Creatine kinase isoenzyme MB assay by electrophoresis

Biomarker Development in Cardiology: Reviewing the Past to Inform the Future

Cardiac biomarkers have become pivotal to the clinical practice of cardiology, but there remains much to discover that could benefit cardiology patients. We review the discovery of key protein biomarkers in the fields of acute coronary syndrome, heart failure, and atherosclerosis, giving an overview of the populations they were studied in and the statistics that were used to validate them. We review statistical approaches that are currently in use to assess new biomarkers and overview a framework for biomarker discovery and evaluation that could be incorporated into clinical trials to evaluate cardiovascular outcomes in the future.

Enzyme activities in serum after extensive exercise, with special reference to creatine kinase MB

It is well documented that elevations of serum enzymes used as criteria in establishing the diagnosis of acute myocardial infarction (AMI) often show a pattern of AMI after physical exercise without other clinical signs of myocardial damage. Since a clinical condition resembling AMI sometimes appears after strenuous physical exercise, this study was designed to show if the new, almost heart-specific, isoenzyme creatine kinase MB (CK-MB) would solve the diagnostic problems. Ten well trained volunteers took part in a 26 km jogging race. None of them had any cardiovascular symptoms, but the 'old' cardiac enzymes rose in some of them above the discriminatory levels, whereas CK-MB was below these levels in all cases. It is concluded that CK-MB determination is a valuable diagnostic tool, also in patients who have recently exercised extensively.

Relationship between serum CK-MB-estimated acute myocardial infarct size and clinical complications

The relationship between acute myocardial infarct (AMI) size and morbidity and mortality was estimated in 317 patients followed for one year or until death. Infarct size was estimated from serum creatine kinase (CK)-MB levels measured thrice daily. The incidence of ventricular arrhythmias, congestive heart failure, cardiogenic shock, and the cardiac performance during exercise were studied during hospitalization. Hospital mortality and one-year mortality were registered. A positive correlation was found between serum CK-MB-estimated infarct size and the incidence of ventricular arrhythmias (p less than 0.05). Patients with congestive heart failure and patients with cardiogenic shock had significantly larger infarct size than patients without (p less than 0.05-0.01), although there was a substantial overlap. During exercise test the rise in systolic blood pressure correlated negatively and the rise in heart rate correlated positively to estimated infarct size (p less than 0.01). Both hospital mortality and one-year mortality were significantly related to estimated infarct size (p less than 0.01). Thus the infarct size, as estimated from serum CK-MB, seems to be of importance for development of the most common and serious complications after AMI.

Significance of mild transient release of creatine kinase-MB fraction after percutaneous coronary interventions

BACKGROUND

The clinical significance of minor elevations in creatine kinase-myocardial band isoenzyme (CK-MB) after coronary interventions has not been systematically evaluated.

METHODS AND RESULTS

We examined 4484 patients who underwent successful percutaneous transluminal coronary angioplasty or directional coronary atherectomy and whose peak CK levels did not exceed twice the upper limit of laboratory normal. Group 1 (3776 patients) had no CK or MB elevation after the procedure (ie, CK < or = 180 IU/L, with MB fraction < or = 4%). Group 2 (450 patients) had a peak CK level between 100 and 180 IU/L, with MB fraction > 4%, and group 3 (258 patients) had a peak CK level between 181 and 360 IU/L, with MB fraction > 4%. The strongest correlate of postprocedure CK-MB elevation was the performance of directional coronary atherectomy (odds ratio, 4.1; P < .0001), followed by the development of > or = 1 in-1ab minor procedural complication (odds ratio, 2.6; P < .0001). Clinical follow-up was available in 4461 patients (99.5%), with a mean duration of 36 +/- 22 months. Survival analysis, adjusted with Cox proportional hazards regression model, showed that the groups with elevated CK-MB had a significantly higher incidence of cardiac death (risk ratio, 1.3; P = .04) and myocardial infarction (risk ratio, 1.3; P = .03). Major ischemic complications (death, myocardial infarction, and coronary revascularization) occurred more frequently in the groups with increased CK-MB (groups 1 versus 2 versus 3, 37.3% versus 43.3% versus 48.9%; P = .01).

CONCLUSIONS

This study shows that minor elevations of CK-MB after successful coronary interventions identify a population with a worse long-term prognosis compared with patients with no enzyme elevations and appear to have an adverse effect on long-term prognosis. Future studies of percutaneous coronary revascularization should include routine measurements of biochemical cardiac markers as important predictors of long-term prognosis.

Comparison of two immunoinhibitory methods with agarose gel-electrophoresis for measuring the MB isoenzyme of creatine kinase in serum from cases of suspected myocardial infarction

Two immunoinhibitory methods for measuring creatine kinase-MB (a dry chemical and a wet chemical method) were compared with the commonly used agarose gel electrophoretic method, using 563 serum samples from 235 patients with suspected acute myocardial infarction. Comparison of the electrophoretic and the dry chemistry methods showed the linear relationship: electrophoretic method = -6.5 U/l + 1.22 x dry chemistry method, r = 0.943. For the wet chemistry method the relationship was: electrophoretic method = -7.2 U/l + 1.19 x wet chemistry method, r = 0.854. Parallel determinations of total creatine kinase were also done and the methods were virtually identical in performance. Compared with the electrophoretic method (which showed a 15% prevalence of acute myocardial infarction), these classifications showed sensitivities of 0.92 and 0.67 and specificities of 0.94 and 0.99 (dry and wet chemistry, respectively; using methods recommended by the manufacturers). After optimization of discriminators the sensitivity was increased to 0.94/0.92 and the specificity to 0.99/0.99.

At what level of serum total creatine kinase activity can measurement of serum creatine kinase MB isoenzyme activity be omitted in suspected myocardial infarction?

The purpose of this study was to establish a discriminatory limit for serum total creatine kinase activity (CK activity) below which CK isoenzyme fractionation is unnecessary. We looked at 2610 serum samples from 1077 consecutive patients with suspected acute myocardial infraction (AMI). The CK activity was determined according to the Scandinavian recommended method. Isoenzymes of CK were separated by agarose gel electrophoresis, followed by fluorometric scanning. When the threshold for CK activity was 150 U/l, none of the samples had a creatine kinase MB isoenzyme activity (CK-MB activity) equal to or higher than 30 U/l (the diagnostic level), which has been found to differentiate between patients with AMI and those without AMI. Only 14 patients (1.3% of all patients investigated) had CK-MB activity peaks between 10 U/l (detection limit) and 30 U/l. Of these, AMI was only diagnosed in one. We recommend that CK-MB activity should be measured only when CK activity is higher than 150 U/l. This would make about 50% of all CK-MB measurements unnecessary.

Reduction of stress/catecholamine-induced cardiac necrosis by beta 1-selective blockade

114 haemodynamically stable patients with acute head injury were randomised, double-blind, to either placebo or atenolol given intravenously (10 mg every 6 h) for 3 days then orally (100 mg daily) for a further 4 days. Both groups were equally stressed as shown by raised arterial noradrenaline levels. In patients receiving placebo, but not in those receiving atenolol, there was a significant (p less than 0.01) positive correlation between arterial noradrenaline and levels of the myocardial isoenzyme of creatine kinase (CKMB). 30% of the placebo group compared with 7.4% of the atenolol group (p less than 0.05) showed CKMB levels greater than 3% of total creatine kinase (compatible with myocardial damage). CKMB levels greater than 6% of total creatine kinase (compatible with acute myocardial infarction) were present in 16.7% of patients receiving placebo but in no patients receiving atenolol (p = 0.053). Atenolol appeared to reduce significantly the likelihood of supraventricular tachycardia and ST-segment and T-wave changes and prevented cardiac necrosis seen at necropsy.

Cerebrospinal fluid creatine kinase isoenzyme BB levels do not predict the clinical outcome in patients unconscious following cardiac resuscitation

It has recently been claimed that an increase in creatine kinase isoenzyme BB(CK-BB) in cerebrospinal fluid (CSF) is well correlated with the cerebral outcome in patients resuscitated after cardiac arrest. Twenty-one such patients consecutively admitted from outside this hospital participated in the study. The patients were divided into two groups: 6 survivors and 15 nonsurvivors. The median CSF-CK-BB value was 5 U/L among nonsurvivors and below detection limit among survivors (NS). However, the predictive value of a positive test is limited, since only 6 of 15 nonsurvivors (40%) had an increase in CSF-CK-BB (predictive value of positive test = 67%). The predictive value of a negative test is limited, since 3 of 6 survivors (50%) showed no rise in CSF-CK-BB (predictive value of negative test = 25%). No relationship between cerebral dysfunction and CSF-CK-BB values was revealed. Thus, CSF-CK-BB does not predict the clinical outcome in patients resuscitated after cardiac arrest.

Nontraumatic rhabdomyolysis during diabetic ketoacidosis

The frequency of nontraumatic rhabdomyolysis in diabetic ketoacidosis was investigated by serial measurements of the serum levels of myoglobin and the serum activity of creatine kinase isoenzyme MM in 12 consecutively admitted ketoacidotic patients. In 5 patients (Group 1) we found hypermyoglobinaemia and elevated activity of creatine kinase isoenzyme MM on admission to hospital, whereas these two variables were normal in 7 patients (Group 2). On admission significantly higher median blood glucose levels and higher median serum osmolality were found in Group 1 than in Group 2 (for blood glucose: 49.6 mmol/l versus 19.0 mmol/l, p less than 0.02; for serum osmolality: 360 mosm/kg H2O versus 315 mosm/kg H2O, p less than 0.05). Decreased renal function was found in Group 1 as reflected by significantly higher beta 2-microglobulin serum concentrations in Group 1 compared with Group 2 on admission (median values 4.1 mg/l versus 1.7 mg/l, p less than 0.01) and during the first 3 days of therapy. The serum concentration of hypoxanthine (an indicator of the cellular energy state) was elevated in all patients on admission, with no difference between patients with or without hypermyoglobinaemia. In conclusion, our findings suggest that nontraumatic rhabdomyolysis with hypermyoglobinaemia and elevated serum activity of creatine kinase isoenzyme MM may be a hitherto unrecognized common feature of diabetic ketoacidosis.

Diagnostic and prognostic implications of transient isolated negative T waves in suspected acute myocardial infarction

The diagnostic and prognostic implications of transient isolated negative T waves were studied in 127 patients in whom acute myocardial infarction (AMI) was suspected. Eight-four patients with no AMI and no electrocardiographic changes served as the control group. The 2 groups were well matched. Twenty-nine patients (23%) with isolated negative T wave had a significant increase in serum creatine kinase (CK)-MB levels and fulfilled the diagnostic criteria for AMI. The increase in serum CK-MB levels did not predict a higher risk of hospital mortality, but during follow-up (median 31 months), a serum CK-MB level above 30 U/liter identified patients with a significantly increased risk of dying (p less than 0.05). Both the number of affected electrocardiographic leads and the sum of negative T-wave amplitudes were significantly related to the follow-up mortality rate (p less than 0.01). The comparison between control subjects and patients with negative T waves during follow-up showed more events among the patients: AMI (17% vs 8%, p less than 0.02); death (24% vs 12%, p less than 0.01); and AMI or death (31% vs 19%, p less than 0.01). Thus, only 25% of patients with aggravated chest pain and isolated negative T waves have AMI. However, the long-term prognosis for the entire group of patients with isolated negative T waves is poor, and any therapeutic intervention should be initiated immediately.

Diagnostic and prognostic significance of minimally elevated creatine kinase-MB in suspected acute myocardial infarction

CK-MB changes were studied using agarose gel electrophoresis in 244 patients admitted to a coronary care unit for suspected acute myocardial infarction (AMI). A range of minimally elevated CK-MB levels, from 1 to 24 IU/liter, was identified as representing uncertain AMI events. Positive AMI events were defined by elevations of 25 IU/liter or more documented in patients with new Q waves or abnormalities in all enzyme and isoenzyme levels. Negative AMI events were defined by elevation of 0 IU/liter, observed in all control subjects. The 1-year cardiac mortality rates in the "positive"-AMI (n = 91) and "uncertain"-AMI (n = 22) groups were identical (22%), and significantly higher than that in the "negative"-AMI group (n = 93) (6%) (p less than 0.05). However, when a larger uncertain-AMI group of 115 patients was compiled by 2 collaborating centers, the 1-year cardiac mortality rate in the 39 patients with chest pain alone was 0%, vs 33% in the 76 patients with accompanying severe medical problems such as cardiac or respiratory failure. Whether minimal CK-MB elevations represent AMI of limited extent is not clear. These elevations occur most often in association with severe medical problems, and in patients without such problems, they may not indicate a poor prognosis.

Quantitative influence of serum creatine kinase isoenzyme MB estimated infarct size and other prognostic variables on one year mortality after acute myocardial infarction

The aim of the present study was to determine the strength of the relation between serum creatine kinase isoenzyme MB estimated infarct size, other prognostic variables, and mortality after acute myocardial infarction. Serum creatine kinase MB estimated infarct size and 11 other prognostic variables were obtained in 317 patients. By Cox regression analysis the prognostic variables significantly related to mortality were identified: congestive heart failure, estimated infarct size, New York Heart Association class, number of previous infarcts, and age. Congestive heart failure and estimated infarct size were most strongly related to mortality. The relation between the prognostic variables and mortality was non-linear, and the variables influenced each others' relation to mortality. A prognostic index based on all five prognostic variables provided the best means of estimating the probability of survival after acute myocardial infarct. Neither serum creatine kinase MB estimated infarct size nor any of the other prognostic variables had a significant independent influence on mortality, and the probability of survival was high in the absence of any of the prognostic variables in combination.

Comparison of ASAT, CK, CK-MB, and LD for the estimation of acute myocardial infarct size in man

The purpose of this study was to set up a simple and reliable procedure for estimating acute myocardial infarct (AMI) size by measuring serum enzymes in a few daily blood samples. Peak enzyme values and estimated infarct size from one, two, or three daily samples of aspartate aminotransferase (ASAT), creatine kinase (CK), CK-MB, and lactate dehydrogenase (LD) were compared with the extent of myocardial necrosis measured at autopsy in 22 patients who died from AMI. The correlation between the extent of the necrosis measured and peak serum enzymes from one daily blood sample was highest for CK-MB (r = 0.78) and LD (r = 0.73) compared to CK (r = 0.68) and ASAT (r = 0.67). To obtain a significant correlation, however, two patients had to be excluded from the ASAT and LD analyses. No significant improvement was obtained by more frequent blood sampling. Estimation of infarct size did not improve the correlation significantly for any enzyme, although the coefficient of correlation for CK-MB increased slightly (r = 0.83). Serum CK-MB determination provides a semiquantitative estimate of infarct size, but the other enzymes may give erroneous estimates owing to lesser cardiospecificity.

Estimation of acute myocardial infarct size in man by serum CK-MB measurements

This study was performed to determine the relationship between myocardial infarct size estimated by serum CK-MB methods and the extent of irreversible injury in acute myocardial infarction. In 321 consecutive patients, infarct size was estimated by different mathematical models, and in 22 patients who died in hospital, the extent of myocardial necrosis was determined by autopsy. We also investigated the depletion of CK-MB in infarcted tissue, the recovery of CK-MB in the plasma volume, and the estimation of CK-MB from plasma. Myocardial CK-MB depletion was relatively greater in the larger infarcts, whereas the recovery of enzyme in plasma was independent of the infarct size. Correction of serum CK-MB for changes in plasma volume improved the estimate significantly (p less than 0.05). The correlation between the measured infarct size (g) and the estimated infarct size (units per liter and gram-equivalents) was highly significant (r = 0.85--0.89, SEE = 23--27%, p less than 0.001). Thus, a semiquantitative expression of the extent of myocardial necrosis can be determined in vivo.

Myocardial infarct size and cardiac performance at exercise soon after myocardial infarction

Infarct size was estimated from serial serum CK MB measurements in a series of 101 patients admitted less than 15 hours after the first acute myocardial infarction. A maximal symptom limited exercise test comprising impedance measurements for the estimation of stroke volume at rest and at different levels of exercise was performed early after admission by 26 patients. There was a slight, though not significant, negative correlation between infarct size and physical capability as measured by the duration of work. The rise in systolic blood pressure during exercise showed a significantly negative and the increase in heart a significantly positive correlation to infarct size. This suggests that the rise in blood pressure, which is less in patients with the larger infarcts, is compensated by an increase in heart rate, so that the same maximum of cardiac performance and myocardial oxygen consumption is reached. The increase in cardiac stroke volume during exercise was negatively correlated with infarct size. Stroke volume only increased during lower levels of exercise; the increase in cardiac output at higher levels of exercise was achieved entirely by an increase in heart rate. The magnitude of ST segment elevation during exercise showed a significantly positive correlation with infarct size, whereas the occurrence of arrhythmias during exercise was independent of it.

Acute myocardial infarct size estimated by serum CK-MB determinations: clinical accuracy and prognostic relevance utilizing a practical modification of the isoenzyme approach

The clinical reliability and relevance of a practical enzymatic method to estimate infarct size (IS) were evaluated in patients with acute myocardial infarction (AMI). The technique utilized was that of relatively few sequential determinations of serum heart specific isoenzyme CK-MB, as corroborated by studies of numerous CK-MB measurements. Isoenzyme IS was determined in 321 consecutively admitted patients with AMI. Autopsies were performed in 22 of the 43 decedents for quantification of myocardial necrosis by histochemical and histologic techniques. A highly significant correlation (r = 0.83 p less than 0.001, SEE = 28%) was observed between IS values calculated from serum CK-MB and IS defined by necropsy examination. The CK-MB median IS was significantly increased in decedents compared to survivors (p less than 0.005), with IS ranges having substantial overlap between the two groups. The present study demonstrates that a practical and reliable estimation of IS in vivo is obtainable by serum CK-MB. While such estimated IS is of relatively moderate value for predicting in-hospital prognosis in single patients, the isoenzyme method appears particularly well suited for clinical evaluation of potentially beneficial interventions anticipated to limit myocardial necrosis in groups of AMI patients.