The role of computed tomography in cardiovascular imaging: from X-ray department to emergency room

Abstract

Computed tomography coronary angiography (CTCA) is widely accepted in the evaluation of patients with stable chest pain. Its use in patients with unstable chest pain is more controversial. CTCA can be performed alone or with a computed tomography pulmonary angiogram and aortogram as a ‘triple rule-out’ scan. Published trial data show that discharging a patient with low-risk acute chest pain after a normal CTCA is a very safe thing to do. Length of stay is generally reduced, but radiation exposure is higher and there is more downstream testing, so it is broadly cost-neutral. Future studies should evaluate this approach in intermediate- to high-risk patients.

Keywords::

• atherosclerosis
• chest pain
• computed tomography
• computed tomography coronary angiography
• coronary artery disease

Financial & competing interests disclosure

This work forms part of the research themes contributing to the translational research portfolio of Barts Cardiovascular Biomedical Research Unit which is supported and funded by the National Institute for Health Research. The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• A computed tomography (CT) scanner with a minimum of 64-slice technology is needed to perform cardiac CT.

• There are two main scan techniques: retrospective ECG-gating and prospective ECG-triggering. Although historically radiation doses were of the order of 15 mSv, a typical dose for a prospectively ECG-triggered scan in 2013 is 2–5 mSv, and <1 mSv is possible in selected patients.

• CT coronary angiography (CTCA) has a well-established place in the evaluation of patients with stable chest pain and low probability of coronary artery disease.

• There is a growing amount of trial data using CTCA in low- to intermediate-risk patients with unstable chest pain.

• Two protocols may be used in unstable chest pain – CTCA, or ‘triple rule out’ (which also assesses for pulmonary embolus and acute aortic syndrome, but which has a higher radiation dose and uses a larger contrast volume).

• Patients with acute cardiac-sounding chest pain, normal biomarkers and normal ECG who are not known to have coronary artery disease can in general be reassured and discharged after a normal CTCA.

• Compared with usual care, a CTCA-based approach to patients at low risk (thrombolysis in myocardial infarction score 0–2) enables more rapid discharge.

• Trials of CTCA have failed to show cost savings. This has generally been because the patients enrolled were so much at low risk that in the usual care arm half were able to be safely discharged with either no further testing or a simple treadmill, while the CTCA generated extra downstream testing such as invasive coronary angiography.

• For the same reason, radiation exposure has in general been higher in the CTCA arm than with usual care, although this may change with newer protocols.

• Although CTCA can be of use in selected low-risk patients with acute chest pain if extra reassurance is needed, future studies need to evaluate intermediate- to high-risk patients. In this cohort, CTCA may have a role in reducing the need for invasive assessment which is in general less safe and less acceptable to patients than non-invasive assessment.

Notes