This work relates to the implementation of NICE guideline CG95 (chest pain of recent onset: assessment and diagnosis). Our local pathway is now to perform coronary CT angiography (CTCA) in all patients with typical, atypical angina or non-anginal chest pain with resting ECG ST-T or Q wave changes, with the exception of individuals with known coronary artery disease and/or prior revascularisation (bypass grafts or percutaneous coronary intervention). This has required ~600% increase in baseline CTCA activity.
We also assess implementation of NICE MTG32 (HeartFlow FFRct for estimating fractional flow reserve (FFR) from CTCA as part of NHS England Innovation Technology Payment 2018 scheme. Specifically, all major epicardial coronary stenoses ≥25% had FFRct correlation where technically feasible. The impact of this additional post-processing was assessed in a prospective quality improvement project of consecutive patients during the first 3 months of the trial period.
Aims and objectives
CTCA is now the first line non-invasive imaging test in patients with symptoms that may be attributable to stable coronary artery disease (CAD). Owing to high sensitivity, CTCA can exclude CAD and prompt work-up of alternative causes. However, many patients with epicardial stenosis on CTCA may undergo layered functional stress testing and/or invasive physiology measurements performed during invasive catheter angiography (ICA) to determine whether revascularisation is required in addition to optimal medical therapy.
FFRct analysis uses post-processing computational fluid dynamics applied to the CTCA data to model blood flow in the coronary arteries and determine if there is a significant pressure drop across a modelled coronary stenosis, similar to those measures acquired invasively. CTCA and FFRct together offer a potential one-stop comprehensive assessment for CAD.
MTG32 suggests routine application of this technology will save £214 per patient. CG95, MTG32 and the existing evidence behind FFRct was reviewed and the technique was deemed to have the potential to streamline care after CTCA in patients with new onset stable chest pain.
The Royal United Hospital Bath NHS Foundation Trust provides care for 500,000 people in Bath, North East Somerset and Western Wiltshire with 759 beds and a comprehensive range of acute services and diagnostic imaging.
The Trust is equipped to perform the entire gambit of non-invasive testing for CAD and ischaemia, with stress SPECT myocardial perfusion imaging, stress echocardiography and adenosine stress perfusion CMR, as well as delivering a large invasive cardiology service. Balancing catheter lab efficiency between STEMI/ACS cases and diagnostic angiography ± proceed, elective complex angiography and specialist procedures is challenging. With the installation of a new high specification cardiac-optimised CT scanner, the Trust was in a strong position to implement CG95 and MTG32. Being a forwarding thinking, research-orientated organisation striving “to provide the highest quality care; delivered by an outstanding team”, one of the Trust’s 5 goals is “quality improvement and innovation each and every day”. The Department of Radiology was successful in a bid to become a pilot site for HeartFlow ITP 2018 scheme during the initial wave.
Our specific aims were to quantify the clinical impact of a CTCA first +/- FFRct pathway in routine clinical practice in the NHS District General Hospital setting.
Reasons for implementing your project
The Royal United Hospitals Bath NHS Foundation Trust provides acute treatment and care for a catchment population of around 500,000 people in Bath, and the surrounding towns and villages in North East Somerset and Western Wiltshire.
The Trust provides 759 beds and a comprehensive range of acute services including medicine and surgery, services for women and children, accident and emergency services, and diagnostic and clinical support services.
The trust vision is ‘To provide the highest quality of care; delivered by an outstanding team who all live by our values’. One out of five of the trusts goals includes: Quality improvement and innovation each and every day.
Patients with stable, recent onset chest pain and suspected angina are usually undergo diagnostic test to identify coronary artery disease by evaluating either coronary anatomy (narrowing) or function (flow/ ischaemia). Tests can be classified as invasive or non-invasive. Some of the invasive investigations require a pressure wire and others require medication or exposure to radiation. FFR is currently measured invasively using a pressure wire placed across a narrowed artery during ICA.
How did you implement the project
With the installation of an ultra-fast pitch 128 slice dual source CT scanner, the radiology department was able to increase CTCA capacity. To achieve optimal heart rate control, image quality and increase the chance of successful FFRct analysis, we devised an electronic pre-scan oral beta-blockade requester protocol. This resulted in 70% of CTCAs sent for FFRct with heart rate ≤60 per minute versus the global HeartFlow figure of 53%. Our documentation has been shared as a template of good practice with other institutions aiming to join the ITP.
In 1 year we increased cardiac trained radiographers from 8 to 16 by pairing experienced CTCA radiographers with learners. We up-skilled existing cardiac radiographers, hosting an expert technologist to hone protocols. Two completed audit spirals have led to scan coverage optimisation and minimised radiation dose.
Our Consultant-supervised list, with on-table image review, ensures the best image quality has been achieved. Our meticulous approach has resulted in HeartFlow acceptance rates in the last 2 quarters of ≥97%, placing us as one of the most successful users of FFRct Nationally, culminating with a recent CTCA quality award.
Initially, IT and IG issues had to be addressed, with the longest delay in legal contracting. Our Trust legal team spent 3 months amending the legal contract with HeartFlow. After several drafts, agreement was reached. Our trust contract has been used as a template by HeartFlow to assist product roll-out across the NHS.
We have amassed one of the largest clinical experiences with HeartFlow in England. We engaged with HeartFlow to understand artefact and false positive results and refined our reconstruction algorithms. We have since been consulted to explain our reconstruction pathways to other institutions. We disseminated our knowledge by organising 2 multidisciplinary cardiology-radiology and cross-institutional educational events.
We conducted a prospective quality improvement project of consecutive CTCAs with ≥1 epicardial coronary stenoses ≥25% sent for FFRct analysis over 3 months from implementation. Clinical details and anatomical CTCA findings were presented to the cardiac MDT and a consensus management plan was recorded whilst blinded to FFRct data. The FFRct data was then unblinded and the consensus management was re-recorded and compared. Impact on waiting time to diagnostic certainty was assessed (using mean waiting times) for investigations selected in the management plans.
We described the findings in an interim analysis (presented at Society of Cardiovascular CT, Winter Meeting, Dublin 2019). The full analysis is currently being finalised for publication in peer-reviewed literature.
An analysis of the first consecutive 127 CT coronary angiogram cases to occur during the commencement of the use of FFRct in the pathway was performed. 127 CTCAs were performed, of which 52 were sent for FFRct analysis. Three analyses were not feasible (sublingual GTN contraindication, presence of coronary stent and inadequate image quality) with 49 successfully analysed resulting in a 94% image acceptance rate.
Following MDT discussion, unblinding the FFRct results led to a change in consensus management relative to CTCA result alone in 67% of patients. Specifically, FFRct-guided management led to cancellation of an invasive coronary angiogram proposed on CCTA-guided management in 18% (9/49) and cancellation of a subsequent functional imaging test in 18% (9/49). Proposed CTCA-guided invasive strategy was modified from a diagnostic angiogram to a focused interventional invasive catheter angiogram, with the option of pressure wires studies, and/or angioplasty/stent in 24% (12/49) after reviewing FFRct results. Importantly, FFRct-guided management was associated with reduced mean time to next investigation/definitive treatment compared to management based on CTCA alone (24±5 vs 41±6 days, p=0.03).
Despite CTCA studies increasing ~600% from baseline, functional imaging activity has not increased. FFRct analysis has reduced the burden on stress CMR lists and increased capacity to perform more non-stress CMR studies. This has helped minimise breaches for patients waiting >6 weeks for a stress CMR study.
Since the implementation of CG95 and MTG32, we have observed a decrease in total cath lab activity, with interventional procedures overtaking diagnostic procedures for the first time. This suggests that despite a decrease in overall cath lab numbers, there has been increased cath lab efficiency. This is because our interventional cardiologists are increasingly using FFRct data to plan invasive procedures and reduce certain cath lab invasive physiology assessments. We are scheduled to be a beta-site for the next iteration of HeartFlow FFRct analysis that allows real-time stent planning.
We have performed a clinical outcome analysis, observing no death, MI, revascularisation or admission with ACS in any patient with FFRct >0.80 and deferred from cath lab
Key learning points
Our key learning points are summarised in alignment with our Trust values.
Everyone matters: Extracting the most information for a patient’s CT study helps the cardiac MDT plan the optimal treatment strategy for the individual patient. It has reduced unnecessary functional imaging tests and helped avoid unnecessary invasive diagnostic testing.
Working together: The process needs buy-in from Radiology and Cardiology to understand the test, its strengths and also its limitations (e.g. use in patients with MI within the last 6 weeks, CABG, prior PCI, motion artefact, very heavy coronary calcification). In addition, we advocate anyone implementing the utilisation of HeartFlow analysis to liaise with institutions with existing experience to harness the experience already gained, and for all to learn from prior challenges, errors and to shorten the learning curve duration and gradient.
Making a difference: Driving up clinical standards, HR ≤60 BPM in 70% of FFRct patients (vs 53% globally), one of the highest image acceptance rates in the country (last quarter 97%) and one of the largest (top 5) UK volume users of FFRct (despite being a DGH without a dedicated cardiac CT scanner). This has been achieved through meticulous attention to detail throughout the patient journey – from the point of referral, patient preparation, supervision of scanning and reconstructions, right through to issuing a verified report and clinic-radiological MDT discussion.