In addition to measurements of troponin, the clinical history and the standard 12-lead ECG constitute the basis for accurate assessment of risk. A thoughtful interpretation of the patient's symptoms is essential for appropriate diagnosis and risk statification. Previous manifestations of ischemic heart disease and comorbidities, such as CHF, diabetes mellitus, or renal dysfunction, are associated with an increased risk of new cardiac events independent oftroponin. The standard 12-lead ECG is an indispensable prognostic tool: it is inexpensive, rapid, and widely available. In patients with a clinical suspicion of an ACS, a perfectly normal ECG on admission is associated with a low risk of future cardiac events, and in combination with a normal troponin result, the associated risk is very low (21). Although a diagnosis of unstable angina remains possible, the combination of a normal ECG and no troponin elevation should lead to reconsideration of the diagnosis of an ACS. ST-segment depression is associated with a high risk of new events, especially when combined with an elevated troponin (10). Furthermore, the more severe the ST-segment depression (in depth and/or in extension), the higher the risk (29). Patients with other abnormal ECG changes constitute a more inhomogeneous group but have a higher risk than patients with a normal ECG (29).
Thus, none of these factors should be considered in isolation. Instead, to make a proper risk assessment in the individual patient, one needs to consider these factors simultaneously and integrate all the available information. Figure 4 presents a simple algorithm for risk stratification based on these factors. An alternative is to use one of the scoring systems that has been developed based on the clinical history, ECG changes, and markers of myocardial
damage. The Thrombolysis in Myocardial Infarction (TIMI) risk score for unstable angina/NSTEMI is the best known and most widely used system (30).
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