Thrombus-in-Transit Across a Patent Foramen Ovale: Echocardiographic Recognition and Multimodality Management of a Fatal Paradoxical Event.

Thrombus-in-transit (TIT) across a patent foramen ovale (PFO) is a rare but life-threatening phenomenon that can result in paradoxical systemic embolism. Simultaneous deep venous thrombosis, pulmonary embolism (PE), and an intracardiac shunt create a critical scenario requiring rapid recognition. We report an 83-year-old woman with recurrent venous thromboembolism who presented with progressive dyspnea, pleuritic chest pain, and lower-extremity swelling. Laboratory evaluation revealed leukocytosis of 13.6 ×10⁹/L, thrombocytopenia of 67 ×10⁹/L, creatinine of 1.42 mg/dL, lactate of 2.57 mmol/L, and D-dimer of 32.53 µg/mL. Arterial blood gas analysis showed a pH of 7.47, pCO₂ of 23 mmHg, and pO₂ of 57.8 mmHg. CT pulmonary angiography demonstrated extensive bilateral pulmonary emboli with a left atrial filling defect, while echocardiography revealed a large mobile thrombus crossing a PFO with severe right ventricular dysfunction. The patient underwent emergent pulmonary embolectomy with PFO closure and left atrial appendage ligation but developed refractory cardiogenic shock and multiorgan failure despite venoarterial extracorporeal membrane oxygenation support and died 48 hours later. This case emphasizes the critical role of multimodality imaging in rapidly identifying TIT across a PFO and guiding time-sensitive multidisciplinary management.