Caught in Transit: Thrombus Traversing a Patent Foramen Ovale.

While a patent foramen ovale (PFO) is a very common anatomic variant, thrombus-in-transit through a PFO is a rare and potentially life-threatening event. Such thrombi can lead to paradoxical emboli, causing multi-organ thromboembolic events with significant hemodynamic and functional consequences depending on the affected systems. Here, we present a case of a 65-year-old man with hypertension who arrived with neurologic deficits, found to have an acute left temporal lobe infarction, and was subsequently found to have a saddle pulmonary embolism. Transesophageal echocardiography then revealed a ten-centimeter thrombus-in-transit across a PFO, and he was later found to have a deep vein thrombosis. The PFO was determined to be the source of his systemic and pulmonary emboli. The patient, initially ineligible for thrombolytics, was managed with mechanical thrombectomy and systemic anticoagulation, leading to gradual clinical improvement. The patient stabilized post-thrombectomy and was ultimately discharged. On ambulatory follow-up, the patient was asymptomatic, without further clotting events. Repeat anticardiolipin testing was negative. This case illustrates the critical need for urgent anatomical assessment for PFO in patients presenting with concurrent right- and left-sided thrombi suggestive of paradoxical embolism. Early detection of thrombus-in-transit can guide risk stratification and inform management, which could potentially improve outcomes for patients with complex thromboembolic presentations.