An atrial septum is a muscular wall that separates the upper chambers of the heart called atria. An ASD is a common congenital heart disease where the septum is not formed properly producing a left-to-right shunt, which leads to mixing of oxygenated and deoxygenated blood. This causes pulmonary hypertension and right heart enlargement.
What are the treatment options for ASD?
Small atrial defects do not need any treatment and close on its own. Even in adulthood small ASDs may remain asymptomatic. Some large defects that persists in adulthood may become symptomatic and need closure. The ASDs can be closed by:
Percutaneous closure using a device
Closure through open heart surgery
Percutaneous device closure is the preferred treatment for certain defects type.
What is Percutaneous Closure of Atrial Septal Defect (ASD)?
A noninvasive procedure known as percutaneous transcatheter approach is considered depending on the size and severity of the defect. Moderate to large-sized ASD along with pulmonary hypertension requires to be closed. The procedure is performed by inserting a special closure device either folded or attached to a catheter into the vein of the leg and is advanced to the heart through the defect, which closes the hole by a special mechanism.
Are there risks associated with the procedure?
The success rate of the procedure is about 95%. But the risks involved, and their estimated incidence of occurrence include:
Device dislodgement leading to emergency heart surgery: 1%
Device erosion (device eroding through the heart walls): 0.3%
Death: less than 1% usually due to perforation of the heart chamber
Dislodgement of clot or air bubbles to the brain leading to other organs: less than 1%
Arrhythmia: 1 to 2%
Allergic dye reaction
Injury to the artery/vein/nerves in the groin
Perforation of the oesophagus
Allergic reaction to the nickel component of the device
Patients with small ASD may not develop any complications, but large-sized defects may lead to serious complications which demands surgery and prolonged hospitalization.
What is the pre-procedure work-up?
Pre-operative tests to assess the general health of the patient include:
A detailed diagnosis of the defect should be performed which includes transthoracic and transoesophageal echocardiogram used to assess the size, location and the suitability of the procedure.
How should I prepare for the procedure?
Patients wearing dentures, glasses or a hearing assist device can plan to wear them during the procedure.
Patient will be instructed about dietary restriction to be followed before the procedure.
Are there any specific instructions about medications?
The healthcare provider may ask you to stop certain medications, such as warfarin or other blood thinners.
If diabetic, consult the physician about how the medication needs to be adjusted.
Provide information about specific allergies regarding iodine, shellfish, X-ray dye, latex or rubber products etc.
What happens during the procedure?
The patient might be asked to have a shower before the procedure.
The patient is asked to wear a hospital gown and lie on an X-ray table where an X-ray camera will move over the chest during the procedure.
Arrangements for intravenous administration of medications or fluids during the procedure will be made.
The site where the catheter will be inserted is cleaned and sterile drapes were used to cover the site to prevent the infection.
Electrodes will be placed on the chest and are attached to an electrocardiograph monitor (ECG).
A sedative might be given to relax, and a local anesthetic is given to numb the site of catheter introduction.
A plastic sheath will be inserted in the groin, through which a catheter is inserted and threaded to the heart.
The physician may also inject a dye which may make you feel hot or flushed for several seconds. Inform the doctor if there is an allergic reaction like itching or tightness in throat, nausea and chest discomfort.
The X-ray cameras are used to obtain the measurements of pressures and oxygen content in the chambers.
The appropriate size and the location of the closure might be visualized using a small catheter connected with an ultrasound transducer.
A special catheter is used to advance the device into the heart and through the defect.
The device is slowly pushed out of the catheter allowing each side of the device to open and close each side of the hole in the septum.
The proper position of the device is ensured and is released from the catheter.
It may take 1-2 hours for the procedure, but preparations must be made to spend about 5-9 hours in the hospital.
The patient should be accompanied by someone who can drive him home, as the patient will not be allowed to drive on the same day.
What care should be taken after the procedure?
The catheter and the imaging probe are removed after the completion of the procedure.
Pressure on the incision site or occasionally a small suture is used to close the vein.
Bed rest is advised for several hours to prevent bleeding, but call the doctor if you notice any bleeding.
You might be advised to drink plenty of water to wash out the contrast material from the body.
Your heart rate and rhythm are monitored; you may be asked to stay overnight in the hospital.
Medications, such as aspirin are prescribed to prevent blood clots.
Strenuous activity and heavy lifting should be avoided for at least six months.
Antibiotic prophylaxis is required for at least six months or lifelong to prevent endocarditis, as per doctor’s advice.
Heart consists of four chambers, of which upper two chambers are called as atria and lower two chambers are called as ventricles. Atrial septal defect (ASD) is a type of congenital heart defect, in which there is an abnormal opening or a hole in interatrial septum (dividing wall between two atria). This opening allows the passage of pulmonary venous blood from left atrium to right atrium, causing mixing of oxygenated and deoxygenated blood in right atrium and increasing the flow of blood to lungs. The increased blood flow may increase the workload of the lungs, and eventually cause damage to heart and lungs.
What causes an ASD?
The exact cause of ASD remains unclear. However, it is believed that during fetal developmental stages, a hole is present in the interatrial septum, which gradually closes before birth or during infancy. If the hole persists, it is called an atrial septal defect.
Types of Atrial Septal Defect or ASD?
Based on the location and development of ASD, it is classified into four types:
Ostium secundum ASD: It occurs in the middle part of the interatrial septum. This is the most common type of ASD and accounts for 75% of all atrial septal defects. This type of ASD is commonly detected in adults in their third and fourth decades of life. Some can be detected in children when an abnormal heart sound is detected at the time of a routine health check or vaccination visit.
Ostium primum ASD (20%): It occurs in the lower part of the interatrial septum, adjacent to atrioventricular (AV) valves. It usually occurs as a part of other congenital heart defects. This defect is usually detected in early life as this is associated with many complications.
Sinus venosis ASD (4%): It occurs in the upper part of the interatrial septum, near the veins that drain into the right and left atrium. This is usually identified in third and fourth decade adults.
Coronary sinus ASD (<1%): It occurs in the interatrial septum between the coronary sinus and the left atrium. This is very uncommon and patients are asymptomatic.
Signs and symptoms
Usually after birth, babies who have ASD may not show any associated signs and symptoms. But, symptoms may appear during adulthood around the age of 30 years. Most of them don’t have any symptoms even after many years.
Some of the common symptoms associated with ASD are:
Heart murmur, a swishing sound that can be heard through a stethoscope
Most ASDs are diagnosed incidentally during regular heath check-ups. If a heart murmur is heard during auscultation, you may be advised to undergo further tests to confirm the diagnosis of ASD:
Echocardiogram: It is a specific diagnostic test for ASD, and provides a detailed image of the heart and blood flow through its chambers. The echocardiogram may show the blood flow through the interatrial septum and the size of defect in the septum.
Chest X-ray: It helps to identify enlarged heart and lung changes.
Cardiac catheterization: A thin, flexible tube called catheter is inserted into the blood vessel at the groin or arm and is guided to the heart. This test is helpful to determine the function of heart and its valves, and to measure the blood pressure in the lungs.
Magnetic resonance imaging (MRI): It uses magnetic and radio waves to create three dimensional images of the heart and other organs. This test is recommended if the ASD is not clearly diagnosed with echocardiogram.
Computerized tomography (CT) scan: It uses a series of X-rays to create detailed images of heart; mainly used if echocardiogram doesn’t help to diagnose ASD clearly.
Treatment of ASD depends on the age at diagnosis and the size, location and severity of the defect. Small ASDs might not need any treatment because it closes on its own. The doctor may recommend surgery if the atrial septal defect is large, even with fewer symptoms to prevent problems later in life. Treatment of ASD includes medications and surgery.
Medications usually do not help in closing the hole, but reduces the signs and symptoms associated with ASD and risks of complications after surgery. Drugs such as beta blockers (to maintain regular heartbeat) and anticoagulants (to prevent the formation of blood clots) are used.
Surgery includes cardiac catheterization and open-heart surgery.
Device closure of ASD
In cardiac catheterization, the doctor closes the hole in the septum with a mesh patch or a plug in the defect place using a catheter. The heart tissue then grows around the mesh slowly, sealing the hole permanently. This procedure is mainly performed to repair only the secundum type of atrial septal defects. Defects not amenable to closure with device may need open-heart surgery.
In open-heart surgery, the defect may be closed with stitches or a special patch. This procedure is done under general anesthesia, mainly for repairing primum, sinus venosus and coronary sinus atrial septal defects.
Prevention of ASD:
Atrial septal defects cannot be prevented, but following certain measures during pregnancy might be beneficial to prevent the risk of ASD, such as:
Immunity test for rubella: If the person is not immune to rubella, it is necessary to get vaccinated.
Monitoring current health conditions and medications use: Pre-existing health conditions and usage of any medications should be carefully monitored during pregnancy to prevent the risk of ASD.
Reviewing family medical history: If a person has a family history of congenital defects, it is advised to visit a genetic counsellor before becoming pregnant to know the risks of atrial septal defects.