The cardiospecificity of the MB isoenzyme of creatine kinase, EC 2.7.3.2, (CK) with its associated diagnostic and research value has resulted in the development of a number of procedures for the separation and quantitation of the three isoenzymes of CK. In our experience methods involving cellulose acetate electrophoresis, apposition incubation, and fluoroscanning for quantitation are of limited linearity, insensitive, and irreproducible. We have, therefore, developed a method which overcomes these difficulties. Our method is based on agarose gel electrophoresis, gel overlay incubation with optimisation of all substrates and elution of the NADPH into solution for isoenzyme quantitation. We have: (1) characterised this technique; (2) used it to verify the extent to which the MB isoenzyme of CK is cardiospyocardial; (3) studied its application to the diagnosis of acute myocardial infarction; and (4) compared it with existing methods involving dithiothreitol activation and ion exchange chromatography.

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In this two-step automated assay of the MB isoenzyme of creatine kinase (CK-MB), developed for the Abbott "IMx" immunoassay analyzer, monoclonal anti-CK-MB antibody immobilized onto latex microparticles and polyclonal anti-CK-MM antibody coupled to alkaline phosphatase are used. Within-run CVs ranged from 3.9% to 9.0%, between-run CVs from 0.0% to 5.6%, and the sensitivity was 0.2 microgram/L. Twenty-four results can be obtained in about 37 min. Analytical recovery of CK-MB added to human serum or plasma ranged from 89% to 109%. Icteric, lipemic, or hemolyzed samples did not interfere with CK-MB recovery. Cross-reactivity with CK-MM and CK-BB was 0.012% and 0.001%, respectively. The normal reference interval was 0-5 micrograms/L. IMx CK-MB results correlated well with CK-MB enzyme activity as determined by electrophoresis (n = 203; r = 0.97; slope = 0.90; y-intercept = -4.29) and with commercial immunoassays. We think that this assay will be useful for confirmation of acute myocardial infarction, both in critical-care units and in the clinical laboratory.

The experimental evidence relating ST segment elevation in the electrocardiogram to the progress and extent of ischaemic myocardial damage is discussed. There are difficulties in applying this to patients: the reproducibility of praecordial mapping was tested using a multiple analysis of variance. This showed that factors such as time after the onset of myocardial infarction and posture can affect measurements of sigmaST elevation significantly. There was a pattern of changes in segmaST elevation and of changes in plasma MB CK activity in a group of patients with uncomplicated anterior infarction. A significant byt weak correlation was found between sigmaST elevation in the first hour and the total MB CK activity released into the plasma, but not at any other time. The use of sigmaST elevation as a measure of the extent of ischaemic damage is unreliable. In 5 patients with a variety of complications of acute anterior infarction, changes in sigmaST elevation werr significantly different from the uncomplicated group, and MB CK release profiles suggested further necrosis. The pattern and time course of ST segment changes may be of use in assessing the progress of ischaemic myocardial damage.

A method has been developed ofpraecordial mapping of changes in R/S ratio and the appearance of Q waves in acute myocardial infarction. Observation of the serial changes in R and Q waves in 40 patients with uncomplicated anterior infarction shows that the loss of electrically active myocardium occurs within 6 hours of the onset of chest pain. Complications, such as recurrent chest pain, associated with extension of myocardial necrosis can be identified and assessed. The total praecordial changes in R/S ratio and Q wave amplitude correlate with the total MB fraction of creatine kinase activity released into the plasma in 20 patients after uncomplicated anterior infarction. This techniquefor identifying thosefactors that may modify the progressive loss of active myocardium in the early phase of acute infarction of the heart is noninvasive and repeatable.In patients with acute myocardial infarction the extent of tissue damage is important in relation to morbidity and mortality. Recently research has been directed to the development of techniques and interventions that will lead to the salvage of active myocardium in acute infarction (Maroko et al., 1971;Maroko, 1974).The electrocardiogram undergoes a series of changes after the onset of acute regional myocardial ischaemia (Johnston et al., 1935; Wilson et al., 1935a, b). The localised loss of R waves and the appearance of Q waves is thought to represent the loss of electrically active myocardium (Johnston et al., 1935;Wilson et al., 1935a;Prinzmetal et al., 1954;Shaw et al., 1954;. Praecordial surface mapping of the electrocardiogram in man has been developed to follow the changes in R/S ratio, and amplitude of R and Q waves during acute myocardial infarction .It is the purpose of this paper to describe the pattern and time course of the loss of electrically active myocardium in a group of patients with uncomplicated anterior infarction. A relation is shown between these changes in the praecordial map and the extent of cell necrosis assessed by the total release of the myocardial fraction of creatine kinase (MB CK). The significance of the loss of R waves and the appearance of Q waves in relation to the underlying pathology and the possibility of limiting infarct size by therapeutic intervention is discussed."This work was financed in part by the British Heart Foundation. Received for publication 28 January 1977 Patients and methods The 45 patients (34 men and 11 women, aged between 42 and 74 years, mean 55 years) were admitted to the coronary care unit at the Hammersmith Hospital with a clinical diagnosis of acute anterior myocardial infarction. All these patients developed electrocardiographic evidence of acute myocardial infarction on the standard 12-lead electrocardiogram and all had a diagnostic rise in serum enzymes. While in the coronary care unit, 40 of the patients did not develop any of the following major complications: (a' recurrent chest pain lasting more than 10 minutes after the initial episode of pain; (b) clinical or chest x-ray evidence of con...