Developmental disorders

III./1.5.: Ductus Botalli persistens (patent ductus arteriosus)

The most frequent developmental disorder, (occurring in 9:10 000 neonates). The Botallo's duct (ductus arteriosus) has an important function in fetal life. Since the lungs are not functional before birth, this vessel connects the two main arteries of fetal circulation: pulmonary trunk and aorta. Normally, the duct gets obliterated after birth, Patency of the duct (ductus Botalli persistens) may lead to circulatory disorder, as described for VSD, first involving hypertrophy and dilation of right ventricle due to overloading, and then leading to cyanosis with reversal of blood flow, owing to elevated pressure in the lung.

III./1.6.: Tetralogy of Fallot

The most complex of all disorders of cardiac development, involving simultaneous occurrence of four defects: 1. pulmonary stenosis or atresia, 2. ventricular septal defect, 3. dextroposition (rightward displacement) of the aorta, 4. hypertrophy of right ventricle. Incidence: 5-9: 10 000 neonates. If associated with atrial septal defect, the condition is termed pentalogy of Fallot.

The predominant defect of tetralogy is stenosis or atresia of the pulmonary trunk. As a secondary consequence, the right ventricle works harder and hypertrophies due to its limited outflow. Robust stenosis leads to a right-to-left shunt and subsequently to serious cyanosis, dyspnea and fits (bouts) of hypoxia . Pulmonary stenosis also underlies dextroposition of the aorta, due to malformation of the embryonic truncus arteriosus. This disorder also involves defective closure of the ventricular septum under the aorta, as a result of which the aorta 'straddles' the septum over both ventricles (overriding aorta).