The symptoms of atrial septal defect are:

• Fatigue
• Shortness of breath
• Stroke (caused by an interrupted blood supply to the brain)
• Swelling of the legs and feet
• Swelling of the stomach
• Heart palpitations (skipped beats or extra beats)
• Heart murmur (a whooshing sound heard by the doctor through a stethoscope)

Atrial Septal Defects can be diagnosed in the following ways:

1. Physical examination: The doctor may check for various symptoms of a septal defect. A heart murmur may indicate a heart defect.
2. Echocardiogram: Sound waves are used to check the heart chambers, measure the pumping strength of the chambers, check the valves of the heart, and also look for signs of heart defects.
3. Electrocardiogram (ECG): This test helps in measuring the electrical activity of the heart and identification of heart rhythm problems.
4. Chest x-ray: The condition of the heart and lungs can be evaluated using a chest x-ray.
5. CT scan and MRI scan: These are imaging tests done to obtain a clear image of the heart and detect any heart abnormalities.
6. Cardiac catheterization: A catheter (thin, flexible tube) is inserted into a blood vessel in the groin or arm region and guided to the heart. It helps the doctor to diagnose any congenital heart defects, check the function of the heart valves, check how well the heart is pumping blood, and measure the pressure of blood in the lungs.
   

For many patients, the atrial septal defect may close on its own during childhood. For septal defects that do not close, treatment may be required.
A few medicines may be recommended to reduce the risk of complications after the procedure. These medications may include anticoagulants (to reduce the risk of blood clots) and beta-blockers (to keep the heartbeat regular).
A medium to large atrial septal defect can be corrected using any one of the following surgical methods:

Cardiac catheterization:

• A thin flexible tube, known as a catheter, is inserted by the doctor into the groin or arm region.
• This catheter is guided to the heart by using imaging techniques.
• The doctor places a plug or mesh patch to close the hole.
• The heart tissue starts growing around the mesh to seal the hole permanently.
• This procedure is performed to repair secundum type of atrial septal defect.
• Larger secundum atrial septal defects may however require open-heart surgery.

Open-heart surgery:

• This type of surgery is performed under general anesthesia, that is, the patient is put to sleep during the surgery.
• The surgeon makes an incision or cut in the chest region.
• The surgeon will use patches to close the hole in the septum.
• This procedure is used to treat primum, coronary sinus, and sinus venosus atrial defects.

Other types of surgeries:

• Atrial septal defects can also be treated by a minimally-invasive surgery, in which the procedure can be performed by making a few small incisions, instead of a large incision.
• The procedure can also be performed as a robot-assisted surgical procedure, where the procedure is performed by robotic arms which are controlled by the surgeon using a monitor.

The complications associated with an atrial septal defect surgery are:

• Bleeding
• Infection
• Blood clot formation
• Allergy to anesthetic agents
• Heart attack
• Pulmonary hypertension 
• Eisenmenger syndrome (permanent lung damage caused due to pulmonary hypertension)
• Kidney failure
• Lung failure
• Irregular heart rhythm
• Damage to the artery from the catheter
• Stroke
• Death

The patient is usually discharged on the next day of a cardiac catheterization surgery.
The patient can go to work one week after the cardiac catheterization surgery.
After open-heart surgery, the patient stays in the hospital for three to seven days. 
It is normal to experience some soreness after the procedure. The doctor may recommend pain-relieving medications for the same.
The doctor prescribes antibiotics to be taken for six months after the atrial septal defect surgery to prevent endocarditis (heart infection).
Complete recovery of the patient may take many weeks.

Contact your doctor right away if you notice any of the following after the surgery:

• Bleeding
• Cyanosis (bluish color of the skin, tongue, lips, and nailbeds)
• Breathing difficulties
• Confusion
• Pain in the chest
• Fever
• Inability to have a bowel movement
• Inability to urinate
• Leg pain, redness, or swelling
• Decrease in activity seen in children
• Decrease in appetite
• Pus drainage or swelling in the incision area
• Echocardiograms are recommended after discharge from the hospital as and when recommended by the doctor.

In cases of small, simple atrial defects that get closed on their own during childhood, an occasional follow-up appointment with the doctor is recommended.
In the case of adults who undergo surgery for atrial septal defect repair, life-long monitoring is required.