Thrombosis, or clotting, can occur in both the deep and superficial veins. Deep venous thrombosis (DVT) receives more attention because it is associated with significant mortality. 275,000 new cases of DVT are seen in the US per year. Those DVT patients who also have pulmonary embolism, in which part or all of the clot becomes dislodged and travels to the lungs, have an 18-fold greater risk of early death than patients with DVT alone. Therefore, deep venous thrombosis must be identified promptly and treated.
Risk factors for developing thrombosis, deep or superficial, fall into 3 categories:
- Factors which result in interrupted blood flow, or stasis. This group includes venous stasis and varicose veins from chronic venous insufficiency, prolonged immobility as occurs during a long surgical procedure, plane ride, or car ride. Those who can move their legs are encouraged to perform “calf pump exercises,” flexing and extending the foot to promote contraction of the calf muscle. This exercise prevents stasis of the blood.
- Alterations in the constitution of the blood resulting in “hypercoagulability.” These include congenital factors such as genetic mutations and clotting factor deficiencies. Acquired factors which alter the blood and increase clotting tendency include pregnancy, use of oral contraceptive pills or hormone replacement therapy, cancer, and smoking, among others.
- Conditions resulting in injury to the vein wall, especially the endothelium or inner lining of the vein. This group includes direct trauma to of vein, use of a medical device such as a central venous catheter or pacemaker, or any condition that produces chronic inflammation.
The diagnosis of DVT can sometimes be made clinically. Although DVT can be silent, signs and symptoms usually include pain, swelling, redness, and tenderness on squeezing the calf (Homan’s sign). Although duplex ultrasound has a greater than 95% accuracy, 80-90% of all scans are negative. Although it was hoped that the d-dimer blood test would reduce the number of scans needed to establish the diagnosis of DVT, it has not proven reliable.
The first line of treatment for deep venous thrombosis is anticoagulation. Agents such as heparin, warfarin, or one of a group of new agents which include Xarelto, Eliquis, and Pradaxa, can be used. Unless there are mitigating factors such as cancer or a history of previous clotting episodes, the initial course of treatment usually lasts 3 months. In patients whose risk of bleeding eliminates anticoagulation as an option, vena cava filters can be used to prevent emboli from reaching the lungs. One potential complication of deep venous thrombosis leads to a chronic condition called the post-thrombotic syndrome. When the patient is anticoagulated, it often takes weeks or months for the thrombus to clear. During this time, the valves in the deep veins may be damaged by the clot. This results in chronic venous insufficiency, similar to what occurs in the superficial veins. One way to reduce damage to the valves is to remove the clot in a more timely fashion surgically or with a catheter which combines the use of a thrombolytic agent (a chemical that can dissolve or loosen clot more rapidly than an intravenous blood thinner), a mechanical tool such as a rotating blade, to break up clot, a balloon which can be inflated above the clot to prevent pieces from traveling, and suction, to remove the clot. This approach has significantly reduced the incidence of valvular damage and post-thrombotic syndrome.
Superficial venous thrombophlebitis (SVT), commonly referred to as phlebitis, appears with pain, reddening of the skin, and swelling of the surrounding tissue. A firm tender “knot” is usually felt over a cluster of varicose veins. A clot forms in this location due to stasis of the blood in the dilated veins. Other risk factors include those mentioned above, namely immobility, hypercoagulability, such as from a genetic mutation or cancer, the use of birth control pills or hormone replacement therapy, or direct trauma to or inflammation around a vein. An ultrasound should be performed to rule out the simultaneous presence of a DVT, found in approximately 15% of patients with SVT. Treatment of superficial phlebitis includes compression stockings, nonsteroidal anti-inflammatory medication, either orally or topically, and exercise. Occasionally, the phlebitis can become so painful that it is necessary to remove thrombus surgically. Suspicion of hypercoagulability should arise when superficial thrombophlebitis occurs in unusual sites or in patients that have no varicose veins.