Cardiac catheterization is necessary before bidirectional Glenn and Fontan procedures in single ventricle physiology.

There are significant mortality and morbidity in bidirectional Glenn (stage II) and Fontan (stage III) procedures for congenital heart diseases with single ventricle physiology. In order to minimize the mortality and morbidity, the presence or absence of hemodynamic and anatomical abnormalities, such as poor ventricular function, coarctation of the aorta, pulmonary artery distortion, high pulmonary resistance, and abnormal collateral vessels, should be evaluated. Echocardiography and magnetic resonance imaging (MRI) can visualize ventricular size and coarctation of the aorta but may fail to visualize pulmonary artery distortion. Furthermore, cardiac catheterization is needed to measure pulmonary resistance. If the pulmonary resistance is > 3 Wood units/m2 before stage II, the risk for the bidirectional Glenn operation may be high. Abnormal aortopulmonary collateral vessels may develop after the stage II procedure and echocardiography and MRI may not visualize these vessels. Coil embolization may be required to treat these vessels. In conclusion, cardiac catheterization is required to evaluate abnormalities, which may be treated by interventional catheterization, and to reduce mortality and morbidity of stage II and III procedures.