Patients should be stratified as being at low, intermediate
or high risk of short-term adverse outcomes in the
context of possible ACS, in line with the joint guidelines of
the National Heart Foundation and Cardiac Society of
Australia and New Zealand (NHF/CSANZ) stratifying
patients with ACS (Box 3).6 This model has performed well
in the ED setting, with 30-day risks of adverse cardiac
outcome of 0, 7% and 26% in these risk strata, respectively,
when the criteria were strictly applied in one cohort.7 Risk
stratification models may have greater utility in the ED,
where the prevalence of ACS is about 10% (compared with
primary care, where rates are lower) and where facilities to
further assess patients at increased risk are readily available.
The main limitation of this risk stratification model is
that few patients qualify as low risk when the criteria are
strictly applied. Alternative approaches include the
Thrombolysis in Myocardial Infarction (TIMI) score, the
Global Registry of Acute Coronary Events (GRACE) score
and the GRACE Freedom-from-Event score.8,9 These
models, derived from higher-risk populations, were not
designed to identify low-risk patients who do not require
detailed assessment for exclusion of ACS. Consequently,
none can be relied on to identify patients who can be safely
discharged from the ED without some period of observation
and additional investigation. Nevertheless, risk stratification
is essential to guide the appropriate use of
resources based on pretest probability of ACS.