In two groups of patients — those who present with
symptoms of ACS and in whom myocardial infarction has
been excluded, and those with a stable pattern of chest pain
symptoms in whom angina cannot be excluded — additional
testing is required to identify those who have prognostically
important coronary artery disease or unstable
angina. This is an area where well established diagnostic
tests exist alongside more recent developments, such as
computed tomography coronary angiography (CTCA). The
anatomical and pathophysiological bases for these tests are
not interchangeable, with some depending on the detection
of abnormal coronary blood flow (myocardial perfusion
scanning) or myocardial ischaemia (stress electrocardiography
and stress echocardiography), while invasive angiography
and CTCA demonstrate the anatomical basis of
coronary artery disease. Each investigation has different
limitations depending on patient factors and the need for
contrast media and ionising radiation, and the availability of
each may depend on access, cost and local expertise (Box 5).