PATENT DUCTUS ARTERIOSUS (PDA)

 

What is Patent Ductus Arteriosus (PDA)?
Normal anatomy of the heart: The normal heart consists of 4 chambers - the right & left atrium (These are the chambers that receive the blood - the right atrium receives impure blood from the rest of the body and left atrium receives pure blood from the lungs.) and the right & left ventricles (These are the chambers that pump the blood from the heart – right ventricle pumps the impure blood to the lungs via the pulmonary artery and left ventricle pumps the pure blood to the rest of the body via another artery called as the aorta).

To understand what is PDA, one has to first understand the circulatory system in the baby while in the mother's womb. While the baby is in the uterus, it does not breathe. Hence, the lungs do not require the blood from the right ventricle. Thus, nature provides a "bypass"- a small blood vessel called DUCTUS ARTERIOSUS that connects the pulmonary artery directly to the aorta. Thus blood that enters the pulmonary artery bypasses the lungs and goes to the aorta to supply blood to other parts of the body.

At birth, when the child taken the first breath, the lungs begin to function. Thus, now the blood from the right ventricle goes to the lungs to get oxygenated and the bypass or DUCTUS ARTERIOSUS closes. When the ductus does not close and remains open, then a condition called as Patent Ductus Arteriosus or PDA develops.

What happens if a child has PDA?
If the ductus arteriosus remains open, shunting of blood takes place as in the fetal life but now in the opposite direction. Soon after birth, the pressure in aorta rises. So blood flows from the aorta (high pressure area) to the pulmonary artery (low pressure area). As a result, more blood flows into the lung than it normally does. This extra blood flow to the lungs can cause frequent chest infections. The blood vessels in the lung due to exposure to constant high lung blood flow become hard and thick leading to pulmonary hypertension (high pulmonary blood pressure) and subsequent heart failure.
If the PDA is left untreated, due to heart failure the child will not grow normally and is not able to feed adequately. If the pulmonary hypertension becomes severe it will lead to irreversible lung and heart damage - a condition called as EISENMENGER SYNDROME.

How is PDA diagnosed?
On examination, a child with PDA will have a soft thrill on the chest like a cat purring due to forceful blood flow across PDA. Echocardiography is diagnostic.

Should PDA always be closed?
When PDA is the single heart defect it needs to be closed.
However in presence of other heart disease where PDA is the only route of blood flow into the lungs or the rest of the body (DUCT DEPENDENT CIRCULATION) PDA should be kept patent till repair of the associated condition is performed. A medicine called prostaglandin is then used to keep the ductus open.

When should a PDA be closed?
In duct dependent circulation, it is closed at the time of repair of other heart defects.
In small children with severe heart failure, it should be closed immediately. In patients with no pulmonary hypertension, closure is not urgent but is required as early as possible to avoid risk of infection and pulmonary hypertension.

How is a PDA closed?
Surgical repair: PDA can be closed through an opening on the left side of the chest. The surgeon identifies the PDA and divides it into two after placing a clamp on both ends and tying them close.
Minimal interventional procedure: It is done using long instruments passed through small puncture holes in the chest and clipping the PDA.
Interventional cardiac catheterization with coil: Here a fine tube is threaded from the artery in the groin to the PDA and “coil” made of metal is placed inside the PDA. When the blood comes in contact with this coil, it clots and blocks the PDA.
Indomethacin: In preterm babies, the PDA may be closed using a medicine called Indomethacin. This works opposite to the prostaglandin. It blocks the prostaglandin and the ductus closes.
Depending on a particular patient, the treating physician can decide which is the best procedure for the closure of PDA for that patient.
After surgery, hospital stay is usually 2 to 7 days while with catheter based and minimal invasive methods, patient is discharged the next day.

Are there any complications while closure?
PDA closure is a safe procedure. When surgical closure is done there is a small risk of hoarseness of voice due to injury to a nerve that controls the vocal cords. Sometimes the duct may reopen following a procedure.

Are there any problems post repair?
Patients return to a normal and productive life post PDA closure. Late complications are rare and depend on the degree of pulmonary hypertension prior to surgery.

 

Last created on 6-05-2003
Last updated on 18-11-2006