Background In 2016, the NICE clinical guideline 95 (’Chest pain of recent onset: assessment and diagnosis’) was updated to include coronary CT angiography (CCTA) as the first-line imaging modality for stable chest pain, and to suggest that fractional flow reserve CT (FFRCT) should also be considered as an option. NICE state FFRCT reduces cath lab utilisation due to better diagnostic performance at detecting significant coronary artery disease (CAD) compared to CCTA, and does not involve additional CT scanner time, radiation or contrast. This technology is not currently available at City Hospitals Sunderland.
Local and international data suggest that CCTA overestimates disease severity compared to findings at invasive cardiac catheterisation (ICC). We investigated the role of including FFRCT in investigation of stable chest pain, including theoretical cost and service utilisation savings, and identified the concordance in grading of CAD between CCTA and ICC.
Method Data on disease grading were collected from reports of CCTAs done between 1 st January 2016 and 31 st December 2017. Data were also collected for those patients who subsequently underwent ICC. For the patients who underwent both CCTA and ICC, the CCTA reports and images were individually reviewed by a consultant cardiologist with experience in CCTA to assess concordance between both studies. A financial model was then created, using cost data quoted by NICE.
Results A total of 163 patients underwent CCTA in the time period. Of these, 113 (68%) had mild-moderate CAD and so were managed medically. The remaining 50 (32%) patients underwent ICC due to either findings of moderate-severe CAD; anatomical aberrancies; or artefact. Of these 50 ICCs, 33 (66%, showing normal arteries or mild CAD) could have been avoided if there was a more sensitive test. 8 patients went on to undergo revascularisation.
Financial modelling estimated that using FFRCT prior to referral for ICC would lead to a cost saving of £22 290 per year (£136.74 per patient per year) and result in more efficient utilisation of the angiography suite, reducing waiting list lengths.
CCTA and ICC agreed on disease grading in 37/47 of cases, which correlates with data in the literature showing high sensitivity but relatively poor specificity.
Conclusion CCTA is the NICE-recommended fist-line investigation for stable chest pain, and is sensitive and clinically useful. However, poor specificity causes unnecessary cardiac catheterisation. This relates to overestimation of luminal stenoses (e.g. due to arterfact from calcium).
Use of FFRCT at City Hospitals Sunderland would reduce unnecessary angiograms and the risks associated with these, and would provide better utilisation of the angiography suite for interventional procedures, at a cost saving to the Trust. Introduction of guidelines such as CAD-RADS (coronary artery disease reporting and data system) would standardise terminology used in reporting and further improve reliability and specificity.
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