Aortopulmonary Window (AP Window)

Question 1

What is an aortopulmonary window (AP window)?

Answer 1

A congenital heart defect characterized by a communication between the ascending aorta and the pulmonary artery in the presence of separate semilunar valves, a right ventricular outflow tract, and separate arterial trunks.

Question 2

What percentage of congenital heart disease cases does AP window represent?

Answer 2

Less than 0.5%.

Question 3

In what percentage of AP window cases are other cardiac defects associated?

Answer 3

25-50%.

Question 4

List some associated anomalies with aortopulmonary window.

Answer 4

• Tetralogy of Fallot
• Aortic arch anomalies (coarctation, type A interrupted aortic arch)
• Anomalous origin of the coronary arteries
• Tricuspid atresia
• Aortic or pulmonary atresia
• Transposition of the great arteries

Question 5

What is the embryological origin of the aortopulmonary septum?

Answer 5

Develops as a wedge of tissue capped by neural crest cells that grows ventrally from the dorsal wall of the aortic sac.

Question 6

What does the aortopulmonary septum fuse with during development?

Answer 6

The distal margins of the embryonic outflow cushions, also capped by neural crest cells.

Question 7

What results from the failure to close the embryonic aortopulmonary foramen?

Answer 7

An aortopulmonary window.

Question 8

Has aortopulmonary window been reported in association with DiGeorge syndrome?

Answer 8

No.

Question 9

What is the risk of associated chromosomal anomalies in aortopulmonary window?

Answer 9

Appears low.

Question 10

Are there known genetic or environmental risk factors associated with aortopulmonary window?

Answer 10

No known genetic or environmental risk factors documented to date.

Question 11

What is the physiological characteristic of an AP window?

Answer 11

A left-to-right shunting lesion

Question 12

What conditions may patients with a large isolated AP window present with?

Answer 12

• Pulmonary overcirculation
• Congestive heart failure
• Development of pulmonary vascular disease with pulmonary hypertension

Question 13

In what circumstance can cyanosis be seen with large defects in AP windows?

Answer 13

Due to bidirectional shunting and mixing at the arterial level

Question 14

When else can cyanosis be observed in patients with an AP window?

Answer 14

If associated with cyanotic congenital heart disease lesions earlier in neonatal life

Question 15

What condition is associated with high pulmonary vascular resistance in neonates?

Answer 15

Mixing at the arterial level is not yet occurring

Question 16

What is the recommended timing for surgical repair of an AP window?

Answer 16

Earlier surgical repair is recommended

Question 17

What is the purpose of earlier surgical repair in AP window cases?

Answer 17

To prevent irreversible pulmonary vascular disease

Question 18

What is a common consequence of pulmonary overcirculation in AP window patients?

Answer 18

Exposure of the pulmonary vasculature to systemic arterial pressures

Question 19

What is Type I AP window defect?

Answer 19

A defect located between the origin of the main pulmonary artery and the ascending aorta immediately above the sinus of Valsalva, due to deficient septation of the aortopulmonary trunk during development. These defects are large, round or oval shaped, and more commonly seen.

Characterized by little inferior rim separating the AP window from the semilunar valves.

Question 20

What is Type II AP window defect?

Answer 20

A defect located between the ascending aorta and the origin of the right pulmonary artery, caused by abnormal migration of the 6th aortic arch during development. These defects are rare and smaller in size.

Less commonly encountered compared to Type I defects.

Question 21

What characterizes Type III AP window defect?

Answer 21

A large defect combining Types I and II, with extension into the right pulmonary artery and anomalous origin of the right pulmonary artery from the ascending aorta, due to unequal septation of the aorto-pulmonary trunk during development.

Features a well-formed inferior rim but little superior rim and is linked with other cardiac anomalies.

Question 22

What is the defining feature of Type IV AP window defect?

Answer 22

An intermediate defect that has adequate superior and inferior rims, making it most suitable for possible device closure.

Represents a more favorable anatomical configuration for intervention compared to other types.

Question 23

Fill in the blank: Type I defects are characterized by a _______ rim separating the AP window from the semilunar valves.

Answer 23

little

Question 24

True or False: Type II AP window defects are more common than Type I defects.

Answer 24

False

Question 25

What developmental issue leads to Type I AP window defects?

Answer 25

Deficient septation of the aortopulmonary trunk during development.

Question 26

What is a common feature of Type III AP window defects?

Answer 26

Anomalous origin of the right pulmonary artery from the ascending aorta.

Question 27

Fill in the blank: Type IV defects are most suitable for possible _______.

Answer 27

device closure

Question 28

What is the gold-standard diagnostic tool for aorto-pulmonary window?

Answer 28

Echocardiography ## Footnote Echocardiography is crucial for diagnosing conditions such as aorto-pulmonary window in patients.

Question 29

Why are neonates with aorto-pulmonary window recommended to use a high-frequency probe for evaluation?

Answer 29

They are likely to present earlier in life due to symptomatic CHF or cyanosis ## Footnote This is due to significant left-to-right shunting or the higher risk of associated congenital heart disease lesions.

Question 30

What are the important views for transthoracic echocardiography?

Answer 30

Parasternal short-axis, subcostal short-axis and long-axis, suprasternal notch views ## Footnote These views are essential for evaluating the aorto-pulmonary window and associated structures.

Question 31

What does the parasternal short-axis view allow visualization of?

Answer 31

Both MPA and aorta ## Footnote This view helps evaluate communications between these structures.

Question 32

What is the purpose of color Doppler in the parasternal short-axis view?

Answer 32

To confirm that a communication truly exists ## Footnote It helps ensure that there is no artifactual drop-out in great arterial vessel walls.

Question 33

What can be assessed in the subcostal short-axis and long-axis views?

Answer 33

Location of the AP window defect, distance from semilunar valves, extent of inferior and superior rims, involvement of ascending aorta and right pulmonary artery ## Footnote These factors significantly affect surgical management.

Question 34

What associated cardiac lesions can be evaluated with the AP window in the subcostal views?

Answer 34

VSD, TOF, TGA ## Footnote These conditions can co-exist with the aorto-pulmonary window.

Question 35

What does the suprasternal notch view allow for?

Answer 35

Evaluation of shunting across the AP window and thorough evaluation of the arch ## Footnote This is important due to the incidence of association of AP window with arch anomalies.

Question 36

True or False: The suprasternal notch view is used to evaluate only the aortic arch.

Answer 36

False ## Footnote It also allows for evaluation of shunting between the great arteries.