The treatment options for a blood clot depend on whether the clot has formed in a vein or an artery and caused a heart attack or stroke. In emergencies, thrombolytic medications (clot busters) may be used to dissolve the blood clot. These medications are administered intravenously (I.V.) to carefully selected patients according to a rigid protocol. To be fully effective, they must be given at least within one hour of the heart attack or within three hours of the stroke.

Thrombolytics are usually used with large clots that are causing severe, life-threatening symptoms. They can cause sudden bleeding and may not be suitable for all patients.

More invasive procedures may also be an option. For example, catheter-directed thrombolysis may be used, in which a catheter delivers thrombolytic enzymes directly to the blood clot. During this procedure, higher concentrations of enzymes can be used and there may be fewer side effects than when the enzymes are given intravenously.

Thrombolytic treatment is usually followed by treatment with anticoagulants to prevent additional blood clots from forming. Anticoagulants may also be prescribed to patients who have a high risk of developing a blood clot.  

Researchers are also working on various catheter-based procedures to quickly treat stroke. One procedure involves using a tiny “corkscrew” device that quickly reverses the damage caused by the stroke. This device is guided to the location of the blood clot, where it retrieves and removes the obstruction. Other emergency methods include a catheter-directed device that may be able to break up and suck out a soft clot or “scoop” out a hard clot from an artery, reducing the risk of complications. These new therapies may someday be available to patients who cannot tolerate clot-busting drugs.

If a blood clot forms in a leg vein (deep vein thrombosis), there is some risk that a pulmonary embolism will develop. A pulmonary embolism is a potentially life-threatening event in which a blood clot breaks off from its original location, travels through the bloodstream and lodges in one of the blood vessels of the lungs.

To prevent a pulmonary embolism, existing blood clots in the legs can usually be treated with a combination of heat, painkilling medications, thrombolytics, anticoagulants and elevation/bandaging of the affected area to reduce swelling. The approach will depend on the size of the clot and the severity of any existing symptoms.

If patients do not respond to anticoagulants, physicians may opt for a procedure using a catheter tipped with a special device called a vena cava filter. The vena cava filter is implanted in the large vein that carries blood from the legs to the heart and lungs, the vena cava. The vena cava filter is a device that catches blood clots in the vein before they are allowed to reach the lungs.

There are some risks associated with vena cava filters, including breakdown of the filter over time and blood clots caused by the filter itself. Researchers are working on developing vena cava filters that can be retrieved after the threat of pulmonary embolism has passed.

Studies have also confirmed that long-term therapy with low-dose anticoagulant drugs helps prevent the recurrence of blood clots among those with a history of deep vein thrombosis or pulmonary embolism.

Each patient’s treatment approach will depend on the location of the clot, its size and the patient’s general health.