Risk stratification of patients with acute chest pain and normal troponin concentrations

Objective: To investigate the outcome of patients with acute chest pain and normal troponin concentrations. Design: Prospective cohort design. Setting: Single centre study in a teaching hospital in Spain. Patients: 609 consecutive patients with chest pain evaluated in the emergency department by clinical history (risk factors and a chest pain score according to pain characteristics), ECG, and early (< 24 hours) exercise testing for low risk patients with physical capacity (n = 283, 46%). All had normal troponin concentrations after serial determination. Main outcome measures: Myocardial infarction or cardiac death during six months of follow up. Results: 29 events were detected (4.8%). No patient with a negative early exercise test (n = 161) had events versus the 6.9% event rate in the remaining patients (p = 0.0001). Four independent predictors were found: chest pain score >= 11 points ( odds ratio (OR) 2.4, 95% confidence interval (Cl) 1.1 to 5.5, p = 0.04), diabetes mellitus (OR 2.3, 95% Cl 1.1 to 4.7, p = 0.03), previous coronary surgery (OR 3.1, 95% Cl 1.3 to 7.6, p = 0.01), and ST segment depression (OR 2.8, 95% Cl 1.3 to 6.3, p = 0.003). A risk score proved useful for patient stratification according to the presence of 0-1 (2.7% event rate), 2 (10.2%, p = 0.008), and 3-4 predictors (29.2%, p = 0.0001). Conclusions: A negative troponin result does not assure a good prognosis for patients coming to the emergency room with chest pain. Early exercise testing and clinical data should be carefully evaluated for risk stratification.