Aorto-pulmonary Window

Aorto-pulmonary Window, also known as aorto-pulmonary septal defect, is very rare, (0.2 to 0.6 % of all CHD) and is a discrete communication of variable size between aorta and pulmonary artery. It is classified according to Mori et. al. by location of the defect into three types: Type 1, the most frequent form, is a communication midway between the semilunar valves and the pulmonary bifurcation. The case shown here in suprastrenal notch echo shows an 8 cm opening between ascending aorta and main pulmonary artery. 
Type 2 is more distal with its distal border is formed by the pulmonary bifurcation; it is commonly associated with an aortic origin of the right pulmonary artery. Type 3 is very rare, consisting of a large and confluent defect involving the entire septum. 



Fifty percent of cases have associated lesions and usually there are two or more defects present. Associated lesions include aortic origin of the right pulmonary artery, type A interruption of the aortic arch, tetralogy of Fallot, anomalous origin of the left coronary artery arising from the pulmonary artery, right aortic arch, VSD, etc. Physiologically this lesion is characterized by a large and generally continuous left to right shunt following the postnatal reduction of pulmonary vascular resistances. Pathologic findings consist of an enlarged heart, pulmonary arteries and branches and a small descending aorta. The shape of the defect is usually circular. 

Clinical manifestations are those of congestive heart failure due to a significant left to right shunt with tachypnea, recurrent respiratory infections, diaphoresis and failure to thrive. 

On physical exam, cardiac examination is remarkable for a prominent right ventricular heave, a loud and narrowly split S2 and a continuous murmur and a mid-diastolic rumble, and bounding pulses. The ECG is not characteristic but it may show bi-ventricular hypertrophy, the chest Xray has cardiomegaly, with increased LA and LV borders and increased pulmonary vascular markings. The echocardiogram is diagnostic, allowing direct visualization of the defect, normal semilunar valves, dilated left atrium and ventricle, and increased pulmonary artery size. Cardiac catheterization is almost never required for diagnosis, except when the echo is not sufficient to provide complete information regarding associated defects. 

Differential diagnosis includes large PDA's, VSD's and Truncus Arteriosus. 

Treatment includes medical management of the congestive heart failure and surgical closure of the defect, usually by exposure and closure of the defect from the aorta. 

Prognosis is excellent when closed early in life before irreversible pulmonary vascular changes occur. 

xray Aorto-pulmonary window in a one year old with substantial L -> R shunt shows cardiomegaly and prominent pulmonary vasculature because of over-circulation of the lungs.

ECG may not be diagnostic but often shows biventricular hypertrophy as in this case.
sax Short axis echo labelled on the left shows the aorto-pulmonary communication. The flow from aorta to pulmonary artery is evident in the color doppler imaging shown on the right.

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Suprasternal notch echo labelled on the left shows the aorto-pulmonary communication (marked with crosses) in a one year-old with substantial L -> R shunting made evident in the color doppler imaging shown on the right.

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Short axis aortic-level view in motion shows the large communication between aorta and the main pulmonary artery.

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Short axis color doppler aortic-level view in motion shows the large amount of left-to-right shunt flowing from aorta into the main pulmonary artery.

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Suprasternal notch color doppler view in motion shows the large amount of left-to-right shunt flowing from aorta into the main pulmonary artery. 

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Short axis color doppler aortic-level view of another patient who happens to have a very small aorto-pulmonary communication shows the limited amount of left-to-right shunt flowing into the main pulmonary artery.