HMGB1 and intermediate coronary syndrome: Serum HMGB1 levels in patients with unstable angina pectoris and acute myocardial infarction were higher than those in patients with stable angina pectoris (both P<0.01), and serum HMGB1 levels in patients with acute myocardial infarction were higher compared with those in patients with unstable angina pectoris (P<0.01; Table II).