01Purpose and principlesWhat the assessment is for and the core concepts behind it.
CTCA has high rule-out value in an appropriate low-to-moderate likelihood population and also identifies non-obstructive plaque that should prompt prevention assessment. It does not directly prove ischaemia.
Acquisition may include heart-rate control and sublingual nitrate under a department protocol. These improve image quality but require blood-pressure, conduction and medicine checks.
Report coronary dominance, origin and course, plaque distribution, stenosis category, image limitations, significant extracardiac findings and the recommended next decision.
Key points
- NICE CG95 recommends 64-slice-or-above CTCA first-line when assessment indicates typical or atypical angina.
- CTCA visualises lumen and plaque; a calcium score quantifies calcified plaque but does not show stenosis or non-calcified plaque.
- NICE no longer uses stand-alone coronary calcium scoring to diagnose stable angina.
- A zero calcium score does not exclude non-calcified coronary atherosclerosis or an acute coronary syndrome.
- Rate regularity, breath-hold, obesity and heavy calcification affect image quality; calcium blooming can overestimate stenosis.
- Intermediate CT stenosis may need functional imaging or validated CT-derived fractional flow reserve before invasive decisions.
- Check pregnancy possibility, renal function where indicated, previous contrast reaction and interacting drugs before iodinated contrast and rate-control medication.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Left main, proximal multivessel or severe stenosis requires prompt specialist correlation and often invasive assessment, particularly with symptoms.
Plaque below an obstructive threshold is not a normal result; address cardiovascular prevention and symptom mechanism.
Motion, blooming or poor opacification can make a key segment non-diagnostic; it must not be silently counted as normal.
An interarterial or intramural course can be clinically important, especially with exertional symptoms, and needs specialist anatomical review.
Bronchospasm, facial or laryngeal swelling, hypotension or collapse after contrast requires an immediate emergency response.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
CT coronary angiographyFirst step - Why
- Exclude or define anatomical coronary disease in stable suspected angina.
- Interpretation and limitations
- A diagnostic study can identify normal arteries, non-obstructive plaque or stenosis; correlate severity and symptoms rather than treating anatomy alone.
- 02
Coronary artery calcium score - Why
- Quantify calcified plaque burden for selected preventive-risk questions.
- Interpretation and limitations
- Agatston score reflects calcified burden, not stenosis; zero does not exclude soft plaque and is not the NICE diagnostic test for stable angina.
- 03
CT-derived fractional flow reserve - Why
- Estimate functional significance of selected intermediate CT stenoses.
- Interpretation and limitations
- Use only validated technology and adequate source images; it complements rather than rescues a non-diagnostic scan.
- 04
Functional imaging - Why
- Assess inducible ischaemia when CTCA shows uncertain functional significance or is non-diagnostic.
- Interpretation and limitations
- Match the perfusion or wall-motion territory to the CT lesion before revascularisation decisions.
- 05
Renal function assessment - Why
- Identify patients at increased risk from iodinated contrast and plan exposure safely.
- Interpretation and limitations
- Use current departmental and contrast-agent guidance; risk depends on kidney function, acute illness, hydration and contrast burden.
04Clinical next stepsHow the result changes management or prompts escalation.
01Preferred routeStable suspected anginaFirst stepPreferredTypical or atypical angina without acute features+
- 1Complete clinical assessment, resting ECG and baseline safety checks.
- 2Offer 64-slice-or-above CTCA under NICE CG95.
- 3If arteries are normal, reconsider non-coronary and vasomotor causes; if plaque is present, address prevention.
- 4For severe disease, uncertain significance or non-diagnostic key segments, proceed to functional imaging or invasive assessment according to risk.
02AlternativeOptimising acquisitionAlternativeHeart rate, rhythm or patient factors may impair CTCA+
- 1Review rhythm, pulse, blood pressure, conduction disease, asthma, ventricular function and current medicines.
- 2Use authorised beta-blocker and nitrate protocols only when safe; formulation and IV dosing are department-specific.
- 3Optimise breath-hold and contrast timing while minimising radiation and contrast dose.
- 4If adequate images remain unlikely, choose a suitable functional modality rather than force a poor CTCA.
03EscalationHigh-risk CT resultEscalationLeft main, severe proximal disease or extensive obstructive CAD+
- 1Contact the responsible clinician promptly and review current symptoms for instability.
- 2Start or optimise guideline-directed antianginal and preventive therapy as clinically appropriate.
- 3Arrange invasive angiography with functional lesion assessment where it will guide revascularisation.
- 4Use multidisciplinary and shared decision-making for PCI versus CABG when anatomy is complex.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Record heart rate, rhythm and blood pressure before rate-control or nitrate administration.
- Observe for immediate contrast reaction and follow the emergency protocol if it occurs.
- Review renal function after contrast only when clinical risk or local contrast policy indicates.
- Document radiation dose and whether every important segment was diagnostic.
- Track preventive treatment and follow-on investigation after plaque or indeterminate stenosis is reported.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
CTCA is anatomical
A 50% stenosis may or may not cause ischaemia; functional correlation can prevent unnecessary intervention.
Calcium blooming
Dense calcium spreads across pixels and can make the residual lumen appear smaller than it is.
Zero is not no disease
Younger patients and acute plaque events can involve non-calcified plaque despite an Agatston score of zero.
Normal coronaries redirect the question
Persistent angina with non-obstructive arteries should raise vasospastic or microvascular mechanisms rather than diagnostic closure.
Incidental findings need ownership
Clinically important extracardiac findings require a named follow-up route, not a buried sentence.
07Common pitfallsFrequent interpretation and management errors.
- 01
Using stand-alone calcium scoring to diagnose stable angina.
- 02
Calling a zero calcium score a lifetime guarantee against coronary disease.
- 03
Sending an unstable ACS presentation to an outpatient CTCA pathway.
- 04
Treating a heavily calcified non-diagnostic segment as unobstructed.
- 05
Proceeding to PCI from CT anatomy alone when an intermediate lesion's functional significance is uncertain.