**6.2.4 Cardiac catheterization and angiography**

With the increasing accuracy of echocardiographic diagnosis, invasive studies are not necessary for diagnosing TGA. Need for rapid relief hypoxemia and acidosis by balloon atrial septostomy and the need for a greater definition of coronary artery anatomy prior to arterial switch procedure may necessitate catheterization and angiography.

In group I patients, vena caval, right atrial, right ventricular and aortic saturations are moderately to severely diminished unless atrial, ventricular or ductal shunting is present. Similarly, the pulmonary venous, left atrial, left ventricular and pulmonary arterial saturations are high with minimal, if any right-to-left shunt. In TGA, the pulmonary artery saturations are higher than those in the aorta.

The left atrial pressure is usually high with a pressure gradient across the atrial septum. The right ventricular pressure is at systemic level without any gradient across the aortic valve. In TGA with intact septum the left ventricular and pulmonary artery pressure are normal without any gradient across the pulmonary valve. However, in the early neonatal period, prior to involution of the pulmonary vasculature, these pressures are elevated, compared to normal. In the presence of significant VSD and/or PS, the left ventricular pressure is elevated and this is usually proportional to the size of VSD and severity of PS. The

roentgenogram. In group II patients with VSD, moderate to severe cardiomegaly and increased pulmonary vascular markings are usually seen. In group III patient, mild to at worst moderate cardiomegaly may be observed. The pulmonary vascular marking may be

The ECG in a neonate with TGA and intact septum (Group I) may be normal with the usual right ventricular preponderance seen during this age. In older infants clear-cut right ventricular hypertrophy is seen and in addition right atrial enlargement may be observed. In group II patients, biventricular hypertrophy and left atrial enlargement are usual. In group

The echo is usually helpful in the diagnosis and assessment. Demonstration of transposition of the great arteries is somewhat difficult in view of the fact that atrial and ventricular anatomy is normal and the aortic and pulmonary valves look similar on echocardiographic study. If one can follow the great vessel arising from the left ventricle and demonstrate its bifurcation, identifying it as a pulmonary artery, the diagnosis is easy. One of the helpful indirect signs is somewhat a posterior course the great vessel off of the left ventricle in a precordial long axis view, indicating pulmonary artery in contradistinction to anteriorly coursing ascending aorta. On-end visualization of the aorta and pulmonary artery on a precordial short axis view of the heart is also helpful in suggesting TGA. The presence of an inter-atrial communication and patent ductus arteriosus and shunt across them by color and pulsed Doppler can also be evaluated. In addition to these, demonstration of VSD and PS

Blood gas values are useful in demonstrating the degree of hypoxemia and ventilatory status. Hemoglobin and hematocrit are particularly useful in the follow-up of older children.

With the increasing accuracy of echocardiographic diagnosis, invasive studies are not necessary for diagnosing TGA. Need for rapid relief hypoxemia and acidosis by balloon atrial septostomy and the need for a greater definition of coronary artery anatomy prior to

In group I patients, vena caval, right atrial, right ventricular and aortic saturations are moderately to severely diminished unless atrial, ventricular or ductal shunting is present. Similarly, the pulmonary venous, left atrial, left ventricular and pulmonary arterial saturations are high with minimal, if any right-to-left shunt. In TGA, the pulmonary artery

The left atrial pressure is usually high with a pressure gradient across the atrial septum. The right ventricular pressure is at systemic level without any gradient across the aortic valve. In TGA with intact septum the left ventricular and pulmonary artery pressure are normal without any gradient across the pulmonary valve. However, in the early neonatal period, prior to involution of the pulmonary vasculature, these pressures are elevated, compared to normal. In the presence of significant VSD and/or PS, the left ventricular pressure is elevated and this is usually proportional to the size of VSD and severity of PS. The

arterial switch procedure may necessitate catheterization and angiography.

increased, normal or decreased, dependent upon the severity of PS.

III, right ventricular or biventricular enlargement is seen.

will place the patients into the respective groups.

**6.2.4 Cardiac catheterization and angiography** 

saturations are higher than those in the aorta.

**6.2.3.4 Other laboratory data** 

**6.2.3.2 Electrocardiogram** 

**6.2.3.3 Echocardiogram** 

pulmonary artery pressure is usually increased with associated VSD while with PS it may be low to normal.

Selective right ventricular angiography reveals a morphologically right ventricle with opacification of an anteriorly and superiorly displaced aorta. The aortic valve is located to the right of the pulmonary valve (d-TGA). The aorta ascends in a normal fashion and usually descends on the left side of the spine. The size and function of the right ventricle and presence of tricuspid insufficiency should be evaluated. If a VSD is present, it may be visualized. A laid-back view of the aortic root angiography along with a lateral view may be useful in demonstrating coronary artery anatomy. Aortography may, in addition, be useful in demonstrating PDA and CoA. Left ventricular cineangiogram reveals a morphologic left ventricle with prompt opacification of the pulmonary artery. The pulmonary valve is located posterior, inferior and to the left of the aortic valve. Left ventricular angiography should be scrutinized for subvalvar and valvar PS. A VSD may be visualized, if present.

#### **6.2.5 Management**

Untreated, TGA with intact septum carries a poor prognosis. The initial management of this and other cyanotic neonates is similar. Monitoring the infant's temperature and maintenance of neutral thermal environment is extremely important. In hypoxemic infants, ambient oxygen should be administered. In cyanotic CHD patients, no more than 0.4 FIO2 is necessary. Metabolic acidosis (pH < 7.25), if any, should be corrected with sodium bicarbonate (usually 1-2 mEq/kg diluted half and half with 5% or 10% dextrose solution) immediately. Respiratory acidosis should be cared for by appropriate suctioning, intubation and assisted ventilation. Hypoglycemia may be a significant problem; therefore, the infant's serum glucose should be monitored and the neonates should routinely receive 10% dextrose in water intravenously. If hypoglycemia (<30 mg/100ml) occurs, 15% to 20% dextrose solution should be administered. Similarly hypocalcemia should be monitored for and treated, if found. If an infant is getting progressively hypoxemic, it is likely that the intercirculatory pathways (patent foramen ovale and patent ductus arteriosus) are closing. Prostaglandin El (PGEI) (0.05 to 0.1 mcg/kg/min) intravenously may help open the ductus, thus improve oxygenation. Balloon atrial septostomy may be necessary to improve hypoxemia even after PGE1. Total surgical correction by arterial switch procedure (Jatene) is the treatment of choice in these neonates and will be discussed here-under.

TGA patients with VSD usually present with heart failure and aggressive anticongestive measures are indeed needed. Balloon atrial septostomy may help relieve pulmonary venous congestion and improve oxygenation. These patients will require Jatene procedure with closure of VSD.

TGA patients with VSD and PS may have varying presentation. If the reason for hypoxemia is poor mixing, balloon atrial septostomy is the treatment of choice. If the hypoxemia is secondary to decreased pulmonary flow, a Blalock-Taussig type of shunt may be needed. Sometimes both balloon septostomy and balloon dilatation of pulmonary valve may be performed via catheters in some of these children. Eventually these patients require a Rastelli type of repair.

Mustard procedure, which was originally described in 1964 was the most commonly used operation for TGA in the past. In this operation, hemodynamic correction of the defect is achieved by re-directing the systemic and pulmonary venous returns by means of an intraatrial baffle. Better understanding of the conduction system and its blood supply coupled

Congenital Heart Defects – A Review 37

An obligatory right-to-left shunt occurs it the atrial level in most types and subtypes of TA. Thus, the systemic and coronary venous blood mixes with pulmonary venous return in the left atrium and exits into the left ventricle. In type I (normally related great arteries) patients with a VSD, left-to-right ventricular shunt occurs, thus perfusing the lungs. In the absence of a VSD (i.e., intact ventricular septum), the pulmonary circulation is derived either via a PDA or through aorto-pulmonary collateral vessels. The presence of either a VSD or other means of blood supply to the lungs is essential for the patient's survival. The aortic blood flow is derived directly from the left ventricle. In type II (with d-transposition of the great arteries), the pulmonary blood flow is directly divided from the left ventricle. The systemic blood

Approximately one-half of the patients with TA present with symptoms on the first day of life and 80% would have had symptoms by the end of the first month of life. The magnitude of pulmonary blood flow determines the timing of and, type of clinical presentation. Two modes of presentation are recognized; those with decreased pulmonary blood flow and

Infants with pulmonary oligemia present with symptoms of cyanosis within the first few days of life; the more severe the pulmonary oligemia, the earlier is the clinical presentation. These hypoxemic infants may have hyperpnea and acidosis if the pulmonary blood flow is markedly diminished. The majority of the infants belong to type Ib (no transposition and pulmonary hypoplasia with a small VSD). Patients with pulmonary atresia (subgroup a, of all types) irrespective of great vessel relationship will also present with early cyanosis, especially when the ductus begins to close. Hypoxic spells are not common in the neonate

flow is via the VSD and right ventricle.

Table 3. A Unified Classification of Tricuspid Atresia

those with increased pulmonary blood flow.

although the spells can occur later in infancy.

**6.3.1 Symptoms** 

with the use of a pericardial baffle (instead of Dacron baffle) has significantly reduced postoperative complications such as arrhythmia and baffle obstruction. Other types of atrial switch operations, originally described by Senning and by Shumacker have also been used in several centers. When venous switch procedure is opted for, Mustard and Senning procedures appear to be selected with equal frequency, depending upon the institution/surgeon. In 1975, Jatene described anatomical corrections for TGA by arterial switch with relocation of the coronary arteries. Initially this procedure was performed for TGA with non-restrictive VSD and subsequently was adapted to TGA with intact septum. The arterial switch procedure has several advantages over the venous switch procedure in that the arrhythmias are less frequent, and the left ventricle rather than the right ventricle serves as a pump to systemic circuit. Arterial switch procedure, however, must be performed in the early neonate prior to deconditioning the left (pulmonary) ventricle in TGA patients with intact septum. Although there are no extensive long term follow-up results available, the short term and medium-term follow-up results are very encouraging and, at this time, the arterial switch procedure with or without LeCompte maneuver is considered the preferable operation for patients with TGA.

#### **6.3 Tricuspid atresia**

Tricuspid atresia (TA) is a cyanotic, congenital cardiac anomaly and has been commonly defined as congenital absence or agenesis of the morphologic tricuspid valve. It is the third most common cyanotic CHD and is the most common cause of cyanosis with left ventricular hypertrophy. Tricuspid atresia accounts for 1.4% of subjects with CHD. The most common type of TA, muscular variety, is characterized by a dimple or a localized fibrous thickening in the floor of the right atrium at the expected site of the tricuspid valve. The right atrium is usually enlarged and its wall thickened and hypertrophied. An inter-atrial communication, which is necessary for survival, is usually a stretched patent foramen ovale. The left atrium is enlarged and may be more so if the pulmonary blood flow is increased. The mitral valve is morphologically a mitral valve, usually bicuspid but its orifice is large and rarely incompetent. The left ventricle is clearly a morphologic left ventricle with only occasional abnormality; however, it is enlarged and hypertrophied. The VSD may be large, small or non-existent (intact ventricular septum) or multiple VSDs may be present. While a variety of VSDs are seen in TA hearts, muscular defects are most common. Also, most of these VSDs are restrictive and produce subpulmonary stenosis in patients with normally related great arteries and subaortic stenosis in patients with transposed great arteries. The right ventricle is small and hypoplastic; its size, by and large, is determined by the anatomic type. The relative position of the great vessels is quite variable and has been the basis for classification of' this anomaly: Type I, normally related great arteries; Type II, d-transposition of the great arteries; Type III, malpositions of the great arteries other than d-transposition; and Type IV, Truncus arteriosus (Table III) (Rao 1980).

Pulmonary outflow tract obstruction may be either subvalvar or valvar in patients with transposition while in patients with normally related great arteries, it is often at the VSD level although, in a few cases, subvalvar pulmonary stenosis, narrow tract of the hypoplastic right ventricle and, rarely, valvar PS may also be responsible for pulmonary outflow tract obstruction. The pulmonary artery may be atretic and in such cases a PDA or aortopulmonary collateral vessels may be present. Association with aortic coarctation is rare with type I patients and is more common in patients with transposition of the great arteries.

with the use of a pericardial baffle (instead of Dacron baffle) has significantly reduced postoperative complications such as arrhythmia and baffle obstruction. Other types of atrial switch operations, originally described by Senning and by Shumacker have also been used in several centers. When venous switch procedure is opted for, Mustard and Senning procedures appear to be selected with equal frequency, depending upon the institution/surgeon. In 1975, Jatene described anatomical corrections for TGA by arterial switch with relocation of the coronary arteries. Initially this procedure was performed for TGA with non-restrictive VSD and subsequently was adapted to TGA with intact septum. The arterial switch procedure has several advantages over the venous switch procedure in that the arrhythmias are less frequent, and the left ventricle rather than the right ventricle serves as a pump to systemic circuit. Arterial switch procedure, however, must be performed in the early neonate prior to deconditioning the left (pulmonary) ventricle in TGA patients with intact septum. Although there are no extensive long term follow-up results available, the short term and medium-term follow-up results are very encouraging and, at this time, the arterial switch procedure with or without LeCompte maneuver is

Tricuspid atresia (TA) is a cyanotic, congenital cardiac anomaly and has been commonly defined as congenital absence or agenesis of the morphologic tricuspid valve. It is the third most common cyanotic CHD and is the most common cause of cyanosis with left ventricular hypertrophy. Tricuspid atresia accounts for 1.4% of subjects with CHD. The most common type of TA, muscular variety, is characterized by a dimple or a localized fibrous thickening in the floor of the right atrium at the expected site of the tricuspid valve. The right atrium is usually enlarged and its wall thickened and hypertrophied. An inter-atrial communication, which is necessary for survival, is usually a stretched patent foramen ovale. The left atrium is enlarged and may be more so if the pulmonary blood flow is increased. The mitral valve is morphologically a mitral valve, usually bicuspid but its orifice is large and rarely incompetent. The left ventricle is clearly a morphologic left ventricle with only occasional abnormality; however, it is enlarged and hypertrophied. The VSD may be large, small or non-existent (intact ventricular septum) or multiple VSDs may be present. While a variety of VSDs are seen in TA hearts, muscular defects are most common. Also, most of these VSDs are restrictive and produce subpulmonary stenosis in patients with normally related great arteries and subaortic stenosis in patients with transposed great arteries. The right ventricle is small and hypoplastic; its size, by and large, is determined by the anatomic type. The relative position of the great vessels is quite variable and has been the basis for classification of' this anomaly: Type I, normally related great arteries; Type II, d-transposition of the great arteries; Type III, malpositions of the great arteries other than d-transposition; and Type IV,

Pulmonary outflow tract obstruction may be either subvalvar or valvar in patients with transposition while in patients with normally related great arteries, it is often at the VSD level although, in a few cases, subvalvar pulmonary stenosis, narrow tract of the hypoplastic right ventricle and, rarely, valvar PS may also be responsible for pulmonary outflow tract obstruction. The pulmonary artery may be atretic and in such cases a PDA or aortopulmonary collateral vessels may be present. Association with aortic coarctation is rare with type I patients and is more common in patients with transposition of the great arteries.

considered the preferable operation for patients with TGA.

**6.3 Tricuspid atresia** 

Truncus arteriosus (Table III) (Rao 1980).

An obligatory right-to-left shunt occurs it the atrial level in most types and subtypes of TA. Thus, the systemic and coronary venous blood mixes with pulmonary venous return in the left atrium and exits into the left ventricle. In type I (normally related great arteries) patients with a VSD, left-to-right ventricular shunt occurs, thus perfusing the lungs. In the absence of a VSD (i.e., intact ventricular septum), the pulmonary circulation is derived either via a PDA or through aorto-pulmonary collateral vessels. The presence of either a VSD or other means of blood supply to the lungs is essential for the patient's survival. The aortic blood flow is derived directly from the left ventricle. In type II (with d-transposition of the great arteries), the pulmonary blood flow is directly divided from the left ventricle. The systemic blood flow is via the VSD and right ventricle.


Table 3. A Unified Classification of Tricuspid Atresia

#### **6.3.1 Symptoms**

Approximately one-half of the patients with TA present with symptoms on the first day of life and 80% would have had symptoms by the end of the first month of life. The magnitude of pulmonary blood flow determines the timing of and, type of clinical presentation. Two modes of presentation are recognized; those with decreased pulmonary blood flow and those with increased pulmonary blood flow.

Infants with pulmonary oligemia present with symptoms of cyanosis within the first few days of life; the more severe the pulmonary oligemia, the earlier is the clinical presentation. These hypoxemic infants may have hyperpnea and acidosis if the pulmonary blood flow is markedly diminished. The majority of the infants belong to type Ib (no transposition and pulmonary hypoplasia with a small VSD). Patients with pulmonary atresia (subgroup a, of all types) irrespective of great vessel relationship will also present with early cyanosis, especially when the ductus begins to close. Hypoxic spells are not common in the neonate although the spells can occur later in infancy.

Congenital Heart Defects – A Review 39

The echo is reasonably characteristic for TA. Two-dimensional echocardiography, apart from showing enlarged right atrium, left atrium, and left ventricle and a small right ventricle, will demonstrate the atretic tricuspid valve directly. In the most common muscular type, a dense band of echoes is seen at the site where the tricuspid valve should be and the anterior leaflet of the detectable atrioventricular valve is attached to the left side of the inter-atrial septum. Apical and subcostal four-chambered views are best to demonstrate the anatomy. Atrial and ventricular septal defects can also be demonstrated by 2-D echocardiography and shunting across these defects can be demonstrated by Doppler echocardiography. Semilunar valves can be identified as pulmonary or aortic by following the great vessel until the bifurcation of the pulmonary artery or arch of the aorta is seen, this will help decide whether there is associated transposition of the great arteries. Measurement of peak Doppler flow velocities across the VSD and right ventricular outflow tract will not only reveal if obstruction is present at these sites but will also allow estimation of pulmonary artery pressures. Suprasternal notch imaging will be of use in demonstrating CoA, which is often seen in type II (transposition) patients. Contrast echocardiography with two-dimensional imaging will clearly demonstrate sequential opacification of the right atrium, left atrium, left ventricle and then the right ventricle. However, such a study is not

The diagnosis of TA based on clinical, electrocardiographic, and echocardiographic features is relatively simple, and cardiac catheterization and selective cineangiography, rarely, if ever, are essential for arriving at the diagnosis. However, these procedures are useful and should be undertaken to resolve issues not clarified by non-invasive studies and to evaluate multiple physiologic and anatomic features prior to planned Fontan-Kreutzer operation

Oxygen saturation data reveal diminished systemic venous saturation; the extent of decrease is related to the systemic arterial desaturation and the severity of congestive heart failure. The pulmonary venous saturation is usually in the normal range. A significant decrease in left atrial saturation is expected because of obligatory right-to-left shunting across the patent foramen ovale. Falsely high or falsely low saturations may be measured in the left atrium because of streaming. The left ventricular saturations are usually well mixed and are more reliable. The saturations in the left atrium, left ventricle and aorta as well as those in the right ventricle and pulmonary artery are nearly equal. Systemic arterial (aortic) desaturation is always present and the extent of desaturation is proportional to the Qp:Qs. The right atrial pressure may be mildly increased. If the foramen ovale is restrictive the pressure in the right atrium is markedly elevated; a mean pressure gradient of 5 mmHg across the patent foramen ovale in favor of the right atrium and giant "a" waves in the right atrium are indicative of an obstructive foramen ovale. The left atrial mean and left ventricular end-diastolic pressures are usually normal, but may be elevated if there is increased pulmonary blood flow, poor left ventricular function or significant mitral insufficiency. The right ventricular pressure is proportional to the size of the VSD in type I (normally related great arteries) patients while it is at systemic level in type II (transposition) patients. Systolic pressure gradient across the VSD may be seen if it is restrictive. The pulmonary artery pressure may be normal or increased depending upon the size of the VSD

**6.3.3.3 Echocardiogram** 

always necessary for diagnosis.

(Rao 1992).

**6.3.4 Cardiac catheterization and selective cineangiography** 

Infants with pulmonary plethora usually present with signs of heart failure within the first few weeks of life although an occasional infant may present within the first few days of life. They are only minimally cyanotic, but present with symptoms of dyspnea, fatigue, difficulty to feed, and perspiration. Recurrent respiratory tract infections and failure to thrive are other modes of presentation. The majority of these patients belong to type II (transposition with a large VSD) although a small number of patients may be of type Ic (no transposition but a large VSD). The association of aortic coarctation with type II patients has already been mentioned and coarctation, when present, makes them vulnerable to early cardiac failure.
