Risk stratification using combined ECG, clinical, and biochemical assessment in patients with chest pain without ST-segment elevation. How long should we wait?

We use clinical, ECG, and biochemical data to stratify risk in patients with chest pain without ST segment elevation. However, the prognostic performance of these studies in relation to time from onset of symptoms is unknown. In a single-center, prospective study, 321 consecutive patients who had been admitted in the emergency room with a suspected acute coronary syndrome without ST segment elevation were included in the study. Blood samples were collected for CK, CK-MB mass, myoglobin, and cardiac troponin T analysis 6, 12 and 18 hours after the onset of pain and other clinical and ECG data were recorded. Univariate and multivariate analysis was used to identify independent prognostic predictors 6 and 12 hours after the onset of chest pain. Five variables were independent predictors of the recurrence of ischemia. The model correctly classified 82% of the patients. Age, history of coronary artery disease, prolonged chest pain at rest in the preceding 15 days, pain, ST-segment changes with pain, and cardiac troponin T in excess of 0.1 ng/m 12 hours after the onset of chest pain were identified by logistic regression. A similar model was analyzed at 6 hours, after changing the cutoff point for cardiac troponin T. Cardiac troponin T was considered positive with values of 0.04 ng/ml 6 hours after the onset of chest pain. More than 80% of the patients admitted to the emergency room with chest pain without ST segment elevation can be correctly classified for new ischemic recurrences using clinical, ECG, and biochemical parameters 6 hours after the onset of pain.