Fibrinolytic therapy, also sometimes called “thrombolytic therapy,” is the use of special drugs to break up blood clots that are blocking a person or animal’s major artery. They are most commonly given to people after a heart attack or when a major blood clot has been discovered in a medical scan. In some places this sort of therapy is also being used, often on an “experimental” basis, for stroke victims. Health care workers sometimes refer to these types of drugs as “clot busters” because of their ability to break down and neutralize otherwise life threatening buildups. They do have the ability to save patients, but often work best either on minor clots or in the very early stages of an attack or episode. In many cases they are just one of many different medical interventions used to divert a health crisis.
How it Works
Blood clots happen when blood proteins coagulate to form a mass. Clots are really important on the surface of the body, as they can help wounds heal and prevent people from bleeding to death. Within veins and arteries, though, they can block blood flow, impede heart function, and sometimes even lead to death if they actually get into the brain, heart, or other organs. Most healthy people perform some level of clot break down as a natural biological process. This isn’t always enough, though. When larger blockages form, pharmaceutical therapy is often required.
Drug-based “clot busting” is typically known as “secondary fibrinolytics,” since it is designed to augment what the body already does or should be doing. It works primarily by using the enzyme plasmin to engage in a process called “thrombolysis,” which basically means breaking clots into smaller, more manageable fragments that can be dissolved or otherwise neutralized. Aminocaporic acid and tranexamic acid are two of the most frequently used inhibitors in this process.
This sort of therapy is almost always administered intravenously, which is to say with either an injection or a direct line into a vein. Sometimes pills or capsules can also be used as supplementation. It is usually only done by a professional health care provider in a hospital or clinic; rarely if ever are these sorts of drugs prescribed for home use or self-care.
Use in Heart Attacks
The therapy is very commonly used in heart attack victims to slow the rate of the attack and to help stabilize blood pressure and flow. A heart attack, also called a myocardial infarction, can happen when blood clots or plaque build up in and subsequently block a major artery that feeds blood to the heart. When blood flow to a specific area of the heart is stopped, that area usually starts to die. This is called ischemia. An ischemic heart can sometimes cause abnormal heart rhythms, which could lead to fainting or sudden death.
The best outcome for a heart attack victim occurs if fibrinolytic therapy is administered within 12 hours or less after the onset of symptoms. The efficiency of the drugs often depends on the age of the clot, since the longer a clot is present, the more fibrin it produces. “Fibrin” is a protein found in blood that helps it to clot. A clot that contains a lot of fibrin is harder to dissolve.
Pulmonary Embolisms
Blood clots can also be problematic even outside of the heart. A variety of deadly clots known as “pulmonary embolisms” are most commonly found in the lungs; on their own they can make it difficult to breathe and can cause chest pain, but the bigger risk is that they could break free and travel through the pulmonary artery directly into the heart, which often causes almost immediate death. Therapy in these cases can break down the clot before it has the chance to become deadly.
Potential Help for Stroke Victims
A number of medical experts are also experimenting with fibrinolytic therapy as a potential treatment for stroke victims. Strokes happen when the brain loses oxygen and cells die as a result. They are sometimes caused by blood and arterial obstructions, but not always; in any event, once they’ve happened it’s often too late to break up a clot or otherwise clear an obstruction. Still, some studies have shown that administering these sorts of drugs to stroke victims, particularly in the moments immediately after the event, may help restore function and improve recovery time.
Risks and Side Effects
Drugs used in fibrinolytic therapy often have a high risk for causing severe bleeding. As a result they shouldn't be given to patients who may have brain cancers, active internal bleeding, or recent trauma. Patients who have had major surgery within three weeks before treatment and pregnant women are generally not be given fibrinolytic drugs either.
Common side effects include low blood pressure, general feelings of weakness, and low energy. Allergic reactions to the therapy’s proteins or other ingredients are rare, but can happen. In isolated cases patients can also develop antibodies to the therapy that prevent it from being effective if used repeatedly.