Unstable angina pectoris as a warning symptom before acute myocardial infarction.

Four hundred patients who were admitted over the last three years with myocardial infarction were questioned about the presence and pattern of angina before its onset. Two hundred and twenty-four (56 per cent) patients had angina before their infarction; 184 (46 per cent) had the unstable pattern of angina. That such a high proportion of patients experience unstable angina as a prodromal symptom makes it possible that myocardial infarction could be prevented in some of these patients. Patients with previous angina had a higher incidence of subendocardial infarction than patients without angina (stable or unstable) (p less than 0.01). In-hospital prognosis was better in patients with chronic or unstable angina than in patients without angina (p less than 0.05).