Co-occurrence of Bilateral Pulmonary Artery Embolism and a Serpentine Right Atrial Thrombus Successfully Managed With Oral Anticoagulation: A Case Report

Serpentine thrombus, also referred to as a snake-like or worm-like floating thrombus, is a rare but life-threatening intracardiac condition representing a true therapeutic emergency. Without treatment, the prognosis is extremely poor. The condition is particularly dangerous due to the risk of thrombus fragmentation and migration, which can lead to complete obstruction of the pulmonary trunk. We report the case of an 80-year-old hemodynamically stable man who presented with progressive dyspnea and severe hypoxemia. Computed tomography pulmonary angiography confirmed bilateral proximal pulmonary embolism, and transthoracic echocardiography (TTE) identified a serpiginous free-floating thrombus in the right atrium, prolapsing into the right ventricle during diastole. Significant right ventricular dysfunction and severe pulmonary hypertension (estimated pulmonary artery pressure 67 mmHg) were documented. Risk stratification yielded a Pulmonary Embolism Severity Index (PESI) score of 110 (Class IV, high risk) and a Venous Thromboembolism Bleeding (VTE-BLEED) score of 3 (high bleeding risk). Given hemodynamic stability and elevated bleeding risk, systemic thrombolysis was deferred. The patient was initially managed with intravenous unfractionated heparin for five days, followed by oral anticoagulation with apixaban (10 mg twice daily for seven days, then 5 mg twice daily). Complete resolution of the intracardiac thrombus was confirmed on TTE on day 15, with concurrent clinical and respiratory improvement. This case adds to the sparse literature supporting oral anticoagulation as a viable therapeutic option in carefully selected, hemodynamically stable patients with serpentine right atrial thrombus and high bleeding risk, when more aggressive strategies are contraindicated or unavailable. It underscores the importance of individualized decision-making and long-term surveillance.