You are in: eMedicine Specialties > Radiology > CARDIAC Tricuspid AtresiaArticle Last Updated: Mar 11, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: George Hartnell, MB, Professor of Radiology, Tufts University School of Medicine, Director of Cardiovascular and Interventional Radiology, Department of Radiology, Baystate Medical Center George Hartnell is a member of the following medical societies: American College of Cardiology, American College of Radiology, American Heart Association, Association of University Radiologists, British Institute of Radiology, British Medical Association, Massachusetts Medical Society, Radiological Society of North America, Royal College of Physicians, Royal College of Radiologists, and Society of Cardiovascular and Interventional Radiology Coauthor(s): Julia Gates, MD, Department of Radiology, Consulting Staff and Assistant Residency Program Director, Baystate Medical Center Editors: S Bruce Greenberg, MD, Professor of Radiology, University of Arkansas for Medical Sciences; Consulting Staff, Department of Radiology, Arkansas Children's Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; John D Newell, Jr, MD, FACR, FCCP, FASER, Co-Director of Thoracic Imaging, UCDHSC; Director of Lung Imaging Center, Professor of Radiology and Professor of Medicine, Department of Radiology, University of Colorado Health Sciences Center, National Jewish Medical and Research Center; Univ. Colorado Hospital; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: single ventricle heart, univentricular heart INTRODUCTIONSection 2 of 12
  BackgroundTricuspid atresia is a variant on the spectrum of univentricular heart, in which absence of the tricuspid valve orifice exists with either an imperforate valve or, more commonly, replacement of the tricuspid valve by tissue in-growth from the atrioventricular (AV) sulcus. A right ventricular outflow chamber and a single ventricle of left ventricular morphology may be present. No right ventricle is present, since by definition, a ventricle requires the inflow of at least 50% of an AV valve. Concordant or discordant arterial connections may be present. Severity of the condition is affected by the presence of other cardiac abnormalities, which can ameliorate the effects of tricuspid atresia (eg, persistent ductus arteriosus) or worsen prognosis (eg, pulmonary atresia). The presence of tricuspid atresia requires outflow from the right atrium through an atrial septal defect (ASD) or stretched foramen ovale. Some way must then be present to return blood to the lungs. This may be via a transposed pulmonary artery with a single ventricle of the left ventricular type (with the transposed aorta arising from an RV outflow chamber), via a pulmonary artery arising with the aorta (truncus arteriosus), or, most commonly, via a pulmonary artery arising from an RV outflow chamber with flow from the ventricle into the outflow chamber through a ventricular septal defect (VSD). In some situations, blood flow to the lungs may be through a ductus arteriosus or aortopulmonary collaterals, especially with pulmonary atresia. Outcome depends on flow at each level, degree of mixing of oxygenated and desaturated blood, and blood flow through the pulmonary arteries.1 PathophysiologyClassification of tricuspid atresia is as follows2:
Alternative classifications regard tricuspid atresia as a variation of univentricular heart in which a single ventricle is present with a rudimentary outflow chamber or a pouch of the right ventricular type.3 The basic problem is that the tricuspid valve has not developed and is atretic, being either imperforate or, more commonly, completely replaced by AV sulcus tissue. The tricuspid valve may be represented by a dimple or depression in a dilated right atrium. This is distinct from a congenitally unguarded tricuspid orifice, in which no tricuspid valve tissue is present but communication exists between the right atrium and right ventricle.4 By definition, since no tricuspid valve exists, no right ventricle can exist. An outflow chamber of right ventricular morphology may be present, which receives blood from the ventricle through a VSD. The size of the chamber and, to some extent, the adequacy of blood flow depends on the size of the VSD. For the child to survive, an ASD must be present to allow systemic venous blood to exit from the right atrium into the left atrium. Right atrial pressure is higher than in the left atrium, and an obligatory shunt runs from the right atrium to the left atrium. In the left atrium, deoxygenated blood from the systemic venous return mixes oxygenated blood from the lungs. The adequacy of mixing depends on the size of the ASD, which may be no more than a stretched foramen ovale. As a consequence of this obligatory mixing, systemic desaturation and cyanosis occur. This blood passes to the ventricle, then on to the aorta and pulmonary artery. The precise route depends on whether both great arteries arise from the ventricle or whether one arises from the outflow chamber. If concordant ventriculoarterial connections are present, pulmonary blood flow usually is reduced by the presence of a restrictive VSD, small right ventricle, or pulmonary stenosis. When discordant arterial connections are present, pulmonary blood flow may be increased. If the great arteries are related normally, the most usual situation is for the pulmonary artery to arise from an anterior outflow chamber. The degree of pulmonary perfusion depends on the size of the VSD and the presence or absence of pulmonary stenosis. Pulmonary stenosis and/or a restrictive VSD produce oligemic lungs, unless a patent ductus arteriosus is present. If pulmonary atresia is present, the lungs are supplied by collateral vessels arising from the aorta. If transposition of the great arteries is present, the degree of pulmonary blood flow depends on the presence of pulmonary atresia, pulmonary stenosis, or pulmonary hypertension. FrequencyUnited StatesTricuspid atresia is uncommon. Although changes in classifications and definitions of the various types of univentricular heart make recording of occurrence difficult, this condition probably accounts for less than 1% of congenital heart disease. InternationalTricuspid atresia is a rare congenital cardiac abnormality. Tricuspid atresia may be uncommonly grouped in families.5, 6, 7 Mortality/MorbidityThe mortality rate is high in patients who are untreated, with 65-75% dying in the first year of life. Survival after surgery depends on numerous factors, including the type of surgery and preparation of the pulmonary circulation. Age at surgery, pulmonary artery size, and the presence of pulmonary hypertension also affect the outcome after surgery. Survival is worst with coexistent pulmonary and tricuspid atresia. Survival in patients who are untreated is best when the degree of pulmonary stenosis allows near-normal blood flow with normal pulmonary vascular resistance. RaceNo racial predilection appears to exist. SexTricuspid atresia occurs with equal frequency in males and females. AgeMost patients with tricuspid atresia present in the first few weeks of life with cyanosis and other symptoms and signs that depend on the degree of pulmonary blood flow and associated lesions. Survival beyond the first year without treatment is unusual but does occur, and some patients have reached adulthood untreated. Most patients surviving with tricuspid atresia have been treated surgically with a systemic-to-pulmonary shunt, such as the Fontan operation.8 AnatomyThe right atrium is large, and shunting occurs through the atrial septum to the left atrium. An outflow chamber or pouch may be connected to a normally related pulmonary artery. Obstruction can occur at the level of the VSD, outflow chamber, or pulmonary valve. A patent ductus arteriosus may be present, which also delivers blood to the pulmonary artery. If arterial transposition is present, the pulmonary artery arises from the single ventricular chamber, with or without pulmonary stenosis, the presence of which determines whether pulmonary plethora or oligemia is present. Numerous other cardiac anomalies can occur with tricuspid atresia and are 3-4 times more common (63% vs 18%) if discordant ventriculoarterial connections are present.5 These include persistent left superior vena cava, juxtaposed atrial appendages, and coarctation of the aorta. Uncommonly, tricuspid atresia may be associated with truncus arteriosus9; divided left atrium and discordant ventriculoarterial connections10; Ebstein anomaly11; absent pulmonary valve12; DiGeorge syndrome and chromosome band 22q11 deletion13; and Wolfe-Parkinson-White syndrome.14 Clinical DetailsTwo basic types of clinical presentation are seen. When concordant arterial connections and restricted pulmonary blood flow are noted, cyanosis is present from birth. Paroxysmal cyanotic spells may occur, which, if the child survives, are associated later with squatting. When the VSD is large and pulmonary blood flow is unlimited or when discordant arterial connections are present, cyanosis exists, but the lungs are plethoric. Heart failure develops with cyanosis. Because the right atrium is obstructed, features of right heart failure with hepatomegaly are present (ie, large a waves, central cyanosis, and clubbing). There may be a murmur of a VSD or pulmonary stenosis. Also, there may be a single second heart sound with pulmonary stenosis and reduced pulmonary blood flow, or there may be no murmur. If pulmonary blood flow is increased, a prominent apical impulse, a split-second sound, a systolic murmur, and features of heart failure may be noted. Older children usually have a history of retarded growth and development with dyspnea, fatigue, and cyanotic spells. Related Medscape topics: Preferred ExaminationPreferred initial examination should be chest radiography. Although chest radiography is a nonspecific investigation, it is required to assess for noncardiac causes of cyanosis. Chest radiographs also determine whether pulmonary blood flow is increased or decreased. In most if not all patients, echocardiography should be the next investigation. These images help make the diagnosis in most patients and allow assessment of other lesions, such as patent ductus arteriosus, pulmonary or aortic stenosis, mitral valve function, and abnormal venous connections. In addition, echocardiography is required to assess for the presence and size of any VSD, the size of an ASD, presence of an outflow chamber or pouch, ventricular function, and arterial connections. Other cross-sectional imaging techniques, such as CT or MRI, usually are reserved for older patients in whom echocardiography is restricted because of limited acoustic access or postoperative distortions of anatomy. MRI is especially good in these situations, since it is safe and allows repeated and accurate assessment of anatomy and function in multiple planes.15 Limitations of TechniquesUsually, changes on chest radiographs are nonspecific but provide useful data on pulmonary perfusion and extracardiac causes of cyanosis. Characteristic features of tricuspid atresia on chest radiography seldom are seen now, since most patients are treated early in life. Echocardiography is the usual best test in children and infants. The limitations usually are seen in older, and especially postoperative, patients in whom acoustic access and anatomic distortion may limit the field of view. Although contrast-enhanced CT scans can demonstrate the findings of tricuspid atresia,16 little reason exists for exposing patients to the radiation and the contrast material required unless both echocardiography and MRI are inadequate. In patients in whom echocardiography provides incomplete information, MRI is the usual next best test. The limitations are related to the need to have a regular heart rhythm and to remain still during the examination. Some patients are unable to enter the magnet because of contraindications such as pacemakers or intracerebral clips. Cardiac catheterization is invasive and carries all the risks of vascular access, catheter manipulation, radiation, and contrast material. It is required when information, such as pressure measurements, cannot be acquired by any other means.17 In patients with very complex anatomy, especially with transposed connections, angiography also may be required, although as experience with other less invasive techniques develops, angiography is used less frequently. Angiography is necessary in some procedures, such as angioplasty, thrombolysis, or septostomy, that may be required for palliation of the effects of tricuspid atresia or complications of surgery. DIFFERENTIALSSection 3 of 12
Anomalous Pulmonary Venous Return Ebstein Anomaly Pulmonic Stenosis Tetralogy of Fallot Tricuspid Valve Disease Truncus Arteriosus Other Problems to Be ConsideredDifferential diagnosis of tricuspid atresia with concordant great artery connections but no restriction to pulmonary blood flow or with discordant great artery connections causing cyanosis with pulmonary plethora includes the following: total anomalous pulmonary venous drainage, truncus arteriosus, transposition of the great arteries, single ventricle, and double-outlet right ventricle. Differential diagnosis of tricuspid atresia with concordant great artery connections and restricted pulmonary flow causing cyanosis with pulmonary oligemia includes the following: Ebstein anomaly, tetralogy of Fallot, pulmonary atresia, and severe pulmonary stenosis. RADIOGRAPHSection 4 of 12
FindingsThe right atrium is enlarged but the overall heart size is often normal in size except when pulmonary blood flow increases, and then cardiomegaly with pulmonary plethora is often present (see Images 1-2). Plethora is seen if a large VSD or transposed great arteries are present. Usually, the size of the pulmonary vessels is normal or small. A hollow pulmonary artery bay may be present because of the undersized main pulmonary artery, especially if pulmonary stenosis or pulmonary atresia is present. The right heart border is taller and more convex and laterally displaced; it may in some cases be straightened because of the small right ventricular outflow chamber. The left heart border may be prominent if great arteries are transposed. A right aortic arch is unusual, occurring in approximately 5% of patients (see Image 2).18 The shape of the heart may be suggestive of tricuspid atresia. The right atrium is prominent. Since the right ventricle is absent, the left ventricle becomes hypertrophied and dilated, causing development of a more rounded cardiac apex (see Image 2). Later, if the patient survives and pulmonary blood flow increases, changes of pulmonary hypertension may develop (see Image 3). This is a bad sign, since it reduces or excludes the chances of a successful Fontan procedure. Degree of ConfidenceChanges in the chest radiograph are nonspecific in most patients; however, radiographs provide useful data on the degree of pulmonary perfusion and exclusion of extracardiac causes of cyanosis. Characteristic features of tricuspid atresia on chest radiography are seen less commonly now, since most patients are treated early in life. CT SCANSection 5 of 12
FindingsWhile changes of tricuspid atresia can be demonstrated on contrast-enhanced CT scans, no reason exists to perform CT routinely. CT requires use of contrast agents, intravenous access, and radiation. The same information can be obtained more completely and more safely using echocardiography and MRI. Although exceptions exist in which CT may be useful in imaging complex anatomy or postoperative changes in which echocardiography is inadequate and MRI is contraindicated, this is uncommon.16 Degree of ConfidenceDegree of confidence in CT is high. False Positives/NegativesInadequate data exist concerning false findings in CT. MRISection 6 of 12
FindingsSpin-echo or gradient-echo MRI imaging techniques are used for anatomic imaging; magnetic resonance angiography (MRA), with or without gadolinium contrast medium, is a noninvasive method to obtain angiographic information. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. Cine MRA can be used to assess the ventricular and mitral valve function and, to some extent, the degree of pulmonary or aortic stenosis. Cine MRA is probably the best way to detect a ductus arteriosus, while breath-hold contrast-enhanced MRA defines aortopulmonary collaterals in patients with pulmonary atresia. This is also important for assessing the size of the pulmonary arteries prior to performing a shunt. Three-dimensional (3D) contrast enhanced MRA or spin-echo imaging can be used to assess arterial connections and relationships, as well as the size of the proximal pulmonary arteries. However, 3D MRA is superior for assessing branch stenosis.19 The acquisition time for the quality of 3D MRA is at least several seconds with current sequences. This requires breathholding in older children and adult patients for initial or follow-up examination. In younger patients, it may be necessary to perform the study under general anesthesia, with respiration suspended by the anesthesiologist. After surgery, the extracardiac conduit of a Fontan procedure can be shown anterior to the heart border (see Image 6), while the thickened AV sulcus tissue replacing the tricuspid valve remains (see Image 7). Degree of ConfidenceDegree of confidence is high in patients who are suitable candidates for MRI and who are cooperative. False Positives/NegativesIt is likely that very few errors occur in expert hands; however, data are inadequate for quantifying accuracy. ULTRASOUNDSection 7 of 12
FindingsEchocardiography findings are those expected from the anatomy (see Anatomy and Pathophysiology).20 A large right atrium is found, with right-to-left shunting across the ASD viewed on Doppler ultrasonography. The ventricle is dilated, and a VSD is visible (see Image 8), with flow into the outflow chamber. Doppler imaging is used to assess any pulmonary or subaortic stenosis. The arterial connections are usually visible in children and infants, although limited acoustic access may make this difficult to assess in older patients. Assessment of pulmonary artery size may be difficult prior to shunting. In postoperative patients, shunts should be evaluated for stenosis or poor flow due to inadequate pulmonary arteries. Postoperative ventricular function is an important predictor of outcomes. This may be assessed better using newly developed techniques, such as 3D echocardiography.21 Degree of ConfidenceDegree of confidence is high in experienced hands. False Positives/NegativesFew false-positive or false-negative studies should occur. Rather, errors in assessing arterial connections or abnormal systemic venous drainage may occur because of limited views. NUCLEAR MEDICINESection 8 of 12
FindingsAs with most other congenital heart diseases, the role of nuclear medicine is limited to assessing ventricular function. Echocardiography is more appropriate for this. Pulmonary perfusion imaging may be helpful in determining the distribution of blood flow between the lungs before and after repair.22 ANGIOGRAPHYSection 9 of 12
FindingsAt cardiac catheterization, right atrial pressures are high. If obstruction to flow across the ASD is excessive, the ASD can be enlarged by using the Rashkind balloon septostomy technique. In older children, this technique may be inadequate because of the thickness of the atrial septal tissue. In these circumstances, a blade septostomy may be required to cut a slit in the atrial septum (see Image 8). Once this is accomplished, the ASD can be enlarged by using a balloon. The diagnostic catheter passes from the right atrium to the left atrium across the ASD. The right ventricle cannot be entered directly (see Images 9-12). The catheter may enter the outflow chamber through a larger VSD; a small restrictive VSD is difficult to enter (see Image 10). The catheter may enter the pulmonary artery directly if the arterial connection from the ventricle is abnormal. Prior to shunting, the size of the pulmonary arteries needs to be assessed and any pulmonary stenosis excluded or treated (by angioplasty). In a patient with poor pulmonary blood flow, the lungs are supplied by aortopulmonary collaterals, especially if pulmonary atresia is present. While these may be lifesaving, they require closure at the time of surgery to reduce the risks of competitive flow impeding shunt flow. Closure can be performed surgically or by use of transcatheter embolization.23 Degree of ConfidenceThe degree of confidence is high for making a diagnosis and imaging great artery anatomy. This may be the only way to obtain information on pulmonary artery pressures prior to shunting. INTERVENTIONSection 10 of 12
Initial palliation of tricuspid atresia may be limited to enlarging the ASD (by using Rashkind septostomy) to allow adequate flow from the right atrium into the left atrium. More frequently, the first part of the Fontan procedure is performed. The Fontan procedure creates a shunt from the superior vena cava and the right pulmonary artery (bidirectional Glenn anastomosis) with closure of the main pulmonary artery and any previous shunts.24 Provided the resulting blood flow is adequate to allow growth of the pulmonary arteries, the Fontan procedure is completed some months later. In the classic Fontan procedure this involves diverting flow from the inferior vena cava (IVC) directly through the right atrium to the pulmonary artery. Several methods are available that can accomplish this, including use of a valved conduit, a valveless Dacron tube, and a direct right atrium-right ventricle anastomosis. In the extracardiac Fontan procedure, a conduit connects the IVC directly to the pulmonary artery, possibly reducing the resistance to flow compared with the classic operation. No consensus appears to exist at present as to which is the best technique. Performing the procedure in 2 stages substantially reduces operative mortality.25 Since no ventricular function is present to drive pulmonary blood flow, it is essential that pulmonary artery pressure and pulmonary vascular resistance not be elevated significantly.26 In patients in whom blood flow is increased through a nonrestrictive VSD or in association with transposed great arteries, the pulmonary artery should be protected by pulmonary artery banding (see Image 13). Usually, the banding is removed at the time of surgery, although use of a temporary device has been described.27 Earlier surgery reduces the adverse effects on subsequent ventricular function.28 Intrinsic defects may be present in the myocardium of patients with tricuspid atresia, which increases the risk of failing ventricular function.29 The Fontan procedure is a palliative procedure. In the classic Fontan procedure, the right atrium has to sustain blood flow through the pulmonary arteries. The ventricle may be abnormal, having been damaged prior to the operation by the need to support two circulations. This leads to a high risk of late-developing arrhythmias, need for repeat operation, and failing ventricular function, which require careful follow-up observation.30, 31 Other complications include atrial thrombus, chronic serous pleural effusions, and protein-losing enteropathy, which can be palliated by fenestrating the Fontan repair.25 Some authors believe that routine fenestration may be superior to the classical Fontan procedure because of the lower incidence of these complications.32 Radiofrequency catheter ablation or alcohol injection may be used for treatment of some arrhythmias.33 Obstruction of the Fontan conduit or anastomotic strictures may be treated using balloon angioplasty.34 Special Concerns
MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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