Patent Ductus Arteriosus (PDA)
The 'ductus arteriosus' is a very important structure of the heart in an unborn baby’s life. It is through the ductus that blood circulates to the lower half of the baby. Usually the ductus arteriosus closes spontaneously after birth due to the effect of oxygen in the air that the baby breathes in. Closure of the ductus can take anywhere between 24-72 hours.
In some babies the ductus does not close and can remain open resulting in Patent ductus arteriosus (PDA). If the PDA is small it may be of little consequence and sometimes can even be left alone. If, however, it is sizable it can lead to increased blood flow to the lungs which can cause breathlessness, poor feeding, sweating, poor weight gain etc. in the baby. If left untreated in the long-term it can give rise to high pressure in the lungs (pulmonary hypertension).
Illustration of Patent ductus arteriosus (PDA)
PDA is ommonly found in premature babies and also in babies of mothers who have had Rubella infection.
The timing of treatment depends on the size of the PDA. If the PDA is large it will need early treatment. If small, it can be observed till 9-12 months of age giving time for spontaneous closure where it closes on its own. PDA usually does not close spontaneously beyond the age of 1 year.
Treatment options for PDA are:
(a) Medical: This is possible in preterm babies where certain medicines like brufen or indomethacin can be given to try and close the PDA. This has to be undertaken under the careful supervision of a children's doctor in the hospital.
Button Device used for Keyhole surgery
b) Keyhole procedure: Here the PDA is closed using a button device. The device is introduced from the leg and inserted without open surgery across the PDA to close it. This technique may not be suitable for very large PDAs in small babies.
(c) Surgery: This involves opening the chest and cutting and tying the PDA to eliminate it. This usually involves a longer hospital stay than keyhole treatment.
Following successful elimination of the PDA the heart is essentially normal and the patient is expected to have a normal childhood and adult life.
PDA closed with the button device and by tying off
Patent Ductus Arteriosus Stenting (Ductal Stenting)
Some children with congenital heart defects do not have a source of blood supply to the lungs. In these patients, there is often no direct connection between the heart and lung arteries (pulmonary atresia) or there is very little blood flowing to the lungs (critical pulmonary stenosis). These babies are kept alive by the blood that flows through the patent arterial duct (also known as patent ductus arteriosus or PDA). The PDA is destined to close in the first few days to weeks after birth but can be kept open temporarily by a medicine known as prostaglandin E1. In the past, these patients would undergo the blalock-taussig (BT) shunt operation. In the last decade, however, cardiologists have increasingly preferred an alternative procedure that can be done in the cath lab. In this procedure, a stent is positioned in the ductus arteriosus before it can close completely and dilated with a balloon to fix it in position. The stent used is 3-4 mm in diameter and is the same as is used for coronary angioplasty in adults.
What is the purpose of Ductal Stenting?
This procedure is aimed at placing a stent through the ductus arteriosus in order to keep it open for the next several months. After stent placement, the medication that is often used to keep it open temporarily (prostaglandin) can be stopped. The stenting procedure allows the baby to grow until surgery can be undertaken with a higher degree of safety.
What are the challenges and complications with the procedure?
The placement of a stent across the PDA in a small baby requires a very high level of precision and a number of potential problems can occur despite the best of precautions. They include:
Problems from incorrect positioning. This may necessitate an emergency shunt surgery.
Blockage of the blood vessel used to access the duct. Newborns in particular have small arteries and veins that can get blocked during catheterization.
Clot formation in the duct during the procedure; is a life-threatening procedure.
Overflooding of the lungs after the procedure. This is particularly common in small newborns. For this reason, these babies will need close observation in ICU for variable periods of time.
This procedure requires the attention of a dedicated team of experts consisting of a pediatric cardiologist, intensive care doctors, anesthesiologists and dedicated nursing and support staff.
What are the specific precautions required during follow-up?
Typically, after a successful procedure, these babies are discharged in about 5-7 days. Aspirin or an equivalent medication needs to be administered daily to keep the stent open and prevent clot formation. Regular check-ups and measurement of oxygen saturation levels are needed as the child gains weight. The oxygen saturation levels typically come down as the child outgrows the stent. At a suitable time, a decision is made about the child getting surgery.