Subcortical vascular dementia: survey of treatment patterns and research considerations

OBJECTIVE: The purpose of this study was to evaluate retrospectively the efficacy of a proposed panel of three cardiac markers (myoglobin, creatine kinase-MB mass [CK-MB], and cardiac troponin I) in the diagnosis of acute myocardial infarction (AMI) in patients with atraumatic chest pain. DESIGN: A total of 110 patients admitted for the evaluation of atraumatic chest pain were examined. Forty-one of these patients were diagnosed with AMI. RESULTS: Five of the 41 patients with AMI had abnormally elevated myoglobin levels, whereas values of CK-MB and/or cardiac troponin I remained negative. Creatine kinase-MB mass alone had a sensitivity of 92.7%, a specificity of 89.9%, a positive predictive value of 84.4%, and a negative predictive value of 95.0% for the diagnosis of AMI. Cardiac troponin I alone had a sensitivity of 90.2%, a specificity of 95.7%, a positive predictive value of 92.5%, and a negative predictive value of 94.3% for the diagnosis of AMI. Cardiac troponin I is a more specific marker for the diagnosis of AMI than CK-MB, particularly in patients with chronic renal failure who are evaluated for chest pain. The combination of CK-MB and cardiac troponin I increased the sensitivity to 100% and the negative predictive value to 100% and had a specificity of 88.4% and a positive predictive value of 83.7%. The panel was diagnostic for all patients with AMI within 12 hours after admission. CONCLUSIONS: Our preliminary results indicate that this panel is highly effective for evaluation of AMI in patients with atraumatic chest pain. Elevated myoglobin levels were useful in detecting patients at high risk for AMI who initially were not detected with other markers. The combination of CK-MB and cardiac troponin I provided much higher sensitivity and had a much higher negative predictive value for the evaluation of AMI than cardiac troponin I or CK-MB alone. The 100% negative predictive value is particularly important because it indicates that patients with negative CK-MB and cardiac troponin I values 12 hours after admission have a negligible likelihood of AMI.     

Comparison of myoglobin, creatine kinase-MB, and cardiac troponin I for diagnosis of acute myocardial infarction

Serial plasma concentrations of myoglobin, creatine kinase MB (CK-MB) isoenzyme, and cardiac troponin I (cTnI) were measured in 25 patients with a confirmed diagnosis of acute myocardial infarction (AMI), and 74 patients who were suspected of AMI but were subsequently ruled out for this diagnosis. The cutoff concentration for the cTnI assay was optimally determined to be 2.5 ng/mL. Of the three markers, myoglobin had the highest clinical sensitivity (50 percent) when blood was collected between 0 to 6 h after the onset of chest pain. Assays for all serum markers used had high clinical sensitivity (> 93 percent) 6 to 24 h after onset. The CK-MB remained highly sensitive for 48 h, while cTnI was sensitive for up to 72 h. Between 72 and 150 h, cTnI had a clinical sensitivity of 70 percent as compared to 21 percent and 18 percent for myoglobin and CK-MB, respectively. The clinical specificity of cTnI for non-AMI patients was equivalent to CK-MB and significantly higher than for myoglobin. The clinical efficiency of cTnI for all samples was better than either CK-MB or myoglobin, owing mainly to the wider diagnostic window. The specificity of cTnI for 59 patients with chronic renal failure, skeletal muscle trauma and disease was better than all of these markers including cardiac troponin T (cTnT). Results of this study show that cTnI is an effective marker for the retrospective diagnosis of AMI, and consideration should be given to its use in place of CK-MB.     

Cardiac markers in the early hours of acute myocardial infarction: clinical performance of creatine kinase, creatine kinase MB isoenzyme (activity and mass concentration), creatine kinase MM and MB subform ratios, myoglobin and cardiac troponin T

We compared early markers of acute myocardial infarction (AMI) in the first 6 h from the onset of symptoms in 133 non-traumatized patients arriving at the emergency department with chest pain suggestive of AMI. Clinical performance parameters were calculated on the basis of 45 patients with AMI and 88 patients with a non-AMI diagnosis. At admission and in the first 0-3 h after the onset of chest pain the creatine kinase-MB (CK-MB) subform ratio was the most sensitive test at a comparable specificity level of 0.95. In the time interval of 3-5 h, myoglobin, the CK-MB mass concentration and the CK-MB subform ratio were associated with the greatest areas under receiver operating characteristic (ROC) curves, but differences between these tests were small and non-significant. At 6 h from the onset of pain, differences in clinical performance between the same three tests were even smaller whether or not samples drawn after the start of thrombolytic treatment were included in the test comparison. For confirmation of AMI at 6 h after onset of pain, CK-MB (activity and mass concentration) demonstrated the highest positive likelihood ratio, and for exclusion of AMI at 6 h the CK-MB subform ratio was associated with the highest negative likelihood ratio. However, differences between the CK-MB subform ratio, CK-MB mass concentration and myoglobin were not significant as estimated by the substantial overlap between the confidence intervals of the likelihood ratios and the ROC areas at 6 h. Cardiac troponin T (cTnT) demonstrated an ROC area equal to the CK-MB isoform ratio and myoglobin at 6 h. However, the likelihood ratio for ruling out AMI was lower, mostly due to the elevated cTnT in unstable coronary disease not defined as AMI. We conclude that the CK-MB subform ratio, CK-MB mass concentration and myoglobin do not demonstrate any significant differences in clinical performance for ruling in or ruling out acute myocardial infarction at 6 h after the onset of chest pain.     

Myoglobin in the early evaluation of acute chest pain

Two thirds of patients hospitalized to rule out acute myocardial infarction (AMI) are eventually found to have a non-AMI diagnosis, whereas 2% to 8% of patients with AMI are inappropriately discharged from the emergency department. Myoglobin has been shown to increase within 2 to 3 hours of myocardial injury. This study evaluates the usefulness of myoglobin in acute chest pain. Serial blood samples were obtained from 89 suspected AMI patients evaluated in the emergency department. Testing included creatine kinase (CK), a creatine kinase isoenzyme (CK-MB), and myoglobin. Twenty five of 89 patients (28%) had a diagnosis of AMI. The sensitivity of myoglobin for the detection of AMI was 56% at the time of admission and 100% 2 hours after admission. Thirteen of 25 AMI patients (52%) had a positive myoglobin before increases in CK or CK-MB, including one patient discharged from the emergency department. More importantly, the negative predictive value for myoglobin at the time of admission was 83% and was 100% two hours after admission. This potential for 100% predictability in excluding AMI by the use of serial myoglobin determinations will be very helpful in the correct triage of patients presenting with acute chest pain.     

Elevated serum cardiac markers in asymptomatic marathon runners after competition: is the myocardium stunned?

Prolonged strenuous exercise may trigger acute myocardial infarction (AMI), as exemplified by the occurrence of sudden cardiac death during marathon running. Serum creatine kinase MB (CK-MB) may be elevated in asymptomatic marathon runners after competition from exertional rhabdomyolysis of skeletal muscle altered by training, limiting its utility for evaluating acute cardiac injury in such athletes. Myoglobin and CK-MB2 isoform levels are emerging as earlier markers of AMI and troponin subunits as more specific than serum CK-MB mass. We tested runners before and sequentially after the 1995 Boston Marathon for conventional and newer markers including myoglobin, CK-MB mass and isoforms, cardiac troponin T, and cardiac troponin I using standard laboratory methods and rapid format assays if available. The mean serum values for myoglobin, CK-MB mass, CK-MB/myoglobin rapid panel tests, and CK-MB2 isoforms were normal or negative pre-race and elevated or positive 4 and 24 h after competition. These markers lack specificity for acute cardiac injury in trained runners. While the mean serum values for cardiac troponins T and I remained normal, 9 of 45 runners (20%) showed an increase in subunits by first-generation assays. All runners remained asymptomatic for cardiac disease and completed subsequent marathons 1 year later, making reversible myocardial injury or stunning unlikely. Elevated values of serum markers for AMI, including first-generation assays for both troponin subunits should be interpreted with caution in trained runners.     

Analysis of creatine kinase, CK-MB, myoglobin, and troponin T time-activity curves for early assessment of coronary artery reperfusion after intravenous thrombolysis

BACKGROUND: Thrombolysis has become the standard therapeutic approach in patients with acute myocardial infarction. To identify patients who may benefit from early invasive procedures, reliable noninvasive assessment of success or failure of thrombolytic therapy is mandatory. METHODS AND RESULTS: In a prospective study in 63 consecutive patients undergoing thrombolysis for their first myocardial infarction, serial measurements of creatine kinase (CK), its isoenzyme CK-MB, myoglobin, and troponin T were done to determine their value for noninvasive prediction of coronary artery patency. Blood samples were drawn every 15 minutes during the first 90 minutes, every 30 minutes during the first 4 hours, every 4 hours during the first 24 hours, and every 8 hours during the first 72 hours. The perfusion status of the infarct-related artery was assessed angiographically 90 minutes after initiation of thrombolysis. For each marker, time to its peak concentration and its early initial slope (start of thrombolysis to 90 minutes thereafter) were determined. Areas under receiver operator characteristic (ROC) curves were 0.83, 0.76, 0.82, and 0.80 for maxima of CK, CK-MB, myoglobin, and troponin T, respectively (p = NS by univariate Z test). The corresponding values for early slopes of CK, CK-MB, myoglobin, and troponin T were 0.79, 0.82, 0.89, and 0.80 (p = 0.23 for comparison between myoglobin and CK-MB; p = 0.07 between myoglobin and CK). Sensitivity, specificity, and positive and negative predictive values regarding noninvasive prediction of coronary artery patency after 90 minutes were 80%, 82%, 95%, and 61% for time to CK maximum; 91%, 77%, 91%, and 77% for time to myoglobin maximum; 87%, 71%, 89%, and 67% for early CK slope; and 94%, 88%, 94%, and 82% for myoglobin slope, respectively. When myoglobin slope was assessed together with other clinical reperfusion markers (resolution of chest pain or ST segment elevation, occurrence of reperfusion arrhythmias) by logistic regression analysis, only the myoglobin slope was an independent predictor of coronary artery patency (p < 0.0001). CONCLUSIONS: With regard to noninvasive prediction of coronary artery patency after thrombolytic therapy, measurement of the early initial slopes of the serum markers within only 90 minutes after the initiation of therapy is as accurate as the determination of the time to their peak concentration. Compared with the other markers examined, myoglobin appears to have advantages because of its earlier rise, yielding a better negative predictive value and a higher area under the ROC curve for determination of its early initial slopes.     

Determination of cardiac troponin-I in prediction of thrombolysis

Acute myocardial infarction (AMI) is a disease with high morbidity and mortality. Diagnosis of AMI using common methods (classical biochemistry, ECG) fails even in the fifth part of patients so that other noninvasive diagnostic methods are preferred. Recently, the biochemical analysis has been restored in the case of AMI diagnostics and also in prediction of coronary reperfusion after administration of a fibrinolytic agent. A suitable markers of AMI diagnostics is a combination of myoglobin and cardial troponin-I which is reported as a marker with high specificity and sensitivity. To determine coronary reperfusion, the examination of cardial troponin-T and CK-MB mass is recommended. In the literature, there exist isolated papers dealing with dynamics of cTn-I suitable for prediction of coronary revascularization. However, these papers do not report any adequate algorithm and subsequently mathematical differences between successful thrombolysis and failing thrombolysis. Therefore the aim of our study was to describe dynamics of cTn-I changes in AMI patients treated by thrombolysis. The study comprised of 8 AMI patients with delay from the occurrence of pains to fibrinolysis application under 4 hours (delay 4 hrs). These probands were examined for concentration of cTn-I and CK-MB mass in 3-hour intervals in the first 48 hours after admission to the clinic and further in 6-hour intervals from the hour 48 to the hour 90 after admission. All probands had a successful reperfusion (estimated using CK-MB peak, in 4 patients reperfusion was verified by subsequent coronarography). However, a simple mathematical prediction of coronary reperfusion after acute myocardial infarction by means of cTn-I dynamics determination is not possible due to relatively low cTn-I differences in individual analyses (CK-MB mass analysis shows more significant differences). Thus, in order to determine coronary revascularization, we recommend to use common analyses of dynamics of cTn-T or CK-MB mass.     

Value of mass dosage of the MB isoenzyme of creatinine phosphokinase in the diagnosis of recent myocardial infarction

In 391 patients admitted 3.7 hours (h) (median) after experiencing infarct-like pain, kinetic monitoring of CK-MB "mass" (threshold: 7 micrograms/l), myoglobin (threshold: 90 micrograms/l) and total CK (threshold: 290 micrograms/l) was carried out at the time of admission and after 1.5, 3, 6, 9, 12, 24 and 48 h. When myocardial infarction (MI) was treated conventionally (102 patients). CK-MB peaked 11 h (median) after the onset of pain, later than myoglobin (9 h), but before total CK (12 h). The peak of the markers was higher in Q+ than in Q-MI (p < 0.05). When MI was treated by thrombolytic medications (44 patients), the increases in CK-MB, myoglobin and total CK were larger, and occurred sooner (peaks 9, 6 and 6 h, after the onset of pain respectively), but did not last as long. In 245 patients who had not had MI (including 123 with spontaneous angina), the levels of the three markers remained stable and well below the decision thresholds. The sensitivities of CK-MB, myoglobin and total CK were respectively 47.1, 51.8 and 34.8% at the time of admission, 67.3, 82.7 and 57.1% after 3 h and 83.1, 76.9 and 88.9% after 6 h. The combined determination of CK-MB and of myoglobin had a higher sensitivity (67.7% at the time of admission, 84.9% after 1.5% and 88.2% after 3 h: but most of this gain was due to myoglobin. The specificity of the three markers and their diagnostic accuracy are comparable. In the course of recent MI, the kinetics of CK-MB mass are thus slower than those of myoglobin, but a little faster than those of total CK. The choice of the most effective biochemical marker depends upon the interval between onset of chest pain and hospitalization of the patient. Repetition of the determinations improves the diagnostic situation.     

Uterine lymphoma: sonographic, Doppler, and CT findings before and after chemotherapy

We studied the performance of the CARDIAC STATus, a new rapid, easy to perform qualitative whole blood bedside test for detection of elevated CK-MB and myoglobin in the emergency room. Blood samples from 182 consecutive patients with chest pain were drawn on admission and at five and seven hours after the onset of symptoms. The CARDIAC STATus tests were performed by coronary care unit nurses and, independently, by a trained laboratory technician. The results were compared with quantitative assays for CK-MB mass and myoglobin. At the end of the study, a second test series using a new lot number of cartridges was performed on the same blood samples because of possible elution buffer contamination. Nurses produced more false negative results than the technician (CK-MB 43 vs. 27 %, p=0.01, myoglobin 31 vs. 13%, p<0.0001), but the technician produced more false positive myoglobin results (9.3 vs. 5.5%, p=0.0001). In the second test series, the nurses produced significantly fewer false negative tests both for CK-MB (19%, p<0.0001) and myoglobin (13%, p=0.0002). The false negative rate for the technician was not different between the first and the second test series. The CARDIAC STATus yields a substantial number of false negative results both for CK-MB and myoglobin when compared to a quantitative assay, and therefore at present has limited value for ruling out an acute myocardial infarction.     

Myoglobin concentration in serum as an early marker of reperfusion in patients with acute myocardial infarction after thrombolytic therapy

Detection of coronary artery reperfusion in patients after thrombolytic therapy because of acute myocardial infarction includes, except angiography, disappearance of anginal pain, regression of electrocardiographic and echocardiographic myocardial ischaemia symptoms, increased activity of creatine kinase (CPK) and its isoenzyme CK-MB. The aim of the study was to check whether changes in myoglobin serum concentration could be an early marker of coronary artery reperfusion after thrombolysis in patients with acute myocardial infarction. The studies comprised 50 patients treated by thrombolysis due to threatening myocardial infarction, including 29 men and 21 women aged 43-84 years. The patients were divided into 2 groups: the first (i)-patients without symptoms of coronary artery reperfusion and the second (ii)-those with symptoms of coronary artery reperfusion. It was assumed that the basis for successful reperfusion would be the reduction of total elevations of the ST segment 70% or more in electrocardiographic recording performed 3 hours after the start of thrombolytic treatment. Reperfusion was considered completely unsuccessful when reduction of total elevations was less than 30%. In patients with reperfusion after thrombolysis the concentrations of myoglobin were much higher and the activity of CPK and CK-MB significantly more intensive in comparison with patients without reperfusion symptoms in electrocardiographic assay. The evaluation of myoglobin concentration, CPK and CK-MB activity in the 3rd hour after the start of thrombolytic treatment in relation to maximum values is characterised by high sensitivity and specificity in the prediction of reperfusion onset Maximum myoglobin concentration in serum appears significantly earlier than maximum CPK and CK-MB activity and this marker is characterised by higher sensitivity and specificity in the evaluation of coronary artery reperfusion than the activity of CPK and CK-MB.     

Biochemical markers of myocardial damage for early diagnosis and prognosis in patients with acute coronary syndromes. Minireview based on a doctorial thesis

In patients with suspected AMI. Monitoring of a combination of myoglobin and CK-MB or tn-T allowed ruling-in AMI within 2-3 hours and ruling-out AMI within 3-6 hours in almost all patients admitted with chest pain and a nondiagnostic ECG. This might have a large impact on the early handling and treatment of these patients. The neural network methodology, with monitoring of myoglobin, CK-MB and tn-T allowed, within the first three hours, reliable diagnosis/exclusion of AMI/MMD and prediction of infarct size in patients admitted with suspicion of AMI. The computer system was faster than clinicians. Thus, neural network methodology might be a useful support for the early assessment of patients with suspected myocardial infarction. In patients with unstable CAD. The risk of subsequent cardiac events is increased by increasing maximal levels of tn-T obtained during the initial 24 hours. Thereby a normal, a slightly elevated and a clearly elevated tn-T level identified a low, intermediate and high risk group, respectively, for MI or death. The tn-T level was an independent prognostic variable for MI or death in a multivariate analysis comparing other early available risk indicators. Furthermore, tn-T seemed to be superior to CK-MB (mass) for risk stratification. In patients able to perform a predischarge ET both the tn-T level and the ET response were independent prognostic indicators for MI or death. The combination of tn-T and the ET response allowed a further improved risk stratification. In patients with tn-T elevation at inclusion, prolonged dalteparin treatment was beneficial. However, in patients without tn-T elevation, long term dalteparin treatment had no protective effect. Thus, tn-T determination provides independent and important prognostic information in unstable CAD. In the selection of treatment strategy for the individual patient, this simple, inexpensive and early available biochemical test might be useful.     

Is myoglobin useful in the diagnosis of acute myocardial infarction in the emergency department setting?

The authors evaluated the usefulness of a rapid fluorometric enzyme immunoassay for myoglobin (Myo) for early diagnosis of acute myocardial infarction (AMI) in patients in the emergency department. The rapid fluorometric enzyme immunoassay for myoglobin was performed on timed blood samples collected previously for serial CK and CKMB determinations from 41 patients who initially presented to the ED with chest pain and were subsequently admitted to patient care units. Twenty-two patients were AMI positive and 19 were AMI negative. In 12 patients who were AMI positive, Myo increased rapidly and significantly peaking at 6.53 +/- 5.45 hours, whereas in the other 10 patients who were AMI positive, only the declining slopes of Myo were observed due to late AMI presentation. In the AMI negative group, Myo values were within reference range in 8 and persistently elevated in 11. Using the initial rate of Myo release of 20 ng/mL per hour as criteria of discrimination, this assay has a sensitivity of 90.1% and a specificity of 74%. Available samples for the two patients who were false negative were past the window of Myo release for AMI detection. All five patients who were false positive were associated with various degrees of muscular trauma or renal disorder. The authors conclude that the initial rate of Myo release demonstrates good utility both at early detection and early exclusion of AMI. However, its tissue nonspecificity may not permit AMI recognition in the presence of muscular injury.     

Class I-restricted cross-presentation of exogenous self-antigens leads to deletion of autoreactive CD8(+) T cells

Intracoronary thrombosis plays a key role in the pathogenesis of acute myocardial infarction (AMI), and the formation of an occlusive thrombus usually precedes the development of myocardial damage. Therefore we evaluated and compared the early sensitivities of thrombin-antithrombin III complex (TAT), D-dimer, myoglobin, creatine kinase (CK) MB mass concentration, and cardiac troponin T (cTnT) on admission to a coronary care unit (CCU) before heparin or thrombolytic therapy was started. We investigated 31 consecutive patients admitted to CCU for evolving AMI within 6 hours from the onset of infarct-related symptoms; the median delay from chest pain onset to CCU admission was 135 minutes. Of all biochemical markers tested TAT had the highest early sensitivity on admission to the CCU, and TAT was significantly more sensitive than cTnT, CKMB mass, myoglobin, and D-dimer. However, TAT increases give no information about the location of clot formation in the body, and the diagnosis of AMI must be subsequently verified by an increase in more cardiac specific proteins, such as troponins or CKMB.     

Absorptive function following small intestinal transplantation

Detection of cardiac troponin I (cTnI) in patients suspected of having an acute coronary syndrome is highly predictive for an adverse outcome. We evaluated a bedside test for cTnI that uses a polyclonal capture antibody and two monoclonal indicator antibodies. Clinical studies were performed in patients with acute coronary syndrome and patients with chest pain but no evidence of acute myocardial injury. The whole-blood, 15-minute assay had a concordance of 98.9% with an ELISA for cTnI and a detection limit of 0.14 microg/L, and the device tolerated temperatures between 4 degrees C and 37 degrees C. Diagnostic sensitivity for myocardial infarction at arrival (3.5 +/- 2.7 h after onset of symptoms) was 60% [creatine kinase isoenzyme MB (CK-MB) mass, 48%; CK activity, 36%; P < 0.01], and 4 h later, diagnostic sensitivity was 98% (CK-MB mass, 91%; CK activity, 61%; P < 0.01). In 38% of the patients with unstable angina, at least one positive cTnI test was found (CK-MB mass, 4%; CK activity, 2%). No false-positive test results were found in renal failure or injury of skeletal muscle. We conclude that the diagnostic efficacy of the cTnI rapid test was comparable with the cTnI ELISA and superior to CK-MB determination. Therefore, this device could facilitate decision-making in patients with chest pain at the point of care.     

Bone lesions of multiple myeloma in three dogs

In 41 survivors of acute myocardial infarction (AMI) a prospective study was performed in 2 sequential phases. In phase 1, the role of baroreflex sensitivity and heart rate variability as predictors of inducible and spontaneous sustained ventricular tachyarrhythmias was evaluated. In phase 2, the effects of transdermal scopolamine on baroreflex sensitivity, spectral and nonspectral measures of heart rate variability were investigated. At a mean follow-up of 10 +/- 3 months after AMI, 5 of 41 patients (12%) developed a late arrhythmic event. Of these, all (100%) had inducibility of sustained monomorphic ventricular tachycardia at programmed stimulation compared with 3 of 36 patients (8%) without events (p < 0.0001). At multivariate analysis, baroreflex sensitivity had the strongest relation to both inducibility of sustained monomorphic ventricular tachycardia (p < 0.0001) and occurrence of arrhythmic events (p < 0.0001). Of 41 patients, 28 (68%) consented to undergo phase 2 of the investigation. Baroreflex sensitivity significantly (p < 0.00001) increased after transdermal scopolamine as well as heart rate variability indexes. Of these, the mean of SDs of normal RR intervals for 5-minute segments (p < 0.0001) and the total power (p < 0.0001) had the most significant improvement after scopolamine. The present investigation confirms that assessment of autonomic function is an essential part of arrhythmic risk evaluation after AMI. Transdermal scopolamine, administered to survivors of a recent AMI, reverses the autonomic indexes that independently predict arrhythmic event occurrence. On the basis of these data, transdermal scopolamine could be a potential useful tool in the prophylaxis of life-threatening ventricular arrhythmias after AMI.     

Clinical evaluation of an immunoinhibition procedure for creatine kinase-MB

We have clinically evaluated the Dade "Cardiozyme" immunoinhibition procedure for determination of creatine kinase isoenzyme MB (CK-MG) in 71 patients who were suspected of having had an acute myocardial infarction. Electrophoresis for CK-MB was also carried out. On the basis of diagnostic sensitivity and specificity for myocardial infarction, we found the Dade procedure for CK-MB to be somewhat inferior to electrophoresis. In 11 patients for whom the time of infarction was known, we observed normal CK-MB results for two of them by both immunoinhibition and electrophoresis during the first 24 h, but subsequently could detect abnormal CK-MB results by both methods. Thus in some patients such data are not helpful for making a diagnosis in the first 24 h. The Dade procedure is easy to perform, but lacks sensitivity in the region of low CK-MB activity, requires a very stable spectrophotometer, is imprecise, and produces negative numerical results in patients without myocardial infarction.     

Early diagnosis of acute myocardial infarction by either electrocardiogram or a logistic regression model: portability of a predictive instrument of acute cardiac ischemia to a small rural coronary care unit

OBJECTIVE: To test the ability of a logistic regression model (LRM) that predicts acute cardiac ischemia to make an early diagnosis of acute myocardial infarction (AMI); the ability of the LRM to predict AMI was also compared with the presenting electrocardiogram (ECG). SETTING: A small rural Irish coronary care unit. METHODS: Clinical and ECG data required by the LRM to predict acute coronary ischemia were recorded in 600 consecutive patients admitted with suspected AMI. Estimates of the LRM were ranked into equal deciles in declining probability of acute cardiac ischemia (pACI), and presenting ECGs were placed into one of seven categories. RESULTS: At presentation 50% of AMI patients were in the two LRM deciles with the highest pACI, and 49% of AMI patients had ECGs with greater than 2 mm ST elevation associated with reciprocal changes. ECG categories had a 76% sensitivity for the early diagnosis of AMI and the LRM had an 84% sensitivity. The specificity, accuracy and positive predictive value for the ECG categories were 92%, 84% and 85%, respectively. The specificity, accuracy and positive predictive value of the LRM were 84%, 84% and 75%, respectively. The areas under the receiver operating characteristic curve of the LRM and ECG categories were almost identical (91% and 90%, respectively). CONCLUSION: AMI can be diagnosed early with comparable accuracy either by placing presenting ECGs into one of seven categories, or by the LRM. The best method and 'cut-off' point for the diagnosis of AMI varies according to clinical circumstances. Categorizing ECGs requires more skill in ECG interpretation, but takes less time. The previously reported performances of the LRM were replicated, confirming portability of its use into different clinical settings and patient populations.     

Improved detection of minor ischemic myocardial injury with measurement of serum cardiac troponin I

This study compared the diagnostic accuracy of the measurement of serum cardiac troponin I (cTnI) with creatine kinase (CK) MB mass in patients with minor myocardial injury whose measured total CK activity did not exceed twice the upper reference limit (300 U/L for men; 200 U/L for women). Forty-eight consecutive patients presenting with chest pain and with in-hospital documentation of myocardial injury were enrolled. Electrocardiogram, echocardiogram, and serial serum CK-MB mass, cTnI, and total CK were measured over 36 h after admission. Peak total CK activity was within normal limits in 28 patients (58%). The mean (+/- SD) peak CK-MB mass and cTnI concentrations were: 16.4 (11.8) micrograms/L and 132 (13.0) micrograms/L; respectively. The peak biochemical marker index (defined as CK-MB or cTnI divided by its respective upper reference limit) was significantly (P < 0.05) higher for cTnI than for CK-MB from 7 to 36 h. The clinical sensitivity for detection of myocardial injury for cTnI was 100% [95% confidence interval (CI): 87.2% to 100%], compared with 81.8% (CI: 67.3% to 91.8%) for CK-MB. Thus, cTnI was more sensitive than CK-MB mass for detection of myocardial injury in patients with small increases of total CK.     

Myocardial infarct extension: incidence and relationship to survival

Myocardial infarct extension, defined as reelevation or reappearance of creatine phosphokinase-MB (CK-MB) 48 hours after the onset of symptoms, was evaluated prospectively in 56 consecutive patients with acute myocardial infarction. Myocardial infarct extension occurred in eight patients (14%). The sensitivity, specificity and predictive accuracy in the diagnosis of myocardial infarct extension were 63%, 85% and 42%, respectively, for recurrent chest pain requiring morphine; 50%, 65% and 19% for recurrent ST-segment elevation on routine 12-lead ECGs; and 88%, 63% and 28% for reelevation of total CK. Three of the eight episodes of extension were clinically silent. Four of eight patients (50%) with extension died, compared with one of 46 patients (2%) without extension (p = 0.0009). CK-MB persisted for 72 hours or longer in 16 patients and identified seven of eight patients who subsequently had infarct extension. We conclude that myocardial infarct extension is an infrequent complication of acute myocardial infarction and is associated with a very high mortality rate. Persistence of CK-MB for 72 hours or more identifies a subgroup of patients at high risk for subsequent infarct extension and death.     

Clinical utility of cardiac troponin I and cardiac troponin T measurements

The measurement of CK-MB remains the test of choice for confirmation or exclusion of AMI and probably will remain the test of choice for routine diagnosis in the near future. Nowadays determination of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) as a method relatively expensive and time-consuming should be restricted to clinical settings that really require their high specificity.