Abstract

Angina is considered unstable if it first presents suddenly or with unusual severity, if it increases markedly in frequency and ease of provocation, or if it occurs at rest. The term usefully encompasses the near-synonyms crescendo angina, acute coronary insufficiency, intermediate coronary syndrome and pre-infarction syndrome. Unstable angina is a medical emergency because, if untreated, it is liable to lead to myocardial infarction (MI) or sudden death. A third of patients with unstable angina give no history of previous angina. The difficulty, sometimes, in distinguishing unstable angina from MI when the patient first presents can complicate the performance and interpretation of clinical studies. Modern management is based on better understanding of the mechanisms of angina and on the results of randomised controlled clinical trials.