Indication for Inferior Vena Cava filter placement?

An inferior vena cava (IVC) filter is a mechanical device inserted into the IVC to trap thromboemboli before they reach the pulmonary circulation. Its placement is indicated in specific, narrow circumstances: recurrent pulmonary embolism (PE) despite therapeutic anticoagulation, or when anticoagulation is absolutely contraindicated — for example, due to active life-threatening hemorrhage, recent intracranial surgery, or a high bleeding risk that makes anticoagulation unsafe. IVC filters are not indicated for all first-time PE patients; most first-time PE cases are managed with anticoagulation alone. A low D-dimer with low clinical probability effectively rules out PE, and an IVC filter would never be placed in this scenario. Routine placement after ten days of heparin in every patient is not evidence-based and would expose patients to device risks (including filter thrombosis, IVC occlusion, and migration) without clinical benefit. The filter is a last resort when anticoagulation fails or cannot be used safely. The keyed answer is correct.