With a new immunoenzymometric assay we measured human glycogen phosphorylase isoenzyme BB (GPBB) in 116 healthy individuals, 14 patients with stable angina, 107 nontraumatic chest pain patients on admission to the emergency department [45 acute myocardial infarction (AMI), 49 unstable angina, 13 other diseases], and in serial samples from 41 AMI patients. GPBB was compared with creatine kinase (CK), CKMB mass, myoglobin, and cardiac troponin T. Receiver-operating characteristic plots demonstrated the significantly greater (P < or = 0.012) discriminatory power of GPBB to detect acute ischemic coronary syndromes compared with all other tested markers. GPBB was the most sensitive marker for detection of AMI during the first 4 h after onset of chest pain, and only GPBB was increased above the upper reference limit (7 micrograms/L) on admission in patients who had unstable angina at rest and reversible ST-T alterations. This and the high early sensitivity of GPBB are most likely explained by its function as a key enzyme of glycogenolysis.
Objective-To determine whether transient ST-T alterations in patients with unstable angina are associated with an increase in plasma glycogen phosphorylase BB concentrations on admission to hospital. Design-Prospective screening of patients with unstable angina for markers of myocardial cell damage. Setting-Accident and emergency department of university hospital. Patients-48 consecutive patients admitted for angina pectoris (18 with transient ST-T alterations). None of the patients had acute myocardial infarction according to standard criteria. Main outcome measures-Creatine kinase and creatine kinase MB activities, creatine kinase MB mass concentration, and myoglobin, cardiac troponin T, and glycogen phosphorylase BB concentrations on admission. Results-All variables except for creatine kinase and creatine kinase MB activities were significantly higher on admission in patients with unstable angina and transient ST-T alterations than in patients without. However, glycogen phosphorylase BB concentration was the only marker that was significantly (p = 0-0001) increased above its discriminator value in most patients (16). In the 18 patients with transient ST-T alterations creatine kinase MB mass concentration and troponin T and myoglobin concentrations were significantly (p = 0-0001) less commonly increased on admission (in five, three, and two patients, respectively). Conclusions-The early release of glycogen phosphorylase BB may help to identify high risk patients with unstable angina even on admission to an emergency department. Glycogen phosphorylase BB concentrations could help to guide decisions about patient management. (Br HeartrJ 1994;72:125-127) Glycogen phosphorylase is the key enzyme of glycogenolysis and has three main isoenzymes: BB (brain), MM (muscle), and LL (liver).' The isoenzymes are encoded by three distinct genes and differ in their functional and immunological properties,1 2 which makes it possible to develop specific immunoassays.Glycogen phosphorylase BB (molecular weight 96000 kDa as a monomer) is the predominant isotype in human myocardium where it occurs alongside the MM subtype.3 The release of glycogen phosphorylase from injured myocardium may reflect the burst in glycogenolysis initiated during acute myocardial ischaemia.4 This is supported by a rapid increase in serum concentrations of glycogen phosphorylase BB in patients with acute myocardial infarction before concentrations of creatine kinase, creatine kinase MB, myoglobin, and cardiac troponin T increase.5 Unstable angina, however, ranges from no myocardial cell damage to non-Q wave myocardial infarction. Myocardial ischaemia induces glycogenolysis and may lead to a transient loss of integrity of the plasma membrane, with a subsequent leakage of soluble cytosolic proteins in more severe cases.6 We therefore investigated whether glycogen phosphorylase BB is also released early from the myocardium-that is, on admission to the emergency department-in patients presenting with unstable angina and transient ST-T alterations...
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