Black, E.

Introduction Hypoplastic left heart syndrome and Fontan procedure predispose to cardiac thrombus formation in the venous pathways due to the unique hemodynamic and hematologic disturbances inherent to the Fontan circulation. Systemic venous blood is routed passively to the pulmonary arteries without a subpulmonary pump, resulting in chronic low‐velocity flow, elevated central venous pressure, and venous stasis—all elements of Virchow's triad that favor clot formation 1 . Additionally, these patients exhibit reduced levels of protein C, coagulation factors II, V, VII, and X, plasminogen, and antithrombin III, along with increased levels of factor VIII 2,3 . Once a thrombotic event occurs, the rationale for lifelong anticoagulation is compelling. We report a case of an adult man that underwent Fontan palliation in infancy, with acute cerebral and renal infarcts, and discuss stroke and systemic embolism prevention. Case presentation A 22‐year‐old male with history of hypoplastic left heart syndrome status post Fontan procedure in infancy with congestive splenomegaly and liver disease presented with acute abdominal pain and was found to have bilateral renal infarcts. Anticoagulation was not initiated acutely and within 24 hours he developed left face and arm weakness, dysarthria and mild aphasia. Intravenous Tenecteplase was administered within 1 hour of symptom onset and was followed by symptoms’ complete resolution within 30 minutes of administration. Brain MRI confirmed scattered cerebral infarcts in the bilateral middle cerebral artery territories. Transthoracic echocardiogram showed atrial level shunting, expected due to fenestrated IVC to left atrium from prior Fontan procedure, and no evidence of atrial or ventricular thrombus. Due to the patient having evidence of multiple infarcts in multiple vascular beds within the brain and kidneys, an extensive hypercoagulable workup was undertaken which was unremarkable. The patient's stroke etiology was presumed to be cardioembolic from his altered cardiac anatomy with susceptibility to form venous thrombi and known surgically‐induced atrial level shunt. Low intensity heparin drip without bolus was started initially, and was transitioned to therapeutic apixaban upon discharge with proposed life long anticoagulation. Conclusions Subjects with hypoplastic heart syndrome display persistent unfavorable hemodynamics and procoagulant state after Fontan procedure. Either antiplatelet or anticoagulants are recommended after performing risk stratification. In high‐risk patients (recent thromboembolic event or stent, recurrent atrial arrhythmias, mechanical valve), therapeutic anticoagulation with either warfarin or direct oral anticoagulant is indicated, given increased vulnerability to recurrent events 1 . In intermediate‐risk subjects, antiplatelet or prophylactic doses of anticoagulation is indicated, whereas in low‐risk patients, antiplatelet agent is preferred.