I C-EO Cardiac catheterization should be performed in adults before initial Fontan surgery or revision of a prior Fontan connection to assess suitability of preintervention hemodynamics for Fontan physiology or revision of a prior Fontan connection. I C-EO New onset or worsening atrial tachyarrhythmias in adults with single ventricle after Fontan palliation should prompt a search for potential hemodynamic abnormalities, which may necessitate imaging and/or cardiac catheterization. IIa B-R In adults with Fontan palliation, it is reasonable to encourage a regular exercise program appropriate to their IIa C-LD Imaging of the liver (ultrasonography, CMR, CT) and laboratory evaluation of liver function for fibrosis, cirrhosis, and/or hepatocellular carcinoma are reasonable in adults after Fontan IIa C-EO In adults after Fontan palliation, it is reasonable to perform biochemical and hematological testing on an annual basis especially for liver and renal function. IIa C-LD Cardiac catheterization can be useful to evaluate a symptomatic adult after Fontan palliation when noninvasive testing is insufficient to guide therapy.S4.4.2-7,S4.4.2-8 IIa C-LD Evaluation for cardiac transplantation is reasonable in adults with Fontan palliation and signs and symptoms of protein-losing Recommendations for Fontan Palliation of Single Ventricle Physiology (Continued) COR LOE Recommendations Table 31. CCTGA: Routine Follow-Up and Testing Intervals Frequency of Routine Follow-Up and Testing Physiological Stage A* (mo) Physiological Stage B* (mo) Physiological Stage C* (mo) Physiological Stage D* (mo) Pulse oximetry As needed As needed Each visit Each visit *See Tables 3 and 4 for details on the ACHD AP classification system. Routine TTE may be unnecessary in a year when CMR imaging is performed unless clinical indications warrant otherwise. CMR may be indicated for assessment of ventricular size and function and valvular function. Baseline study is recommended with periodic follow-up CMR, with frequency of repeat imaging determined by anatomic and physiological findings. 