Transposition of the great arteries

Transposition of the great arteries is a lethal and relatively frequent malformation, accounting for 5% to 7% of all congenital cardiac malformations. Without treatment, about 30% of these infants die in the first week of life, 50% within the first month, 70% within 6 months, and 90% within the first year. Today, aggressive medical and surgical interventions in the neonate can provide >90% early and midterm survival and, for many patients, the prospect of a vigorous adolescent and adult life. the aorta arises from a morphologically right ventricle, and the pulmonary from a morphologically left ventricle. The consequence is that desaturated venous blood of right ventricle is pumped in aorta and arteriosus blood of left ventricle is pumped in pulmonary artery.

-Fig. 6.5
Transposition of the Great Arteries. Venous blood (empty arrow ) is pumped in aorta by the right ventricle; oxygenated blood (full arrow) is pumped in pulmonary artery by the left ventricle. Both circulation can mixed only in the atria because of the patent foramen ovale -.

The pulmonary and systemic circulation mix only because of the foramen ovale. But is enough to maintain the newborn alive only for few days.

Children with TGA and VSD have better mixing between the two circulation. Transposition is suspected because of a persistent severe cyanosis. Echocardiography must be performed immediately and in case of confirmed diagnosis a cardiac catheterization must be done within first hours of life. The cardiac catheterization is a therapeutic procedure because with a particular type of catheter it is possible to enlarge the foramen ovale and create a larger communication between the atria (fig. 6.5) and obtain a better oxygenation of the neonate. This procedure is called Atrial septostomy of Rashkind. It allows to save the neonate's life and prepare safely the surgery. This is performed within the first 7-10 days of life and consist in reconnecting aorta with left ventricle and pulmonary artery with right ventricle. This intervention is called arterial switch. Nowadays this intervention has a 5% mortality and results are excellent. The arterial switch has substituted the Mustard and Senning intervention which consisted in an inversion of the atrial blood flow without modification of the anatomy.

Children with TGA and VSD may not undergo surgery in neonatal period but after few months. In patient with TGA, VSD and severe pulmonary stenosis the Rastelli surgery is performed: it consist in the creation of a tunnel through the VSD which act as left ventricle outflow in aorta. The right ventricle is connected to the pulmonary artery with a conduit.

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