Aortopulmonary window is an abnormal connection between the aorta and the main pulmonary artery, which causes a large left-to-right shunt. Symptoms and signs are due to heart failure, including tachypnea, poor feeding, and diaphoresis. Diagnosis is by physical examination findings, ECG, and imaging. Treatment is with surgical repair.
(See also Overview of Congenital Cardiovascular Anomalies.)
Aortopulmonary window is very rare and accounts for < 0.6% of all cardiac malformations. The abnormal connection can be isolated or occur with other cardiovascular abnormalities, such as atrial septal defect, ventricular septal defect, coarctation of the aorta, interrupted aortic arch, or tetralogy of Fallot. The defect results from incomplete septation of the truncus arteriosus during fetal cardiac development. The size of the direct aortic to pulmonary artery connection varies and may extend from just above the coronary sinuses to the proximal right pulmonary artery.
Pathophysiology of Aortopulmonary Window
Large left-to-right shunts cause excess pulmonary blood flow and left ventricular volume overload and also lead to lower lung compliance and higher airway resistance. The amount of left-to-right shunting leading to pulmonary overcirculation is dependent on both the size of the defect and the pulmonary vascular resistance.
Some degree of pulmonary hypertension is almost always present. The degree is determined by the size of the defect between the aorta and pulmonary artery. If the aortopulmonary connection is large, pulmonary hypertension equal to systemic pressure will be present.
Recurrent respiratory infections may occur.
If the defect is unrepaired, the high pressure and large left-to-right shunt results in pulmonary vascular disease and Eisenmenger syndrome eventually develops.
Symptoms and Signs of Aortopulmonary Window
A left-to-right shunt may lead to heart failure, with symptoms and signs that include tachypnea, poor feeding, and diaphoresis. Low lung compliance and higher airway resistance can cause dyspnea and signs of labored breathing (eg, flaring, grunting, chest wall retractions). Infants may have failure to thrive and recurrent pneumonia.
In patients with an isolated aortopulmonary window, examination findings depend on the size of the defect and the pulmonary vascular resistance (PVR). Generally the cardiac examination reveals a parasternal lift from right ventricular overload, a loud single second heart sound (S2) resulting from pulmonary hypertension, and increased peripheral pulses.
With a large defect, the PVR may remain elevated in the first weeks or months of life, and the amount of pulmonary overcirculation is modest. The modest overcirculation results in a relatively soft basal systolic ejection murmur without a diastolic component and a loud single S2. As the PVR drops during the first months, the left-to-right shunting of blood into the lungs progressively increases, the systolic murmur becomes louder and longer and may extend into diastole, becoming a continuous murmur.
A small aortopulmonary defect may result in a murmur typical of a patent ductus arteriosus because there is a pressure gradient from the aorta to the pulmonary artery throughout systole and diastole.
If the defect is large and unrepaired, Eisenmenger syndrome eventually occurs over years with reversal of the shunt. The clinical findings may then only reveal a parasternal lift from right ventricular hypertrophy, a loud single S2 from pulmonary hypertension, absence of any murmur, and cyanosis.
Diagnosis of Aortopulmonary Window
Chest x-ray and ECG
Echocardiography and sometimes CT or MR angiography
Diagnosis is by physical examination findings, ECG, and imaging. The ECG demonstrates right ventricular hypertrophy or biventricular hypertrophy. The chest x-ray shows cardiomegaly, a large main pulmonary artery segment, and increased pulmonary vascular marking.
Echocardiography usually demonstrates the defect, but the absence of the wall between the aorta and main pulmonary artery and proximal right pulmonary artery may be relatively subtle, and the etiology of the pulmonary hypertension may initially be obscure. When findings of pulmonary hypertension are noted without an obvious intracardiac defect, the proximal great vessels should be scanned to look for a defect between the aorta and main pulmonary artery near the pulmonary artery bifurcation and proximal right pulmonary artery.
MR or CT imaging clearly defines the presence and extent of the defect. Cardiac angiography is rarely necessary, but in some instances may be helpful in clarifying the degree of shunting and pulmonary hypertension.
Treatment of Aortopulmonary Window
Surgical repair
Surgical repair of aortopulmonary window should be done as soon as possible after diagnosis. In rare cases, the defect may be small enough and not in proximity to the aortic valve, allowing consideration of transcatheter closure.
Key Points
Aortopulmonary window is an abnormal connection between the aorta and the main pulmonary artery, which causes a large left-to-right shunt.
Aortopulmonary window is very rare and accounts for < 0.6% of all cardiac malformations.
Symptoms are those of a left-to-right shunt, which may lead to signs of heart failure (eg, tachypnea, poor feeding, diaphoresis).
Diagnosis is by physical examination findings, ECG, and imaging.
Treatment is with surgical repair, which should be done as soon as possible after diagnosis.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
American Heart Association: Common Heart Defects: Provides overview of common congenital heart defects for parents and caregivers
