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How do CCTA and Conventional Angiography Compare?

For those at risk of coronary artery disease (CAD), screening exams are very important. CAD occurs when plaque (composed of fat, cholesterol, or calcium) builds up inside the arteries around the heart – too much plaque narrows the arteries and reduces blood flow. Screening tests help determine the amount of plaque, its nature (hard or soft), and what treatment options are applicable.

To help diagnose CAD, patients are usually referred for one of two main screening exams: a coronary angiography or a Coronary Computed Tomography Angiography (CCTA). Currently, there is some debate over which test is more accurate and safe.

During a coronary angiography, a thin, hollow tube called a catheter is inserted into an artery (usually in the arm or leg) and threaded up into the heart. A contrast dye is then sent through the catheter to help the arteries show up on an X-ray.

For a CCTA, Computed Tomography (CT) is used to non-invasively examine the coronary arteries. CT imaging uses a combination of X-rays and computer technology to produce comprehensive, detailed images. In particular, CCTA detects both hard and the more difficult to find soft plaques, which may be more likely to cause heart attacks and death. This exam also uses imaging contrast, but it’s injected through a vein in the arm and pictures of the arteries are taken from outside the body.


Coronary angiography is the most common method for detecting coronary artery stenosis, or narrowing of an artery that may require a stent or bypass surgery. In these cases, it can be used for both diagnosis and treatment in a single session, since the images are finely detailed and precise. This procedure is most often recommended for patients with a high risk of coronary artery disease and typical symptoms.

CCTA is quick, precise and relatively painless with results that are detailed enough for doctors to make decisions that are 95-99 percent accurate in patients without severe disease. It’s able to reliably rule out coronary artery disease in patients with atypical symptoms and low-to-medium risk of disease, reducing the need for invasive angiography and rendering it a safe and effective tool when it is needed. It also requires very little preparation and no recovery time.


A coronary angiography is an invasive procedure, which in rare cases can lead to serious problems like heart attack or stroke. There is also a risk of a tear or sudden closure in an artery, allergic reaction to the dye, and bleeding or bruising where the catheter was inserted. It also requires fasting before the procedure and hours of hospitalized recuperation afterward. Plus, there is potential for overuse when diagnosing patients with atypical symptoms and low-to-medium risk of disease.

CCTA also has the possibility of an allergic reaction to the contrast dye. As well, certain patients may not be good candidates for this exam, such as:

  • Patients over 450 pounds who may not fit into the machine
  • Patients with irregular or fast heart rhythms who are unable to take medication to slow their heart rate, since CCTA requires a slow, regular heart rate for accurate images
  • Patients who are not able to lie flat, follow voice instructions, or hold their breath for up to 20 seconds
  • Patients with many areas of old, hardened plaque, which is often the case in older patients


There is ongoing debate over when to use CCTA versus coronary angiography and for which types of patients. Some recent studies have shown that the diagnostic abilities of the two exams are equivalent, but due to lower costs and improved safety CCTA is thought to be a better gatekeeper and first-line test to triage patients and determine the need for medical therapy or invasive evaluation. Plus, the current CT scanners have lower doses of radiation and improved accuracy as compared to older machinery, and patients often prefer CCTA for coronary disease testing since it’s less invasive.

For more information on how to request a CCTA scan, you can download the CCTA Requisition, or visit the exam page for preparation and procedure information.


Barnes, Eric (2016) Is it time for CCTA to replace invasive angiography? February 24

Barnes, Eric (2016) CCTA can cut complications and hospital stays. November 1

Doh, J. H., et al. (2014) “Diagnostic value of coronary CT angiography in comparison with invasive coronary angiography and intravascular ultrasound in patients with intermediate coronary artery stenosis: results from the prospective multi-centre FIGURE-OUT (Functional Imaging criteria for GUiding REview of invasive coronary angiOgraphy, intravascular Ultrasound, and coronary computed Tomographic angiography) study.” European Heart Journal Cardiovascular Imaging. August, 15(8): 870-7

Government of Alberta (2016) Cardiac Catheterization.

Government of Alberta (2016) Computed Tomography Angiogram (CT Angiogram).

Government of Alberta (2016) Heart Disease: Should I Have an Angiogram?

Radiological Society of North America (2016) Coronary Computed Tomography Angiography (CCTA) July

Stefanini, G. G. and Windecker, S. (2015) “Can Coronary Computed Tomography Angiography Replace Invasive Angiography?” American Heart Association Journals. January 26, 131: 418-426

University of Wisconsin Hospitals and Clinics Authority (2016) Heart, Vascular and Thoracic Care: Cardiac Computed Tomography Angiography (CCTA). Taken from on December 16, 2016

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