• Thrombosis is the formation of blood clots in veins or arteries. Clots can threaten the blood supply to the heart, lungs, or brain.
  • Thrombolysis, also called clot-busting therapy, uses specialized catheters to deliver medications to dissolve blood clots or mechanically breaks up the clot.
  • Thrombolysis can be associated with serious side effects, and therefore is usually reserved for major blood clots in serious circumstances, or is used after other drugs have failed.
  • 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.
  • The presence of atherosclerotic plaque on blood vessel 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
    • People who have broken large bones
  • To dissolve a clot, a physician may use thrombolysis, a treatment method that breaks up a clot with specialized catheters that either mechanically break up the clot or directly deliver drugs to the affected area.


Usually physicians will withhold thrombolytic therapy for blood clots because other drugs, most specifically anticoagulants such as heparin or warfarin, which help prevent clots from forming, may also reduce the risk of complications from clots but with fewer side effects. Thrombolytic therapy with clot-busting drugs is usually reserved for patients in critical situations, such as patients having or at imminent risk of having a heart attack or stroke because a clot has already formed.


Patients most likely to undergo thrombolysis are those with symptoms of a heart attack, pulmonary embolism, or stroke, for instance chest pain, numbness, blurred vision, or slurred speech.

However, the drugs used in thrombolysis may be harmful for patients with:

  • Severe hypertension
  • Hemorrhagic stroke or other bleeding conditions
  • Allergies to the medication
  • Severe liver disease
  • Recent falls, injuries, or surgical medical procedures

Patients on antibiotics or some non-steroidal anti-inflammatory drugs (NSAIDS) may not be candidates for thrombolytic therapy.


Before the procedure, the physician may perform a blood test and adjust the patient’s medication. In addition, patients may be asked to limit their food and liquid intake before the procedure. Typically, the procedure will begin with the doctor performing an arteriogram to locate the clot.

During the procedure, the patient’s skin is cleaned and any hair around the insertion point is shaved. The insertion point is numbed with a local anesthetic, and the physician makes a tiny incision to access the artery. The physician punctures the artery with a hollow needle and advances a fine wire into the artery. A catheter is threaded over the wire and manipulated to the desired location using the X-ray machine to “see” the catheter as it moves through the arteries.

Once the catheter is in place, it is used to inject x-ray dye in the patient. During and after the injection, X-ray images are taken at timed intervals to capture the flow of the dye through the arteries and locate the clot.

Once the clot has been located, the physician will begin to administer the medication using a machine that will deliver a precise dose to the clot. While the procedure is ongoing, medical professionals will monitor the patient’s heart rate, blood pressure, medication rate, the insertion point, and signs of bleeding.

Once the clot has been dissolved or if it cannot be dissolved further, the physician will discontinue the medication, remove the catheter, and apply manual pressure to the area for 10 to 20 minutes. The arm or leg into which the catheter was inserted should be kept straight for several hours afterward.


Thrombolytic therapy is usually reserved for emergencies because of its high complication rate, though most complications are manageable. Bleeding complications are the most common. Patients older than 65 years and patients with high blood pressure have a higher risk of developing complications.


Because thrombolytic therapy is almost exclusively a crisis management approach, follow-up care is related more to the originating problem than to the specific thrombolytic product or approach used.

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Medical Review Date: June 19, 2007 / Copyright © 2012 NorthPoint Domain, Inc. All rights reserved. This material cannot be reproduced in digital or printed form without the express consent of NorthPoint Domain, Inc. Unauthorized copying or distribution of NorthPoint Domain’s Content is an infringement of the copyright holder’s rights.