Detection of cardiac-specific creatine kinase isoenzyme in sera with normal or slightly increased total creatine kinase activity.

We describe a spectrophotometric kinetic assay for detecting creatine kinase MB isoenzyme activity in the 1 to 10 U/liter range. The MB isoenzyme was isolated [Clin. Chem. 20, 36 (1974)] and assayed (Rosalki method) with an Abbott ABA-100. Good reproducibility was demonstrated for MB isoenzyme activities near 1 U/liter (CV = 2.6%). Sera with normal or slightly increased total creatine kinase activity were evaluated. Sera of 14 patients with acute myocardial infarction contained, per liter, 84 to 236 U of total creatine kinase activity and 4.6 to 28.0 U of isoenzyme MB activity; corresponding ranges for sera from healthy lab technicians and patients with noncardiac disease were 36 to 277 and 0 to 2.6 U. MB isoenzyme activity for infarction patients rose and fell sharply within three days after the infarction. Atypical time-course patterns, MB isoenzyme activity remaining abnormally great for five days, were observed in serum from patients with prolonged atrial fibrillation and congestive heart failure or cardiomyopathy; the BB isoenzyme (1 to 5 U/liter) was also detected in sera of such patients but was absent in sera from infarcation patients. Quantification of column-isolated MB by the assay described is rapid, easy, specific, and extremely sensitive for measuring MB in the 1 to 10 U/liter range.     

Secretion of creatine kinase MB isoenzyme by an immature teratoma with predominant rhabdomyosarcomatous elements

A 37-year-old man with metastatic immature (malignant) teratoma with prominent rhabdomyosarcomatous elements had markedly increased activity of creatine kinase (EC 2.7.3.2) MB in serum. There was no electrocardiographic evidence of infarction or ischemia, and autopsy revealed no myocardial infarction, significant coronary atherosclerosis, myocarditis, or invasion of the heart by tumor. A high proportion of the creatine kinase activity in a homogenate of the tumor was attributable to the MB isoenzyme. Persistent increases of creatine kinase-MB and an unusually high MB isoenzyme activity, out of proportion to total creatine kinase activity, may indicate a nonmyocardial origin of this isoenzyme.     

New manual and automated method for determining activity of creatine kinase isoenzyme MB, by use of dithiothreitol: clinical applications.

The method is based on the selective activating capacity of dithiothreitol on creatine kinase isoenzyme MB, after isoenzyme MM is activated by glutathione. Isolated isoenzymes MM and MB of human and canine origin were assayed individually and in mixtures of known activities. When glutathione was present in the assay medium the activity of each isoenzyme could be measured individually, but glutathione did not activate isoenzyme MB if it was present in a mixture with MM. Dithiothreitol, added to the serum before assay, activated the isoenzyme MB in the mixture. Values for MB activities obtained for isolated isoenzyme MB and for the isoenzyme mixture after dithiothreitol was added averaged 110 and 111 U/liter, respectively (r = 0.998; y = 1.007 x + 0.298; n = 10). In the serum of 40 patients with documented acute transmural myocardial infarction, the mean proportion of isoenzyme MB activity measured in this way was 5.5% (coefficient of variation, 7.7%). Isoenzyme MB activities measured by use of dithiothreitol compared well with those obtained by conventional electrophoresis/spectrophotometry (r = 0.998; y = 1.09x -0.65) and spectrofluorometry (r = 0.996; y = 1.10 x + 0.80). The assay of MB activity by the dithiothreitol method was automated, by use of an Abbott Bichromatic Analyser and a Calbiochem Super-Stat Pack Kit. In 60 isoenzyme MB determinations the manual and automated method correlated well (r = 0.990; y = 1.0x -1.36). The simplicity of isoenzyme MB determination by use of dithiothreitol and its ease of automation allow routine monitoring of the isoenzyme activity in patients with ischemic heart disease.     

Improved column method for separating lactate dehydrogenase isoenzymes 1 and 2

Lactate dehydrogenase (LD) isoenzymes 1 and 2 in human serum were separated on a column of diethylaminoethyl-Sephadex. Samples layered on mini-columns were eluted with buffered sodium chloride (100, 150, and 200 mmol/liter). Lactate dehydrogenase activity in column effluents was measured by the Wacker method, and their isoenzyme content was evaluated by electrophoresis on polyacrylamide gel. Results for column-fractionated LD-1 and LD-2 were expressed in two ways: LD-1/LD-2 ratios and total LD-1 + LD-2 activities. The former is a more specific indicator of myocardial infarction than the latter. Sera from 10 patients with acute myocardial infarction (increased creatine kinease isoenzyme MB activity) exhibited ratios in the range of 0.92 to 1.56, ratios for 10 patients without heart disease (normal creatine kinase MB) ranged from 0.33 to 0.69.     

Comparison of catalytic activity and mass concentration of serum creatine kinase MB isoenzyme in the detection of coronary reperfusion in acute myocardial infarction after therapeutic thrombolysis

Serum creatinine kinase MB isoenzyme time-activity curves are useful for the assessment of coronary reperfusion after acute myocardial infarction. The purpose of this study was to compare serum creatine kinase MB catalytic activity with mass concentration for the determination of coronary reflow after therapeutic thrombolysis. Creatine kinase MB mass was determined immunoenzymometrically. Creatinine kinase MB catalytic activity concentration was determined by electrophoresis. Serum was collected every 4 hours for 96 hours in two groups of myocardial infarction patients: A (n = 10), urokinase induced reperfusion; B (n = 10), conventional therapy without urokinase. Peaks of mass and activity occurred at similar times in groups A and B. Both were significantly earlier in the urokinase treated patients. The maximal rate of increase of creatine kinase MB (based on either mass or catalytic activity) was threefold greater in the urokinase group. There are no important differences between the behaviour of creatine kinase measured as catalytic concentration or as mass concentration. Mass concentration is therefore equally useful as an indicator of coronary reperfusion.     

Creatine kinase and lactate dehydrogenase isoenzymes in serum of patients suffering burns, blunt trauma, or myocardial infarction

Medical records of 53 burn and trauma patients were reviewed to assess the possibility of myocardial damage. Except for electrophoretically detectable creatine kinase MB isoenzyme, none showed evidence of myocardial injury. Lactate dehydrogenase isoenzyme tests, electrocardiograms, myocardial pyrophosphate scans, clinical course, and results of (two) autopsies were all negative for myocardial necrosis or ischemia. Types of patient, number, mean peak value (U/L) for serum creatine kinase, and ranges of percentage MB isoenzyme were as follows. Burns from direct electrical contact: 28, 16 600, 0-29; electrical flash or other thermal burns: 10, 4340, 0-22; blunt trauma (mostly from automobile accidents): 15, 3430, 0-18; myocardial infarction: 57, 1520, 4-46. Evidently creatine kinase MB isoenzyme is nonspecific in burn and trauma patients and should not be the only test result used to assess myocardial involvement.     

Etude de la myoglobinemie et de son evolution au cours de l'infarctus du myocardeStudy on myoglobinemia and its development during myocardial infarction

Thirty six patients suffering from myocardial infarction were investigated by assay of their serum myoglobin, total creatine kinase and creatine kinase isoenzyme MB activities. Determination of serum myoglobin presents, with regard to creatine kinase MB, two major advantages: a very early increase after the onset of the pain (about three hours later) and a very quick clearance, allowing the diagnosis of a second episode of necrosis after about one day.     

Serum CK-MB isoenzyme after aortic and mitral valve replacements

A release of the MB fraction of creatine kinase (CK) enzyme into the serum due to myocardial manipulation and trauma occurs in patients undergoing cardiac surgery. Thus, the appearance of CK-MB activity as such is not sufficient to indicate of perioperative myocardial infarction. The mean (+/- SD) serum CK-MB isoenzyme level was 95 +/- 103 U/l 18 hours after aortic or mitral valve replacement in 76 patients. Thirteen patients undergoing closure of an atrial septal defect served as controls. They had a significantly lower (p less than 0.01) isoenzyme level postoperatively: 45 +/- 39 U/l. Two patients had the ECG changes of definite myocardial infarction after valve replacement and they also showed high CK-MB values, while the other patients with high enzyme level had no ECG signs suggesting acute infarction. CK-MB values correlated with the aortic cross-clamping time (r = 0.39, p less than 0.001) and weakly with the precordial ECG voltage of SV1 + RV5 (r = 0.25, p less than 0.01). While these findings may reflect the sensitivity of a thick myocardial wall to ischaemia during surgery, the postoperative recovery was not related to the serum CK-MB level.     

Determination of creatine kinase isoenzyme MB activity in serum using immunological inhibition of creatine kinase M subunit activity. Activity kinetics and diagnostic significance in myocardial infarction.

This is a new method for the determination of creatine kinase isoenzyme MB activity in serum. The method uses direct activity measurement of creatine kinase B subunit activity after blocking of CK-M subunit activity by inhibiting antibodies. The test takes no longer than 15 min. The method yields an intra-serial C.V. of 2.0-12.9%, and a C.V. from day to day of 5.5%. The detection limit is 3.4 U/l creatine kinase MB. In the 95 cases with proven myocardial infarction several types of creatine kinase MB activity kinetics could be determined. The percentage of creatine kinase MB of peak CK-total is 6-25%, with a mean of 11.1%. The amount of creatine kinase MB with respect to total CK activity after reinfarction is higher than the amount after initial infarction.     

Atypical increase in serum creatine kinase activity in hospital patients.

We use an ion-exchange column-chromatographic technique for separating creatine kinase isoenzymes in serum, and occasionally observe what appears to be sustained increase in the MB fraction. Most patients whose sera show such behavior have myocardial disease, but not necessarily a recent myocardial infarction. Electrophoretic analysis of a small sampling of such sera revealed that the apparent MB migrates atypically, appearing distinctly between isoezymes MB and MM. In another electrophoretic system, the peak might easily be mistaken for MM. This unusual isoenzyme does not appear to be "macro" creatine kinase. In laboratories that use the ion-exchange technique, the possibility of a falsely positive MB value should be considered in subjects who show persistent increases together with normal or nearly normal values for total creatine kinase activity. A suitable electrophoretic method that clearly demonstrates this unusual isoenzyme should be used in such cases, for confirmation.     

Use of creatine kinase MB isoenzyme for diagnosing myocardial infarction when total creatine kinase activity is high

The usefulness of measuring creatine kinase MB isoenzyme for diagnosing myocardial infarction when activities of total creatine kinase are very high is unclear. We conducted a retrospective study in an urban hospital that serves a largely indigent population. We concentrated on 146 patients whose creatine kinase activity was greater than 1000 U/L (upper limit of normal: 165 U/L for women and 225 U/L for men), with MB isoenzyme greater than 10 U/L and less than 5% of total creatine kinase. The positive predictive value of MB isoenzyme (isoimmune method) values greater than 10 U/L was between 11.6% and 56.8% when the value for total creatine kinase exceeded 1000 U/L. Using different values (MB greater than 4% of total creatine kinase) as positive for myocardial infarction would have resulted in far fewer false-positives, but 10 cases of myocardial infarction would have been missed. The most appropriate cutoff value for MB isoenzyme in this population (total creatine kinase greater than 1000 U/L) was found to be greater than 2% of total creatine kinase.     

Evaluation of a commercial immunoenzymometric assay kit for creatine kinase MB isoenzyme determination using monoclonal antibodies

A simultaneous two-site immunoenzymometric assay for creatine kinase MB determination (Hybritech Tandem-E CK-MB) using monoclonal antibodies was evaluated and compared with cellulose acetate electrophoresis using fluorometric scanning densitometry. The assay has satisfactory precision (between-day analysis gives a coefficient of variation between 2.1 and 9.4%) and is not susceptible to interference by concentrations of creatine kinase MM up to 5000 micrograms/l (3400 U/l) and creatine kinase BB up to 1000 micrograms/l (1085 U/l). The upper limit of MB isoenzyme concentration in 250 apparently healthy people was 5.5 micrograms/l. Comparison between the immunoenzymometric assay (y) and electrophoresis (x) yielded the following linear regression equation: y = 0.37x + 1.9, with a correlation coefficient of 0.828. The characteristics of the temporal kinetics of MB isoenzyme, calculated by two methods, in 49 patients with acute myocardial infarction, were nearly identical in terms of the rate of creatine kinase MB release and the time at which the peak value is obtained, but not in terms of the rate of elimination of the isoenzyme. The fractional disappearance rate of MB isoenzyme from the circulation was significantly higher if calculated with Tandem-E results rather than with electrophoresis results (-0.035 vs -0.028, p less than 0.001). Whereas in the first day after infarction immunoenzymometric assay and electrophoresis had the same clinical sensitivity for identifying patients with acute myocardial infarction, in specimens collected more than 24 hours after the onset of the chest pain, the clinical sensitivity of the immunoenzymometric method was lower. Our results show that it is still premature to draw definitive clinical conclusions from the immunoassay results.     

手足口病患儿联合检测肌酸激酶同工酶MB、心肌肌钙蛋白Ⅰ在合并病毒性心肌炎诊断中的价值

目的探讨手足口病患儿联合检测血清中肌酸激酶同工酶MB（CK—MB）、心肌肌钙蛋白Ⅰ（cTnI）水平对诊断合并病毒性心肌炎的价值。方法将188倒HFMD患儿分为确诊合并精毒性心肌炎组、疑似舍并病毒性心肌炎组、无合并病毒性心肌灸组。所有惠儿清晨空腹采集静脉血,检测血清中的肌酸激酶同工酶MB（CK—MB）、心肌肌钙蛋白Ⅰ（cTnI）水平,对结果进行统计分析。结果确诊合并病毒性心肌炎组与疑似合并病毒性心肌炎组血清中CK—MB、cTnI均高于无合并病毒性心肌炎组,差异有统计学意义（P〈0．05）;确诊合并病毒性心肌炎组血清中CK—MB、cTnI与疑似合并病毒性心肌炎组比较差异无统计学意义（P〉0．05）。确诊组与疑似组两项检测中的总异常率均分别高于两纽中CK—MB、cTnI单独检测异常率（P〈0．05,P〈0．05）。结论CK—MB、cTnI在HFMD中诊断合并病毒性心肌炎有重要意义;HFMD患儿同时检测血清中CK—MB、cTrI水平,可以提高合并病毒性心肌炎的捡出率。     

Relation of creatine kinase isoenzyme MB to postoperative electrocardiographic diagnosis in patients undergoing coronary-artery bypass surgery.

We compared (a) the frequency of detection of isoenzyme MB of creatine kinase (CK; EC 2.7.3.2) in serum of patients undergoing coronary-artery bypass surgery, (b) the interval during uhich its activity was supranormal in serum, and (c) an index of the amount of CK released into blood ("CK-MB area") with postoperative electrocardiographic changes in 80 patients. The frequency of detection of CK-MB is a function of frequency of sampling during the early postoperative period. Because the duration of appearance and the calculated CK-MB area increased as the electrocardiogram became more specific for infarction (p less than 0.01), a twice-daily sampling schedule proved clinically relevant. Only 5.4% of patients had electrocardiographic evidence of infarction when CK-MB was absent by the second postoperative morning. When CK-MB was still detected at that time, 69.6% of patients had persistent new Q waves, consistent with infarction. In three patients who died postoperatively, significant myocardial necrosis was demonstrated. All three had had persistently increased values for CK-MB, related to electrocardiographic changes of infarction in one patient and ischemic changes in two. Evidently CK-MB is a more sensitive indicator of myocardial necrosis than the electrocardiogram and CK-MB area should be a useful criterion in evaluating methods of intra-operative myocardial protection.     

Activities of mitochondrial aspartate aminotransferase and creatine kinase isoenzyme MB in serum following coronary bypass surgery

The mitochondrial isoenzyme of aspartate aminotransferase showed only slight increases in serum of twenty-seven patients after uncomplicated coronary bypass surgery, which contrasted the rapid and substantial increases in creatine kinase MB. In seven patients suffering perioperative infarction or serious complications, substantial increases in mitochondrial aspartate aminotransferase were detected and the elevations in creatine kinase MB were prolonged. Mitochondrial aspartate aminotransferase may appear as a specific marker of myocardial necrosis following coronary bypass surgery. The elevations of creatine kinase and creatine kinase MB were detected as early as 5 minutes after onset of coronary reperfusion and slightly higher activities were measured in coronary sinus blood than in systemic blood sampled simultaneously. Increases in mitochondrial aspartate aminotransferase, however, could first be measured 8 hours after reperfusion.     

Creatine kinase isoenzyme variants in human serum

In serum from about 800 patients, total creatine kinase and its subunit B activities were determined by the recommended Scandinavian creatine kinase method in the absence and presence of a creatine kinase M subunit inhibitory antibody. Eight patients had supranormal subunit B activities, but normal or near-normal values for total creatine kinase activity. Electrophoresis of sera from these eight patients showed, in addition to the normally migrating isoenzyme MM, one or two abnormally migrating creatine kinase isoenzyme bands, located between normally migrating isoenzymes MM and MB. Experimental data suggest that these abnormal bands may be isoenzyme BB with changed electrophoretic mobility. The eight patients had no particular disorder in common.     

Lactate dehydrogenase isoenzyme-1/total ratio: accurate for determining the existence of myocardial infarction

We have gradually revised our medical protocols for measuring creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase isoenzyme-1 (LD-1) because of identifiable problems in the use of an interpretation of CK-MB isoenzyme associated with slowly evolving or small myocardial infarct, the use of thrombolytic therapy, or burn and trauma, each of which affects the rate of appearance and composition of isoenzymes present. Despite recent evidence of the efficacy of LD-1 isoenzyme measurement in the first 12 to 24 h of myocardial infarction, this test is not widely used because of overstated assumptions about the value of CK-MB. Here we studied the adequacy of the current isoenzyme assays by determining the value of CK-MB and LD-1 at optimum serum sampling times and establishing the contribution of individual and combined predictors to diagnostic efficiency. We conclude that the LD-1/total LD activity ratio in serum is superior to measurement of CK-MB or LD-1, or both, in the diagnosis of acute myocardial infarction. Moreover, this ratio is most valuable when interpretation of the result for CK-MB isoenzyme is equivocal in patients with small or evolving myocardial infarcts.     

Normal CK, elevated MB predicts complications in acute coronary syndromes

The implications of an elevated Creatine kinase (CK)-MB isoenzyme (MB) in suspected acute coronary syndromes, with a normal total CK, is not well established. Despite many guidelines on managing patients with acute coronary ischemia, none indicates strategies for patients with elevated MB and with a normal CK. The outcome consequence of this result is not firmly established. Our objective was to prospectively evaluate outcomes in patients with suspected acute coronary syndromes, normal initial total CK, and increased MB. All Emergency Department patients with suspected acute coronary syndromes and creatinine <2.0 mg/dL were eligible for study entry. Serial CK and MB fractions were measured on arrival in the Emergency Department, then 8 and 16 h postpresentation. A composite outcome of death, Q-wave myocardial infarction, or revascularization was defined at the index visit and 6 months later. Outcomes were determined by blinded record review and by telephone contact. In the 698 patients entered, the acute composite outcome rate was 25% (175) and 6.3% (44) at 6 months. Acute and 6 month adverse outcome rates were statistically the same for all patients with an elevated MB fraction, regardless of the total CK level. An elevated MB conferred a higher event rate than did a normal MB. We conclude that the adverse event rate for patients with suspected acute coronary syndromes and an elevated MB is the same whether or not the total CK is elevated. These patients should be considered as having had an acute coronary syndrome.     

Correlation of antemortem serum creatine kinase, creatine kinase-MB, troponin I, and troponin T with cardiac pathology

BACKGROUND: Spurious increases in serum troponins, especially troponin T, have been reported in patients with and without acute myocardial syndromes. METHODS: We studied 78 autopsied patients without clinical myocardial infarction (MI) and correlated histologic cardiac findings with antemortem serum creatine kinase (CK), its MB isoenzyme (CK-MB), cardiac troponin I (cTnI), and cardiac troponin T (cTnT). RESULTS: There was no significant myocardial pathology in 15 patients. Cardiac pathologies were in five groups: scarring from previous MI or patchy ventricular fibrosis (n = 9), recent MI (n = 27), healing MI (n = 7), degenerative myocyte changes consistent with congestive heart failure (CHF; n = 12), and other cardiac pathologies (n = 8). The median concentrations in the five groups were not significantly different for either CK or CK-MB. Compared with the no-pathology group, only the MI group was significantly different for cTnI, and the MI and other pathology groups were significantly different for cTnT. For patients with MI, 22%, 19%, 48%, and 65% had increased CK, CK-MB, cTnI, and cTnT, respectively; for CHF and other cardiac pathologies combined, the percentages were 28%, 17%, 22%, and 50%. For patients with increased cTnI, 72% and 28% had MI and other myocardial pathologies, respectively; patients with increased cTnT had 64% and 36%, respectively. Patients without myocardial pathology had no increases in CK-MB, cTnI, or cTnT. CONCLUSIONS: All patients with increased serum CK-MB, cTnI, and cTnT had significant cardiac histologic changes. The second-generation cTnT assay appears to be a more sensitive indicator of MI and other myocardial pathologies than the cTnI assay used in this study.     

Stability and electrophoretic characteristics of creatine kinase BB extracted from human brain and intestine

Creatine kinase (CK; EC 2.7.3.2) isoenzyme BB extracted from brains of rats reportedly undergoes modification at 37 degrees C, leaving an electrophoretic variant that accounts for most of the residual CK activity. This variant, called CK-BB', migrates on electrophoresis similarly to creatine kinase isoenzyme MB. Using electrophoresis and immunoinhibition with antiserum to creatine kinase isoenzyme MM, we found CK-BB to be the only identifiable cytoplasmic isoenzyme in surgical samples from human brain and intestine. In contrast, we found that some samples of brain obtained at autopsy contain CK-BB'. We also found that CK-BB extracted from human brain was converted to CK-BB' upon incubation in serum or plasma at 37 degrees C. We found a similar development of CK-BB' in incubation mixtures of serum or plasma containing CK-BB obtained from surgical samples of human intestine. The development of CK-BB' during infarction of the gastrointestinal system may thus be a source of false-positive CK-MB in the laboratory verification of myocardial infarction when electrophoresis is used as the only method to identify CK isoenzymes.