When the Filter Becomes the Source: POCUS Detection of Inferior Vena Cava Filter Thrombosis Extending Into the Right Atrium

INTRODUCTION: Inferior vena cava (IVC) filters are used to prevent pulmonary embolism in patients with venous thromboembolism when anticoagulation is contraindicated. Although uncommon, filter thrombosis can result in thrombus propagation and potentially life-threatening embolic complications. Point-of-care ultrasound (POCUS) provides a rapid bedside assessment of the heart, lungs, and may facilitate the prompt recognition of unexpected thromboembolic complications. CASE PRESENTATION: A 43-year-old man with hypertensive intracerebral hemorrhage was admitted to the intensive care unit requiring mechanical ventilation and vasopressor support. Six days after admission, he developed sudden severe hypoxemia, tachycardia, and hypotension requiring reinitiation of norepinephrine. POCUS demonstrated bilateral anterior A-lines, left femoral and popliteal deep vein thrombosis, and preserved right ventricular (RV) function without echocardiographic evidence of RV strain. Catheter-based pulmonary angiography confirmed subocclusive thrombosis involving segmental branches of the right middle and lower lobes, which was treated with mechanical thromboaspiration, followed by IVC filter placement because anticoagulation was initially contraindicated. Four days later, he developed a new episode of acute hypoxemia despite remaining hemodynamically stable. Repeat POCUS demonstrated a large mobile thrombus in transit within the right atrium. Subcostal longitudinal imaging of the IVC demonstrated a large elongated thrombus attached to the IVC filter, with a freely mobile portion extending into the right atrium. Urgent mechanical thrombectomy and IVC filter replacement were performed. The new filter was positioned approximately 2 cm below the confluence of the hepatic veins with the inferior vena cava. Approximately 24 h later, follow-up POCUS showed no evidence of new thrombus formation. More than 2 weeks after admission, following a follow-up brain CT showing no significant progression of the intracerebral hemorrhage, anticoagulation with enoxaparin was initiated and progressively increased to a full therapeutic dose. CONCLUSION: This case highlights the value of POCUS for the prompt bedside recognition of an established and potentially life-threatening complication of IVC filter placement. Systematic bedside cardiac and venous ultrasound may identify thrombus propagation into the right atrium even in the absence of RV dilation or echocardiographic evidence of RV strain, facilitating timely endovascular intervention.