Initiation of anticoagulation therapy should not delay any emergency interventions required in order to stabilize the patient. Recommendations *17. For patients with AF and hemodynamic instability undergoing urgent cardioversion (electrical or pharmacologic), we suggest that therapeutic-dose parenteral anticoagulation be started before cardioversion, if possible, but that initiation of anticoagulation must not delay any emergency intervention (Weak recommendation, low quality evidence). *18. For patients with AF and hemodynamic instability undergoing urgent cardioversion (electrical or pharmacologic), after successful cardioversion to sinus rhythm, we suggest therapeutic anticoagulation for at least 4 weeks after successful cardioversion to sinus rhythm rather than no anticoagulation, regardless of baseline stroke risk (Weak recommendation, low quality evidence). Remark: Decisions about anticoagulation beyond 4 weeks should be made in accordance with our risk-based recommendations for long-term antithrombotic therapy in recommendations 1 and 2. Patients Undergoing Elective or Urgent Cardioversion for Atrial Flutter There are no speci c trials which have considered electrical cardioversion in the context of atrial utter and associated anticoagulation. Despite the low risk of thromboembolism after cardioversion for atrial utter, which has been suggested by some observational studies, even in absence of anticoagulation, other studies have shown a similar risk of thromboembolism in patients after cardioversion for atrial utter and AF,234,274,275 perhaps due to co-existence of AF and atrial utter. Adults with congenital heart disease represent a growing, important population with atrial utter where long-term studies of outcomes with anticoagulation are required. Recommendation *19. For patients with atrial utter undergoing elective or urgent pharmacologic or electrical cardioversion, we suggest that the same approach to thromboprophylaxis be used as for patients with atrial brillation undergoing cardioversion (Ungraded consensus-based statement). 