Angina pectoris is the cardinal symptom of coronary heart disease and is a symptom with which physicians are very familiar. The clinical diagnosis of ischaemic heart disease is often based largely on a history of typical chest or arm pain, and the major therapeutic endeavour in such patients is directed towards abolition or amelioration of angina. Indeed physicians have, at least up until recently, been confident in assuming that angina is a reliable marker of ongoing ischaemia and that success of medical or surgical treatment of coronary heart disease can be accurately gauged according to improvement or disappearance of anginal symptoms (Cohn & Braunwald, 1988). However, the results of a number of important clinical studies, reported over that last 10 to 15 years, appear to challenge these traditional medical assumptions. In many patients with coronary heart disease, acute episodes of myocardial ischaemia are frequently unaccompanied by angina, often referred to as "silent myocardial ischaemia" (Epstein et al., 1988; Fox, 1988; Cohn, 1985; Maseri, 1985). It has to be pointed out that not all painless ischaemic episodes are truly silent. Instead of experiencing pain during some episodes of acute myocardial ischaemia, patients may, on occasion, instead report symptoms such as dyspnoea or palpitations (these symptoms being known as "anginal equivalents") (Cohn & Braunwald, 1988). Nevertheless, the great majority of painless ischaemic episodes are, truly silent and not accompanied by "anginal equivalents", which has led to the trend in the recent literature to regard the terms "silent" and "painless" myocardial ischaemia as synonymous.