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Aortopulmonary Window (AP Window)


An aortopulmonary window (AP Window) is sometimes called an aortopulmonary septal defect. This defect is very rare, as less than 0.5% of congenital heart disease cases are aortopulmonary windows.

An aortopulmonary window is a hole connecting the two major arteries coming from the heart. This hole creates a "window" that allows blood to flow between the aorta (the major artery that brings oxygen-rich blood to the body) and the pulmonary artery (the major artery that brings oxygen-depleted blood back to the lungs to get more oxygen).

In about 50% of cases, the AP Window is the only congenital heart defect. The other 50% of cases are associated with heart defects such as:

  • Atrial septal defect
  • Interrupted aortic arch
  • Patent ductus arteriosus
  • Pulmonary atresia
  • Tetralogy of Fallot
  • Truncus arteriosus

How does a healthy heart work?

In a healthy heart, the right side pumps blood to the lungs through the pulmonary artery, where the blood then picks up oxygen and goes back to the left side of the heart.

The left side of the heart pumps this oxygen-rich blood to the rest of the body through the aorta.

The arteries both come off the top of the heart, but the oxygenated blood going to the body never mixes with the deoxygenated blood going to the lungs.

What happens with an aortopulmonary window?

In an aortopulmonary window, the heart has an opening between the aorta and the pulmonary artery. This hole allows the blood to move between the two arteries. In most cases, it is a left to right shunt where blood from the aorta flows through the hole into the pulmonary artery, which increases the pressure in the pulmonary arteries and the lungs.

Symptoms

If the defect is small enough, you may not see any symptoms, but most of them are large enough to cause symptoms.

Since the left side of the heart pumps blood throughout the entire body, the pressure in the aorta (the artery leading to the body) is much higher than the pressure in the pulmonary artery.

When an AP window is present, blood shunts from the aorta into the pulmonary artery and causes higher pressures and too much blood in the pulmonary artery and the lungs. This is a condition known as pulmonary overcirculation.

Symptoms of pulmonary overcirculation include:

  • Congestive heart failure
  • Delayed growth
  • Frequent respiratory or lung infections
  • Irritability
  • Poor appetite
  • Poor weight gain
  • Rapid heart rate
  • Rapid respiratory rate
  • Increased fatigability

If left untreated, an AP window leads to high blood pressure in the lungs (pulmonary hypertension) and pulmonary vascular disease (damage to the artery going to the lungs).

In large AP windows, blood mixes between the two arteries instead of only moving from the aorta into the pulmonary artery. Oxygen-rich and oxygen-depleted blood moves back and forth between the two while blood with very little oxygen can be circulated to the body. Cyanosis (a bluish hue to the nail beds and lips) can be an indication of this condition.

Causes and risk factors

An aortopulmonary window is a congenital heart defect. The aorta and the pulmonary artery do not separate correctly during fetal development. As a result, an open window is left between them, which allows blood to flow to the wrong place.

This condition has no known environmental or genetic risk factors. While the baby is developing in the womb, the aorta and the pulmonary arteries simply do not separate as they should.

Diagnosis

Your doctor will be able to hear a heart murmur, or abnormal heart sounds, through their stethoscope. If they suspect a heart defect, they will order tests to determine the problem.

Several tests can give doctors a better view of the heart and how it is functioning:

  • Chest x-ray
  • Echocardiogram
  • Cardiac catheterization
  • MRI of the heart

Treatment

An early surgical repair, usually while the infant is still a newborn, is the recommended treatment.

This will help prevent irreversible pulmonary vascular disease, which is injury to the blood vessels in the lungs. The doctor will apply a patch to the hole during surgery to prevent the blood from shunting and mixing.

With early surgery to repair the AP window, a baby will generally be able to live a healthy life.

Complications

Complications can develop from an AP window if it is not repaired quickly:

  • Pulmonary hypertension is high blood pressure in the lungs, which occurs from the extra blood flowing into the pulmonary artery from the aorta.
  • Congestive heart failure (CHF) can occur when the lungs cannot handle the volume of blood pumped into them.
  • Eisenmenger syndrome is a set of symptoms resulting from irregular blood flow and high blood pressure in the lungs and heart
  • Someone may experience an early death if they do not get early treatment and surgery.

Summary

An aortopulmonary window is a hole between the two large arteries leading away from the heart. Too much blood flows into the lungs, leading to pulmonary hypertension and congestive heart failure. In some cases, the blood can mix between the two arteries and prevent the body from receiving fully-oxygenated blood.

Early diagnosis, treatment, and surgery to repair the hole offer infants with this condition an excellent chance to live a healthy life.

Sources:

Boston Children's Hospital. (2022). Aortopulmonary Window. Aortopulmonary Window (childrenshospital.org)

Dhillon, Gary, MD. (2022). Aortopulmonary Window. Aortopulmonary Window | Pediatric Echocardiography (pedecho.org)

Medline Plus. Aortopulmonary Window. Aortopulmonary window: MedlinePlus Medical Encyclopedia

Mount Sinai. (2022). Aortopulmonary Window. Aortopulmonary window Information | Mount Sinai - New York

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