Blood Clot (Thrombosis)

What is thrombosis?

Thrombosis is the presence of a blood clot within an artery or vein. This blood clot has the potential to break away from an artery or vein and either partially or completely block the flow of blood to a particular area of the body. Depending upon the area of blockage, this can result in a variety of debilitating or fatal conditions, including stroke and heart attack.

How does a blood clot occur?

When the flow of blood slows down, usually due to inactivity, illness, or injury, the blood may collect in a small pool. If this pool of blood hardens or coagulates, a blood clot forms. Thrombus formation can also occur from a condition known as endothelial dysfunction. This causes a disruption in the integrity of the inner walls of blood vessels, and is usually associated with high blood pressure and/or diabetes.

How is a blood clot detected?

Blood clots are difficult to detect, as they often do not cause any symptoms. Doctors will often look for a blood clot following a surgical procedure (especially a knee or hip replacement surgery). If your doctor suspects that you may have a blood clot, he or she will order any of the following tests to make the diagnosis:

  • Doppler Ultrasound
  • Angiography
  • Computed Topography (CT) Scan, especially if they suspect a clot in the lungs
  • Ventilation-Perfusion Scan (Nuclear lung scan) if clot is suspected

What are the treatment options for a blood clot?

To treat a thrombosis, your physician may prescribe medications or perform specific procedures. Much of the treatment depends upon the severity of the blood clot.


There are three types of medications your doctor may prescribe:

  • Anti-Coagulants weaken blood clots and prevent them from expanding in size
  • Thrombolytic Agents dissolve blood clots, and are generally prescribed for larger, more dangerous clots; the most common thrombolytics are TPA (Tissue Plasminogen Activator) and TNK (a newer version of TPA)
  • Antiplatelet Agents are preventive drugs, and work to avoid new clot formation

Various therapies and procedures can also destroy blood clots. These are described below.

Intravenous (IV) Therapy

Thrombolytic Therapy: Thrombolytic agents, such as streptokinase or TPA, can be given intravenously (IV) to dissolve larger clots in the blood vessels. Thrombolytic therapy requires hospitalization to 1) administer the IV drug and 2) monitor patients for complications usually related to excessive bleeding.


Patients who cannot tolerate anti-coagulant medications due to allergies or excessive bleeding, or who develop a pulmonary embolism, may require a minimally invasive procedure to destroy a blood clot. These procedures are:

  • Filters
  • Thrombectomy (Embolectomy)