A UK Cardiac Centre Experience of Low-risk, Stable Chest Pain Patients With Calcium Score of Zero

Muhammad Ali Abdool; Reza Ashrafi; Michael Davies; Santosh Raga; Huw Lewis-Jones; Erica Thwaite; Peter Wong; Gershan Davis

Disclosures

Br J Cardiol. 2014;21(2) 

In This Article

Abstract and Introduction

Abstract

The 2010 UK National Institute of Health and Care Excellence (NICE) guidelines for assessing patients with 'chest pain of recent onset' recommend coronary artery calcium scoring (CACS) to assess patients with a low risk of coronary artery disease (CAD) according to defined criteria. This study aims to evaluate the implementation of these guidelines in an area with a prevalence of CAD higher than the national average.

Consecutive patients with recent onset stable chest pain were assessed by cardiologists in outpatient clinics at University Hospital Aintree, Liverpool, between January and December 2011. A total of 186 patients with a low risk of CAD underwent CACS and follow-on computed tomography coronary angiography (CTCA) if CACS ≤400.

A CACS of zero was found in 94 patients and three of these were excluded due to motion artefacts. Of the remaining 91 patients, 75 (82.4%) had no visible atheroma, 10 (11%) had minor plaque, five (5.5%) had moderate disease and one (1.1%) had apparent severe disease, which was shown to be a false-positive result on subsequent invasive coronary angiography.

This study shows a negative predictive value for severe disease of 99% for a CACS of 0 in stable patients with a low pre-test probability of CAD. This supports the NICE guidelines, with CACS being the investigation of choice in the UK to rule out significant CAD in selected patient populations. The fact that almost half of all the patients referred for CTCA had a CACS of zero makes this a good quick rule-out tool and, hence, avoids the need for follow-on CTCA.

Introduction

The North West Health Authority has the third highest prevalence of coronary artery disease (CAD) in England at 4.0%.[1] The average for the prevalence of CAD in England, as of 2010, is 3.4%, and this makes the prevalence of CAD in the northwest region higher than the national average.[1] The investigation of new-onset stable chest pain by a non-invasive and safe test in low-risk symptomatic individuals is highly relevant. To this effect, the recent National Institute for Health and Care Excellence (NICE) guidelines[2] have highlighted a need for calcium scoring as an alternative to exercise treadmill testing to rule out CAD in stable, symptomatic low-risk individuals. Raggi et al.[3] showed a substantial cost benefit of the use of coronary artery calcium scoring (CACS) over the use of exercise testing in this very population. In the light of the new UK guidelines, exercise treadmill testing has become obsolete in diagnosing CAD and has been removed from the latest iteration of the guidelines.[2] Indeed, Lamont et al.[4] did show that coronary calcium had lower false-positive results than the exercise treadmill test as compared to the gold-standard invasive angiography.

The NICE guidelines use Table 1[2,5] to attribute a risk profile to patients presenting with chest pain, which will then guide the choice of investigation options in patients with new-onset and stable chest pain syndromes.

The table uses the character and typicality of the pain, together with age, sex and risk factors, to attribute a pre-test probability of CAD. If the pre-test likelihood of having CAD is 10–29%, then the flowchart (figure 1[2]) is used and a CACS is performed.

Figure 1.

Coronary angiography calcium (CACS) scoring pathway2
Key: CAD = coronary artery disease; CT = computed tomography
Adapted from National Clinical Guideline Centre2

Using CACS to screen low-risk symptomatic individuals before proceeding to computed tomography coronary angiography (CTCA) has numerous advantages. If the CACS is zero, as per the above flowchart, then there would be no need to proceed to CTCA. Therefore, the risk of stochastic and deterministic injury is reduced due to lower radiation exposure, as compared with CTCA and invasive angiography.[6] With new algorithms, better detectors and improved software, the radiation exposure can be kept as low as 1.0 mSv.[7] Additionally, there is no use of iodinated contrast in calcium scoring and, hence, no risk of adverse reactions to contrast agents.[8] Another major advantage of CACS is that it takes half of the time to perform a CACS as compared with a CTCA.

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