How should the possibility of asymptomatic coronary disease (ostial, compression) and ischemia be assessed? Single ventricle/ Fontan Is warfarin or aspirin beneficial in patients with a Fontan? Are PAH therapies beneficial? Is exercise capacity predictive of mortality? What liver screening is appropriate and at what intervals? How is protein-losing enteropathy best medically treated? Why do some patients fail with preserved ejection fraction, whereas other have decreased ejection fraction? What are the long-term outcomes of hypoplastic left heart syndrome? What is ideal timing for heart transplantation in single ventricle Fontan patients, and should liver issues prompt earlier transplantation than might be felt necessary from a cardiac perspective? Which has better long-term outcomes, the Fontan operation or bidirectional Glenn alone? Coronary anomalies Does surgical intervention in anomalous aortic origin of coronary arteries improve survival? ACE indicates angiotensin-converting enzyme; ACHD, adult congenital heart disease; ARB, angiotensin-receptor blocker; ASO, arterial switch operation; CCTGA, congenitally corrected transposition of the great arteries; CHD, congenital heart disease; CMR, cardiac magnetic resonance; ICD, implantable cardioverter- defibrillator; HF, heart failure; PA, pulmonary artery; PAH, pulmonary artery hypertension; PS, pulmonary stenosis; SCD, sudden cardiac death; TGA, transposition of the great arteries; TOF, tetralogy of Fallot; and VSD, ventricular septal defect. Table 35. Continued CLINICAL STATEMENTS AND GUIDELINES 5. EVIDENCE GAPS AND FUTURE DIRECTIONS There are multiple challenges to developing evi- denced-based care for patients with ACHD. The heterogeneity of conditions leads to small numbers of specific ACHD populations from which to derive guidelines. Additionally, lack of infrastructure to track prevalence, fragmented care systems, loss to follow-up, and changes in treatment strategies over time all contribute to the challenges of developing Comprehensive multicenter and pop- ulation registries and databases are needed to have adequate numbers of patients to address clinical questions. 