MECHANISMS OF MYOCARDIAL-ISCHEMIA

Traditionally, myocardial ischemia has been viewed as an imbalance in the supply and demand of myocardial oxygen. Stable angina is usually considered to involve a fixed lesion, whereas unstable angina involves a fixed lesion as well as such components as platelet aggregation, thrombotic processes, and vasospasm. Variant angina involves primarily vasospasm, A newer concept holds that most angina results from mixed mechanisms in which both fixed lesions and vasomotor alterations play a role. These mechanisms are responsible for mixed ischemic events, characterized by episodes at varying levels of exertion, with or without anginal pain. This concept would seem to be supported by the occurrence of silent ischemia in the setting of stable, unstable, or variant angina, despite differing pathophysiologic conditions. Ischemic events have important prognostic significance; unfortunately, many are unrecognized by patients the question whether the treatment of ischemic events will improve prognosis remains a matter of debate.