Fontan circulation, coined by Cardiothoracic Surgeon Francis Fontan, connects systemic venous return to the pulmonary artery without support from the ventricle. Patients with this circulation are at risk for thromboembolic events due to venous stasis, generalized reduced cardiac output, and imbalance of procoagulant and anticoagulant factors. The Fontan procedure connects the right atrium to the pulmonary artery and is done in patients with a hypoplastic ventricular system to reduce volume overload and improve arterial saturation. Frequency of stroke after this procedure varies in the literature from 5-33% with a cumulative stroke incidence up to age 40 of 1.5%. Mortality associated with thromboembolic events is as high as 25% based on autopsy data. Guidelines vary regarding the use of antiplatelet agents and anticoagulants for these patients.

A 38yo woman presented with left hemiparesis and mild dysarthria with NIH stroke scale of 7. She had a history of double inlet left ventricle with hypoplastic right ventricle treated with Fontan conversion several years prior and insertion of dual chamber epicardial pacemaker and warfarin. Noncontrast CTH demonstrated a dense right MCA sign with CTA head showing proximal right MCA occlusion. She was not a candidate for tPA as her INR was elevated at 1.75. She underwent mechanical thrombectomy resulting in complete recanalization of the right MCA. Echocardiography showed no intracardiac thrombus. She was treated with a heparin to warfarin bridge with target INR 2.5-3. Her discharge modified Rankin Scale was 1 and she was discharged to acute rehabilitation.

Our patient developed a large vessel occlusion while on warfarin but with a subtherapeutic INR. Although our patient had a favorable outcome, stroke remains an important contributor to mortality in patients with Fontan circulation. More studies are needed to establish a robust standard of anticoagulant therapy to prevent stroke in this hypercoaguable population.