Transposition of the Great Arteries Workup

Updated: Apr 11, 2017
  • Author: John R Charpie, MD, PhD; Chief Editor: Howard S Weber, MD, FSCAI  more...
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Workup

Laboratory Studies

Abnormal pulse oximetry findings with a discrepancy between the upper and lower extremities is consistent with inadequate intracardiac mixing.

A hyperoxia test (for cyanotic congenital heart disease) may be indicated in patients with transposition of the great arteries (TGA).

In a patient with arterial hypoxemia, an arterial blood gas (ABG) measurement is obtained on 100% oxygen for 10 minutes.

Pulmonary disease (not cyanotic congenital heart disease) is suspected if the partial pressure of oxygen increases to more than 150 mm Hg with oxygen.

Note the following:

  • Admit patients with TGA for preoperative testing and surgical interventions.

  • Carefully monitor medication doses and side effects.

  • Monitor adequacy of repair and palliation with periodic physical examinations and possibly echocardiograms.

  • Periodic electrocardiograms and/or 24-hour Holter monitoring to monitor for atrial arrhythmias should be employed, particularly following atrial-level switch operation (ie, Senning or Mustard procedure).

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Procedures

Cardiac catheterization

Neonatal diagnostic cardiac catheterization is usually reserved for the subgroup of patients for whom echocardiography does not adequately delineate the coronary artery anatomy. See the angiograms below.

This right ventricular angiogram shows a patient w This right ventricular angiogram shows a patient with transposition of the great arteries. The aorta arises directly from the right-sided anterior right ventricle (70° left anterior oblique [LAO]).
This left ventricular angiogram shows a patient wi This left ventricular angiogram shows a patient with transposition of the great arteries. The pulmonary artery arises directly from the left-sided posterior left ventricle (30° right anterior oblique [RAO]).
This left ventricular angiogram shows a patient wi This left ventricular angiogram shows a patient with transposition of the great arteries. The pulmonary artery arises directly from the left-sided posterior left ventricle (20° cranial).

In addition, cardiac catheterization may be necessary to improve left-to-right shunting at the atrial level (see the following videos demonstrate a restrictive atrial septal communication before and following balloon atrial septostomy).

This echocardiographic video (subcostal view) in a 1-day-old newborn reveals transposition of the great vessels and inadequate intracardiac mixing at the atrial level, resulting in severe desaturation. The video was obtained before the infant underwent balloon atrial septostomy. Video courtesy of Howard S Weber, MD, FSCAI.
This two-dimensional echocardiographic video (subcostal view) was obtained immediately following emergent balloon atrial septostomy in the same newborn discussed in the previous video. It now demonstrates a nonrestrictive atrial communication, which resulted in alleviation of the infant's cyanosis. Video courtesy of Howard S Weber, MD, FSCAI.

Postcatheterization precautions include hemorrhage, vascular disruption after balloon dilation, pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm.

Complications may include rupture of blood vessel, tachyarrhythmias, bradyarrhythmias, and vascular occlusion.

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Chest Radiography

The chest radiograph may appear normal in newborns with transposition of the great arteries and intact ventricular septum with adequate atrial level mixing, but it may demonstrate the classic "egg on a string" appearance in approximately one third of patients. In newborns who present with extreme cyanosis, the pulmonary vascularity will appear to be increased, indicating inadequate atrial level mixing.

With a ventricular septal defect, cardiomegaly usually occurs with increased pulmonary arterial vascular markings.

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Echocardiography

Echocardiographic images should be diagnostic of transposition of the great arteries by demonstrating the bifurcating pulmonary artery arising posteriorly from the left ventricle in the parasternal long-axis view.

The parasternal short-axis view shows the relationship of the great arteries to one another. The aorta is usually anterior and rightward of the pulmonary artery in cross-section.

Most associated anatomic lesions, including atrial septal defects, ventricular septal defects, and patent ductus arteriosus, are also diagnosed readily by echocardiography.

The coronary artery anatomy needs to be ascertained and may be abnormal in nearly one third of patients. The coronary artery origins and branching pattern are often delineated by echocardiography.

In a retrospective study of the relationship between interatrial communication, ductus arteriosus, and pulmonary flow to help predict postnatal desaturation in transposition of the great arteries and intact ventricular septum in 45 affected fetuses compared with 50 age-matched controls, echocardiography in fetuses with postnatal saturations of 50% or lower revealed a smaller interatrial communication as well as the presence of a retrograde diastolic flow in most of these fetuses relative to those with postnatal saturations over 50%. [8]  Compared with the control fetuses, those with transposition of the great arteries had a lower flow through the ductus arteriosus.

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Magnetic Resonance Imaging

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (MRI) studies may have the potential to help clinicians stratify risk in patients with transposition of the great arteries following atrial switch procedure. [9] In a single-center prospective study of 55 patients with transposition of the great arteries who underwent LGE MRI, investigators found that the presence of systemic right ventricular fibrosis was strongly associated with adverse clinical outcomes, particularly new-onset sustained tachyarrhythmias. [9]   MRI studies may be useful in evaluating the supravalve pulmonary, aortic, and branch pulmonary artery regions if significant stenosis is suspected.

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