01Purpose and principlesWhat the assessment is for and the core concepts behind it.
CT coronary angiography combines an iodinated contrast bolus with rapid, ECG-related computed tomography to display the coronary lumen and vessel wall. Thin axial images are reconstructed into multiplanar and curved planes that follow each artery. CTCA detects calcified and non-calcified plaque, estimates stenosis severity and maps coronary origin and course. It is non-invasive and highly useful for excluding obstructive epicardial disease when image quality is diagnostic.
The scan answers an anatomical question. A stenosis is a reduction in lumen diameter; ischaemia is an inadequate increase in myocardial blood supply under stress. These overlap imperfectly because lesion length, location, collateral supply, microvascular function and myocardial demand all influence physiology. An intermediate-looking lesion may therefore need CT-derived fractional flow reserve, CT perfusion or a separate stress-imaging test, whereas extensive high-risk anatomy may justify invasive evaluation without another non-invasive step.
In the NICE pathway for recent-onset stable chest pain, clinical assessment comes before imaging. CTCA is offered when typical or atypical angina is suspected, or when non-anginal pain is accompanied by resting ST-T changes or Q waves. People with established coronary disease and uncertainty about ischaemic symptoms enter a functional-testing pathway. CTCA is not a population screening test and is not the initial investigation for an unstable presentation.
The useful report states whether the examination was diagnostic, describes plaque composition and burden, gives the maximum stenosis and its location, records relevant modifiers such as stents or bypass grafts, and reports significant cardiac or extracardiac findings. CAD-RADS 2.0 standardises this communication, but the detailed impression and clinical context remain essential.
Key points
- CTCA is an anatomical test that shows coronary plaque, luminal narrowing, anomalous origins and selected extracoronary structures.
- For stable typical or atypical angina without established coronary disease, NICE recommends 64-slice or higher CTCA as the diagnostic imaging test.
- Good acquisition needs a stable rhythm, limited coronary motion, adequate contrast delivery and an appropriate radiation protocol tailored to the patient.
- A normal interpretable CTCA strongly argues against flow-limiting epicardial coronary atherosclerosis, but it does not exclude microvascular or vasospastic angina.
- Moderate anatomical stenosis may not cause ischaemia; uncertain functional significance should lead to an appropriate functional test when the result will change management.
- Heavy calcification, motion, small vessels, stents and poor contrast timing can overestimate narrowing or make segments non-diagnostic.
- Read the narrative report, plaque burden and modifiers with the stenosis category because a single CAD-RADS number cannot capture every clinical implication.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
A fully diagnostic study with no coronary plaque provides strong anatomical reassurance. Persistent typical symptoms should redirect attention toward vasospasm, microvascular dysfunction or non-coronary diagnoses rather than repeating the same test.
Calcified, non-calcified or mixed plaque may be present without a severe focal stenosis. It still establishes coronary atherosclerosis and should prompt clinical risk-factor and preventive management review.
Focal or diffuse luminal narrowing should be described by artery, segment and severity. Anatomical importance rises with left main, proximal or multivessel involvement, but functional significance is not inferred from appearance alone when uncertainty remains.
Motion, step artefact, blooming from calcium, low contrast, noise or a small distal vessel can obscure the lumen. A non-diagnostic segment cannot be treated as normal and may determine the next test.
Define origin, proximal course, dominance and any interarterial or intramural relationship. Clinical importance depends on the exact anatomy, symptoms and evidence of ischaemia, not merely the word anomaly.
Review the aorta, valves, pericardium, lungs and mediastinum within the reconstructed field. Report consequential abnormalities through an agreed pathway while avoiding overcalling benign findings from a limited cardiac acquisition.
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
- Define coronary plaque, lumen, origins and course in a diagnostic-quality anatomical study.
- Interpretation and limitations
- Report image quality first, then maximum stenosis, plaque burden, distribution, modifiers and relevant non-coronary findings; non-diagnostic segments retain uncertainty.
- 02
Non-contrast coronary calcium scoring - Why
- Quantify calcified coronary plaque in selected risk or protocol contexts.
- Interpretation and limitations
- Calcium indicates atherosclerotic burden but does not show the contrast-filled lumen, excludes neither non-calcified plaque nor stenosis, and is not interchangeable with CTCA.
- 03
CT-derived fractional flow reserve or CT perfusion - Why
- Add lesion-specific or myocardial physiological information after suitable CTCA findings.
- Interpretation and limitations
- Use only with technically adequate source images and interpret alongside anatomy; the output estimates functional significance rather than changing the visible stenosis.
- 04
Non-invasive functional imaging - Why
- Identify inducible myocardial ischaemia when CTCA is non-diagnostic or functionally uncertain.
- Interpretation and limitations
- A reversible stress abnormality links symptoms to ischaemia; a negative result is less reassuring when stress, image quality or disease pattern is inadequate.
- 05
Invasive coronary angiography - Why
- Define lumen invasively and enable pressure assessment or treatment planning when clinically indicated.
- Interpretation and limitations
- NICE places it after inconclusive non-invasive functional imaging in the stable diagnostic sequence, while urgent anatomy or acute presentations may require a different route.
04Clinical next stepsHow the result changes management or prompts escalation.
01Stable chest pain pathwayChoose CTCA after clinical assessmentFirst stepRecent-onset stable chest discomfort remains typical or atypical angina, or non-anginal pain has relevant resting ECG changes.+
- 1Document pain typicality, cardiovascular history, risk factors, resting ECG and whether coronary disease is already established.
- 2Check renal function, previous contrast reaction, pregnancy possibility, rhythm, heart rate and ability to cooperate with breath holding.
- 3Perform diagnostic-quality 64-slice or higher CTCA with patient-tailored acquisition and medication safety checks.
- 4EscalationAct on anatomy: redirect after normal or non-obstructive findings, obtain functional assessment for uncertain significance, and escalate high-risk disease promptly.
02Acquisition pathwayCreate interpretable coronary imagesCTCA has been selected and the patient arrives for scanning.+
- 1Confirm identity, indication, contraindications, intravenous access and baseline observations, then explain breath-hold instructions and expected sensations.
- 2Optimise rhythm and coronary calibre using the local supervised protocol only when clinically safe, recording what was administered.
- 3Time contrast and ECG-related acquisition to capture homogeneous arterial enhancement while limiting motion and unnecessary radiation exposure.
- 4Inspect source and reconstructed images before discharge so remediable acquisition failure or an immediate adverse event is recognised.
03Intermediate or uncertain resultSeparate stenosis from ischaemiaCTCA shows coronary disease whose functional significance is uncertain, or an important segment is non-diagnostic.+
- 1Identify exactly which lesion or unseen segment creates uncertainty and whether resolving it would alter treatment or invasive referral.
- 2Review symptoms, lesion location, plaque burden, image limitations and any high-risk anatomical features with cardiology or imaging expertise.
- 3Select CT physiology or stress imaging that the source study, patient and local expertise can support.
- 4Use invasive angiography when non-invasive functional imaging remains inconclusive or when the integrated clinical picture independently requires it.
04Symptoms despite non-obstructive CTCAReframe the diagnostic questionTypical exertional or episodic chest symptoms persist despite no obstructive epicardial disease on a diagnostic scan.+
- 1AlternativeConfirm that all clinically important coronary segments were interpretable and that no anomaly or alternative cardiac finding was overlooked.
- 2Assess whether symptoms and risk merit evaluation for microvascular dysfunction, vasospasm or another cardiac mechanism.
- 3Consider gastrointestinal, pulmonary, musculoskeletal and anxiety-related causes without dismissing the patient's symptom burden.
- 4Avoid repeating anatomical CT solely for reassurance when the remaining question is physiological or non-coronary.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Record whether every major coronary segment was diagnostic; future clinicians need to know the difference between a negative study and an incomplete one.
- Ensure non-obstructive plaque leads to cardiovascular risk assessment and preventive treatment review rather than being communicated as a completely normal heart.
- Track the downstream question after uncertain stenosis: which functional test was selected, whether it was adequate, and how it changed management.
- Do not schedule serial CTCA routinely for stable symptoms; repeat imaging should answer a new question and account for cumulative radiation and contrast exposure.
- Use direct, time-stamped communication for left main, severe multivessel, occlusive or major incidental findings, with responsibility for action documented.
- After a non-diagnostic examination, address the cause before re-imaging and consider a different modality when the same limitation is likely to recur.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Calcific blooming overstates lumen loss
Dense calcium spreads beyond its true boundary on CT and can make the residual lumen appear smaller. Orthogonal reconstructions and physiological testing may be needed before treating a calcified intermediate lesion as flow limiting.
Plaque burden carries separate information
Two patients can share the same maximum stenosis while having very different total atherosclerotic burden. CAD-RADS 2.0 therefore separates the stenosis category from plaque-burden descriptors and modifiers.
Image quality is patient specific
Fast or irregular rhythm, inability to hold breath, large body habitus and poor contrast delivery increase noise or motion. Protocol adjustment should occur before exposure whenever possible.
Stents and grafts change the question
Metal and small stent diameter can limit lumen evaluation, whereas bypass grafts are larger and less mobile but require a wider scan range. Prior revascularisation should be clear on the request.
Anatomy and symptoms can disagree
A severe-looking lesion may be asymptomatic and a modest lesion may coexist with limiting ischaemia. Management integrates anatomy, functional testing, symptom control, myocardial territory and patient preferences.
07Common pitfallsFrequent interpretation and management errors.
- 01
Requesting elective CTCA before excluding an acute coronary syndrome or another time-critical cause of current chest pain.
- 02
Calling a scan negative when one clinically important segment was obscured by motion, calcium or poor contrast enhancement.
- 03
Equating any coronary calcium with an obstructive stenosis, or interpreting a zero calcium score as a contrast angiogram.
- 04
Treating an intermediate anatomical narrowing as proven ischaemia without considering whether functional assessment would change the decision.
- 05
Reading the CAD-RADS category without the narrative description, plaque burden, modifiers, uncertainty and extracoronary findings.
- 06
Repeating CTCA for persistent symptoms when the first diagnostic study has already redirected the question toward microvascular or non-coronary disease.