Unstable angina. (The Effective Physician).

Background

Ongoing reassessment of clinical trial data has prompted the American College of Cardiology and the American Heart Association to issue an update for the management of unstable angina and non-ST-segment elevation myocardial infarction (NSTEMI).

Conclusions

The term "acute coronary syndrome" is now used to describe patients with unstable angina and ST-segment elevation myocardial infarction. Unstable angina usually represents rest angina (usually greater than 20 minutes), new-onset angina (class III or greater), or increasing angina.

[beta]-blockers benefit patients with acute coronary syndrome by decreasing cardiac work and myocardial oxygen demand. By slowing heart rate, they also increase the duration of diastole and enhance coronary artery blood flow.

Ticlopidine and clopidogrel antagonize adenosine biphosphate and inhibit platelets via a pathway separate from aspirin. They appear to have similar or slightly enhanced efficacy for secondary prevention compared with aspirin but have a delayed onset of action that can take several days for the full effect to be seen. Clopidogrel appears to have a better safety profile and faster onset than ticlopidine. The Clopidogrel in Unstable Angina to Prevent Recurrent Ischemic Events (CURE) trial provided strong evidence of enhanced outcomes by adding clopidogrel to aspirin in patients with unstable angina and NSTEMI.

Low-molecular-weight heparin is now being used more frequently in the care of patients with acute coronary syndromes although unfractionated heparin is more readily reversed. Unfractionated heparin is preferred in patients who are likely to undergo coronary artery bypass surgery.