Deep Vein Thrombosis: Pathogenesis

00:00 A little bit about the pathogenesis: You've seen this slide before. As you heard, 90% of DVTs and pulmonary emboli occur in the veins of the leg. Often, they start as very small clots in the popliteal vein, and often, they will dissolve and heal without any problem.

00:20 But once they get up into the femoral vein, which is a lot of people—you see, 42% of people—there is a greater likelihood of the clot growing. And then you can see, once it gets up into the common femoral vein or the iliac vein, inferior vena cava, there's a very significant chance that a large mass of clot will embolize to the lung and might prove to make the patient either very sick or even die. Just to emphasize one more time: The consequences of venous thromboembolism—pulmonary embolism—can be fatal. It can cause a very serious illness, acute morbidity. Once you've had one, you're at high risk for more. Thrombophlebitis itself, as you know, can lead to the postthrombotic syndrome, with edema and ulcers and, in a rare case, even amputation. So thrombophlebitis is defined as the presence of a thrombus in the vein. It's accompanied by inflammation in the vessel wall. It can happen, of course, in superficial or deep veins. The dangerous one is one that occurs in deep veins, not in the superficial veins. Of course, the danger is pulmonary embolism, and we've already talked about all the things that can lead to deep venous thrombosis, including long periods of sitting or standing, or a long plane trip. We've also already mentioned the postthrombotic syndrome. This is a long-term complication of DVT and venous insufficiency, where the internal veins are not working well. The valves are not working. Blood pools. The vein dilates. There's a great tendency for a blood clot to form. Edema forms. There's poor skin nutrition, and often, ulcers develop. The blood proteins and other blood products (hemoglobin) are deposited in the tissues, giving a brown discoloration, and the ulcers can be exceedingly difficult to heal, taking many months to heal with constant therapy.

02:28 Again, just to reiterate for how common DVT is: Patients in the United States in one year will have clinically evident venous thromboembolism—a total of 900,000 patients. And the deaths there are about… that are due to pulmonary embolism are about 300,000. And the annual incidence of venous thromboembolism increases by age and sex, as you can see in the graph.

02:58 Particularly as patients get above age 55 to 65, there's a marked increase in venous thromboembolism. Males a little more than females, but not very, very much difference.

03:11 Again, a huge increase. This data comes from the Worcester Vein Study in Worcester, Massachusetts.

03:19 The University of Massachusetts Medical Center has been studying all cases of DVT/PE in Worcester County over many years. The symptoms: I think we've already talked