Atrial Septal Defect (ASD) Closure

Overview
The heart is divided into four separate chambers. The upper chambers, or atria, are divided by a wall called the atrial septum.


FIGURE 1: Anatomy of Normal Heart.

Atrial Septal Defect
Septal defect is a hole in the septum. A defect between the heart's two upper chambers (the atria) is called an atrial septal defect (ASD). Atrial septal defects are one of the most common heart defects, and are caused by incomplete growth of the septal wall during fetal development. When an atrial septal defect is present, blood flows through the hole, usually from the left atrium to the right atrium. This increases the blood volume in the right atrium, which causes more blood to be pumped to the lungs. Because it is receiving so much extra blood, the right side does more than normal share of work. This may cause you to feel tired, have difficulty in breathing or be sick more often with respiratory infections such as cold or pneumonia.

Long Term Effects
Under normal circumstances, the right side of the heart pumps blood low in oxygen saturation to the lungs and left side pumps blood high in oxygen saturation to the body. When ASDs occur, oxygenated and deoxygenated blood gets mixed together reducing efficiency of the hearts function.

The risks associated with ASDs is greater when the size of the defect is large (greater than 2cm). 
These may include:

Right heart enlargement (right heart failure)

Heart rhythm disturbances including atrial fibrillation or atrial flutter:

Stroke

Pulmonary hypertension (high blood pressure in the arteries that supply the lungs). If pulmonary hypertension is severe, flow across the ASD (normally left to right) can reverse (become right to left). As a result, oxygen levels in the blood will decrease, leading to a condition known as Eisenmenger syndrome.

Leaking tricuspid and mitral valves as a result of the enlargement of the heart

Causes of ASDs
Congenital heart problems are caused by specific genetic defects, meaning it is a defect exists at time of birth. Stated another way, the defect is an abnormality, not a disease. The septum between the two atria of the heart did not develop normally before birth. What is known is that about 20 percent of ASDs that occur in infants close on their own in the first years of life.
Most congenital heart defects are likely due to maternal environmental factors combined with genetic predisposition and other medical conditions (Down’s syndrome, for example). These environmental factors include alcohol and street drugs, as well as diseases such as diabetes, lupus and rubella.  Sometimes a viral infection can cause heart defects to develop.

Diagnosis
Atrial Septal Defects (ASD) assessment and diagnosis may be done using:

• ECG – an electrocardiogram, a graph of the heart’s electrical activity (heartbeat)

• Chest X-ray – to evaluate the size of the heart and lungs

• Transthoracic echocardiography – an ultrasound image of the heart combined with measurements of blood flow to assess the heart’s structure and function

• Transesophageal echocardiography (TEE) – an ultrasound image obtained via the esophagus to provide a clearer image of the atria, more precisely define the defect’s size and shape and to evaluate the health of the heart valves. Using TEE, the physician can easily distinguish a PFO from other types of ASD.

• Right heart catheterisation – a procedure during which a small thin tube (catheter) is inserted into the heart via the peripheral vein. Pressures are measured in each chamber as well as the oxygen saturations (how much oxygen is present in the blood). The latter measurements determine how much blood is flowing across the defect by measuring how much the oxygen level increases beyond the site of the defect.

Treatment
Upon confirmation of ASD, treatment depends on the type and size of the defect, its effect on the heart, and whether of any other related conditions, such as pulmonary hypertension, valve disease or coronary artery disease are present. Your cardiologists is the best person to determine what type of repair is warranted. ASDs can be treated non-surgically (preferred method of treat for most secundum ASDs) however surgery might be needed to repair other types of ASDs.. Surgical repair may be needed for large secundum atrial septal defects. Surgical repair is usually performed using a tissue patch, preferably from the patient’s own pericardium. Some secundum ASDs can be surgically closed with sutures alone. 
Prior to the introduction of non-surgical approach,  ASDs were only treated surgically, regardless of the type of defect. Here at Mercy Angiography Unit we use AMPLATZER Septal Occluder to treat the septal defect.

FIGURE 3: AMPLATZER Septal Occluder

AMPLATZER® Septal Occluder, is made made from an alloy of nickel and titanium. Each Occluder is made of a Nitinol wire mesh that is shaped into two flat discs and a middle, or "waist" to fit the defect size, with polyester fabric inserts designed to help close the hole and provide a foundation for growth of tissue over the occluder after placement.

The procedure takes place in a special room called a catheterisation laboratory ( cath lab ) where many minimally invasive, non-surgical procedures such as coronary angiogram/angioplasty are performed. The Septal Occluder is delivered into the heart via a small plastic tube called catheter, by an interventional cardiologist to access the heart and place the occluder using x-ray and echocardiography. The interventional cardiologists then deploys the occluder to expand each disc on either side of the defect, closing off the hole.

Post Procedure
After recovery from anesthesia and with adequate bed rest you should be able to sit up and move around. If there are no complications, you will be allowed to go home after staying overnight in the hospital. Because the procedure is less invasive than open-heart surgery, your recovery should be easier. You may have an adhesive bandage where the catheter was inserted. You also may have a minor sore throat if an imaging probe (Transesophageal echo probe) was used. Before you leave the hospital, the cardiologists will give you guidelines for activities and medications. Your doctor should tell you when you can resume normal daily activities. Medications will be an important part of your treatment. Your doctor will prescribe drugs that you should take at home. The drugs should prevent blood clots from forming.Notify your doctor if your medications cause unpleasant reactions; but do not stop taking them unless instructed to do so.

Video Demonstration

 ASD closure device deployment: Radiographic illustration 
 The Amplatzer Septal Occluder 
 Septal Occluder Placement 

Associated Documents

 Pre-visit instructions for Atrial Septal Defect (ASD) closures
 Amplatzer Septal Occluder: A Patient's Guide