Most windows are large, so that, if not recognized in early childhood, they will cause a significant left to right shunt, often resulting in pulmonary hypertension. Therefore, they are frequently associated with high pulmonary blood pressures and pulmonary vascular obstructive disease (PVOD) when first diagnosed in the adult patient.

The symptoms that are associated with this defect depend on the size of the window. Small windows often cause enlargement (dilatation) of the left ventricle and/or heart failure and are characterized by a continuous heart murmur. The more common large aortopulmonary windows result in cyanosis (blueness caused by oxygen poor arterial blood) affecting the whole body, pulmonary hypertension, and Eisenmenger Complex.

Echocardiography is used to confirm the diagnosis and to determine the amount of left to right shunting. A cardiac catheterization procedure may be used to measure the degree of pulmonary hypertension and resistance, if present.

Once the window has been recognized and evaluated, it may be closed surgically or through a catheterization procedure. Regular follow-up after the repair will be necessary and lifelong antibiotic therapy is usually prescribed to guard against infection of the heart's internal lining (bacterial endocarditis).