Atrial septal defect (ASD) can be described as congenital heart defect wherein the wall that isolates the top heart chambers (atria) doesn't close entirely. Congenital usually means the defect occurs at childbirth.
In fetal blood circulation, there exists an opening between the two atria (the upper chambers of the heart) permitting blood to bypass the respiratory system. This opening generally closes around the time the baby is born.

If the ASD is chronic, blood continuously flow from the left to the right atria. This is known as a shunt. If excessive blood goes towards the right side of the heart, pressures in the lungs build-up. The shunt can be reversed so that blood moves from right to left. Small atrial septal defects typically cause few complications and could be found much later. Many troubles can happen if the shunt is big, nevertheless. In advanced and extreme cases with large shunts the increased pressure on the right side of the heart would result in reversal of blood flow (now from right to left). This usually results in major shortness of breath.
Through normal growth and development of the fetal heart, it has an opening up in the wall (septum) isolating the left and right upper chambers of the heart. Normally, the opening closes before birth, but if it doesn't, the child is given birth to with a hole in between the left and right atria. This irregular opening is called an atrial septal defect and causes blood from the left atrium to flow (or "shunt") across the hole into the right atrium.

Different types of atrial septal defects happen, and they are classified based on where in the separating wall they can be found. Probably the most commonly found atrial septal defect, called secundum atrial septal defect, occur in the middle of the atrial septum and makes up about 70 percent of all atrial septal defects.

Unusual openings also form in the upper part of the atrial septum (called sinus venosus ASD) where the superior vena cava and right atrium join, and lower parts of the atrial septum (called primum ASD). A sinus venosus ASD usually requires the right upper pulmonary vein, while a primum ASD mostly occurs together with an abnormality in the mitral valve and/or tricuspid valve, and causes some blood leakage (regurgitation) back via the valves.

Atrial septal defects can occur alone or in combination with other congenital heart issues, such as ventricular septal defect. They may be no more than a pinpoint or as large as the area where the entire septum needs to be positioned.
Factors

Abnormal openings in the atrial septum occur in the course of fetal development. These problems may go unseen if the opening is small and produces no abnormal symptoms. If the defect is big, oxygen-rich blood from the left atrium flows back to the right atrium and gets pumped back to the lung area again, triggering more work for the heart and lungs. The right atrium may get bigger or expand to hold the extra blood.

In some instances, an atrial septal defect enables blood clots from the body to enter the brain and create a stroke . Untreated atrial septal defect can lead to pulmonary hypertension , chest infection, Eisenmenger's syndrome, atrial fibrillation, atrial flutter, stroke, or right-sided heart failure.

Signs and symptoms

Anyone born with an atrial septal defect may have no signs and symptoms in child years, and the problem may go undetected into their adult years. Stunted growth may be a symptom of atrial septal defect. Different symptoms that might develop over time include:

breathlessness
fainting
abnormal heart beats or palpitations (abnormal heart beats that seem like fluttering in the chest)
inability to physical exercise without becoming over-tired
difficulty breathing with exercise or physical activity
Remedy
Twenty percent of atrial septal defects in kids correct themselves without having treatments by the time a child is 2 yrs older. When the opening will not close on its own, it must be repaired to counteract the pulmonary arteries from becoming thickened and blocked due to higher blood flow. If this problem (pulmonary vascular obstructive disease) remains neglected, it can certainly raise the risk of death by Twenty five %.