Chapter 20

COMPLETE TRANSPOSITION

ANATOMY

    In this particular malformation both atrium and ventricles are in concordant position. The abnormal relationship is between the ventricles and great arteries. In other words, both superior and inferior vena cavas are normally draining in the right atrium which is connected to the right ventricle. The right ventricle is followed by the aortic artery. In the left side the left atrium connects to the left ventricle which drains into the pulmonary artery.
    There is usually hypertrophy of the right atrium and right atrial appendix. The right ventricle is also enlarged and there is in time, moderate left ventricular hypertrophy.
    The aortic artery is located anteriorly and originates in the right ventricle. The level of the aortic valve is much higher than usual. The pulmonary artery arises posteriorly from the left ventricle.
    Both coronaries originate as usual from the aorta, but the left coronary runs anteriorly to the pulmonary artery trunk. At times, the circumflex artery can originate from the right coronary artery.
    The marked right ventricular hypertrophy is due to the fact that it should support systemic pressures. If VSD is present it may be located above or below the crista supraventricularis.
    Pulmonary valvular andlor subvalvular stenosis develops many times and is not unusual the association with ASD and/or PDA.

PHYSIOLOGY AND HEMODYNAMICS

    These patients need at time of birth a connection at the atrial or ventricular level to survive.
    Complete transposition of the great arteries determines early cyanosis in more than 90% of the patients.
    Complete transposition is the most common cause of congestive failure during the first two months of life.
    If the newborn with complete transposition has a VSD with pulmonic stenosis, which is not uncommon, the signs of failure will be reduced, but the cyanosis will be more severe. These blue babies can be easily confused with Tetralogy of Fallot and can survive with no surgery until adolescence. Otherwise, in most of these patients, pulmonary hypertension rapidly develops and congestive failure will lead to an early death, unless surgery is contemplated early. Complete transposition is four times more frequent among males than females.

CLINICAL PICTURE

    Cyanosis at birth in 90% of the cases.
    Congestive heart failure usually appears after second week of life. (This is the most common cause of CHF in newborns.)
    The weight at birth may be normal but delay in normal growth is the rule.
    If no surgery is performed early, the majority of these patients die before 8 months.
    If VSD and pulmonary stenosis are present at birth, the patient will be more cyanotic than usual but congestive failure is less severe and longer survival is possible. These cases closely simulate Tetralogy of Fallot.
    Localized cyanosis in the upper part of the body suggests PDA with inverted shunt.

PHYSICAL EXAMINATION

    Strong and single second sound is the rule (anterior aortic valve) due to poor transmission of the pulmonary component. After the second week S₃ can be seen if CHF is present.
    In case of VSD, systolic murmur will be audible in the LLSB with a palpable thrill.
    In case of pulmonary stenosis, P₂ will be delayed in the phonocardiogram.

ELECTROCARDIOGRAM

    The ECG is essential for a proper diagnosis and for differentiation from Tetralogy of Fallot.
    If the shunt is small, immediately after birth, the tracing can be normal and the only sign of right ventricular hypertrophy will be positive T waves in leads V₁, V₂, V₃. (Typically these patients have a normal size heart at birth.)
    After a few days of life and with the progressive biventricular hypertrophy, more typical features will appear.
    The main axis over the frontal plane tends to have impressive deviation to the right. Large S wave is frequently seen in I, II, III which is not as frequent in Tetralogy of Fallot.
    In case of VSD, tall R waves will be seen in the right precordial leads and a deep S wave in the same leads will correlate with left ventricular hypertrophy (biventricular hypertrophy).
    Real time echocardiography may be a promising technique in the study of this patients.
    Positive T waves in the right precordial leads are almost the rule, indicating systolic right ventricular overload in the initial few months of life.
    In case of complete transposition with normal ventricular septum tall R waves in the right precordial leads are seen with normal S waves.

ROENTGENOGRAM

    In these patients the most typical radiological features are:

1. Normal cardiac silhouette at birth, with
2. Rapid and progressive enlargement of the cardiac shadow
3. Pulmonary hilar plethora
4. Narrow supracardiac shadow

ECHOCARDIOGRAM IN TRANSPOSITION OF THE GREAT ARTERIES

    The normal relationship between the echoes of the pulmonary artery and aorta are lost. (Normally the pulmonary artery begins anterior to the aorta and then twists around the aorta, being posterior to that vessel in a upper level.)
    Many times both vessels will be seen running parallel to each other. The level of the pulmonary valve is recorded below the aortic valve. (Normally it must be superior to the aortic valve.)
    The right ventricular hypertrophy and thickening of the right ventricular walls can usually be easily detected.
    However, due to the frequent association of transposition with other congenital malformation, the echocardiographic diagnosis of this congenital diagnosis is still unreliable.

CARDIAC CATHETERIZATION AND ANGIOGRAPHY

    The right sided catheterization reveals:

1. Arterialization of the right atrium and ventricular blood (atrial or ventricular step-up depending on the location of the shunt).
   
2. Low oxygen saturation in the aorta and peripheral arteries, passing of the catheter toward left heart cavities when performing a right catheterization.
   
3. Right ventricular pressure higher than left ventricle and pulmonary artery pressures.
      If VSD is present both left and right pressures are usually equal and pulmonary stenosis develops (more often due to subvalvular hypertrophy).
4. The pulmonary flow is larger than systemic blood flow.

    The angiography reveals:

1. Aortic arch with a higher than normal valvular level.
2. Aortic arch arising anteriorly and from the right ventricle (better appreciated in lateral view).
3. Posterior origin of the pulmonary artery which arises from the left ventricle.
4. If patent foramen ovale, ASD, VSD, or PDA are present, the remainder of the catheterization and angiographic findings will depend on what associated defect is present.
5. The injection of contrast in the right ventricle will reveal the typical trabecular pattern of such heart chamber.

MEDICAL AND SURGICAL TREATMENT

    Prevention of SBE and proper care of upper respiratory tract infections is necessary.
    The medical management of congestive failure is very difficult but should be attempted.
    Appropriate treatment of the complications arising from severe policytemia (refer to Tetralogy of Fallot Chapter) should be attempted.
    Early use of the Rashkind's balloon catheter for creation of large ASD is essential; otherwise the patient will promptly die between one and eight months of age due to CHF and severe cyanosis.
    The early banding of the pulmonary artery will prevent the patient from developing irreversible pulmonary hypertension.
    In a second stage, corrective surgery can be attempted as follows:
    Albert procedure (Mayo Clinic 1969) is probably the best way to approach patients with associated VSD and hypoplastic pulmonary artery, using an aortic homograft to create an external liaison between the right ventricle and distal pulmonary artery. At the same time the VSD is repaired so that the left ventricle ejects into the aortic artery.
    Early surgery is essential for good results (mortality is below 5% in many specialized centers). If surgery is delayed until severe policytemia and congestive failure develop, the hospital mortality rises to 25% to 50%.
    Results are better when the ventricular septum is intact than when VSD exists.

Diagrammatic representation of incomplete transposition of the great arteries with the aortic artery located anteriorly to the pulmonary artery.

Pattern of circulation in incomplete transposition of the great arteries where the pulmonary artery arises anteriorly overriding a large ventricular septal defect. This particular arrangement of incomplete transposition is also known as Taussing-Bing Syndrome.

Electrocardiogram of a 2 year-old boy, markedly cyanotic with Complete Transposition and Ventricular Septal Defect (VSD).