Background
Venous thromboembolism (VTE) is a serious complication that is frequently encountered in medical and surgical practice. Approximately 2 million people each year will suffer from a deep vein thrombosis (DVT), and approximately 600,000 of these individuals will suffer a pulmonary embolism (PE), which is fatal in about 200,000 patients annually. 1 Pulmonary hypertension can be expected to develop in approximately 30,000 patients who survive their PE. The postthrombotic syndrome (PTS) will be seen in approximately 800,000 patients annually in the United States; 7% of these individuals will have a severe form of the problem and become permanently disabled. 2 One of the most troubling statistics is the fact that 50% of the 2 million cases of DVT yearly are "silent." Occasionally, the first sign or symptom of the disease is a fatal PE. 3 Furthermore, it has been estimated that approximately 1 of 20 hospitalized medical patients will suffer a fatal PE if they have not received appropriate thrombosis prophylaxis. 4 Another serious complication of DVT is nonhemorrhagic stroke that may occur in a patient with a patent foramen ovale. 5 A clot in the deep venous system of the leg can break off and travel to the right atrium, dilating that heart chamber. If the patient is one of the 25 or 30% who have a nonfunctioning patent foramen ovale, this atrial dilatation can open the patent foramen and allow the clot to enter the left side of the heart and proceed to the brain, producing a stroke. 6 The diagnosis of this problem is difficult because once the right atrium returns to normal size, the patent foramen ovale may be difficult to detect. Often when the clot breaks off from the leg, it does so cleanly without residual damage that can be detected on subsequent duplex examination. 6 Table 1 shows some of the commonly seen problems that at first glance