Typically, the pain will resolve within three minutes. Back to Index. It may herald an impending myocardial infarction. Sudden change in the pattern of angina usually means a physical change within the coronary arteries, such as hemorrhage into an atherosclerotic plaque, rupture of a plaque with intermittent thrombus formation, or spasm. About a third of patients with the clinical syndrome of unstable angina will already have coronary thrombosis on catheterization.
Some experts regard any new-onset angina as unstable.
Typically, unstable angina is defined as angina of increasing severity, frequency, duration, or showing increasing resistance to nitrates, or angina occurring at rest. Untreated, unstable angina progresses to myocardial infarction within three months in half of cases. The patient with new onset or unstable angina should be hospitalized for intensive medical treatment. Back to Index. The pain of myocardial infarction is typically substernal, diffuse, with a squeezing or pressure quality.