Thrombolytic or "clot-busting" therapy is used to stop a heart attack in its tracks. Drugs such as tPA or streptokinase prevent or limit heart muscle damage by dissolving clots that block an artery. This opens the artery and restores the flow of oxygen and nutrients in the heart muscle.

Clot-busting drugs must be given as soon as possible after heart attack symptoms begin. The sooner they are started, the more good they do, and the greater the chances for a full recovery.