In patients with cyanotic and other complex congenital heart disease and isch- emic stroke or TIA of presumed cardioembolic origin, treatment with warfarin is reasonable in the absence of contraindications to oral anticoagula- tion (eg, increased risk of bleeding). Knowledge Gaps and Future Research A subset of patients with Fontan palliative surgery have a fenestration between the Fontan path- way and the pulmonary venous atrium to provide a controlled right-to-left shunt to augment ven- tricular preload and to partially offload systemic venous (Fontan) hypertension. Right-to-left shunt from a fenestration can be a potential source of thromboembolism and stroke.584 Catheter closure of Fontan fenestration along with anticoagulation has been performed in some patients with a patent fenestration presenting with stroke,585 although more data are needed to determine whether this approach is of real incremental benefit to prevent ischemic stroke or TIA compared with oral antico- agulation therapy alone. DOACs have been demonstrated to be noninferior or superior to dose-adjusted warfarin therapy to prevent thromboembolism and bleeding in patients with nonvalvular AF, and they have rapidly become the standard of care for these patients. Important advantages of DOAC therapy compared with war- farin include a more predictable pharmacokinetic profile requiring no monitoring, fewer interactions with other drugs, and a rapid onset/offset of action. Thus far, data on the efficacy and safety of DOACs to prevent recurrent thromboembolism in patients with congenital heart disease and history of isch- emic stroke or TIA are limited to small observational series. Larger-scale multicenter observational data will be necessary to achieve adequate statistical power and to clarify whether DOACs can be used safely in patients with congenital heart disease. 