Patent Ductus Arteriosus (PDA)

Heart With Patent Ductus Arteriosus (PDA)

An animation of how a heart with patent ductus arteriosus (PDA) functions.

Note: To view heart animations, you need the latest version of the
Adobe Flash Player.

The ductus arteriosus is a normal connection in utero between the pulmonary artery and the aorta. Since the lungs are still developing, the baby receives oxygenated blood from the mother during pregnancy. The ductus arteriosus allows the greater part of the oxygenated blood to bypass the non-aerated lungs by flowing directly from the pulmonary artery to the aorta. After the baby is born and begins breathing, hormonal changes occur causing the ductus arteriosus to close. A patent ductus arteriosus, or PDA, is when this connection does not close as it normally should. If the ductus remains open, the direction of flow reverses and some of the oxygen-rich blood from the aorta flows to the pulmonary artery and into the lungs. This may cause an excessive amount of blood flow to the lungs.

There are two reasons that necessitate the closure of a PDA. The first is the size of the ductus, which in turn determines the volume of extra blood being directed to the lungs. A large volume overload may result in enlargement of the heart and over time heart failure. The second reason is to avoid the risk of developing an infection in the heart known as endocarditis. Approximately, one-eighth of patients with a PDA will develop endocarditis. This increases mortality by 50% whereas the risk of surgery is almost zero.

Depending on the size of the ductus, a PDA may be treated in one of two ways. If the ductus is large, the child may require surgery that involves closing off the ductus with a clamp or suture. However, in many cases, the PDA can be closed using a spring coil or a synthetic plug. Both devices are introduced through a heart catheter, which is passed through a vein in the leg that leads up to the heart.

How Does Patent Ductus Arteriosus (PDA) Differ From Normal Cardiac Anatomy?

If your child has patent ductus arteriosus (PDA) or another congenital heart defect, there's usually something wrong with the structure of his or her heart.

Learn More About How Patent Ductus Arteriosus (PDA) Differs From Normal Cardiac Anatomy

Heart with Normal Cardiac Anatomy

Note: To view heart animations, you need the latest version of the
Adobe Flash Player.

When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.

There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.

Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.

Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.

ECG (Electrocardiogram)

An electrocardiogram (ECG) measures the heart's electrical activity to help evaluate its function and identify any problems that might exist. The ECG can help determine the rate and regularity of heartbeats, the size and position of the heart's chambers, and whether there is any damage present.

How Is an ECG Done?

There is nothing painful about getting an ECG. The patient is asked to lie down, and a series of small metal tabs (called electrodes) are fixed to the skin with sticky papers. These electrodes are placed in a standard pattern on the shoulders, the chest, the wrists, and the ankles. After the electrodes are in place, the person is asked to hold still and, perhaps, to hold his or her breath briefly while the heartbeats are recorded for a short period. The patient also might be asked to get up and exercise for a while.

The information is interpreted by a machine and drawn as a graph. The graph consists of multiple waves, which reflect the activity of the heart. The height, length, and frequency of the waves are read in the following way:

  • The number of waves per minute on the graph is the heart rate.
  • The distances between these waves is the heart rhythm.
  • The shapes of the waves show how well the heart's electrical impulses are working, the size of the heart, and how well the individual components of the heart are working together.
  • The consistency of the waves provides relatively specific information about any heart damage present.

A person's heartbeat should be consistent and even. ECGs look for abnormally slow and fast heart rates, abnormal rhythm patterns, conduction blocks (short-circuits of the heart's electrical impulses that cause rhythm inconsistencies between the upper and lower chambers) — and four types of heart damage:

  1. ventricular hypertrophy — an abnormal thickening of the heart muscle
  2. ischemia — caused by an abnormally decreased blood supply
  3. cardiomyopathies — abnormalities in the heart muscle itself
  4. electrolyte and drug disturbances — these can alter the heart's electrochemical environment

Computerized ECGs can be combined with other tests to provide a multimedia account of the heart. These additional tests include echocardiograms (which are basically "ultrasound" tests that bounce sound off the heart and use the echoes to produce an image) and thallium scans (which are kind of like X-rays and use a radioactive tracer, injected into the bloodstream, to help draw a picture of the heart).

In the past, the ECG was recorded on a machine that drew on long strips of paper, with records from each electrode presented in a standard sequence. Now the ECG tracings are stored as computer files that can be called up and printed.

How Long Will it Take to Get Results?

Results of the ECG are available immediately. In fact, the ECG machine's computer even provides an instant interpretation of the findings as it makes the report. However, the doctor also might ask an expert, usually a cardiologist, to help analyze and interpret the ECG.

Reference ranges for heart rate and the relative lengths and sizes of the various components of the heartbeat figures vary, and diagnostic differences may be subtle, requiring an expert eye to detect them.

Reviewed by: Steven Dowshen, MD
Date reviewed: September 26, 2016