Laboratory Studies
Clinical laboratory studies (eg, hematologic analysis, urinalysis) are not likely to be of diagnostic help; late findings may include polycythemia, but this and other findings of chronic cyanosis are nonspecific.
Imaging Studies
Echocardiography is used to evaluate anatomy, hemodynamics, and function of the heart both prior to and after surgical repair or palliation, and it is the most important means of establishing diagnosis of double outlet right ventricle (DORV) with transposition of the great arteries. Four important findings are as follows:
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Both great arteries arise from the right ventricle (RV).
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The aorta (AO) is to the right of or anterior to the pulmonary artery (PA).
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No course of egress of blood from the left ventricle (LV) other than a ventricular septal defect (VSD) is present.
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Fibrous discontinuity of mitral and semilunar valves is present.
In experienced centers, the accuracy of the prenatal echocardiographic diagnosis (and prognosis) of fetuses with conotruncal anomalies in general is good (ie, correct diagnosis in 77% of cases in a major center). [13] However, defining the exact spatial relationship of the great arteries can be problematic in some fetuses (ie, 7 of 17 fetuses with DORV anatomy, of which 6 were thought to have a subpulmonary VSD, had incorrect prenatal assessment of the great artery relationships). [13]
Some authors have described real-time 3-dimensional echocardiography as a way to improve cardiac imaging and diagnosis of complex congenital heart disease (CHD) through a clear display of cardiac morphology using volumetric views combined with sequential segmental approach. [14] However, others have recently concluded that information provided by real-time 2-dimensional echocardiography in fetuses with and without CHD were consistent with that provided by real-time 3-dimensional echocardiography. Therefore, no clear advantage of real-time 3-dimensional echocardiography over real-time 2-dimensional echocardiography has been documented.
Sometimes chest radiography may provide valuable clues for the diagnosis of DORV with transposition of the great arteries. Chest radiography for patients with either subaortic or subpulmonary VSD without PS may show cardiomegaly with increased pulmonary vascular markings and the main PA segment may be prominent; however, these findings are not specific for DORV. If PS is present, chest radiography may show near normal heart size and normal-to-decreased pulmonary vascular markings.
CT has been described as an effective diagnostic modality, especially in identifying coronary artery anomalies prior to cardiac surgery to aid in adequate procedure planning. [15]
MRI may serve as an adjunct tool to echocardiography for determination of visceral and atrial situs as vasculo-vascular and vasculo-visceral relationships. In some patients with DORV with remote VSD, MRI may aid in defining the spatial relationship between VSD and the semilunar valves. A new modality in MRI is the 3-dimensional MRI, which is increasingly used as an adjuvant to echocardiography and angiography for such purposes.
Angiography (see images below) may add anatomic and physiologic details to information found by echocardiography.
This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries. Injection of contrast though the catheter (arrow) into the left ventricle (LV) shows that blood is directed toward the right ventricle (RV) through a remote or doubly committed ventricular septal defect (VSD). The aorta (AO) is anterior to the pulmonary artery (PA) and both clearly arise from the RV.
This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries (see Media file 2). Blood fills the aorta (AO) and pulmonary artery (PA) almost simultaneously, which is another indicator of a remote or doubly committed ventricular septal defect (VSD) (curved arrow). LV indicates the left ventricle, RV indicates the right ventricle, and the small arrow to the left indicates the catheter.
Other Tests
ECG in patients with DORV with transposition of the great arteries reveals no specific findings indicative of the diagnosis. Usually, normal sinus rhythm and possible prolonged PR interval are present. Right axis deviation and right ventricular hypertrophy (RVH) are present most often. Left axis deviation is present in patients with atrioventricular (AV) septal defect.
Some ECG variations may be noted, depending on the type of DORV with transposition of the great arteries. ECG in patients with subaortic VSD with no PS may show superior QRS axis (-30° to -170°) with either RVH or biventricular hypertrophy and left atrial enlargement. First-degree AV block may be present with this lesion. ECG in patients with subpulmonic VSD or in those with subaortic VSD and PS reveals right axis deviation, RVH, and often right atrial enlargement.
Procedures
Echocardiography has mostly eliminated the need to perform cardiac catheterization in these patients; however, catheterization may still be necessary in certain circumstances.
Catheterization may be required for the following reasons:
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Need for further definition of coronary artery anatomy
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Need to determine coexistent conditions that cannot be elucidated by echocardiography
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Need to confirm restrictive VSD by measuring ventricular pressures
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Need to determine pulmonary vascular resistance (and reactivity) in patients suspected of having increased resistance
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Double outlet right ventricle (DORV) with transposition of the great arteries accounts for 26% of cases of DORV. The aorta (AO) is anterior and to the right of the pulmonary artery (PA), and both arteries arise from the right ventricle (RV). The only outflow from the left ventricle (LV) is a ventricular septal defect (VSD), which diverts blood toward the RV. Pulmonary veins drain into the left atrium (LA) after blood has been oxygenated in the lungs (L). Systemic venous return is to the right atrium (RA).
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This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries. Injection of contrast though the catheter (arrow) into the left ventricle (LV) shows that blood is directed toward the right ventricle (RV) through a remote or doubly committed ventricular septal defect (VSD). The aorta (AO) is anterior to the pulmonary artery (PA) and both clearly arise from the RV.
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This is an angiogram obtained during catheterization of a patient with double outlet right ventricle (DORV) with transposition of the great arteries (see Media file 2). Blood fills the aorta (AO) and pulmonary artery (PA) almost simultaneously, which is another indicator of a remote or doubly committed ventricular septal defect (VSD) (curved arrow). LV indicates the left ventricle, RV indicates the right ventricle, and the small arrow to the left indicates the catheter.
