Early Diagnostic Efficiency of Cardiac Troponin I and Troponin T for Acute Myocardial Infarction

Objective : To compare the early diagnostic efficiency of the cardiac troponin I (cTn-I) level with that of the cardiac troponin T (cTn-T) level, as well as the creatine kinase (CK), CK-MB, and myoglobin levels, for acute myocardial infarction (AMI) in patients without an initially diagnostic ECG presenting to the ED within 24 hours of the onset of their symptoms. Methods : A prospective, observational, cohort study was performed involving chest pain patients admitted to a large urban community hospital. Participants were consecutive consenting ED chest pain patients ≥30 years of age. Exclusions included duration of symptoms >24 hours, inability to complete data collection, receipt of CPR, and ST-segment elevation on the initial ECG. Measurements included levels of cTn-I, cTn-T, CK, CK-MB, and myoglobin at the time of presentation and 1, 2, 6, and 12–24 hours after presentation as well as presenting ECG and clinical follow-up. Confirmation of the diagnosis of AMI was based on World Health Organization criteria. Results : Of the 177 patients included in the study, 27 (15%) were diagnosed as having AMIs. The sensitivities of all 5 biochemical markers for AMI were poor at the time of ED presentation (3.7–33.3%) but rose significantly over the study period. The sensitivity of cTn-T was significantly better than that of cTn-I over the initial 2 hours, but both markers' sensitivities were low (<60%) during this time frame. The cTn-I was significantly more specific for AMI than was the cTn-T, but not significantly better than CK-MB or myoglobin. Likelihood ratio analysis showed that the biochemical markers with the highest positive likelihood ratios for AMI during the first 2 hours following ED presentation were myoglobin and CK-MB. From 6 through 24 hours, the positive likelihood ratios for cTn-I, CK-MB, and myoglobin were superior to those of CK and cTn-T. Conclusions : cTn-I, CK-MB, and myoglobin are significantly more specific for AMI than are CK and cTn-T. Myoglobin is the biochemical marker having the highest combination of sensitivity, specificity, and negative predictive value for AMI within 2 hours of ED presentation. Neither cTn-I nor cTn-T offers significant advantages over myoglobin and CK-MB in the early (≤2 hours) initial screening for AMI. The cardiac troponins are of benefit in identifying AMI ≤6 hours after presentation.     

Myoglobin for Early Risk Stratification of Emergency Department Patients with Possible Myocardial Ischemia

OBJECTIVES: To determine and compare the prognostic abilities of early, single-sample myoglobin measurement with that of creatine kinase-MB (CK-MB), with cardiac troponin T (cTnT), and with physician judgment in the absence of marker results among emergency department (ED) patients with possible myocardial ischemia. METHODS: Prospective collection of clinical and serologic data using an identity-unlinked technique from patients with possible myocardial ischemia at two urban EDs. Outcome data concerning the occurrence of adverse events (AEs) during the 14 days after enrollment were used to calculate and compare the relative risks (RRs) and predictive values (with 95% confidence intervals) of the various markers for predicting AEs. RESULTS: Among 396 analyzed patients, 65 (16.4%) accrued 104 AEs, including 13 deaths (3.3%) and 31 (7.8%) myocardial infarctions. Myoglobin predicted AEs (RR = 3.36 [95% CI = 2.19 to 5.15]) with significantly higher sensitivity (50.8% [95% CI = 38.6 to 62.9]) than either CK-MB (15.4% [95% CI = 6.6 to 24.2]) or cTnT (24.6% [95% CI = 14.1 to 35.1]), but with lower specificity (81.9% [95% CI = 77.7 to 86.0]; CK-MB = 99.7% [95% CI = 99.1 to 100]; cTnT = 93.1% [95% CI = 90.3 to 95.8]). Myoglobin had prognostic ability among patients with chest pain (3.86 [95% CI = 2.39 to 6.22]) and atypical (non-chest pain) presentations (2.71 [95% CI = 1.09 to 6.71]), including those with a nondiagnostic electrocardiogram (3.11 [95% CI = 1.44 to 6.69]). The combination of myoglobin and physician decision making identified 63 of the 65 patients (96.9% [95% CI = 92.7 to 100]) with subsequent AEs. CONCLUSIONS: The early prognostic sensitivity of myoglobin may allow identification of some high-risk patients missed by physician judgment, CK-MB, and cTnT. Myoglobin should be considered for use in the ED based on both its diagnostic and prognostic abilities.     

Evaluation of a New Assay for Cardiac Troponin I vs Creatine Kinase-MB for the Diagnosis of Acute Myocardial Infarction

Objective : To compare a new assay for cardiac troponin I (cTn-I) with an assay for creatine kinase-MB (CK-MB) for the diagnosis of acute myocardial infarction (AMI).
Methods : A prospective cross-sectional study of patients presenting with symptoms consistent with cardiac ischemia was performed at a university teaching hospital. Serum sampling for cTn-I and CK-MB was performed at 0, 1, 3, 8, and 16 hours after presentation. Normal values were defined as CK-MB ≤ 7 ng/mL and a relative index ≤ 2%, cTn-I ≤ 1.4 ng/mL. Final diagnosis was made using World Health Organization criteria, including standard enzyme sampling. Consecutive patients with AMI were compared with a randomly selected subset of patients without AMI to determine the sensitivity and specificity of the cTn-I and CK-MB assays for AMI, stratified by time from symptom onset. The ability of the biochemical cardiac markers obtained within 6 hours of symptom onset to predict later complications or need for interventions was assessed using odds ratios (ORs).
Results : Thirty-five patients who had AMI were compared with 136 patients who did not have AMI. The sensitivities and specificities of the cTn-I and CK-MB assays, stratified by time from symptom onset, were: Patients who had elevations in either CK-MB or cTn-I within 6 hours of symptom onset were at increased risk for cardiovascular complications and/or interventions (CK-MB, OR 5.8; cTn-I, OR 6.3).
Conclusion : cTn-I was as sensitive and specific for AMI as was CK-MB in ED patients who presented within 24 hours of symptom onset. However, cTn-I was more sensitive in patients who presented ≥ 24 hours after symptom onset. Elevations of either marker within 6 hours of symptom onset predict an increased risk of complications and/or need for interventions.     

Release kinetics of serum cardiac troponin i in ischemic myocardial injury

Objectives: The study was undertaken to evaluate the release kinetics of cardiac troponin I (c-cTn-I) in ischemic myocardial injury.

Design and Methods: The reference range for cTn-I was established by determination of cTn-I in sera and plasma obtained from 622 healthy volunteers (Group 1). cTn-I was compared to: (a) Creatine kinase (CK) MB mass and myoglobin in 12 patients with severe skeletal muscle damage (Group 2); (b) CK-MB activity in 48 patients with myocardial infarction (MI) receiving intravenous thrombolysis (Group 3) (in this group, an additional 43 patients with MI were analyzed separately to characterize cTn-I patterns in thrombolyzed and nonthrombolyzed populations); and in 44 patients with unstable angina (Group 4).

Results: In Groups 1 and 2, no positive results (0.1 μg/L) were obtained. In Group 3, the time-courses of cTn-I were mostly monophasic in form. A pathologic increase occurred earlier in cTn-I than in CK-MB activity (p = 0.0002); the period with increased cTn-I was longer (p = 0.001), the overall sensitivity of cTn-I (93.9%) was higher than that of CK-MB activity (p = 0.00001). cTn-I was more sensitive at admission (p = 0.0004). In additional patients, the cTn-I peak occurred and cTn-I disappeared significantly later in nonthrombolyzed than in the thrombolyzed group. In Group 4, positive tests results were detected in 45% of patients for cTn-I, 16% for CK-MB activity, and 32% for CK-MB mass.

Conclusions: The cTn-I assay appears to be ideally suited for the detection of ischemic myocardial injury in complex clinical situations because of its high specificity; cTn-I indicates myocardial tissue damage in patients with unstable angina and is superior to CK-MB activity and mass in this respect.     

Time-course of cardiac troponin I release from isolated perfused rat hearts during hypoxia/reoxygenation and ischemia/reperfusion.

The study was designed to determine the time-course of cardiac troponin I (cTn-I) release in isolated and Langendorff-perfused rat hearts during hypoxia and reoxygenation (H/Reox), and after various durations of total ischemia and subsequent reperfusion (I/R). For this purpose, in H/Reox, cTn-I was measured with the conventional Access immunoassay (ng/ml) and a new immunoassay which operates at pg/ml, and compared with creatine kinase (CK), lactate dehydrogenase (LD) and cardiac troponin T (cTn-T). In I/R, cTn-I was compared with CK and LD. The anti-Tn-I mAbs used in cTn-I assays cross-react with cTn-I of the rat. A clear difference between time-courses and concentration levels of cTn-I in I/R and H/Reox models was found. In I/R, maximum release of cTn-I, CK and LD similarly occurred within minutes following reperfusion; however cTn-I did not return to baseline values. cTn-I levels were not linked to the duration of ischemia. In I/R, we were only able to detect small cTn-I concentrations. In H/Reox experiments, cTn-I, CK and LD increased time-dependently. We found higher cTn-I maximal peak levels detected with the Access immunoassay than with the new assay (median, 0.346 ng/ml per min/g dry wt vs 132 pg/ml per min/g dry wt). cTn-T maximal concentrations were lower than maximal cTn-I levels (median, 0.117 ng/ml per min/g dry wt). Time-courses of cTn-I release were roughly similar with both assays in the H/Reox model (r = 0.90). These data indicate that the cTn-I time-course is related to experimental model (I/R or H/Reox), but also likely depends on the sensitivity of cTn-I assays in such experimental conditions.     

Utility of Troponin I in Patients with Cocaine-associated Chest Pain

Baseline electrocardiogram abnormalities and market elevations not associated with myocardial necrosis make accurate diagnosis of myocardial infarction (MI) difficult in patients with cocaine-associated chest pain. Troponin sampling may offer greater diagnostic utility in these patients. OBJECTIVE: To assess outcomes based on troponin positivity in patients with cocaine chest pain admitted for exclusion of MI. METHODS: Outcomes were examined in patients admitted for possible MI after cocaine use. All patients underwent a rapid rule-in protocol that included serial sampling of creatine kinase (CK), CK-MB, and cardiac troponin I (cTnI) over eight hours. Outcomes included CK-MB MI (CK-MB >or= 8 ng/mL with a relative index [(CK-MB x 100)/total CK] >or= 4, cardiac death, and significant coronary disease (>or=50%). RESULTS: Of the 246 admitted patients, 34 (14%) met CK-MB criteria for MI and 38 (16%) had cTnI elevations. Angiography was performed in 29 of 38 patients who were cTnI-positive, with significant disease present in 25 (86%). Three of the four patients without significant disease who had cTnI elevations met CK-MB criteria for MI, and the other had a peak CK-MB level of 13 ng/mL. Sensitivities, specificities, and positive and negative likelihood ratios for predicting cardiac death or significant disease were high for both CK-MB MI and cTnI and were not significantly different. CONCLUSIONS: Most patients with cTnI elevations meet CK-MB criteria for MI, as well as have a high incidence of underlying significant disease. Troponin appears to have an equivalent diagnostic accuracy compared with CK-MB for diagnosing necrosis in patients with cocaine-associated chest pain and suspected MI.     

Value of a single troponin T at the time of presentation as compared to serial CK-MB determinations in patients with suspected myocardial ischemia

BACKGROUND: Prior studies with cardiac markers have focused predominantly on subjects presenting to the emergency department with chest pain or unstable angina, and have relied on serial markers for the diagnosis of acute myocardial infarction. We evaluated the diagnostic utility of a single cardiac troponin T (cTnT) determination at the time of presentation as compared to serial creatine kinase (CK) MB determinations in a broad spectrum of patients with suspected myocardial ischemia. METHODS: A total of 267 consecutive patients presenting to the emergency department with suspected myocardial ischemia had a single, blinded cTnT determination drawn at the time of presentation to the emergency department in addition to routine serial electrocardiographic and CK-MB determinations. RESULTS: The specificity (93.7% vs. 87.1%; p<0.05) and positive predictive value (80.0% vs. 69.4%; p<0.05) of a single cTnT determination were superior to that of serial CK-MB determinations without compromising sensitivity. Forty-six percent of patients with confirmed myocardial infarction and an abnormal cTnT at presentation had a normal initial CK-MB determination. Conversely, 20% of patients without acute coronary syndromes had an abnormal CK-MB determination in the setting of a normal cTnT. The initial cTnT was abnormal in all patients with confirmed myocardial infarction and a symptom duration of at least 3.5 h. CONCLUSIONS: In a heterogeneous population of patients with suspected myocardial ischemia, the initial cTnT determination drawn at the time of presentation is a powerful diagnostic tool that, when used in context with symptom duration, allows for more rapid and accurate triage of patients than serial CK-MB determinations.     

Prehospital identification of acute coronary ischemia using a troponin t rapid assay

Objective. To evaluate the performance of a rapid assay for cardiac troponin T (cTn-T) in patients with chest pain in the prehospital setting. Methods. A prospective, observational clinical trial in a rural county served by a single emergency medical services system and two emergency departments. Patients fulfilling prehospital criteria to identify acute coronary ischemia (ACI) had a blood sample applied to the cTn-T rapid-assay device. Quantitative analysis of cTn-T was also performed on each sample at a later time. Medical records were reviewed to determine ultimate diagnoses. Non-admitted patients were followed by telephone at one week. Main outcome measures included the sensitivity, specificity, positive predictive value, and negative predictive value of the rapid cTn-T assay for detecting ACI defined as acute myocardial infarction (AMI) or unstable angina (UA) within one week of presentation. Results. Of 87 patients enrolled, 29 were identified with ACI. This included 15 patients diagnosed as having AM1 and 14 patients diagnosed as having UA. The cTn-T rapid-assay device was positive for five of 87 patients (5.7%); three were associated with AMI and two with UA. Measurement of a single cTn-T to detect ACI had a sensitivity of 17.2% (0.058, 0.358), specificity of 100% (0.950, l), positive predictive value of 100% (0.549,1), and negative predictive value of 70.7% (0.609, 0.806). Conclusion. The cTn-T rapid-assay device may be useful in the prehospital setting to identify a small number of patients with ACI. The authors caution, however, that a negative test in the prehospital setting cannot be used to rule out significant disease.     

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.     

Release of cardiac troponin in acute coronary syndromes: ischemia or necrosis?

Analysis of cardiac troponin T and I have been shown to be effective in detecting minor myocardial injury in cardiac patients who present with acute coronary syndromes (ACS). Determination of minor myocardial injury is significant, as these patients have a higher short-term morbidity and mortality than other unstable angina patients with normal concentrations for these markers. In this report, two theories are given as to why cardiac troponin is superior to other markers such as CK-MB for risk stratification. The 'low cut-off concentration model' is based on the fact that troponin is not increased in patients with skeletal muscle disease or injury, resulting in low baseline concentrations of the cardiac isoforms in the absence of active cardiac disease. This enables the use of low decision limits. Troponin also has a higher myocardial tissue content relative to CK-MB, thereby also increasing its clinical sensitivity to irreversible injury. In the 'reversible ischemia model', cytoplasmic free troponin T and I leak across the membrane of myocytes as the result of reduced coronary blood flow. Jeopardized myocardial tissue can recover with acute recanalization. Support for this model comes from clinical observations and animal studies.     

5项心肌标志物联合检测对先兆子痫心肌损伤的诊断价值研究

目的探讨超敏肌钙蛋白-T(hs-cTnT)、人心型脂肪酸结合蛋白(H-FABP)、B型尿钠肽(BNP)、缺血修饰清蛋白(IMA)和肌酸激酶同工酶(CK-MB)对先兆子痫心肌损伤的诊断价值。方法正常妊娠50例纳入妊娠组,诊断为先兆子痫167例为先兆子痫组,分为心肌损伤组42例和无心肌损伤组125例。另选择50例健康非妊娠女性为对照组。采用ELISA一步法测定血清中H-FABP,微粒子化学发光免疫法检测hs-cTnT和BNP,清蛋白-钴结合试验测定IMA,以及免疫抑制法测定CK-MB。结果先兆子痫组中心肌损伤组的CK-MB、H-FABP、IMA、hs-cTnT和BNP水平明显高于对照组、妊娠组和无心肌损伤组,差异有统计学意义[(t=8.521、7.489、7.256;7.561、6.897、6.235;12.314、9.236、10.251;13.657、11.023、12.031;11.301、10.364、15.567),(P=0.008,0.030,0.035;0.027,0.031,0.033;0.002,0.005,0.003;0.002,0.004,0.003;0.003,0.004,0.001)]。先兆子痫组中无心肌损伤组的CK-MB和hs-cTnT与对照组、妊娠组比较,差异无统计学意义[(t=1.678、1.401;1.887、1.784),(P=0.339、0.401;0.289、0.398)]。无心肌损伤组和妊娠组的IMA、H-FABP和BNP明显高于对照组[(t=4.784、4.021;3.894、3.784;5.801、5.215),(P=0.024、0.032;0.037、0.041;0.021、0.029)]。无心肌损伤组的IMA、H-FABP和BNP与妊娠组比较,差异无统计学意义[(t=1.325、1.257、1.241);(P=0.451、0.329、0.378)]。5项标志物联合检测灵敏度明显高于单个标志物(χ2=3.021、3.561、4.215、4.496、5.249;P=0.027、0.024、0.019、0.015、0.009)。结论采用心肌标志物判断孕妇心肌损伤时,应考虑到妊娠这一特殊的生理周期,5项心肌标志物联合检测,有利于早期诊断先兆子痫的缺血性心肌损伤。     

急性有机磷农药中毒患者血清肌钙蛋白T与心肌酶学的变化及意义

目的:探讨急性有机磷农药中毒(AOPP)患者肌钙蛋白及心肌酶学变化规律与中毒程度的关系。方法:对92例AOPP患者抽取中毒后1、2、3、5、7天空腹静脉血两组各3mL,对患者的肌钙蛋白T及心肌酶学(CK-MB、CK、AST、LDH)进行测定并将结果与30例健康体检者(抽血一次,两组各3mL)作为对照组进行比较。结果:AOPP患者肌钙蛋白T与心肌酶学均有不同程度的增高,与中毒程度相一致,并随病情好转而恢复。结论:AOPP患者肌钙蛋白T及心肌酶学水平变化能够作为较好地判断中毒程度及预后的参考指标之一。     

CK-MB isoforms for early risk stratification of emergency department patients

The potential clinical utility of single sample CK-MB isoforms measurement for early risk stratification of Emergency Department (ED) patients with possible myocardial ischemia was evaluated among 405 patients presenting to two urban EDs. Clinical and serologic data were prospectively collected and the occurrence of adverse events (AEs) and myocardial infarction (MI) during the 14-day outcome period was recorded and utilized to calculate and compare relative risks (RR) and predictive values of isoforms and CK-MB alone. Among the 405 patients, 67 accrued 105 AEs. Both isoforms and CK-MB alone were predictive of AEs with RR of 3.32 (2.09, 5.27) and 6.28 (4.64, 8.52), respectively. Isoforms had higher sensitivity for AEs compared to CK-MB (65.7% [54.3, 77.0] vs. 14.9% [6.4, 23.5]; p<0.01) but lower specificity (69.2% [64.3, 74.2] vs. 99.7% [99.1,100.0]; p<0.01). Isoforms’ superior sensitivity allowed identification of many high risk patients missed by CK-MB alone. Further, for the prediction of MI, isoforms had superior diagnostic sensitivity and equivalent specificity. This investigation supports the emergency department use of early, single sample CK-MB isoform testing.     

Evaluation of the chemiluminescence immunoassays for the measurement of troponin I, myoglobin and CK-MB using the IMMULITE system in comparison to other measuring systems

We evaluated the chemiluminescence immunoassays for the detection of the cardiac markers troponin I, myoglobin and CK-MB on the IMMULITE System (Diagnostic Products Corporation) in comparison to the same analytes of other companies. The IMMULITE assays are two-site solid phase immunometric assays using a murine monoclonal capture antibody on the solid phase and a polyclonal antibody conjugated with alkaline phosphatase (except CK-MB monoclonal, murine) for detection. Precision was investigated using serum pools with a low, a cutoff and a high concentration of the respective analyte. The results were satisfactory with an intra-assay precision coefficient of variation, CV of 1.7% - 3.2% for troponin I, 2.6% - 5.1% for myoglobin, 2.7% - 5.3% for CK-MB and an interassay precision of 5.1% - 6.9% for troponin I, 5.7% - 7.3% for myoglobin and 3.8% - 8.4% for CK-MB. In linearity studies with various dilution steps, a mean value of 105% was found for troponin I, 103% for myoglobin and 117% for CK-MB. The average recovery was 85% for troponin I, 100% for myoglobin and 95% for CK-MB. The clinical validity of the assays in the diagnosis and therapy of myocardial infarction was investigated in 120 patients who were sent to the hospital with suspected myocardial infarction. Four hours after admission all patients with clinically verified myocardial infarction showed troponin I and troponin T values above the cutoff value. A maximum rate of 32% of the patients (IMMULITE Troponin I) with an instable angina pectoris showed troponin values above the cutoff for myocardial infarction (1.0 microg/L), 4 hours after admission. A cutoff-reduction to 0.2 pg/L for troponin I increased the number of patients to 45%. The negative predictive value was constantly 67%. The results obtained by IMMULITE assays were compared to the Elecsys cardiac assays (Roche Diagnostics) and the AxSYM-cardiac assays (Abbott Diagnostics). The highest correlation (r = 0.99) was found for IMMULITE Troponin I (DPC) and Troponin I (Abbott). The Abbott-Troponin I showed the highest diagnostic sensitivity within 4 hours after admission. All compared methods showed a similar diagnostic sensitivity (close to 100%) > 4 hours after admission. For all investigated methods the percentage of discrepant results decreased to a minimum 4 hours after admission.     

心肌标志物作用的系统分析

目的：获取心肌生化标记物的最佳应用证据。方法：查循、浏览对心肌肌酸激酶同工酶MB（CK－MB）、肌红蛋白、心肌肌钙蛋白T（cTnT）和心肌肌钙蛋白I（cTnI）用于诊断心肌梗塞（MI）和对急性冠状动脉综合症分级的系统评价和Meta－分析的文献资料。结果：在症状发生后的12－48小时采样分析CK－MB质量对于诊断MI的临床灵敏度和牧场划性分别是98．8％和89．6％。肌红蛋白有高的阴性预示值,在症状发生后的2－6小时采样分析有高的临床灵敏度。在症状发生后的12采样cTnI,诊断MI的临床灵敏度和特异性分别是98．2％和68．8％,其临床特异性降低与检测到微小心肌受损有关。结论：cTnT和cTnI比CK－MB对诊断心肌梗死和预测急性冠状动脉综合症危险性更有价值。     

Frequency and outcomes of transient myocardial ischemia in critically ill adults admitted for noncardiac conditions.

BACKGROUND: Critically ill adults admitted for noncardiac conditions are at risk for acute myocardial ischemia. OBJECTIVES: To detect myocardial ischemia and injury in patients admitted for noncardiac conditions and to examine the relationship of myocardial ischemia, injury, and acuity to cardiac events. METHODS: Transient myocardial ischemia, acuity, elevations in serum troponin I, and in-hospital cardiac events were examined in 76 consecutive patients. Transient myocardial ischemia, determined by using continuous electrocardiography, was defined as a 1-mm (0.1-mV) change in ST level from baseline to event in 1 or more leads lasting 1 or more minutes. Acuity was determined by scores on Acute Physiology and Chronic Health Evaluation II. RESULTS: A total of 37 ischemic events were detected in 8 patients (10.5%); 32 (86%) were ST-segment depressions, and 35 (96%) were silent. Twelve patients (15.8%) had elevated levels of troponin I. Transient myocardial ischemia, elevated troponin I levels, and advanced age were significant predictors of cardiac complications (R2 = 0.387, F = 15.2, P < .001). Acuity correlated only modestly with increased length of stay in the intensive care unit (r = 0.26, P = .02) and elevated troponin I levels (r = 0.25, P = .03). Patients with transient myocardial ischemia had significantly higher rates of elevations in troponin I (P < .001) and cardiac events (P < .001) than did patients without. CONCLUSIONS: Transient myocardial ischemia and advanced age are predictors of cardiac events and may indicate patients at risk for cardiac events.     

16例急性心肌梗死患者肌钙蛋白T的临床分析

目的：探讨肌钙蛋白T(cTnT)在急性心肌梗死(AMI)早期诊断中的作用。方法：前瞻性对比分析16例AMI患者与35例非AMI的cTnT与肌酸激酶同工酶(CK-MB)的变化。结果：cTnT在AMI患者的血中出现较早。与CK-MB比较，其对AMI的敏感性高、特异性强。结论：cTnT检测是较理想的早期诊断AMI方法之一，特别在基层医院。     

Clinical predictors of 30-day cardiac events in patients with acute coronary syndrome at a community hospital

OBJECTIVE: We sought to determine predictors of coronary events (cardiac death, acute myocardial infarction, and urgent revascularization) within 30 days after admission. METHODS: We prospectively collected data on 400 patients admitted through our emergency room for unstable angina and acute coronary syndromes. Patients with ST-segment elevation myocardial infarction and those who required thrombolysis were excluded. RESULTS: Of 383 patients who were eligible, 120 patients had coronary events within 30 days. Statistically significant variables associated with coronary events were advanced age, male sex, family history of premature coronary artery disease (CAD), diabetes mellitus, tobacco abuse, prior congestive heart failure, prior myocardial infarction, and history of CAD. Symptoms at presentation associated with cardiac events were typical angina and shortness of breath. Objective measures of ischemia associated with cardiac events were elevated troponin T, elevated creatine kinase MB, and ischemic electrocardiographic changes. Using forward stepwise regression analysis, we generated a model to predict 30-day major adverse cardiac events. The strongest predicting variable was serum troponin T (accounting for 33% of predicting r2, P < 0.001) followed by typical angina (r2 increasing to 37%), ischemic electrocardiographic changes (40%), prior CAD (42%), family history of premature CAD (44%), shortness of breath (46%), and positive creatine kinase MB (48%). The positive predictive power of the complete model was r2 = 48%, P < 0.001. CONCLUSION: Our model incorporating elements from the patient's demographic, medical history, presentation, and ischemic assessment identified 48% of patients presenting with unstable angina and acute coronary syndromes who will suffer a major adverse cardiac event within 30 days of admission. Although the strongest predictor was identified as serum troponin T, other clinical criteria offered improvement in our predictive abilities. Therefore, good initial clinical evaluation in addition to simple tests such as serum cardiac markers and electrocardiography are valuable in risk stratification of patients presenting with acute coronary syndromes and cardiac chest pain. Additional testing may be necessary to improve the positive predictive value of the model. Cardiac enzymes and electrocardiographic changes have the highest negative predictive value for occurrence of major adverse cardiac events. Identification of high-risk patients is essential to direct resources toward these patients and to avoid unnecessary costs and risk to the low-risk population.     

Can Electrocardiographic Criteria Predict Adverse Cardiac Events and Positive Cardiac Markers?

OBJECTIVES: To determine electrocardiogram (ECG) predictors of positive cardiac markers and short-term adverse cardiac events in an undifferentiated chest pain population presenting to emergency departments (EDs). The authors hypothesized that specific ECG findings, other than those previously identified in higher-risk populations, would be predictive of cardiac outcomes and positive cardiac markers. METHODS: This study used data from a prospectively collected, retrospectively analyzed Internet-based data registry of undifferentiated chest pain patients (i*trACS). Logistic regression modeling was performed to determine the ECG findings that were predictive of 1) positive cardiac markers and 2) short-term adverse cardiac events. RESULTS: ST-segment elevation (STE), ST-segment depression (STD), pathological Q-waves (PQW), and T-wave inversion were associated with increased odds of percutaneous coronary intervention or catheterization, myocardial infarction, or coronary artery bypass grafting. The odds of creatine kinase-MB (CK-MB) measuring positive were increased if STE, STD, or PQW were present [odds ratio (OR) 2.495, 2.582, and 1.295, respectively]. A right bundle branch block tended to decrease the odds of CK-MB measuring positive (OR 0.658). A similar pattern of results was observed for troponin I (OR 3.608 for STE, 3.72 for STD, 1.538 for PQW). Troponin T showed an increased odds of measuring positive if any of STE, STD, left bundle branch block, or T-wave inversion were evident (OR 2.313, 2.816, 1.80, and 1.449, respectively). CONCLUSIONS: Initial ECG criteria can be used to predict short-term cardiac outcomes and positive cardiac markers. These findings can be important aids in the risk-stratification and aggressive treatment regimens of chest pain patients presenting to EDs.     

血清缺血修饰白蛋白测定在心肌缺血早期的临床应用价值

目的探讨血清缺血修饰白蛋白（IMA）测定在心肌缺血早期的临床应用价值。方法检测46例急症胸痛最终确诊为急性冠状动脉综合征（ACS）的患者及50名健康体检者的血清IMA水平和临床常用的心肌损伤标志物[肌酸激酶同工酶（CK-MB）、心肌肌钙蛋白T（cTnT）]。通过绘制IMA在该人群中用于诊断ACS的受试者工作特征（ROC）曲线判定最佳临界值,确定IMA诊断ACS的敏感性、特异性、阳性预测值和阴性预测值。结果与正常对照组比较,ACS组IMA水平显著升高,为（81．88±21．89）U／mL（P〈0．01）。根据ROC曲线,当以Cut—off值为64．5U／mL时,此时IMA检测的敏感性、特异性、阳性预测值和阴性预测值较高,分别为82．61％、88．00％、86．36％和84．62％。46例ACS患者中,入院即刻IMA测定值超过最佳Cut—off值者为38例,阳性率达82．61％;而同步测定cTnT阳性者仅为9例,阳性率为19．57％;CK—MB阳性者仅为6例,阳性率为13．04％。IMA阳性率与其他两者比较差异有统计学意义（P〈0．05）。结论IMA是ACS的早期敏感指标,是评价早期出现的可逆性心肌缺血的生化标志物。