Comparative efficacy testing — Fractional flow reserve by coronary computed tomography for the evaluation of patients with stable chest pain
Introduction
It is currently estimated that up to 1.5% of visits to primary healthcare services will be for symptoms of chest pain, with only 8% of these patients being eventually diagnosed as having coronary artery disease [1]. Despite this low incidence, the adverse consequences for a missed diagnosis of CAD where early treatment can be highly effective are substantial [2]. This recognition has led to the development of rapid access chest pain clinics whereby general practitioners may refer patients with chest pain to experienced specialists with access to further basic and advanced diagnostic testing [3]. Here, it is recommended that the 2010 National Institute for Health and Clinical Excellence (NICE) guidelines for stable chest pain be followed [2]. These recommend the risk stratification of patients by the DF criteria into pre-test likelihood categories of patients having obstructive CAD [4]. For those patients with a pre-test likelihood of CAD < 10% no further testing is required, 10–29% — coronary computed tomographic angiography (CTA), 30–60% — non-invasive functional imaging, 61–90% — invasive angiography and > 90% — clinical judgement.
Despite these recommendations, it is recognised that there is widespread heterogeneity in RACPC practice within the United Kingdom. Although the reasons for this are complex, it is likely that this reflects local referrer preferences along with individual accessibility, availability and experiences of the various functional and anatomical imaging modalities. This variability also exposes current pathways to the risk of unnecessary layering of investigations, increased NHS costs [5] and a delay in the time to patient diagnosis.
Ideally strategies evaluating patients with chest pain should incorporate the reference standard technique for the evaluation of lesion specific ischaemia. Although fractional flow reserve (defined as the ratio between maximal blood flows achievable in a stenotic artery compared to normal maximal blood flow in the same vessel) is widely accepted as the gold standard [6], [7], [8], it has been restricted in its use owing to its inherent requirement for invasive cardiac catheterisation. Recently, a number of studies have shown a high diagnostic accuracy for fractional flow reserve by coronary CTA (FFRCT) [9], [10], [11]. This new development has the potential to extend the current diagnostic capabilities of coronary CTA from an anatomical assessment of CAD in patients with a low pre-test risk of CAD (10–29%), to a “one-stop” anatomical and functional assessment of CAD in patients with a pre-test risk of CAD extending from 10–90%. Its use and economic viability in a RACPC however have not been evaluated before.
The aims of the current study were two fold. The primary aim was to evaluate contemporary tertiary centre RACPC practice in the United Kingdom. The secondary aim was to apply this data to a novel pathway incorporating FFRCT into existing NHS RACPC pathways and to determine its economic impact.
Section snippets
Methods
We retrospectively studied all patients referred to the RACPC at our institute over a 12-month period from April 2012 through March 2013. All patients' notes were reviewed for clinical symptoms, cardiovascular risk factors and a 12-lead electrocardiogram. The pre-test likelihood of obstructive coronary artery disease was then calculated based on the recorded typicality of the chest pain, age, gender, cardiovascular risk factors and relevant 12-lead electrocardiogram findings. Patients were then
Rapid access chest pain clinic
There were 410 patients with a median age of 57 (31–85) years of whom 217 (53%) were women. The majority presented with atypical chest pain (77%), with 21% presenting with typical chest pain and 2% non-cardiac chest pain. The commonest cardiovascular risk factors were hypercholesterolaemia in 54%, hypertension in 52% and current tobacco smoking in 35%. Only 22% of the population had diabetes mellitus and 19% a positive family history of premature cardiovascular disease. Table 2 gives the
Discussion
There are a number of observations from the current study. Firstly, in a tertiary centre rapid access chest pain clinic there is a marked deviance from the current NICE guidelines for the evaluation of patients with stable chest pain. Secondly, the recommended pre-test likelihood criteria by Diamond and Forrester markedly overestimate the risk of coronary disease. Thirdly, the current NICE guidelines may result in overtesting of patients and layering of investigations in all but the > 90% PTL
Conclusions
Current practice for evaluating patients with stable chest pain varies widely with a poor adherence to nationally recommended guidelines. The current study suggests that conventional risk prediction algorithms are imperfect at predicting the risk of patients having CAD and that coronary CTA may be extended beyond its current restriction to low PTL patients. Novel strategies incorporating functional and anatomical testing such as FFRCT hold considerable promise in refining current complex
Conflicts of interest
None to declare.
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