Tetralogy of Fallot With Pulmonary Atresia Workup

Updated: Nov 22, 2015
  • Author: Michael D Pettersen, MD; Chief Editor: Howard S Weber, MD, FSCAI  more...
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Workup

Approach Considerations

Pulse oximetry in the newborn, now the standard of care prior to discharge, is critical in determining the degree of systemic desaturation, which might not be obvious on clinical examination. An abnormal newborn screening pulse oximetry evaluation would result in additional diagnostic testing by a pediatric cardiologist.  In older, unrepaired cyanotic patients, obtain a complete blood cell (CBC) count to determine hemoglobin and hematocrit levels. In infants, arterial blood gas (ABG) measurement can assess their partial pressure of oxygen (PO2) and acid-base status, although at this age it is very unusual to demonstrate a metabolic acidosis.

Electrocardiographic (ECG) findings are similar to those of other patients with tetralogy of Fallot. Right ventricular hypertrophy with right-axis deviation is usually present. Biventricular hypertrophy may occur in infants with cardiac failure from excessive pulmonary blood flow.

Fluorescent in situ hybridization (FISH) analysis may be performed to detect a chromosome arm 22q deletion.

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Radiologic Studies

Although chest radiography, magnetic resonance imaging (MRI), and multidetector computed tomography (MDCT) scanning can be helpful in the evaluation of a patient with tetralogy of Fallot and pulmonary atresia (TOF-PA), 2-dimensional (2-D) ultrasonography (echocardiography and Doppler) is the most important imaging modality for this condition.

Radiography, MRI, and MDCT scanning

Chest radiography demonstrates a normal-sized, boot-shaped heart with decreased pulmonary vascular markings in cyanotic patients. A concavity in the region of the main pulmonary artery is evident, and approximately 26-50% of these patients have a right-sided aortic arch. Increased pulmonary vascularity may be observed in the presence of large aortopulmonary collaterals (major aortopulmonary collateral arteries [MAPCAs]).

In centers with expertise, MRI may be used as a noninvasive method of visualizing the pulmonary arteries and their collateral supply. [16, 17] MDCT scanning can also provide excellent delineation of the pulmonary arterial circulation. [18, 19]

O'Meagher et al suggest that right ventricular mass is associated with exercise capacity in adults with repaired tetralogy of Fallot and, thus, right ventricular mass as measured on cardiac MRI may be a novel marker for clinical progress in this patient population. [20] In their study of 82 adults with repaired tetralogy of Fallot, including 9 patients with repaired TOF-PA with ventricular septal defect, peak work was significantly and positively associated with right ventricular mass, independent of other cardiac MRI variables. [20]

2-D Ultrasonography

2-D echocardiography with color flow and 2-D Doppler is the most important tool in the diagnosis of tetralogy of Fallot with pulmonary atresia.

Parasternal long-axis view

The parasternal long axis view reveals a large aortic valve that overrides a large malalignment ventricular septal defect (VSD). 2-D and color flow imaging demonstrates lack of patency of the right ventricular outflow tract (see the videos below).

Parasternal long axis two-dimensional echocardiographic image demonstrating a large malalignment ventricular septal defect with overriding of the aorta over the ventricular septum.
Parasternal long axis two-dimensional echocardiographic image in a patient status post complete repair of tetralogy of Fallot with pulmonary atresia. A patch is visualized closing the ventricular septal defect.
Parasternal long axis color compare echocardiographic image showing the pulmonary artery conduit arising from the right ventricle.

Suprasternal and high parasternal views

The suprasternal and high parasternal views provide information regarding the pulmonary trunk, right and left pulmonary artery size, and their confluence (see the following video). The pulmonary arteries usually appear hypoplastic and may not be visualized at all.

Suprasternal long axis color flow echocardiographic image showing a large patent ductus arteriosus supply confluent pulmonary arteries.

Other

Color-flow imaging may help to identify sources of pulmonary artery blood flow, including the ductus arteriosus (DA) and aortopulmonary collaterals (MAPCAs). Significant hypoplasia of the central pulmonary arteries is highly predictive of an absent or very small DA prenatally and the presence of aortopulmonary collaterals (MAPCA's). [21] If collaterals are suspected, echocardiography alone is inadequate for complete delineation of pulmonary blood flow, and further imaging by MRI or angiography is recommended. [22]

See the videos below for the presence of aortopulmonary collaterals and pulmonary valve atresia, respectively.

Aortopulmonary view angiogram, with injection in the descending thoracic aorta demonstrating multiple aortopulmonary collaterals supplying pulmonary blood flow.

Determination of aortic arch sidedness and the branching pattern of the brachiocephalic vessels is important, particularly if an initial aorta-pulmonary artery shunt is planned.

Subcostal sagittal plane two-dimensional echocardiographic image showing pulmonary valve atresia, with confluent and well-developed pulmonary artery branches.
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Cardiac Catheterization and Angiography

Cardiac catheterization with angiography is recommended in most patients before surgical repair. Careful delineation of all sources of pulmonary blood supply is necessary to facilitate surgical planning. This includes determination of the presence, size, and confluence of the native pulmonary arteries and the presence of major aortopulmonary collaterals that may need to be either ligated or incorporated into the repair.

Technique

A femoral venous approach may be used to perform the right heart catheterization. The catheter does not pass across the pulmonary valve but can easily pass across the ventricular septal defect (VSD) into the left ventricle and aorta.

Coronary artery anatomy is delineated by an aortic root injection, although this is usually not necessary in newborns unless a complete surgical repair via a Rastelli procedure (right ventricle to central pulmonary artery conduit) is being considered.

Angiographic depiction of the pulmonary arteries may be performed either via a transvenous or retrograde arterial approach. This also allows easier access to imaging of both surgical shunts and aortopulmonary collaterals. Biplane angiography that includes both lung fields is important in defining the complete anatomy of both pulmonary arteries. Determining the confluence and patency of pulmonary arteries is of utmost importance. Further selective angiograms may be obtained to delineate the systemic-to-pulmonary collateral flow and anatomy.

In some patients, ventriculography and aortography do not demonstrate central true pulmonary arteries. In these patients, pulmonary vein reverse wedge angiography may provide this information. An end-hole catheter is passed across the atrial septum and wedged into a pulmonary vein. (Bilateral injections may be necessary.) A forceful injection of contrast medium by hand causes the contrast to flow retrograde through the pulmonary veins, reaching the central pulmonary arteries.

Findings

Venous catheterization usually reveals normal right atrial pressures. Right and left ventricular pressures are equal and systemic because of the presence of a large VSD. The aortic pressure is normal if pulmonary blood flow is normal or decreased. A wide pulse pressure may be observed in the presence of a large ductus arteriosus or large MAPCAs. Pulmonary artery pressures are difficult to delineate in view of the multiple sources of pulmonary blood flow.

Systemic arterial saturation is dependent on the amount of pulmonary blood flow.

The pulmonary arteries may be depicted as confluent or nonconfluent, and areas of stenoses or hypoplasia in the pulmonary arteries may be observed. Special attention is necessary to determine the presence of a dual supply of a particular lung segment. Intercommunications between the different collateral vessels and the peripheral pulmonary artery segments may be observed.

Postprocedure precautions

Taking appropriate precautions often avoids the potential complications of cardiac catheterization, including blood vessel injury, perforation, tachyarrhythmias, bradyarrhythmias, and vascular occlusion.

General postcatheterization precautions include monitoring for hemorrhage, pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm. Pay special attention to the hydration status of infants who require multiple angiograms to outline their pulmonary arterial anatomy. Attempt to limit the amount of contrast medium to 5-6 mL/kg. These patients are hypoxemic, requiring continuous pulse oximetry, and may require oxygen during and after the procedure. Give special attention to obtaining hemostasis and applying a pressure dressing at the access sites postcatheterization.

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