right ventricle, the spatial relationship of both great arteries, the location of the VSD and its relationship to semilunar valves, and the presence of associated anomalies such as coarctation, the straddle/override of atrioventricular valve in relation to the VSD, and the presence of restrictive VSD.
In addition, fetal echocardiography has been used to prenatally diagnose cases of double outlet right ventricle. This imaging modality can also reveal other congenital cardiac anomalies that may be present in addition to double outlet right ventricle. Prenatal quantification of left ventricular size is important. One study noted that, in patients with double outlet right ventricle and borderline left ventricular size, only 33% of pregnancies proceeded to live birth. [8] Of those patients, only 25% successfully underwent biventricular repair. Patients with double outlet right ventricle may demonstrate other abnormalities on fetal ultrasonography. However, even in patients with isolated double outlet right ventricle, diagnosis is possible based solely on limited fetal echocardiography, provided a long-axis view is included. [9]
MRI
MRI can help clarify ambiguities that remain after echocardiography.
MRI reveals the relationship between the great arteries, the anatomy of the outlet septum relative to the ventricular septum, and the relationship of the VSD to the great arteries.
One study reported that, in patients with doubly committed or noncommitted VSDs, MRI more reliably predicted the feasibility of a biventricular repair than did echocardiography. [10]
Limitations include the need for prolonged evaluation, deeper sedation, and incomplete atrioventricular valve definition. MRI may also fail to reveal the presence of aberrant chordae tendineae.
Other Tests
Abnormalities are often present on electrocardiography (ECG) but are not diagnostic of double outlet right ventricle.
If obtained after the newborn period, ECG reveals right ventricular hypertrophy. Left ventricular hypertrophy may develop in the presence of a restrictive VSD that leads to left ventricular pressure overload or an increased pulmonary venous return that leads to left ventricular volume overload.
Right atrial enlargement is common. Left atrial enlargement may be present if pulmonary venous return or mitral stenosis/atresia is increased.
Usually, left axis deviation of the frontal plane QRS is present because of displacement of the bundle of His posterior to VSD.
Procedures
Cardiac catheterization may delineate anatomy and hemodynamics. Objectives of catheterization include the following:
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Evaluation of right and left ventricular volumes
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Evaluation for possible gradient across VSD and pulmonary vascular resistance (PVR)
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Evaluation of relationship between VSD and great arteries
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Evaluation of coronary artery and aortic arch anatomy
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Assessment of degree of mixing of the 2 circulations
If a restrictive atrial septal defect (ASD) is present, increased pulmonary blood flow with aortic saturations below 70%, or 10% less than pulmonary saturations, indicates the possibility of improvement with atrial septostomy (termed transposition physiology).
Diagnostic angiographic features of double outlet right ventricle include the following:
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Opacification of both great arteries following right ventriculography
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Similarity of aortic and pulmonary valve horizontal planes
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Frequent anterior malposition of the aorta
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Presence of a filling defect dividing the 2 outflow tracts
Histologic Findings
Findings vary depending on the clinical presentation; various physiologic effects determine histology of cardiac structures.
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Neonate with double outlet right ventricle. Chest radiograph shows a mildly enlarged heart with symmetrically slightly increased pulmonary vasculature.
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Double outlet right ventricle with subaortic ventricular septal defect. Arrow shows flow of oxygenated blood from left ventricle to aorta.
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Repair of double outlet right ventricle with subaortic ventricular septal defect.
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Double outlet right ventricle with subpulmonary ventricular septal defect (Taussig-Bing anomaly).
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Complex repair of double outlet right ventricle with subpulmonary ventricular septal defect.
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Double outlet right ventricle with doubly committed ventricular septal defect.
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Repair of double outlet right ventricle with doubly committed ventricular septal defect showing VSD patch and intraventricular baffle.
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Double outlet right ventricle with noncommitted ventricular septal defect.
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Repair of double outlet right ventricle with noncommitted ventricular septal defect using a long ventricular septal defect patch.
