Based on the pathophysiologic characteristics of venous thromboembolism (VTE), the inferior vena cava filter (IVC) should work. Placed between the proximal vessels of the lower extremities—the main source of venous emboli1-3—and the right side of the heart, the IVC filter should capture a blood clot before it reaches the pulmonary circulation and should improve outcomes. This theory, however, has never been validated by empirical studies. This may seem surprising for a device so well established in medical practice. The history of the IVC filter provides valuable insight into the shortcomings of medical device approval in the United States.