Deep Vein Thrombosis

Deep Vein Thrombosis

DVT/PE Relationship

DVT is the leading cause of pulmonary embolism.

Virchow Triad

The "Virchow Triad" comprises three factors that predispose an individual to deep vein thrombosis; each of the three elements of the Virchow Triad contribute to the formation of clots in the blood vessels.

Endothelial injury promotes clotting – endothelial injury can be due to fracture, surgery, trauma, or even previous deep vein thrombosis.

Upon injury, the endothelium responds by triggering the clotting cascade (review of hemostasis). If this process goes unchecked, and the clots are not ultimately dissolved, they can be problematic.

Venous stasis is another predisposing factor – venous stasis can be caused by immobility (if a person is bed-ridden or on a long flight, for example), elevated central venous pressure, heart failure, and obesity.

To prevent DVT in hospitalized patients, we use SCD's (sequence compression devices), which prevent venous stasis in the legs.
In select patients, we use prophylactic anticoagulants, which includes low doses of enoxaparin or heparin.
Note that heparin-induced thrombocytopenia is a worrisome complication of anticoagulant, but, overall, in the correct population, prophylactic anticoagulants can be an important way of preventing DVT.

Hypercoagulation states are predisposing medical conditions

Pregnancy (which is also associated with inferior vena cava stasis)
The post partum period
Smoking (which is also associated with endothelium damage)
Cancer
Medications, including combined hormonal contraceptives and some hormonal replacement therapies
Coagulation disorders, such as Factor V Leiden disorder.

Be aware that individuals with multiple predisposing factors (i.e., pregnant women who are put on bed rest, for example), are at higher risk for developing deep vein thrombosis.

Symptoms

When present, symptoms of deep vein thrombosis tend to arise unilaterally in the legs, leaving them swollen, tender, and with signs of venous dilation.

Deep vein thrombosis can occur in the upper body, too, but this is less common.

Post thrombotic syndrome

Post thrombotic syndrome occurs when the venous valves are damaged.

Diagnosis of DVT

For the diagnosis of deep vein thrombosis, we rely on the Wells Score for Deep Vein Thrombosis, which gives points based on several factors including the presence of swelling, edema, and the likelihood of alternative diagnosis.

D-dimer level is an important way to try to rule out low-probability DVTs.

If deep vein thrombosis is highly suspected, imaging with contrast venography or venous ultrasonography with compression can verify the presence of thrombus.

For references, please see our tutorial on Pulmonary Embolism and Deep Vein Thrombosis

Deep Vein Thrombosis

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