CTCA is the most rapidly evolving test for assessing
patients with chest pain and is the most sensitive noninvasive
test for identifying coronary artery disease.22 Recent
studies have shown that this technique allows patients to be
safely discharged from the ED.24 A CTCA-based strategy
may also be faster than other strategies, particularly when
these rely on hospital admission for myocardial perfusion
scanning.24,25 However, this finding is of limited value in
Australia, where myocardial perfusion scanning has not
been the principal investigation for chest pain assessment.
It is important to recognise some limitations of CTCA.
Elevated heart rate, coronary calcium and obesity all impair
image quality. The use of iodinated contrast media is risky in
patients with renal impairment or in those taking metformin.
In the widely cited Coronary Computed Tomographic
Angiography for Systematic Triage of Acute Chest
Pain Patients to Treatment (CT-STAT ) trial, only 11% of the
patients screened met the study’s inclusion criteria.25 Early
studies suggested that CTCA should not be performed until
after a second troponin measurement, as myocardial infarctions
caused by moderate, rather than severe, coronary
stenoses could potentially be missed.26 This emphasises that
the strength of CTCA lies in excluding coronary atheroma.
Furthermore, in the presence of known coronary artery
disease, functional testing for ischaemia may be a more
appropriate choice of investigation.27