Caught in Transit: Mobile Right Atrial Thrombus in Intermediate-High-Risk Pulmonary Embolism Treated With Half-Dose Alteplase

Objective:Unusual clinical course Background:Pulmonary embolism is associated with increased morbidity and mortality, yet the patient can sometimes look deceptively calm at the bedside.A normal blood pressure reading does not rule out a struggling right ventricle, and patients classified as intermediate-high-risk can deteriorate quickly.A mobile right-heart thrombus (clotin-transit) adds another layer of urgency because embolization can be sudden and unpredictable. Case Report:A 45-year-old woman with a previous pulmonary embolism presented with abrupt dyspnea, tachycardia, and hypoxemia shortly after stopping apixaban.Bedside transthoracic echocardiography showed marked right ventricular dilation and a mobile right atrial thrombus consistent with clot-in-transit.Computed tomography pulmonary angiography confirmed bilateral segmental/subsegmental pulmonary embolism.Although she remained normotensive, biomarker positivity and a lactate rise suggested early hypoperfusion.After immediate anticoagulation with unfractionated heparin, the Pulmonary Embolism Response Team was activated, and, after multidisciplinary discussion, we decided to treat the patient with reduced-dose systemic alteplase (50 mg over 2 hours).The patient improved rapidly without bleeding complications and was discharged on long-term anticoagulation.She remained in excellent clinical condition at her 2-month follow-up. Conclusions:This case demonstrates that in pulmonary embolism, stability is more than a blood pressure reading.The presence of right ventricular strain together with a clot-in-transit can justify immediate treatment escalation.Reduced-dose systemic thrombolysis can be a reasonable option in carefully selected patients, but decisions should remain individualized.