Evaluation

Cardiac CT Angiography

CT coronary angiography provides a non-invasive, high-resolution view of the heart’s arteries

Cardiac CT angiography, also known as CT coronary angiography, is a non-invasive imaging investigation that uses high-resolution, ECG-gated CT with intravenous contrast to produce detailed three-dimensional anatomical images of the coronary arteries. It detects atherosclerotic plaque — including non-calcified and mixed plaque types invisible to calcium scoring — quantifies stenosis severity, and characterises plaque vulnerability. CTCA has high sensitivity and negative predictive value for significant coronary artery disease, making it the preferred first-line investigation for ruling out CAD in patients with stable chest pain and intermediate pre-test probability.

What CTCA Detects

CTCA provides comprehensive coronary anatomical assessment — identifying calcified, non-calcified (soft), and mixed atherosclerotic plaque; quantifying luminal stenosis severity; and detecting coronary anomalies, aneurysms, and bypass graft patency. Plaque characterisation is clinically important: lipid-rich, low-attenuation non-calcified plaques are associated with higher rupture risk and acute coronary syndrome compared to calcified or fibrous lesions — information that influences the intensity of medical therapy. Results are reported using the CAD-RADS (Coronary Artery Disease Reporting and Data System) classification, providing standardised stenosis grading from CAD-RADS 0 (no plaque) to CAD-RADS 5 (total occlusion), with functional assessment and management recommendations at each grade.

CT-FFR — Functional Assessment Without Catheterisation

CT-derived Fractional Flow Reserve (CT-FFR) uses computational fluid dynamics applied to CTCA data to calculate the haemodynamic significance of each coronary stenosis — determining whether a narrowing is actually restricting blood flow sufficiently to cause ischaemia. A CT-FFR value of 0.80 or below at a stenosis indicates haemodynamically significant flow limitation warranting intervention; values above 0.80 indicate the lesion can be managed medically. CT-FFR provides functional assessment equivalent to invasive FFR measurement — without catheterisation, without wire placement, and without adenosine administration. Clinical trial evidence from the PLATFORM and ADVANCE trials demonstrates that CTCA with CT-FFR reduces unnecessary invasive angiography, avoids unnecessary revascularisation, and guides targeted treatment to only functionally significant lesions.

Who Should Have CTCA

CTCA is the investigation of choice for patients with stable chest pain or breathlessness and intermediate pre-test probability of coronary artery disease — where it provides diagnostic certainty and guides management without the risks of invasive angiography. It is recommended for patients with abnormal or equivocal stress test results requiring anatomical clarification, patients with new atrial fibrillation or heart failure where coronary disease needs exclusion, and patients being evaluated prior to non-cardiac surgery with elevated cardiac risk. CTCA is also used for assessment of coronary anomalies, bypass graft patency, and prior to transcatheter valve procedures requiring coronary anatomy mapping.

How the Scan Is Performed

Heart rate optimisation is essential for image quality — beta-blockers are administered orally or intravenously before the scan to achieve a heart rate below 65 beats per minute, minimising motion artefact during image acquisition. Sublingual nitrates are given immediately before scanning to dilate the coronary arteries and improve visualisation of smaller vessels. A small intravenous cannula is inserted for contrast injection. The scan itself takes under one minute, with total appointment time of approximately 1–2 hours including preparation. Fasting for four hours beforehand and caffeine avoidance on the day of the scan are required. Patients are encouraged to stay well hydrated before and after to support contrast clearance.

Contraindications & Limitations

CTCA requires iodinated contrast — patients with contrast allergy or significantly impaired renal function (eGFR below 30 mL/min) require careful risk-benefit assessment and pre-hydration or alternative imaging. Severely irregular heart rhythms — particularly uncontrolled atrial fibrillation — reduce image quality and may limit diagnostic accuracy. Heavily calcified vessels, particularly in diabetic patients, can cause beam-hardening artefact that overestimates stenosis severity; in these cases, functional stress testing or invasive angiography may provide complementary information. Radiation exposure for modern CTCA is approximately 2–5 mSv — comparable to the background radiation from two to three years of normal daily life.

After the Scan — What Happens Next

CTCA results are classified using CAD-RADS grading and reviewed by Dr. Peter Chang in the context of symptoms, risk factors, and CT-FFR values where applicable. CAD-RADS 0–2 (no or minimal disease) confirms low coronary disease burden and guides preventive medical management. CAD-RADS 3 (moderate stenosis 50–69%) triggers CT-FFR analysis to determine functional significance before proceeding. CAD-RADS 4–5 (severe stenosis 70% or above, or total occlusion) typically prompts referral for invasive coronary angiography and revascularisation planning. Incidental findings — pericardial disease, pulmonary nodules, aortic pathology — are reported and managed appropriately.

Experiencing chest pain, abnormal stress test results, or concerned about coronary artery disease? Dr. Peter Chang arranges and interprets CTCA with CT-FFR analysis at Paragon Medical Centre, Orchard Road. Book a cardiac assessment today.