Chapter 15

    This is a rare congenital heart disease which usually presents associated with another malformation. (ventricular septal defect, tricuspid atresia, complete transposition of the great arteries, etc.)
    The patent ductus arteriosus is almost the rule and essential for the passing of blood to the lungs.
    These patients will usually show a large hypertrophy of the right atrium. The right ventricle will appear small in many patients, but may be dilated and with a marked hypertrophy in some other ones. Typically the aortic artery will be much larger than the pulmonary artery.
    Patent foramen ovale is the rule and in few cases ostium secundum and ostium primum may be seen.
    Pulmonary atresia at many times simulates Ebstein's anomaly and as a matter of fact as a congenital malformation is difficult to be distinguished from this anomaly in many patients.
    The condition of the tricuspid valve (competent or incompetent) will be essential in relation to the development of the right ventricle. If the tricuspid valve is competent there will be no right ventricular hypertrophy or dilatation. If the tricuspid valve is incompetent, progressive dilatation of the right ventricle will be seen.

PATHOPHYSIOLOGY

    In the congenital malformation, the blood will pass from the right atrium toward the left atrium with the consequent mixture of the venous and arterial blood in the peripheral circulation.
    Then the blood will pass toward the left ventricle and from the left ventricle toward the aorta. Through the patent ductus arteriosus the blood will enter the lungs to be further oxygenated. This is one of the few congenital malformations where keeping the ductus arteriosus patent is essential and where experimentally prostaglandins are being used in this regard.
    If the ductus arteriosus is closed the circulation will be conveyed to the bronchial arteries with a consequent increase in the patient's cyanosis.
    In many cases thrombosis can occur in the cavity of the right ventricle.

CLINICAL PICTURE

    Cyanosis will start immediately after birth and usually is very significant.
    The larger the ductus arteriosus the better the clinical picture and the less marked the cyanosis.
    These infants will present marked dyspnea mainly during feeding.
    The physical examination will show a patient with marked cyanosis and in most of the cases, clubbing and polycythemia.
    The most striking findings during auscultation will depend on the competence or incompetence of the tricuspid valve.
    Typically the second sound is single as a consequence of a non-functioning pulmonary artery valve.

ELECTROCARDIOGRAM

    The electrocardiogram does not differ significantly from the one of marked pulmonary valve stenosis and marked right axis deviation on the frontal plane is the rule.
    Usually R or qR waves will be present in Lead VI. R wave may be more than 10 mm with marked T wave inversion in the precordial leads in correlation with the right ventricular systolic overload. Typical P pulmonale will be seen and at times abnormal AV conduction.

ROENTGENOGRAM

    Moderate enlargement of the cardiac silhouette is seen mainly due to the enlargement of the right atrium. If tricuspid valve is incompetent, right ventricular hypertrophy will also be present. There is no pulmonary artery arch, and there is almost always moderate enlargement of the ascending aorta.
    Many times in place of the pulmonary artery arch the left atrium may produce a similar convexity.
    Marked diminution of the pulmonary artery vasculature is almost the rule.

CARDIAC CATHETERIZATION AND ANGIOCARDIOGRAPHY

    Cardiac catheterization is important for evaluation of the hemodynamic condition, final diagnosis and study of associated malformations.
    The right cardiac catheterization will show typically giant a waves. The most typical finding in these patients is the impossibility of progession from the right ventricle toward the pulmonary artery. Marked elevation of the systolic pressure will be seen in the right ventricle with progressive elevation of the right ventricular and diastolic pressure in relation with the degree of right ventricular insufficiency.
    Oxygen saturation in the right ventricle is typically lower than in the other three main chambers of the heart.
    From the right atrium the catheter will tend to pass toward the left atrium and then is easy to get into the left ventricle.
    Angiocardiography will demonstrate the atresia of the pulmonary valve and will show the status of the right ventricle and eventually the significance of any tricuspid incompetence.
    Injection of contrast in the right or left atrium will contrast the left ventricle and the ascending aorta and through the patent ductus arteriosus, both the right and left main branches of the pulmonary artery may be visualized.
    Angiocardiography is essential in the detection of associated malformations which are so common in this disease.

THE MAIN DIFFERENTIAL DIAGNOSIS

    Should be done with tricuspid atresia and pulmonary valve stenosis with intact ventricular septum.

THE MEDICAL TREATMENT

    Should be elected toward the treatment and prevention of the complications of the polycythemia and marked cyanosis.
    Bacterial endocarditis should be prevented. Injections, in general, should receive special consideration to avoid brain abscess due to the right to left shunting.
    Otherwise, surgery is only palliative and anastomosis between the subdavian and pulmonary artery or similar procedures can be attempted.