Myoglobin, creatine-kinase-MB and cardiac troponin-I 60-minute ratios predict infarct-related artery patency after thrombolysis for acute myocardial infarction: results from the Thrombolysis in Myocardial Infarction study (TIMI) 10B.

OBJECTIVES: We examined the diagnostic performance of serum myoglobin, creatine-kinase-MB (CK-MB) and cardiac troponin-I (cTnI) for predicting the infarct-related artery (IRA) patency in patients receiving TNK-tissue plasminogen activator (TNK-tPA) therapy for acute myocardial infarction (AMI) in the Thrombolysis in Myocardial Infarction (TIMI) 10B trial. BACKGROUND: A reliable noninvasive serum marker of IRA patency is desired to permit early identification of patients with a patent IRA after thrombolysis. METHODS: We measured myoglobin, CK-MB and cTnI concentrations in sera obtained just before thrombolysis (T0) and 60 min later (T60) in 442 patients given TNK-tPA and who underwent coronary angiography at 60 min. RESULTS: Angiography at 60 min showed a patent IRA (TIMI flow grade 2, 3) in 344 and occluded IRA (TIMI flow grade 0, 1) in 98 patients. The median serum T60 concentration, the ratio of the T60 and T0 serum concentration (60-min ratio) and the slope of increase over 60 min for each serum marker were significantly higher in patients with patent arteries compared with patients with occluded arteries. The area under the receiver-operating characteristic (ROC) curve for diagnosis of occlusion was 0.71, 0.70 and 0.71 for the 60-min ratio of myoglobin, cTnI and CKMB, respectively. The 60-min ratios of > or =4.0 for myoglobin, > or =3.3 for CK-MB and > or =2.0 for cTnI yielded a probability of patency of 90%, 88% and 87%, respectively. CONCLUSIONS: The diagnostic performance of serum myoglobin, CK-MB and cardiac troponin-I (cTnI) 60-min ratios was similar. The probability of a patent IRA was very high (90%) in patients with 60-min myoglobin ratio > or =4.0, and early invasive interventions to establish IRA patency may not be necessary in this group. Serum marker determinations at baseline and 60-min after thrombolysis may permit rapid triage of patients receiving thrombolytic therapy by ruling out IRA occlusion.

Myoglobin, creatine kinase MB, and cardiac troponin-I to assess reperfusion after thrombolysis for acute myocardial infarction: results from TIMI 10A.

BACKGROUND: The availability of a reliable, noninvasive serum marker of reperfusion may permit early identification of patients with occlusion after thrombolysis who might benefit from further interventions. METHODS: We measured myoglobin, creatine kinase MB (CK-MB), and cardiac troponin-I (cTnI) concentrations in sera obtained just before thrombolysis (T0) and 60 minutes later (T60) in 30 patients given TNK-tPA for acute myocardial infarction as part of the Thrombolysis in Myocardial Infarction (TIMI) 10A trial. RESULTS: Angiography at T60 showed reperfusion (TIMI flow grade 2 to 3; n = 19) or occlusion (TIMI flow grade 0 to 1; n = 8). The median serum T60 concentration, the ratio of the T60 and T0 serum concentration, and the slope of increase over a 60-minute period for each serum marker were significantly higher in patients with patent arteries compared with patients with occluded arteries. The areas under the receiver operator characteristics curve for diagnosis of occlusion were 0.96, 0.91, and 0.87 for the T60 concentration of myoglobin, CK-MB and cTnI, respectively. Although the T60 levels of <469 ng/ml for myoglobin, <11.5 ng/ml for CK-MB, and < 1.1 ng/ml for cTnI identified all patients with occlusion, the specificity of myoglobin (94%) was higher than that of CK-MB (61%) and cTnI (67%). Similar results were obtained for the 60-minute ratios and 60-minute slopes for each marker, with indexes for myoglobin having the highest specificity. CONCLUSIONS: In this pilot study, noninvasive diagnosis of occlusion 60 minutes after thrombolysis was achieved with a high degree of sensitivity and specificity with the myoglobin, CK-MB, and cTnI concentrations measured at that time point. These preliminary findings may permit a new strategy for assessment of the success of reperfusion, with triage to rescue angioplasty for patients in whom the 60-minute cardiac marker values or indexes are consistent with occlusion of the infarct-related artery.

Evaluation of a rapid bedside assay for detection of serum cardiac troponin T.

OBJECTIVE: To evaluate a rapid, qualitative, bedside immunoassay for cardiac-specific troponin T (cTnT) using a handheld device containing monoclonal antibodies. DESIGN: Comparison of rapid cTnT assay with clinical standard for diagnosis of myocardial infarction (MI). SETTING: Tertiary care university medical center. PATIENTS: A cohort of 100 patients admitted for evaluation of chest pain who had sufficient blood samples at presentation for measurement of creatine kinase, creatine kinase MB fraction, and rapid cTnT as well as adequate clinical data to establish the diagnosis of MI. INTERVENTION: None; treating physicians were blinded to rapid cTnT results. MAIN OUTCOME MEASURES: Sensitivity and specificity of rapid cTnT assay for MI; likelihood ratios of positive and negative rapid cTnT assay results; relative risk (RR) for serious cardiac events with positive rapid cTnT assay result on admission. RESULTS: Sensitivity of the rapid cTnT assay increased from 33% within 2 hours from the onset of chest pain to 86% after 8 hours (P < .001); specificity ranged from 86% to 100% during the same time intervals. The odds of an MI increased sixfold with a positive assay result within 2 hours of chest pain and decreased sixfold with a negative assay result after 8 hours. The RR for experiencing death or nonfatal MI was 6.8 for patients presenting with a positive rapid cTnT assay. CONCLUSIONS: The rapid cTnT assay is a simple, efficient test that for the first time provides clinicians with a useful laboratory tool for point-of-care evaluation of patients with chest pain.