Classification of myocardial infarction and unstable angina: a re-assessment.

True or impending myocardial injury is being defined as an acute coronary syndrome (ACS), and includes ST-segment elevation MI, non-ST-segment elevation MI, and unstable angina. According to the revised MI definitions, patients with ischemic symptoms but with only a minor rise and fall in any biomarker are now being classified as having true myocardial injury. Against this background, this paper re-examines the position of "unstable angina" within the ACS context. It now must be acknowledged that the most recent definition of unstable angina, from 2000, which divided patients with unstable angina in those who were troponin-positive and those that remained troponin-negative, overlaps with the current MI definition. The seminal 1989 clinical definition of unstable angina thus remains the most appropriate description of that ACS entity. This "paradigm shift" has significant bearing on both the numbers of patients with non-ST-segment elevation MI, as well as on their prognosis. The same is true for patients now being diagnosed as having "unstable angina." To a large extent, future cardiovascular risk is determined by clinical parameters, and their proper assessment thus remains paramount. Elevated age, previous MI, diabetes and/or renal dysfunction and, in particular, the presence of recent onset of symptoms (Braunwald category IIIB) with concomitant ECG changes should identify those at high risk. Patients with such characteristics should benefit from thorough medical management, including extensive platelet inhibition in most and coronary revascularization in many.