Utility of cardiac troponin I, creatine kinase-MBmass, myosin light chain 1, and myoglobin in the early in-hospital triage of "high risk" patients with chest pain

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Abstract
OBJECTIVE To evaluate the use of cardiac troponin I (cTnI), creatine kinase-MBmass (CK-MBmass), myosin light chain 1 (MLC 1), and myoglobin in identifying “high risk” patients with chest pain who will experience serious cardiac events (SCEs) in hospital. DESIGN Prospective study. SETTING University affiliated medical centre in Philadelphia, USA. PATIENTS 208 patients with chest pain, at > 7% risk of acute myocardial infarction (MI), but without new ST segment elevation on their presenting ECG. INTERVENTIONS cTnI, CK-MBmass, MLC 1, and myoglobin concentrations were obtained on admission (0 hour) and at 4, 8, 16, and 24 hours. MAIN OUTCOME MEASURES The sensitivity, specificity, positive and negative predictive value, and pre- and post-test probabilities of patients suffering an SCE in hospital were determined. SCEs included cardiac death, acute MI, cardiac arrest, life threatening cardiac arrhythmia, cardiogenic shock, and urgent coronary revascularisation. RESULTS Admission concentrations of all markers were poor predictors of SCEs in hospital but improved substantially at subsequent timepoints. cTnI and CK-MBmass were consistently the most useful prognostic indicators. If both were negative at 0, 4, and 8 hours, then 99% (95% confidence interval 96% to 100%) of patients remained free from SCEs. The only SCEs not thus predicted were revascularisation procedures and associated complications. Additional tests after 8 hours, or the inclusion of additional markers, did not improve predictive accuracy further. CONCLUSIONS Patients with high risk clinical features on admission who have negative cTnI and CK-MBmass concentrations at 0, 4, and 8 hours later have a favourable in-hospital prognosis and could be considered for early triage out of coronary care units.