FEW IMAGES are scarier than a venous ultrasound examination that demonstrates a long thrombus with its tail wobbling in the lumen of the femoral or iliac vein. The intuitive approach in this situation is almost irresistible: place an inferior vena caval filter as soon as the interventional angiographer can be summoned from home. (This scenario almost always occurs at night or on weekends.) If we pause to consider whether such a strategy follows "evidence-based medicine," the reaction from both the referring physician and the patient's family is likely to be, "How can you ask such a question? Why are you delaying? Are you certain the patient will not suffer a major and possibly fatal pulmonary embolism?"
Why hesitate to place a filter? Should filter placement for a free-floating thrombus simply be listed as a necessary step in critical pathways developed to manage venous thrombosis? Is there ever justification for pause