What is Patent Ductus Arteriosus?
The ductus arteriosus is a blood vessel in the fetus that allows the blood from the placenta, which is rich in oxygen, to avoid the lungs while in the womb. When the baby takes its first breaths at birth, the lungs fill with air. This changes how blood flows through the body, allowing the right part of the heart to send blood to the lungs to get oxygen. Now, with more oxygen in the blood, this causes the ductus arteriosus to start closing. In healthy babies born full-term, this vessel is usually functionally closed within 12 to 24 hours after birth and permanently closed within 2 to 3 weeks.
In premature babies, the ductus arteriosus does not close quickly and may need medicine or surgery to close it and manage any side effects.
While in the womb, the ductus arteriosus is a normal structure that lets the blood from the right part of the heart bypass the lungs and go inside the descending aorta, the main artery that carries oxygen-rich blood from the heart to the rest of the body. After birth, this vessel typically closes within 1 to 2 days. Structurally, it is a part of the sixth aortic arch and connects the aorta close to the main artery to the lungs. The ductus arteriosus can be found just behind the aortic arch where it enters the front of the main lung artery. Although its shape is generally larger at the aortic end and narrower at the end connecting to the lung artery, the size and length can vary.
For surgeons, a good marker to identify the ductus arteriosus is the recurrent laryngeal nerve, which is a nerve in the neck that moves behind the ductus arteriosus and back up behind the aorta to the voice box (larynx). This nerve is often at risk of injury during surgery to close the ductus arteriosus.
The ductus arteriosus is categorized based on its visible shape and size features and it can be:
- Type A: Conical
- Type B: Window
- Type C: Tubular
- Type D: Complex
- Type E: Elongated
What Causes Patent Ductus Arteriosus?
Before a baby is born, the blood has a low level of oxygen and their lungs don’t function yet. The presence of chemical compounds called prostaglandins, which come from the placenta, keep a small opening in the heart called the ductus open. When a baby is born and starts to breathe, oxygen levels increase and that opening begins to close, as the prostaglandins start to get broken down.
Usually, this small hole, known as the ductus, closes within the first day of a baby’s life. This is due to the muscle of the ductus contracting, which is sensitive to things like oxygen and certain chemical compounds. While the functional closing happens in the first day, the physical closing can take a couple of weeks. During that time, the ductus turns into fibrous tissue, and by 2-3 weeks, most babies’ ductus will fully close. If the ductus hasn’t closed after 8 weeks, it needs to be closed. It’s extremely rare for this opening to close on its own after this time.
A patent ductus arteriosus (PDA) is when the ductus doesn’t close, and it’s rare in healthy newborns. However, the chance of having a PDA increases the earlier a baby is born. In fact, among extremely premature babies, especially those with breathing problems, up to 80% may have a PDA by the time they’re 3 days old. Some genetic conditions, as well as maternal diabetes, drug exposure during pregnancy, and birth at a high altitude, among other things, have been associated with a higher risk of PDA. Similarly, premature birth, breathing problems, bacterial infection, too much fluid, certain medications, and others can also contribute to PDA.
Risk Factors and Frequency for Patent Ductus Arteriosus
The ductus arteriosus, a blood vessel in a baby’s heart, usually closes within the first three days after birth in most healthy, full-term newborns. However, in premature babies, its closure is related to how early they were born. For instance, babies born after 30 weeks of pregnancy have a 90% chance of having their ductus arteriosus closed by the fourth day, and 98% of them have it closed by the time they leave the hospital.
Babies that are born weighing less than 1000 grams are at a higher risk for having an open ductus arteriosus. In fact, about 70% of them still have it open on the seventh day after birth. Also, in about 10% of other cases with heart problems present from birth, the ductus arteriosus may remain open.
- The ductus arteriosus usually closes within three days after birth in healthy, full-term newborns.
- In premature babies, the likelihood of the ductus arteriosus closing is linked to how early they were born.
- Babies born after 30 weeks into pregnancy have their ductus arteriosus closed by the fourth day in 90% of cases, and by the time they go home in 98% of cases.
- Babies born weighing less than 1000 grams have a higher risk for an open ductus arteriosus, with 70% still having it open a week after birth.
- In 10% of cases with other heart problems present from birth, the ductus arteriosus may remain open.
Signs and Symptoms of Patent Ductus Arteriosus
Patent ductus arteriosus (PDA) is a heart condition often identified by a continuous humming sound, known as a “machinery” murmur, audible with a stethoscope just below the collarbone, sometimes extending to the back. It can also present as a murmur that occurs during the whole of or just a part of the heartbeat. Affected infants often have a noticeable heartbeat that can be felt over the chest, a rapid heart rate, and strong pulses in the arms and legs due to the heart’s higher work rate. This condition is more noticeable in babies who weigh less than 1000 grams.
The pulse pressure, or the difference between the highest and lowest blood pressure during a heartbeat, is particularly wide (>30mmHg) in these cases. This is due to an increase in systolic (top number) blood pressure to compensate for decreased blood flow due to the PDA. Additionally, there is a lower diastolic (bottom number) blood pressure because of the runoff of blood through the PDA. This combined pressure change often leads to certain symptoms such as difficulty in breathing and low oxygen levels due to fluid buildup in the lungs. If the heart starts failing due to overwork, an enlarged liver (hepatomegaly) can be noticed.
Testing for Patent Ductus Arteriosus
An X-ray of the chest might show signs of fluid in the lungs and increased blood flow. An echocardiogram (or an ‘echo’), which is a type of ultrasound, can confirm the presence of a patent ductus arteriosus (PDA). This is a heart condition where an abnormal blood vessel causes the blood flow pattern in your heart to change. If the blood flow in the PDA flows from the left side of the heart to the right, it’s a typical PDA. If it flows from right to left it could be a sign of high blood pressure in the lungs. In this case, the PDA might be a result of this high blood pressure.
An echo can also show whether the PDA is causing problems with the heart’s function. If the PDA is large enough to cause problems, the echo might show an increase in the size of the left chamber of the heart. It can even detect a change in the blood flow in the abdominal aorta (the large blood vessel in the abdomen) at the level of the diaphragm, though this is technically challenging. Therefore, even if this change isn’t seen on the echo, it may still be present.
Changes in blood tests that assess kidney function, such as increased creatinine levels and reduced urine output, could also indicate problems caused by the PDA. These changes can show how much the kidneys have been affected by the PDA.
Treatment Options for Patent Ductus Arteriosus
In the case of babies born at or near full term, a condition called patent ductus arteriosus (PDA) whereby a blood vessel fails to close after birth, may resolve on its own. During this waiting period, doctors might try to manage symptoms and support the baby’s overall health with measures such as controlling fluid intake and using a technique known as peak end-expiratory pressure (PEEP) to handle any fluid accumulation in the lungs due to PDA. Though diuretics, which help remove excess fluid from the body, have been considered for treating PDA, their benefits are contentious. For very premature infants, these medications may bring about unwelcome side effects, like fluctuations in electrolyte levels (minerals required for normal body function) and may even delay PDA closure.
If the baby’s PDA is causing problems, medications such as indomethacin, ibuprofen, or acetaminophen/paracetamol might be considered. However, infants who weigh more than 1000 grams at birth generally don’t require drugs for PDA closure. Even though their PDA might take longer to close compared to those in full-term healthy infants, a majority will close naturally before the baby leaves the hospital.
If there are signs of PDA-related issues that don’t improve with conservative approaches such as PEEP or fluid restriction, doctors may resort to indomethacin, ibuprofen, or acetaminophen/paracetamol. Indomethacin and ibuprofen have similar effectiveness, but a second course of these drugs may carry risks for kidney function. Indomethacin, in particular, has been linked to potential gut problems. Nevertheless, research revealed no increase in severe gut complications in infants fed minimal amounts of milk during indomethacin treatment when compared to those who were not fed.
Acetaminophen/paracetamol is another potential option for managing PDA. Although early studies indicate it’s comparable to indomethacin and ibuprofen, it may not work as well in infants already treated with these drugs or in the smallest infants. Despite this, liver function should be monitored in babies given acetaminophen/paracetamol due to potential drug-induced liver damage.
In cases where PDA leads to severe symptoms or impacts the baby’s kidneys or breathing, and other treatments aren’t suitable or aren’t working, a surgical procedure to close the ductus, called ligation, can be carried out.
What else can Patent Ductus Arteriosus be?
When considering heart conditions, here are some that a doctor might look into:
- Coronary artery fistula
- Sinus of Valsalva aneurysm
- Aortopulmonary defect
- Persistent truncus arteriosus
- Pulmonary arteriovenous fistula
- Total anomalous pulmonary venous return
What to expect with Patent Ductus Arteriosus
For babies with only a PDA, or patent ductus arteriosus, the outlook is typically good. However, for premature infants, the prognosis depends on any additional health conditions they may have. Once the PDA is closed, most children can expect to live a normal lifespan. It’s rare for a PDA to close by itself.
With the use of a medicine called indomethacin, nearly 80-90% of infants will have successful closure of the PDA. In adults, surgery is always necessary to close the PDA, unless the patient has developed fixed pulmonary hypertension, which is a type of high blood pressure that affects the arteries in the lungs and the right side of the heart.
The potential complications, or morbidity, and risk of death, or mortality, are associated with the amount of blood flowing through the PDA. If a PDA is not treated, it can lead to the development of pulmonary hypertension, which can cause early death. Premature infants with PDA could develop respiratory distress syndrome, meaning they have trouble breathing.
There are potential risks associated with the surgery to treat PDA. These include injury to the recurrent laryngeal nerve, which is important for speaking and swallowing, blockage of the descending aorta, which carries blood from the heart to the lower body, injury to the pulmonary artery, which carries blood from the heart to the lungs, damage to the phrenic nerve, which controls the diaphragm and thus our ability to breathe, and in the worst cases, death.
Possible Complications When Diagnosed with Patent Ductus Arteriosus
- The Eisenmenger phenomenon, a heart condition that leads to high blood pressure in the lung arteries
- Closure of the aorta, the main and largest artery in the body, during surgery
- Recurrent laryngeal nerve injury, a medical issue affecting a nerve in the neck which can affect speech
- Necrotizing enterocolitis, a serious illness in which tissues of the small intestine become damaged and start to die
- Pulmonary hypertension, a type of high blood pressure that affects the arteries in the lungs and the right side of your heart
- Right heart failure, a condition in which the right side of the heart can’t pump blood effectively
Recovery from Patent Ductus Arteriosus
After closing a heart-related medical issue, it’s necessary to take preventative measures against endocarditis – which is an infection in the inner lining of your heart – for the first 6 months. This is usually done through medication.