Pediatric Tricuspid Atresia Workup

Updated: Jan 17, 2017
  • Author: Syamasundar Rao Patnana, MD; Chief Editor: Howard S Weber, MD, FSCAI  more...
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Workup

Laboratory Studies

Studies that are indicated in tricuspid atresia are discussed below.

Pulse oximetry and arterial blood gas determination

Estimation of systemic arterial oxygen saturation by means of pulse oximetry, which is readily available in most outpatient and inpatient settings, is a useful adjunct in the clinical assessment. Arterial oxygen saturations less than 70-80% are of concern and lead one to expedite intervention to relieve pulmonary oligemia.

Arterial blood gas (ABG) determinations provide accurate information regarding PO2, the partial pressure of carbon dioxide (PCO2), and base deficit. This test provides data about blood oxygen values (ie, PO2), ventilatory status (ie, PCO2), and metabolic status (ie, base deficit) or lactic acid. However, this is an invasive test and is not reliable if the child is agitated or crying during blood sampling. If an arterial line is already in place, blood gas analysis is valuable.

Hemoglobin and hematocrit measurements

Whereas the oxygen saturation measurement gives the value at one point in time, the level of hemoglobin indicates the degree and duration of hypoxemia. A rapid increase in hemoglobin suggests severe or long-standing hypoxemia.

The author routinely obtains RBC indices to ensure that no relative iron-deficiency anemia is present. Microcytosis and hypochromia suggest iron deficiency and warrant treatment with iron supplements.

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Imaging Studies

Chest radiography

Chest radiography is a useful adjunct in the evaluation of any congenital heart defect, including tricuspid atresia. The radiographic features are also useful in evaluating the pulmonary blood flow and categorizing them into pulmonary oligemia and pulmonary plethora groups.

If the pulmonary blood flow is decreased, the heart is normal in size or only mildly enlarged. If pulmonary blood flow is excessive, moderate-to-severe cardiac enlargement is observed. The cardiac silhouette has been characterized in the literature as egg, bell, square, or boot shaped (coeur en sabot). However, in the experience of the author and of others, no consistent pattern is diagnostic of tricuspid atresia. [36]

Concavity in the region of the pulmonary artery segment is observed in patients with pulmonary oligemia and a small pulmonary artery or pulmonary atresia. The right atrial border may be prominent, especially if interatrial obstruction is present. With a restrictive atrial septal defect (ASD), the right atrial shadow may be prominent.

A right aortic arch, which is frequently observed in patients with tetralogy of Fallot (25%) or truncus arteriosus (40%), is present in only 8% of patients with tricuspid atresia. In rare types of tricuspid atresia (type III, subtypes 1 and 5), an unusual contour of the left border of the heart secondary to leftward and anterior displacement of the ascending aorta is present. [61]

Chest radiography is also useful in depicting the position of the heart; visceroatrial situs; and abnormalities of lungs, diaphragm, or vertebrae.

The most useful aspect of chest radiography is that it allows for the differentiation of decreased and increased pulmonary vascular markings. This distinction is often all that is necessary to establish a diagnosis after history taking, physical examination, and electrocardiography are performed.

Echocardiography

2D echocardiography reveals a small right ventricle and an enlarged right atrium, left atrium, and left ventricle. [61] In the most common muscular type of tricuspid atresia, a dense band of echoes is observed where the tricuspid valve is usually located (see the image below). The anterior leaflet of the detectable atrioventricular valve is attached to the left side of the interatrial septum. These echocardiographic features are best demonstrated in the apical and subcostal 4-chamber views. The size of the left atrium and the size and function of the left ventricle can be assessed with M-mode echocardiography. Repeated measurements during follow-up are useful in evaluating left ventricular function.

Subcostal 4-chamber 2-dimensional echocardiographi Subcostal 4-chamber 2-dimensional echocardiographic view of a neonate with tricuspid atresia shows an enlarged left ventricle (LV), a small right ventricle (RV), and a dense band of echoes where the tricuspid valve echo should be. Atrial and ventricular septal defects and the mitral valve are also seen. Note the attachment of the anterior leaflet of the detectable atrioventricular valve to the left side of the interatrial septum. Reprinted from Rao, Fetal and Neonatal Cardiology, 1990, with permission from Elsevier Science.

Demonstration of ASDs and ventricular septal defects (VSDs) by means of 2D echocardiography is essential, and shunting across the defects can be documented by using Doppler echocardiography. Semilunar valves can be similarly identified as pulmonic or aortic by following the great vessels until the bifurcation of the pulmonary artery or the arch of the aorta is seen. Coarctation of the aorta, which is more frequent in patients with tricuspid atresia type II, may be demonstrated in the suprasternal notch view.

Doppler echocardiography is useful for demonstrating the degree of obstruction across the ASD or VSD, for detecting stenosis of the right ventricular outflow tract and pulmonary valve, and for showing aortic coarctation.

For detailed discussion of echocardiographic Doppler features, along with images, the reader is referred to book chapters published elsewhere. [62, 63]

Contrast echocardiography with an injection of agitated sodium chloride solution or other contrast material demonstrates sequential opacification of the right atrium, left atrium, left ventricle, and, subsequently, the right ventricle, although such a study is not required for diagnosis.

Radionuclide scanning

Radioisotopic scanning studies may be used to identify and quantitate a right-to-left shunt, to demonstrate cardiac anatomy by means of nuclear angiography, and to quantitate relative perfusions to both lungs. [61]

However, pulse oximetry, blood gas analysis, and echocardiography are preferred because they are more simple and less cumbersome than nuclear scanning for demonstrating a right-to-left shunt and cardiac anatomy.

Quantitative pulmonary perfusion scans are useful if stenosis of a branch pulmonary artery is suspected.

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Other Tests

In an infant with cyanosis, electrocardiographic findings are virtually diagnostic of tricuspid atresia. [64, 65] Electrocardiography reveals right atrial hypertrophy, an abnormal and superiorly oriented major QRS vector, the so-called left axis deviation in the frontal plane, left ventricular hypertrophy, and decreased right ventricular forces.

Right atrial hypertrophy, manifested by tall and peaked P waves (≥2.5 mm) in lead II and right chest leads may be present in 75% of patients with tricuspid atresia. In the so-called P-tricuspidale, a double peak, spike and dome configuration may be present. [64, 65] The initial tall peak is related to right atrial depolarization, and the second small peak is presumed to be secondary to left atrial depolarization. Regardless of the P wave configuration, its duration is prolonged, which may be caused by right atrial enlargement.

An abnormal superior vector (left axis deviation 0° to -90° in the frontal plane) is present in most patients with tricuspid atresia (see the image below). This abnormal vector is present in 80% of patients with tricuspid atresia type I (normally related great arteries) but only 50% of patients with tricuspid atresia type II or III. Normal (0° to +90°) or right axis deviation (+90° to ± 180°) is present in a minority of patients, mainly those with tricuspid atresia type II or III.

Frontal plane mean QRS vector in 308 patients, plo Frontal plane mean QRS vector in 308 patients, plotted by anatomic type. Most patients with tricuspid atresia type I (normally related great arteries) have an abnormally superior vector, also called left axis deviation. Only one half of patients with tricuspid atresia type II have an abnormally superior vector. Most patients with tricuspid atresia type III (subtype A) have an inferiorly oriented frontal plane vector. From Rao PS, Kulungara RJ, Boineau JP. Electrovectorcardiographic features of tricuspid atresia. In: Rao PS, ed, Tricuspid Atresia. 2nd ed. Mt Kisco, NY: Futura Publishing Co; 1992:141, with permission.

Numerous mechanisms have been postulated to explain the abnormal superior vector, including destructive lesions on the left anterior bundle, fibrosis of the left bundle branch, a long right bundle branch along with an early origin of left bundle branch, a small right ventricle, and a large left ventricle. Data from ventricular activation studies suggest that the superior vector is likely due to the interaction of several factors. The most crucial findings are right-to-left phase asynchrony of ventricular activation, right-to-left ventricular disproportion, and asymmetric distribution of the left ventricular mass favoring the superior wall. [65]

Regardless of the abnormality in the frontal-plane vector, left ventricular hypertrophy is observed in most patients. This usually manifests as increased amplitude of S waves in leads V1 and V2 and R waves in V5 and V6. ST–T-wave changes indicative of left ventricular strain are present in 50% of patients. The pattern of left ventricular hypertrophy is related to the anatomic nature of the lesion and left ventricular overload, and it is also secondary to a lack of opposition to the left ventricular electrical forces by the small right ventricle. Biventricular hypertrophy is occasionally observed; when such a pattern is present, it is usually tricuspid atresia type II or III with a good-sized right ventricle. Decreased R waves in leads V1 and V2 and S waves in leads V5 and V6 are secondary to a hypoplastic right ventricle.

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Procedures

Cardiac catheterization  [66, 67]

Indications for cardiac catherization

Perform cardiac catheterization if noninvasive evaluation provides insufficient data to address the management issues. [67] Catheterization is usually not necessary for diagnostic purposes in the neonate and young child, but it may be indicated before planned surgical correction is performed to provide the surgeon with important anatomic and physiologic detail. Accurate data about the pulmonary-artery anatomy, size, and pressures and about left ventricular end-diastolic pressure (LVEDP), size, and function are needed before a Fontan procedure can be performed.

Perform a methodic evaluation of Choussat criteria (ie, normal vena caval drainage, normal right atrial volume, mean pulmonary artery pressure < 15 mm Hg, pulmonary vascular resistance [PVR] < 4 U/m2, pulmonary artery–to–aortic root diameter ratio >0.75, normal left ventricular function [ejection fraction >0.60], no mitral insufficiency, and undistorted pulmonary arteries). However, exceptions to most of these criteria have been made. Introduction of the bidirectional Glenn procedure before the Fontan procedure and fenestrated Fontan have changed the need for rigid adherence to some of these criteria.

Also, cardiac catheterization is indicated as an integral part of transcatheter therapeutic intervention, which may be necessary in some patients.

Catheter insertion

The percutaneous femoral venous route is preferred because it facilitates access into the left side of the heart. [68] The percutaneous jugular venous route may be used when a bidirectional Glenn procedure was already performed or if infrahepatic interruption of the inferior vena cava with azygos or hemiazygos continuation is present. Percutaneous femoral arterial access is also used to define aortic coarctation and subaortic stenosis, to visualize collateral vessels to the lungs, or to aid in performing balloon coarctation angioplasty or coil occlusion of aortopulmonary collateral vessels.

Catheter course

The course of the catheter in the right side of the heart is abnormal. The right ventricle cannot be directly entered from the right atrium because of the atretic tricuspid valve. Instead, the catheter can be easily advanced into the left atrium through the interatrial defect, especially when femoral venous access is used. From the left atrium, the left ventricle can be entered across the mitral valve. In neonates, further catheter manipulation to enter a great vessel or the right ventricle is usually unnecessary; hemodynamic and angiographic information is usually adequate. Cardiac catheterization in neonates is rarely needed for diagnostic purposes.

With the availability of balloon-tipped catheters and various catheters and guide wires, the right ventricle may be catheterized through the VSD. In patients with normally related great vessels (type I), the aorta and pulmonary artery may also be catheterized from the left and right ventricles, respectively. In patients with transposed great vessels (type II), the aorta and pulmonary artery may also be catheterized from the right and left ventricles, respectively.

The course of a retrograde arterial catheter is normal in patients with tricuspid atresia type I, whereas it traverses anteriorly as it enters the right ventricle from the aorta in patients with tricuspid atresia type II. In patients with corrected transposition (type III, subtypes 1 and 5), the catheter courses anteriorly and to the left. (See Tricuspid Atresia for typical catheter positions in tricuspid atresia. [66, 67] )

Oxygen saturations

Oxygen saturation in the vena cavae is decreased. The extent of this reduction is proportional to the systemic arterial desaturation and the degree of congestive heart failure. A step up in right atrial oxygen saturation is not ordinarily observed because of the obligatory right-to-left shunt. In some patients, a step up in oxygen saturation may be observed and explained on the basis of instantaneous pressure differences between the atria. [69]

The oxygen saturation in the pulmonary veins is usually normal, with a step down in saturations in the left atrium secondary to obligatory right-to-left shunt at the atrial level. Oxygen saturation in the left ventricle is also decreased and may reflect a better admixture of the pulmonary venous and systemic venous returns. The left atrial, left ventricular, right ventricular, pulmonary arterial, and aortic saturations are similar, reflecting complete admixture of systemic and pulmonary venous returns in the left atrium. The aortic oxygen saturation is always lower than normal and proportional to the Qp:Qs. [67]

The oxygen saturations are generally lower in patients with a type I defect than those in patients with a type II defect. This difference appears to be related to the relatively high prevalence of pulmonary oligemia in patients with a type I defect. [66, 67]

Pressures

Right atrial pressure is normal or slightly elevated and depends on the LVEDP. The a waves are usually prominent. Interatrial obstruction results in giant a waves in the right atrial pressure recording. A mean atrial pressure difference of more than 5 mm Hg indicates interatrial obstruction. If the LVEDP is markedly elevated, the interatrial pressure difference may be eliminated, even in the presence of considerable interatrial obstruction. [67]

The left ventricular end-diastolic and left atrial pressures are usually normal. They increase with increasing Qp:Qs and diminishing left ventricular function. Prominent left atrial v waves may be observed with a high Qp:Qs and mitral insufficiency. [67]

The peak systolic pressure in the left ventricle is usually normal but may be elevated in subaortic obstruction and aortic coarctation. Aortic systolic pressure is normal unless aortic coarctation is present. Aortic diastolic pressure may be decreased because of diastolic runoff secondary to a patent ductus arteriosus or a surgical aortopulmonary shunt. In patients with type II (transposition) defects, perform careful pressure pullback recordings across the aortic valve and across the VSD. A pressure gradient between the ventricles (across the VSD) indicates subaortic obstruction due to spontaneous shrinkage of the VSD. [26, 50]

In patients with normally related great arteries (type I), the systolic pressure in the right ventricle is proportional to the size of the VSD; the larger the VSD, the higher the pressure. Of course, pulmonary stenosis influences the right ventricular pressure. In patients with transposition of the great arteries (type II), the right ventricular pressure is at a systemic level. [67]

Pulmonary artery pressure is usually normal in patients with tricuspid atresia type I; however, in those with tricuspid atresia type I with a large VSD, it may be elevated depending on the size of the VSD. In tricuspid atresia type II, the pulmonary pressures are high unless a clinically significant subvalvar or valvar pulmonary stenosis is present.

Because of the importance of pulmonary artery pressure in the overall treatment of patients with tricuspid atresia, every attempt should be made to measure pulmonary artery pressure. Pulmonary venous wedge pressure should be measured to estimate pulmonary artery pressure if all methods of catheterizing the pulmonary artery fail. [67, 70]

Calculated variables

Calculation of systemic and pulmonary blood flows and shunts are made using the Fick principle, either by measuring oxygen consumption (preferred) or by assuming it from the tables of normal values. Detailed methods and formulas for calculation may be found in Tricuspid Atresia. [67] The Qp:Qs and PVR are particularly critical calculations.

The reliability of Qp:Qs is not adversely influenced by not measuring the oxygen consumption.

A PVR of more than 4 U/m2 is a contraindication for Fontan operation.

Mair et al suggested that the preoperative catheterization index (PCI) is useful for predicting poor results after Fontan surgery. [71] The index is calculated as PVR + [LVEDP/(PI + SI)], where LVEDP is in millimeters of mercury, PI = the pulmonary flow index in liters per minute per meters squared, PVR is in units per meters squared, and SI is the systemic flow index in liters per minute per meters squared.

An index of less than 4 U/m2 is associated with an overall lower mortality rate. Although it has some limitations, this index reflects the importance of PVR and left ventricular function in the preoperative selection of patients for Fontan surgery.

Another measure that may be useful is transpulmonary gradient (mean pulmonary artery pressure minus mean left atrial pressure); a value of 5-7 mm Hg may be considered suitable for Fontan surgery.

Summary

Characteristic findings in tricuspid atresia are nonentry of the right ventricle directly from the right atrium and complete admixture of systemic, pulmonary, and coronary venous returns in the left atrium with similar oxygen saturations in the left atrium, left ventricle, right ventricle, aorta, and pulmonary artery. Systemic arterial oxygen saturation, Qp:Qs, pulmonary artery pressure and resistance, transpulmonary gradient, and LVEDP are useful in evaluating patients with tricuspid atresia prior to Fontan operation. Routine evaluation for interatrial obstruction in all patients and for subaortic obstruction at the VSD level in patients with type II (transposition) is important.

Cineangiography

Lack of direct anatomic continuity between the right atrium and right ventricle is the hallmark angiographic finding of tricuspid atresia. After tricuspid atresia is demonstrated, the ventricular anatomy, type and size of VSDs, ventriculoarterial connections, pulmonary artery anatomy, sources of pulmonary blood flow, and associated defects should be defined. [72]

Right atrial angiography

Selective cineangiography from the superior vena cava or right atrium demonstrates successive opacification of the left atrium and left ventricle without opacification of the right ventricle (see the image below). The negative shadow between the right atrium and left ventricle, called the right ventricular window, corresponds to the unfilled right ventricle. These features are best illustrated on a posteroanterior view. Although initially thought to be pathognomonic for tricuspid atresia, these signs may be present in a number of other conditions, including pulmonary atresia or severe pulmonary stenosis with intact ventricular septum, tetralogy of Fallot with ASD (pentalogy), total anomalous venous return to coronary sinus, and cor triatriatum dexter. [72]

Selected cineangiographic frames from superior ven Selected cineangiographic frames from superior vena caval (SVC) and right atrial (RA) frontal angiography in 2 patients in the frontal view. Note sequential opacification of the left atrium (LA) and left ventricle (LV) without opacification of the right ventricle. The RA on the right, the LA superiorly, and the LV on the left form a nonopacified right ventricular window (arrow). This is a classic appearance of the muscular variety of tricuspid atresia. From Rao PS. Tricuspid atresia: anatomy, imaging, and natural history. In: Brawnwald E, Freedom RM, eds. Atlas of Heart Disease: Congenital Heart Disease. Vol 12. Philadelphia, PA: Current Medicine; 1997:14.1 with permission.

The size and location of the interatrial communication is optimally visualized on hepatoclavicular or lateral views. Opacification of the left atrium through an obstructed patent foramen ovale may produce the onionskin or waterfall appearance.

During right atrial angiography, contrast material refluxes normally into the vena cavae and hepatic veins and does not indicate interatrial obstruction. However, dense opacification of the coronary sinus (see the image below) suggests interatrial obstruction. [72] Aneurysmal formation of the atrial septum may also suggest a restrictive atrial defect.

Selective superior vena caval (SVC) injection for Selective superior vena caval (SVC) injection for a 4-chamber projection (hepatoclavicular) shows tricuspid atresia and filling of the left atrium (LA) through a somewhat restrictive atrial septal defect (arrows). Note the retrograde filling of the coronary sinus (CS). RA = right atrium. From Schwartz DC, Rao PS. Angiography in tricuspid atresia. In: Rao PS, ed. Tricuspid Atresia. 2nd ed. Mt Kisco, NY: Futura Publishing Co; 1992:223, with permission.

Right atrial angiography is also useful in demonstrating the size and position of the right atrial appendage and morphologic variants of the atretic tricuspid valve

Left ventricular angiography

Selective left ventricular angiography demonstrates a finely trabeculated, morphologically left ventricle, which is typical in most cases of tricuspid atresia. The left ventricle is slightly enlarged, and its size is proportional to pulmonary blood flow. The size and position of the VSDs, the presence of mitral insufficiency, and the origin and relative positions of the great vessels should also be evaluated. [72]

Left ventriculography is initially performed in posteroanterior and lateral views. Left anterior oblique, hepatoclavicular, or long axial oblique views may also be used, depending on the structure that needs greater definition. Particular attention is needed to define the size of the VSD in type II (transposition) because of the potential for development of subaortic obstruction. [26, 50]

Right ventriculography

In cases of type II (transposition), right ventricular cineangiography can be accomplished by passing a catheter antegrade from the left ventricle or retrograde from the aorta. Right ventriculography may improve assessment of the size of the right ventricle compared with left ventriculography. This information was of considerable importance in the past, when incorporation of the right ventricle into the Fontan circuit and its potential for growth were serious considerations. However, this issue is no longer as important since the advent of total cavopulmonary connection.

Aortography

Aortography should be performed in patients with tricuspid atresia type II because of a high incidence of aortic arch anomalies, particularly aortic coarctation. An anterograde or retrograde approach via the femoral artery may be used. In addition, aortography is used to define sources of pulmonary blood flow and the origin and distribution of the coronary arteries. [72]

Sources of pulmonary blood flow and pulmonary arterial anatomy [72]

These sources should be defined using anterograde or retrograde aortography. Selective angiography with a catheter positioned proximal to the ductus or a surgically created shunt clearly demonstrates the pulmonary arterial anatomy. Likewise, injections close to suspected aortopulmonary collateral vessels may help depict the pulmonary arteries. Angiography in the ventricle giving origin to pulmonary artery may demonstrate pulmonary artery anatomy. Finally, if the pulmonary artery cannot be entered with an angiographic catheter, pulmonary venous wedge angiography should be obtained to demonstrate the pulmonary artery anatomy.

Hepatoclavicular and lateral views are preferred to demonstrate the main pulmonary artery and the confluence of branch pulmonary arteries. Right and left anterior oblique views are preferred to demonstrate the right and left pulmonary arteries.

The size of the pulmonary arteries can be directly measured and compared with the size of the aorta, and the Nakata index or McGoon ratio can be calculated, according to the cardiologist or surgeon's preference. If the pulmonary artery cannot be catheterized, pulmonary venous wedge angiography may be attempted to demonstrate the pulmonary artery. [73]

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