What is Coronary Computed Tomography Angiography (CCTA)?
CCTA is a noninvasive imaging test that uses multidetector computed tomography with intravenous iodinated contrast to visualize the coronary arteries, assess for stenosis, and characterize atherosclerotic plaque. 1
Technical Overview
CCTA employs multidetector CT scanners (16 to 256 detector rows) with ECG-gated acquisition to minimize cardiac motion artifacts and produce high-resolution images of the coronary arterial tree 1. The technique requires:
- Intravenous injection of iodinated contrast media to opacify the coronary lumen 1
- ECG-gating protocols to synchronize image acquisition with the cardiac cycle 2
- Breath-hold commands during scanning to minimize respiratory motion 2
The examination can assess vessels as small as 1.5 to 2 mm in diameter for atherosclerotic narrowing 1.
Clinical Applications
Diagnostic Capabilities
CCTA provides comprehensive evaluation beyond simple lumen visualization:
- Detects and quantifies coronary stenosis with sensitivity of 93-97% and specificity of 80-90% for obstructive coronary artery disease 2
- Characterizes plaque composition including calcified, non-calcified, and mixed plaque types 2
- Identifies high-risk plaque features such as positive remodeling, low-attenuation plaque, spotty calcification, and napkin-ring sign 2
- Assesses total atherosclerotic burden which correlates with future cardiovascular events 2
- Evaluates coronary anomalies including anomalous origin and course of coronary arteries 1
Guideline-Recommended Indications
The European Society of Cardiology recommends CCTA as a first-line test for patients with low to moderate (15-50%) pre-test likelihood of obstructive CAD due to its excellent negative predictive value exceeding 95% 2. The American College of Cardiology similarly endorses CCTA as the default first-line test for stable chest pain patients with low-to-intermediate pre-test probability 2.
For acute chest pain presentations, CCTA is now a Class I recommendation for low to intermediate risk patients in the emergency department 1.
What CCTA Images Beyond the Coronary Arteries
Unlike invasive catheter angiography which visualizes only the coronary lumen, CCTA captures additional cardiac and thoracic structures 1:
- Cardiac valves
- Great arteries (aorta, pulmonary arteries)
- Myocardium
- Pericardium
- Adjacent lung tissue
Reports must comment on any abnormalities in these surrounding structures 1.
Important Limitations and Contraindications
Technical Limitations
Heavy coronary calcification represents the most significant limitation, causing false-positive findings and rendering segments non-evaluable for stenosis assessment 1, 2. Coronary stents, particularly those smaller than 3.0 mm, are difficult to assess for in-stent restenosis 2.
Patient-Related Limitations
- High or irregular heart rates degrade image quality 1, 2
- Inability to hold breath compromises diagnostic quality 2
- Significant obesity adversely affects image quality 2
- Renal insufficiency is a relative contraindication due to nephrotoxicity risk from iodinated contrast 1
- Contrast allergy poses risk of anaphylactoid reaction 1
Radiation Exposure
The predominant risk of CCTA is radiation exposure, though newer protocols have significantly reduced doses to sub-millisievert levels 1, 2. Radiation risk is particularly concerning in children, where projected lifetime cancer mortality from CT exposure is significantly higher than in adults 1.
Advanced Applications
CCTA can be complemented with:
- CT-derived fractional flow reserve (CT-FFR) to assess hemodynamic significance of intermediate stenoses 2
- CT myocardial perfusion imaging for functional assessment 1
- 3D guidance for percutaneous coronary interventions to assist in procedural planning 3, 4
Standardized Reporting
Results should be reported using the CAD-RADS (Coronary Artery Disease Reporting and Data System) classification 1, 2, which standardizes stenosis severity grading, plaque burden assessment (P1-P4), and provides management recommendations based on findings 1.