Discussion
This is the second BSCI/BSCCT national initiative aimed at improving CTCA service quality across the UK and follows on from the prospective national radiation dose survey of 2017.7 We have shown CTCA to be a robust diagnostic tool with 96% of scans being diagnostic, across a broad age range of patients, with a mean BMI of 29 kg/m² and gender equality in application. Three-quarters of patients are ‘triaged’ by CTCA to not require further testing as there is a high probability that their chest pain symptoms are not due to ischaemia. Accordingly. the utilisation of downstream testing in patients from the CAD-RADS 0–2 group was very low, and only 2 of 3883 patients underwent revascularisation with PCI. Nevertheless, a large subgroup of these patients (36% of the total population) have atheroma and have been identified as potential candidates for preventive therapies based on their CTCA result8; this group would not be identified with functional testing for ischaemia.
The total population ICA rate of 12% appears relatively modest. Furthermore, those patients selected for onward ICA with a CAD-RADS score of either 4 or 5 were likely to undergo revascularisation, at rates of 64% and 74%, respectively. Of the diagnostic population undergoing ICA, only 12% underwent CABG. Interestingly, even in the CAD-RADS 5 group, the mode of revascularisation was more commonly PCI (59% PCI vs 41% CABG). This later finding may be explained by the intrinsic challenges CTCA faces in differentiating between critical stenosis and a short, occluded segment.9 This is relevant to procedural planning. Our data support the scheduling patients requiring ICA after CTCA for ICA±PCI rather than ICA as a second-line stand-alone diagnostic test.
Despite the clear recommendations in CG95 (2016) that ICA ought to be used as a third-line and not second-line investigation when evidence of CAD of uncertain functional significance is found or if the CTCA is non-diagnostic, this advice is often not followed. ICA was frequently favoured as the second-line test, and this contributes to the high rate of ICA with no resulting revascularisation (48%). The conversely low ICA to PCI conversion rate of 39%, which is consistent with the rate described for the UK by Asher et al in 2019, remains disappointingly low and could be improved.10 The ‘uncertain functional significance’ of CAD-RADS 3 patients is worthy of further attention. Only 6% of the population with CAD-RADS 3 underwent revascularisation. This suggests that even the recommended ‘functional testing for ischaemia when diagnostic doubt remains’ (or indeed FFRCT) ought not to be used without serious consideration. It would certainly seem that ‘blanket testing’ for all CTCA-detected coronary artery stenosis of uncertain functional significance is unnecessary. Indeed, less than 10% (46/624) of patients who underwent either functional testing for ischaemia or FFRCT also underwent revascularisation. Nevertheless, if second-line investigation is indeed thought necessary in either clinical scenario, utilisation of functional testing for ischaemia, rather than ICA, would undoubtedly reduce the rate of duplicated coronary angiographic assessment with no resulting revascularisation.
The data presented in this report may help inform our discussions with patients. The likelihood of a variety of different outcomes is evident at different stages of the patient journey. For example, at the outset of stable recent-onset chest pain investigation, the likely need for follow-on testing after CTCA is low, and the chances of requiring CABG are very low (1%–2%). Patients may be listed for ICA because of ongoing clinical concerns and a moderate CTCA stenosis, but there is 74% chance it will not result in intervention. This report also allows follow-up consultation planning and economic modelling, with >70% of patients reasonably dischargeable back to their general practitioner after CTCA without further testing.
Therefore, in terms of service quality improvement, this may be achieved by taking the onward revascularisation rate into account when considering the need for onward testing and then:
These measures may reduce the number of patients undergoing duplicated coronary angiographic assessment with no resulting revascularisation. In turn, this may improve and facilitate the journey of patient with chest pain at less cost and risk.
Strengths and limitations
Our study provides extensive novel data regarding the contemporary investigation of patients with stable chest pain, although given the timing of data collection the findings may be considered as generally representative of the ‘pre-FFRCT era’. A major strength of this work is the prospective, multicentre design. The patient numbers are convincing, and the ‘real-world’ nature of the data allows direct translation to clinical care. It is accepted that the reasons a cardiologist may undertake ICA after a CTCA are heterogeneous and unique to the individual patient. Unclear or suboptimal CTCA reporting may contribute to the decision-making process, and therefore ‘ICA with no resulting revascularisation’ or ‘duplication of coronary angiographic assessment without revascularisation’ may be crude as a marker for ICA overuse in this context.
There are of course limitations to a service improvement initiative, which involves collection of data in an observational manner. There may be unadjusted confounding factors and referral bias. The report is intended to provide an overview of the national approach to downstream testing after a NICE CG95 (2016) CTCA, rather than an attempt to identify local geographical variation in patient populations or practice between centres. Every effort has been taken to ensure data collection was accurate and complete, including ensuring that data analysis was reassessed by each contributing centre to ensure accuracy. However, as with all analyses involving healthcare records, these may be incomplete, inaccurate or unclear. One centre did not transfer data with clearly identified CAD-RADS scores and was excluded from the analysis. Other centres successfully clarified any unclear or incomplete data entries.