Splenic Infarction and Recurrent Pulmonary Embolism in Atrial Fibrillation Associated With Subtherapeutic Anticoagulation and Medication Nonadherence: A Case Report.

Atrial fibrillation (AF), the most common sustained arrhythmia worldwide, remains a major cause of cardioembolic stroke and systemic thromboembolism due to impaired atrial contraction, blood stasis, and endothelial injury within the left atrial appendage. Although oral anticoagulation with vitamin K antagonists or direct oral anticoagulants substantially reduces thromboembolic risk, maintaining stable and uninterrupted therapeutic exposure remains a persistent clinical challenge. Splenic infarction (SI) represents a rare extracerebral manifestation of systemic embolization and may present with nonspecific abdominal pain, often delaying diagnosis. We report a 60-year-old man with chronic AF maintained on warfarin who presented with acute abdominal pain and was found to have multiple splenic infarcts, pulmonary emboli, and a left atrial appendage thrombus in the setting of recurrent subtherapeutic anticoagulation. During hospitalization, he received parenteral anticoagulation with appropriate transition to apixaban at discharge; however, he did not obtain or initiate the prescribed medication and returned two days later with recurrent pulmonary embolism and persistent symptoms. His readmission was further complicated by pneumonia, likely acquired through household exposure, potentially intensifying a prothrombotic state during a period of anticoagulation instability. By illustrating the consequences of fluctuating anticoagulation control and documented nonadherence, this case reinforces the importance of vigilant therapeutic monitoring, careful transitions between regimens, early imaging in anticoagulated patients with unexplained abdominal pain, and coordinated management strategies aimed at preventing recurrent and potentially life-threatening embolic complications.