3 Clinical need and practice

The problem addressed

3.1 The primary focus of this evaluation is to assess the diagnostic accuracy, effect on patient outcomes and cost effectiveness of specific new generation cardiac CT scanners in:

  • Adults (18 years or older) with suspected coronary artery disease in whom imaging with earlier generation CT is difficult (see section 3.4) and with a 10–29% pre-test likelihood of coronary artery disease

  • Adults (18 years or older) with known coronary artery disease in whom imaging with earlier generation CT is difficult (see section 3.4) and in whom revascularisation is being considered.

The condition

3.2 Coronary artery disease is characterised by narrowing of the coronary artery. It is most commonly caused by atherosclerotic deposits of fibrous and fatty tissue, leading to a reduction in blood flow to the heart, and angina. The NICE clinical guideline on the assessment and diagnosis of chest pain of recent onset defines significant coronary artery disease as 70% or greater diameter stenosis of at least one major epicardial artery segment or 50% or greater diameter stenosis in the left main coronary artery.

3.3 The NICE clinical guideline on chest pain of recent onset, before the 2016 update, recommended CT coronary angiography and invasive coronary angiography to assess arteries and identify significant stenosis. The guideline recommended using a 64-slice (or above) CT scanner in people with an estimated likelihood of coronary artery disease of 10–29% and a calcium score of 1–400.

3.4 Conditions that make CT imaging difficult are:

  • obesity

  • high levels of coronary calcium (calcium score above 400)

  • arrhythmias

  • high heart rates that cannot be lowered pharmacologically (after consultation with clinical experts, the definition of high heart rate was broadened from over 70 beats per minute as stated in the scope, to over 65 beats per minute, in order to avoid loss of potential data)

  • stents

  • previous bypass grafts.

Prevalence and risk

3.5 In the UK an estimated 2.6 million people have coronary artery disease, with 2 million having symptoms of angina. In 2007, coronary artery disease was estimated to have caused 91,000 deaths in the UK (approximately 19% of deaths in men and 13% in women).

3.6 It was not possible to estimate the number of people with cardiac disease in whom imaging would be difficult. However, a range of data sources can be used to give an estimate of this population in whom coronary imaging would be difficult. According to the Health Survey for England (2009), 22% of men and 24% of women are obese. Hospital Episode Statistics show that there were a total of 313,765 unique patients with arrhythmias, stent implantations and bypass grafts in England in the last 3 years. If the estimated number of people with a heart rate of over 65 beats per minute and intolerance to beta blockers is included, the number of people in England in whom imaging with earlier generation CT scanners is difficult can be estimated to range from 10 million to 18 million.

The diagnostic and care pathways

3.7 The care pathway for this evaluation was taken from the NICE clinical guideline on chest pain of recent onset, before the 2016 update. The key elements (for the imaging strategy) from the guideline's care pathway are as follows:

  • People with chest pain who have an estimated likelihood of coronary artery disease of 10–29% should be offered calcium scoring, followed by CT coronary angiography if the calcium score is between 1 and 400. A calcium score above 400 indicates that imaging using earlier generation CT scanners would be difficult, and the guideline recommends invasive coronary angiography if this is considered clinically appropriate.

  • People with chest pain who have an estimated likelihood of coronary artery disease of 30–60% should be offered non-invasive functional imaging for myocardial ischaemia.

  • People with chest pain who have an estimated likelihood of coronary artery disease of 61–90% should be offered invasive coronary angiography if clinically appropriate and if coronary revascularisation is being considered.

3.8 The key options for non-invasive functional imaging are:

  • myocardial perfusion scintigraphy with single photon emission computed tomography or

  • stress echocardiography or

  • first-pass contrast-enhanced magnetic resonance perfusion or

  • magnetic resonance imaging for stress-induced wall motion abnormalities.

3.9 People diagnosed as having significant coronary artery disease should be initially managed as having stable angina. Management of these people was assumed to follow the recommendations from the NICE clinical guideline on managing stable angina when modelling patient outcomes and cost effectiveness.

  • National Institute for Health and Care Excellence (NICE)