Chapter 22

ANATOMY

    The most distinguishable feature in this malformation is the aortic position. This vessel originates anteriorly and to the left to the pulmonary artery.
    There is a functional right ventricle but with the anatomical structure of the left, with a right valve connecting the right atrium with the ventricle, which resembles the bicuspid mitral valve. The ventricle located to the left, which functions as a true left ventricle, but has the anatomical structure of the right ventricle with multiple trabeculae, and, is connected to the left atrium by a valve which resembles the tricuspid valve. The aorta, at any rate, arises from the left ventricle, and the pulmonary artery originates in the right ventricle.
    In this malformation there is a double transposition of the great arteries and both ventricles, which functionally corrects the physiology of these patients, determining a normal blood flow.
    The symptomatology of these patients, if present, will be due to associated malformations, most often a ventricular septal defect.
    On some occasions, insufficiency of the auricular ventricular valve in the left side may be seen, and more rarely, atrial septal defect and patent ductus arteriosus.

CLINICAL PICTURE

    The physical findings and symptomatology in these patients, as previously observed, will result from the associated anatomical malformations. Otherwise, if the patient does not present other abnormalities, he may have a normal life, and during auscultation the only anomaly will be a loud and unique second sound due to the relative proximity of the aortic valve to the anterior chest wall.

ELECTROCARDIOGRAM

    The ECG will reflect the atrial ventricular and intraventricular conduction defects which are relatively common in these patients.
    In this regard a prolongation of the PR interval is rather common (first degree AV block). P pulmonale is present in 75% of cases (tall P wave in Leads II, III and AVF). As a consequence of the transposition of the ventricles, the initial vector of the QRS complex is oriented toward the left and upward which will determine the initial Q wave in Leads II, III, AVF, V₄R and V₁. Q wave will be absent in Leads I, V₅ and V₆.
    In the case associated with VSD, left axis deviation will be present with deep S waves in the right precordial leads.
    Many times, deep T wave inversion in the antero-lateral precordial leads is noted.

ROENTGENOGRAM

    Typically the left border of the cardiac shadow will show only two convexities instead of three (aorta and systemic ventricle).
    The pulmonary artery arch is absent since the pulmonary artery is deviated posteriorly and toward the right in relation to the aortic artery.
    The position of the ascending aorta many times produces a straight contour in the upper part of the cardiac silhouette.
    A higher position of the right hilar shadow is very often described.

CARDIAC CATHETERIZATION AND ANGIOGRAPHY

    Since the cardiac pressures will be normal (if no associated defects are present), the cardiac catheterization will not necessarily be useful in these cases. The angiography is much more important since it will demonstrate the abnormal position of the arteries and the unusual internal structure of the left and right ventricle.
    If ventricular septal detect, left atrial ventricular valve insufficiency, pulmonic stunosis, etc., are present, the typical pressure changes and angiographic findings of such abnormalities will be seen.
    Patients occasionally may show levocardia and destrocardia with malpositions and abnormal rotations of the abdominal organs. Complete third degree AV block can be seen in approsimately 15% of these patients.
    It is important to mention, that corrected transpositions have associated malformations in close to 70% to 80% of the cases.
    Real time echocardiography is particularly helpful in the study of this pathology.

MEDICAL AND SURGICAL TREATMENT

    This will depend on the associated malformations and will probably be the same as observed in ventricular septal defect, pulmonary Stenosis or mitral insufficiency, etc.