Antithrombotic Agents in Coronary Artery Disease

Four large trials using aspirin in patients hospitalized with unstable angina have shown marked reductions of MI and cardiac death. Two of these trials have also evaluated heparin, and the combination among such patients. Full-dose heparin tended to be more effective than aspirin alone in the trial in which the patients appeared to have a more unstable form of angina managed with a high rate of coronary angiography and intervention. Further data from this trial indicate that the benefits of heparin alone were rapidly lost upon discontinuation, whereas the benefits of the combination of heparin and aspirin were sustained when the heparin was discontinued. In the other trial, heparin alone was less effective than aspirin alone, but the combination of heparin and aspirin appeared to have the greatest reduction of MI and death in the first five days. Accordingly, there is a good argument to start aspirin immediately upon the diagnosis of unstable angina and to continue it indefinitely. Those patients who appear particularly unstable with profound episodes of ischemia, particularly with recurrences in the CCU, are likely to benefit from the addition of heparin (APTT 1.5 to 2 x normal) to their aspirin therapy for the duration of the period of instability of their angina. If cardiac surgery is planned, heparin may be given in preference to aspirin, until immediately postoperatively.

One large study of ticlopidine among patients with unstable angina found significant reductions of nonfatal and fatal MI, indicating that this drug would be a suitable substitute for patients with aspirin intolerance or allergy.