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

OBJECTIVE: To evaluate the use of cardiac troponin I (cTnI), creatine kinase-MB(mass) (CK-MB(mass)), 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-MB(mass), 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-MB(mass) 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-MB(mass) 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.