**General Review of Atrial Septal Defects**

**1**

 *USA* 

P. Syamasundar Rao

**Atrial Septal Defect – A Review** 

*University of Texas at Houston Medical School, Houston, Texas,* 

Defects in the atrial septum cause left to right shunt because the left atrial pressure is higher than that in the right atrium. This causes volume overloading of the right ventricle. While this is generally well tolerated in infancy and childhood, development of exercise intolerance and arrhythmias in later childhood and adolescence, and the risk for development of pulmonary vascular obstructive disease in adulthood make these defects important. There are four major types of atrial septal defects (ASDs) and these include ostium secundum, ostium primum, sinus venosus and coronary sinus defects. The clinical features are essentially similar and I will present detailed discussion of ostium secundum

Persistent patency of the foramen ovale in nearly one third of normal population makes the patent foramen ovale (PFO) a normal variant, although these become important in the presence of other structural abnormalities of the heart and when they become the seat of right to left shunt causing paradoxical embolism resulting in stroke/transient ischemic attacks or other problems, such as migraine, Caisson's disease and platypnea-orthodexia syndrome. The

Atrial septal defects constitute 8% to 13% of all congenital heart defects (CHDs). Pathologically, there is deficiency of the septal tissue in the region of fossa ovalis. These may be small to large. Most of the time, these are single defects, although, occasionally multiple defects and fenestrated defects can also be seen. Because of left-to-right shunting across the defects, the right atrium and right ventricle are dilated and somewhat hypertrophied. Similarly, main and branch pulmonary arteries are also dilated. Pulmonary vascular

Mitral valve abnormalities, including mitral valve prolapse and mitral insufficiency may be seen in some patients. It is not clear whether these abnormalities are to due to right ventricular volume overloading or intrinsic abnormality of the mitral valve. Pulmonary valvar pressure gradients are seen frequently and are thought to be related to increased flow and/or differences in expression of kinetic and potential energies in the right ventricle and pulmonary artery (Rao et al 1973); however, true pulmonary stenosis is present in only 5%

of ASD patients. Persistent left superior vena cava may be present in 10% patients.

and primum ASDs followed by brief presentation of the other two defects.

issues related these types of PFOs will be briefed at the conclusion of this chapter.

**1. Introduction** 

**2. Secundum atrial septal defect** 

obstructive changes are not usually seen until adulthood.
