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Abstract
Introduction CT coronary angiography (CTCA) is recommended by NICE [CG95] for diagnosis of coronary artery disease (CAD) in patients with stable chest pain. HeartFlow FFRCT utilises a standard CTCA data set to provide a non-invasive fractional flow reserve (FFR) estimate by computational fluid dynamics. Analysis of FFRCT demonstrated a high level of diagnostic accuracy & FFRCT has been advocated by NICE [MTG32]. Adoption of FFRCT should streamline assessment of CAD, ensuring limited invasive resources are used in patients more likely to need revascularisation. We evaluated introduction of FFRCT in a large district general hospital and its impact on clinical assessment of CAD.
Methods CTCA studies were performed as per local guidelines. Studies with coronary stenoses between 30 & 90% were forwarded to HeartFlow for FFRCT analysis. The referring cardiologist viewed both anatomical & functional data before deciding on treatment. Demographic & outcome data were analysed for the first 15 months by scrutinising electronic patient records. An FFRCT ≤0.80 was considered to demonstrate significant obstructive CAD.
Results A total of 1938 CTCA studies were undertaken over 15 months. 584 (30.1%) met criteria for HeartFlow FFRCT analysis. 66 studies (11.3%) were rejected due to quality. FFRCT analysis was received for 518 patients (mean age 66.1±9.7 years; 62.2% male; hypertension 69.1%; hyperlipidaemia 64.5%; diabetes 21.0%; smoking history 67.0%; family history CAD 43.8%). Median time to CTCA was 43±26 days.
346 patients (66.8%) had one or more vessels with an FFRCT result of ≤0.80. 167 patients (32.3%) had 2 or 3 vessels with FFRCT values ≤0.80. Of patients with FFRCT ≤0.80, 201 (58.1%) were investigated further by invasive coronary angiography (median time to angiogram after CTCA 43±56 days). 62 (17.9%) had invasive FFR assessment, with good correlation to the FFRCT result. Of the 346 patients with FFRCT lesions ≤0.80, 154 (44.5%) required either percutaneous coronary intervention (PCI – 120; 34.7%) or coronary artery bypass grafting (CABG – 34; 9.8%). The other 192 patients (55.5%) were managed with optimal medical therapy (OMT).
Of 172 patients (33.2%) without FFRCT positive lesions (i.e. all lesions >0.80), the majority (98.3%) received OMT. Only 8 patients (4.7%) required subsequent invasive angiography, with 3 patients (1.7%) needing PCI (all of whom had invasive FFR studies).
Conclusion Less than half of the patients sent for FFRCT required invasive angiographic assessment. An FFRCT >0.80 safely identified patients that could be managed with OMT. As clinicians became more confident of the accuracy of FFRCT, less invasive FFR was undertaken; and clinicians increasingly deferred invasive angiography after identification of FFRCT lesions ≤0.80 located in the distal coronary circulation. FFRCT allows streamlining of management of CAD by identifying patients who would best benefit from invasive treatment, freeing up limited resources.
Conflict of Interest None