Heart Attack and Acute Coronary Syndrome

Description

Alternative Names

Medications

Thrombolytic, or clot-busting, drugs are now mainstays in the early treatment of many patients with heart attacks. These drugs dissolve the clot, or thrombus, responsible for causing artery blockage and heart-muscle tissue death.

Specific Thrombolytics

The standard thrombolytic drugs used are recombinant tissue plasminogen activators or rt-PAs. They include alteplase (Activase and reteplase (Retavase)). Both are similar in effectiveness, although reteplase is easier to administer. Tenectaplase (TNKase), a newer agent, can be delivered more rapidly than alteplase, and to date, survival rates are similar. Streptokinase (Kabikinase, Streptase) is sometimes used but is somewhat less effective that the others. Other agents include anistreplase (Eminase) and urokinase (Abbokinase)--not available in the U.S.

Thrombolytic Administration

The earlier thrombolytic drugs are administered, the better. The advantages of thrombolytics are highest in the first 90 minutes and are still considerable at three hours. Administering these drugs more than 6 hours after symptoms have started adds little or no benefit. Of interest, some of these agents can now be given by emergency medical technicians (EMTs) before the patient reaches the hospital. Whether this will improve survival compared to angioplasty or other blood-thinning approaches, is not yet clear.

A thrombolytic agent, such as alteplase or tenecteplase, is typically administered with intravenous heparin, an anticoagulant agent. (Heparin, like aspirin, cannot destroy existing blood clots but can prevent clots from reforming after they are broken up.) Enoproxin, a form of heparin called low-molecular weight heparin, may be more beneficial than standard heparin.

Other anti-clotting agents are being tested in combination with thrombolytic agents. For example, studies are reporting modest improvements with the addition of glycoprotein IIb/IIIa receptor antagonists to low-dose thrombolytics.

Complications

Hemorrhagic stroke, usually occurring during the first day, is the most serious complication of thrombolytic therapy, but fortunately it is rare. Streptokinase given without heparin poses the lowest risk (although it is also less effective than other regimens in restoring blood flow). In general, the mortality rate from bleeding is only three in every 1,000 patients treated with thrombolytics, whereas 39 patients out of 1,000 would die without these clot-busting drugs. Recent evidence suggests that the survival benefits of thrombolytic therapy, particularly in combination with aspirin, last for years.