There is no universally accepted threshold for repair, nor is the role of indexing to body size clearly defined in adults, as is done in pediatric populations. For purposes of categorization and timing of follow-up imagingS2.2-2 S2.2-4 : Mild aortic enlargement is defined as maximum diameter 3.5 3.9 cm Moderate aortic enlargement is defined as maximum diameter 4.0 4.9 cm Severe aortic enlargement is defined as maximum diameter 5.0 cm Arrhythmia Arrhythmias are very common in patients with ACHD and may be both the cause and consequence of deteriorating hemodynamics, valvular dysfunction, or ventricular dysfunction. Arrhythmias are associated with symptoms, outcomes, and prognosis,S2.2-5 S2.2-8 thus are categorized based on presence and response to treatment. No arrhythmia: No documented clinically relevant atrial or ventricular tachyarrhythmias Arrhythmia not requiring treatment: Bradyarrhythmia, atrial or ventricular tachyarrhythmia not requiring antiarrhythmic therapy, cardioversion, or ablation Arrhythmia controlled with therapy: Bradyarrhythmia requiring pacemaker implantation Atrial or ventricular tachyarrhythmia requiring antiarrhythmic therapy, cardioversion, or ablation AF and controlled ventricular response Patients with an ICD Refractory arrhythmias: Atrial or ventricular tachyarrhythmia currently unresponsive to or refractory to antiarrhythmic therapy or ablation Concomitant VHD Severity defined according to the 2014 VHD guideline.S2.2-2 Mild VHD Moderate VHD Severe VHD End-organ dysfunction Clinical and/or laboratory evidence of end-organ dysfunctionS2.2-9 S2.2-11 including: Renal (kidney) Hepatic (liver) Pulmonary (lung) Exercise capacity Patients with ACHD are often asymptomatic notwithstanding exercise limitations demonstrated as diminished exercise capacity when evaluated objectively.S2.2-12 S2.2-14 Thus, assessment of both subjective and objective exercise capacity is important (see NYHA classification system below). Exercise capacity is associated with prognosis.S2.2-15 S2.2-17 Abnormal objective cardiac limitation to exercise is defined as an exercise maximum ventilatory equivalent of oxygen below the range expected for the specific CHD anatomic diagnosis.S2.2-18 Expected norms for CPET values should take into account age, sex, and underlying congenital diagnosis. 