Patients with CHD comprise an increasingly prevalent population of patients presenting with symptoms due to arrhythmic syndromes and bradycardia. Due to reduced hemodynamic reserve, onset of arrhythmias in patients with complex CHD is a frequent cause of symptomatic deterioration or even sudden cardiac death. Effective arrhythmia management and risk stratification remains challenging due to limited data which in most cases are extrapolated from data in adults with ischemic heart disease. Important clinical markers that predict poorer outcome and increased risk of heart rhythm disorders include presence of uncorrected hemodynamic defects, surgical repair later in life, and older age (i.e., longer follow-up). Patients who present with new onset of an atrial or a ventricular arrhythmia require comprehensive hemodynamic and electrophysiological assessment.