Atrial septal defect

Atrial septal defects (ASDs) are communications in the wall between the right and left atrium called atrial septum. They are classified according to their location relative to the fossa ovalis. Interatrial communications in the region of the fossa ovalis may represent either an ostium secundum ASD or a patent foramen ovale. Defects anterior to the fossa ovalis are ostium primum defects and are often associated with anomalies of mitral valve.

Superior Vena Cava
Aorta
Pulmonary VeinsPulmonary ArteryPulmonary Veins
Left Atrium
Right Atrium
Left Ventricle
Right Ventricle
Inferior Vena Cava

-Fig. 4.1
Atrial septal defect. The indicates the blood flow from left to right atrium-.

Those posterior and superior to the fossa ovalis are sinus venosus defects, and frequently associated with anomalous connection of the right pulmonary veins. Finally, interatrial communications at the site of the coronary sinus ostium are often associated with an unroofed coronary sinus and left atrial connection of a persistent left superior vena cava.
In this setting there is an amount of blood, which depends on the size of the defect, that flows through the defect to lungs which receive more blood than normal.
Ostium secundum ASDs represent 6-10% of all cardiac anomalies and are more frequent in females than males by about 2:1. Generally the ASD does not produce symptoms during infancy because of the compliance of the right cavities of the heart and the lungs. Only some children with large ASD present exercise intolerance. Although ASD is a congenital malformation, present since birth, it is usually discovered later because heart murmurs are note striking. Cardiac catheterization is not necessary for  the diagnosis.  Frequently neonates present a communication of a couple of millimeter between the atria that heals over spontaneously in few weeks. Sometimes little ASD (4-5 mm) can heal over spontaneously in few months. An ASD with evident sizes should be closed during preschool years. The closing is made by cardiac surgery. Right atrium is opened and the ASD closed with a direct suture or if it is large with a patch of synthetic material. The results are excellent and the child is to be considered cured
Transcatheter techniques and devices for ASDs closure have been available for several years. During the time devices have undergone several evolutionary changes in an attempt to improve the design, the technique and the safety of devices delivery. By the end of the 90s Amplatzer Septal Occluder became the device of for the treatment of ostium secundum ASDs. Amplatzer Septal Occluder is a round self expanding, self-centering and repositionable double-disc device constructed of a dense mesh of Nitinol wires. The two discs are connected by a short cylindrical waist. The device is connected to a delivery cable by a microscrew  that avoid accidental detachment.

Patent Foramen Ovale
The foramen ovale is a normal interatrial communication present during fetal life; its functional closure occurs after birth as pressure in the left atrium exceeds that in the right atrium. The valve of the fossa ovalis is then pressed against the limbus and forms a competent closure which will develop during the first year of life, in a permanent anatomic seal and an imperforate atrial septum. In about 25% of people, however, this process of closure does not occur, and a potential interatrial channel persists through which blood or air may shunt whenever pressure in the right atrium exceeds that in the left atrium.


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