What is Coronary (CT) Angiography?

cardiac imaging

Coronary Angiography (CT angiogram) is a screening working towards entirely eradicating the risk of symptomatic coronary artery disease (heart attack) amongst appropriate groups. The test provides a highly accurate computerised image of the heart, far more accurate than any historic tests and entirely non-invasive. It provides rapid and definitive cardiac assessment.

When is CT angiography used?

The purpose of a CT coronary angiogram is to precisely differentiate between patients who have coronary heart disease and those who do not, and will not.

What is the difference among coronary angiography, ECG and calcium scoring?

The CT angiography scan is far more specific and reliable that the traditional approach to screening – exercise ECG (treadmill/bike) testing and is a ‘one-off’ – it does not need to be repeated each year.

We wouldn’t generally recommend calcium scoring as a screening method for coronary artery disease in asymptomatic patients either, as the technique cannot show soft plaques in the arteries; so it is impossible to exclude the presence of the disease. The majority of heart attacks are also caused by soft plaques rupturing, so the scan is potentially missing a vitally important factor.

How accurate is CT angiography?

CT angiography is accurate, aiming to diagnose plaque (atheroma) damaging and infiltrating coronary arteries at the earliest possible stage, thus allowing the clinician to make simple and effective interventions.

The imaging is unique in demonstrating damage and narrowing of the coronary arteries when present. It is not dependent on evaluating relatively inaccurate “risks” such as cholesterol, smoking habits and levels of physical activity.

  • The test provides a definitive answer about the presence or absence of coronary artery disease
  • It differentiates soft cholesterol-rich, but dangerous, plaque, from calcified stable plaque
  • The scan defines any areas of narrowing
  • In combination with traditional dynamic testing, such as Bruce protocol exercise testing; it becomes the most robust method of identifying asymptomatic disease and preventing further coronary damage.

The technology used is ground-breaking. London City Healthcare only advocate the use of the state-of-the-art Toshiba Aquilion ONE scanner. The scan is carried out on a walk-in, walk-out basis, no preparation is required and no untoward side effects are felt by patients.

What happens if a problem is found?

Roughly 1 in 3 patients require onward referral to interventional cardiology following the identification of stenosis in a coronary artery. The CT angiography is limited in ascertaining whether the narrowing found is functionally significant – whether the blood flow to the heart muscle is inadequate.

Historically, assessing any occlusion of the coronary arteries involved referral to an interventional cardiologist for secondary assessment, using invasive angiography (where blood flow in the heart is monitored and measured using contrast dye and x-ray imaging). The test had notable risks (a catheter was inserted through the femoral artery) and the patient was immobilised for a period of at least 3-4 hours afterwards.

FFR (fractional flow reserve)

FFR (fractional flow reserve) scoring is a well established technique [1] and has shown significant clinical benefits [2] when used with invasive cardiac catheterization. It was used to identify functionally significant coronary artery stenosis [3]. However, FFR can now be measured without any invasive surgery, using FFR CT.

What is an FFR CT scan?

FFR CT is a revolutionary, non-invasive, test that uses computational fluid dynamics to measure the coronary artery blood flow and pressure, to calculate a patients’ FFR score [4]. It provides both anatomic and functional data, dramatically improving the assessment of which lesions are significant. It is at the leading edge of cardiac medicine and is redefining traditional cardiac care pathways.

Applying FFR CT to CT angiograms where there is greater than 30% narrowing provides the highest possible accuracy in determining which cases are most at risk of ischaemia, ensuring that only those patients who are clinically significant are referred to interventional cardiology.

The advent of CT angiography and FFR CT combined therapy enables markedly improved coronary prevention and overall treatment costs to be significantly reduced [5].

CT coronary angiography risks

The most notable risk associated with CT angiography is the exposure to a small dose of radiation, however, as technology continues to advance the dose has decreased markedly over time. The radiation exposure associated with CT angiography at the centres used is now referred to as being equivalent to a two-week holiday in Cornwall.

As the test is a ‘one-off’, the consensus amongst our clinicians is that the benefits of the test far outweigh the risks.

Please contact our team on 020 7236 3334 for any further information, assistance or support.

[1] http://en.wikipedia.org/wiki/Fractional_flow_reserve

[2] http://www.nejm.org/doi/full/10.1056/NEJMoa1408758

[3] http://content.onlinejacc.org/article.aspx?articleid=1138219

[4] http://heartflow.com/

[5] http://content.onlinejacc.org/article.aspx?articleid=2462067

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