Basic Facts

  • Thrombosis is the formation of blood clots in veins or arteries. Clots can be stationary or can travel through the circulatory system and lodge in critical veins and arteries such as those supplying blood to the heart, lungs, or brain.
  • Thrombolysis, also called clot-busting therapy, breaks up a blood clot with specialized catheters that either mechanically breakup the clot or directly deliver drugs to dissolve blood clots that otherwise could lead to a pulmonary embolism, heart attack, or stroke.
  • Thrombolysis can be associated with serious side effects and is usually a second-line approach to clots--after other drugs have failed or during an emergency.

Usually blood is liquid so blood cells and other molecules may travel smoothly through the arteries and veins. Sometimes, however, clots form in a process called coagulation, during which platelets interact with clotting factors to form clumps of cells. Such clotting is the body’s way of stopping blood loss because of injuries or punctures in blood vessels. 

However, pieces of these clots can break off and enter the circulatory system, and then lodge in blood vessels, potentially blocking blood flow. Clots also can form when blood flow is sluggish, or when the interior walls of blood vessels become damaged and rough such that blood products catch on the walls and snag other bloodstream components, eventually blocking all or part of the blood vessel. 

Atherosclerosis, the buildup of cholesterol and fat (plaque) on the artery walls, is a major risk factor for clot formation. Damage to blood vessels walls because of an injury or surgery also increases the risk for blood clots.

A pulmonary embolism, a clot lodged in the pulmonary artery, can also obstruct the blood supply to the lungs and is a potentially fatal situation, to be treated as an emergency.

Others at risk for clot formation include: 

  • People with cancer because of factors associated with a tumor,
  • People with reduced lower-leg circulation because of bed-rest after surgery or during pregnancy,
  • People who are immobilized because of spinal cord injury or head injuries, and
  • People who have broken large bones.

Thrombolysis FAQ