Prognostic value of biochemical markers, 12-lead ECG and patient characteristics amongst patients calling for an ambulance due to a suspected acute coronary syndrome

Objectives. To evaluate whether a 12-lead ECG, together with a multi-marker strategy that used point-of-care measurements of myoglobin, creatine kinase (CK-MB) and troponin I, was able to predict patients at short- and long-term risk of death, when simultaneously considering age, gender, previous history, symptoms and clinical findings on arrival of the ambulance. Design. Prospective observational study. Setting and subjects. Consecutive patients (n=511) in ambulances in Stockholm and Goteborg in Sweden who called for an ambulance due to chest pain or other symptoms raising a suspicion of acute coronary syndrome. Intervention. In almost all patients, a diagnostic ECG, patient baseline characteristics and measurements of CK-MB, troponin I and myoglobin were recorded. Results. In univariate analysis, the highest 30-day mortality (17%) was found amongst patients with the combination of ECG signs of myocardial ischaemia and the elevation of any biochemical marker. The highest 1-year mortality (20%) was found amongst patients with ECG signs of myocardial ischaemia and the elevation of any biochemical marker. Increasing age (RR 1.07; 95 CI 1.02-1.13) lack of symptoms of chest pain and a previous history of hypertension (3.02; 1.08-8.79) were independent predictors of 30-day mortality. Myoglobin was the only biochemical marker independently associated with 30-day mortality (6.66; 1.83-22.3). Increasing age (1.11; 1.06-1.16), previous history of diabetes (3.42; 1.41-8.25) heart failure (2.64; 1.26-5.52) and other symptoms than chest pain and dyspnoea (5.23; 2.14-12.76) were independent predictors of 1-year mortality. In many of the variables the confidence limits were wide. Conclusion. Amongst patients with a clinical suspicion of acute coronary syndrome, those with the combination of ECG signs of myocardial ischaemia and the elevation of any biochemical marker on arrival of the ambulance form a group with a particularly high risk of death. However, age as well as aspects of clinical history and type of symptoms independently contribute to prognostic information.