Diagnosis is confirmed with echocardiography. The severity
of the subpulmonary obstruction, its dynamic component,
the size of the right and left pulmonary arteries, and
any additional sources of flow of blood to the lungs will
all be delineated (Figures 6, 7a, 7b). The degree of aortic
override, the size of the interventricular communication,
as well as the presence of other associated lesions, will be
identified (Figure 8). Cardiac catheterisation is now rarely
needed due to the high sensitivity and specificity of
echocardiographic images.