Deep Vein Thrombosis (DVT)

SAMUEL E. GREENBERG, M.D.

Deep Vein Thrombi (clots) occur when blood slows down, encounters obstructions, or is in hypercoagulable state. This generally occurs in the deep veins of the legs or the solar plexus blood vessels and occasionally in the deep vessels of the upper extremities. Within 5-10 days the clot adheres to the vein wall.

Before that it may propagate up the vein or a piece may break off and travel to the lung, causing a Pulmonary Emboli, resulting in consequences, varying from the absence of symptoms to death from hypoxia and shock. The local sequelae consists of venous varicosities, edema, stasis dermatitis, stasis ulcers, and even amputation, depending on the size and location of the clot.

Diagnosis of Deep Vein Thrombosis (DVT) is not always obvious, but if 3 or more risk factors are present along with certain physical findings, its presence is highly likely. Confirmation of the diagnosis is bolstered by Ultrasound/Doppler, MRI, Contrast Venography, etc. Treatment consists of thrombolysis, anticoagulation, bed rest, elevation of the extremity, heat, etc. Prevention is the best approach and consists of basic common sense knowledge such as, not sitting in one position for prolonged periods, wearing support hose, elevating the legs, etc.

Pieces of DVT, called emboli, are trapped in the lung because of the small vessels in that region. If too large an area is blocked off, then oxygen cannot reach the blood stream and the brain is deprived of oxygen. The patient may experience chest pain, shortness of breath, or coughing up of blood and tests will substantiate the diminution of oxygen in the blood. Special lung scans are used to confirm the emboli’s presence. Fibrinolytics, anticoagulants, and even surgery may be necessary, if a large portion of the lung’s vasculature is obstructed. A filter may be placed in the Inferior Vena Cava to prevent further emboli from traveling from DVTs in the legs to the lungs.

Blood has an inherent tendency to clot. This is especially expressed whenever it slows down, encounters rough surfaces, or is in a hypercoagulable state. This is referred to as Virchow’s Triad. These conditions exist in many circumstances, varying from trauma to the venous wall to prolonged sitting to clotting disorders. This is especially likely to occur in the deep veins in the extremities and in the solar plexus vessels and is noteworthy for 2 reasons: Local inflammation and Pulmonary Emboli.

Once a clot (thrombus) forms, it takes from 5 to 10 days to organize and adhere to the lining of the vein wall. Before that, it frequently dissolves, spontaneously, but it some cases, it may propagate proximally, extending into other veins, or a piece (embolus) may break off and travel to the heart and, subsequently, be trapped in the lung (Pulmonary Emboli).

After the Deep Vein clot organizes and adheres to the vein wall, it may slowly undergo recanalization, whereby the center of the clot breaks down and blood can once again traverse this area through the new channel. More frequently, inflammatory changes occur in the venous wall and signs and symptoms develop suggesting inflammation and peripheral obstruction to blood flow develops, such as swelling, warmth, redness and pain. The extent of the DVT will determine the extent of the signs and symptoms. If the thrombus is not dissolved by treatment, often it will disrupt the valves in the deep vein or completely occlude the venous lumen, retarding the blood return through that vein and forcing that blood to return to the heart by the remaining deep veins. This added volume causes the other veins to dilate, often disrupting their valvular integrity, resulting in varicosities, edema, skin breakdown, ulcers and even gangreen.

Risk Factors:

1.) Age,
2.) Immobilization for 3 or more days,
3.) Pregnancy and Post Partum,
4.) Major Surgery,
5.) Previous DVT,
6.) Cancer, which may cause a hypercoagulable state,
7.) Congestive Heart Failure, where blood is slowed down in the extremities,
8.) Stroke, where the muscle contractions, needed to pump the blood out of the extremities is lost.
9.) Acute Heart Attack, necessitating bed rest and diminished blood pulsation,
10.) Sepsis,
11.) Excessive edema, from fluid retentive illnesses, such as the Nephrotic Syndrome, and diminished Albumin,
12.) Ulcerative Colitis,
13.) Trauma, which damages the inner lining of the vein,
14.) Burns,
15.)Fractures,
16.)Spinal Cord injury,
17.) Polycythemia and Thrombocytosis, which consists of increased red blood cells and platelets, respectively, causing the blood to be to thick and increasing the tendency to clot,
18.) Certain drugs such as contraceptives, Estrogen, which induce a hypercoagulable state, and IV drug use, which injures the lining of the vein wall.

Diagnosis: The presence of 3 or more of the above risk factors is very helpful in suggesting the propensity for DVT to develop. Along with this are the signs and symptoms, while not being specific, are very helpful.

Signs &Symptoms:

Swelling, Pain, Tenderness, Warmth, unilateral edema, prominent superficial veins, diminished emptying of peripheral veins when the extremity is elevated to and above the heart level. Sometimes a cord is palpable, especially when superficial thrombophlebitis is associated. Fever may be present. Pain in the calf with straight knee and dorsiflexion of foot (Homans Sign) is suggestive, but not specific.

Laboratory Studies:

1.) D-dimer blood test - this is a product of the degeneration of fibrin in the blood. This is a screening test, but is non-specific.
2.) RBC agglutination assay - screening test. (not accurate for Calf Vein Thrombi). (about 50-60 % accurate).
3.) Qualitative ELISA assay - not accurate as a test for Calf Vein Thrombi ( about 79% accurate).

Radiology :

1.) The gold standard for diagnosis of DVT is a venous angiogram, but this is tedious and expensive, and often a test of last resort.
2.) The Duplex Ultrasound study, utilizing Ultrasound and Doppler modalities, measuring the blood flow by compressing the deep vein is 98% specific and sensitive.

3.) Impedence Pletysmography, which measures the blood volume in relationship to venous outflow is used by many Physicians, but is not as sensitive as the Duplex U/S study.

4.) MRI- is an expensive, but very helpful study and is often used in confusing situations.

The most difficult DVT to detect is when the thrombus is either non-occluding, or proximal to the inguinal ligament or in the calf. Sometimes a repeat evaluation and study is necessary when the first test is equivocal.

Treatment: Thromboysis- if instituted early, these drugs, such as may dissolve the clot entirely.

Anticoagulants- started early to prevent the DVT from propagating, proximally, up the vein and to prevent other clots from forming.
Elevation and Support Hose to encourage the blood to flow faster in it’s return to the heart. Heat to encourage rapid inflammatory resolution and adherence of the clot to the vein wall.

Prevention: This is most important. Sitting or standing for too long stagnates the blood. Crossing the legs, or letting them hang down for long periods slows the blood. Obesity and edema in the lower extremities from other causes places a burden on the deep veins. Failure to elevate the legs after trauma, which distorts the blood flow through damaged veins is causational. Prolonged bed rest without elevation, active and passive exercises of the extremities is a risk. Failure to use Compression Stockings post-operatively or post-partum is risky. Tight elastic top stockings will slow the blood down. Don’t let these things happen!