QAngio XA 3D/QFR (Medis) imaging software is used for the physiologic assessment (quantitative flow ratio; QFR) of coronary artery obstructions. It is designed to be used with all invasive coronary angiography (ICA) systems; biplane or monoplane. It uses 2, 2D X‑ray angiographic projections, taken at least 25 degrees apart – and ideally between 35 and 50 degrees apart – to create a 3D‑reconstruction of a coronary artery; this shows the QFR values across the artery. QFR is an assessment (by frame count) of the pressure (blood flow velocity) drop over the artery, with a value of 1 representing a normally functioning artery with no pressure drop. A 20% or more drop in blood pressures (QFR value of 0.8 and less) is considered a significant obstruction where revascularisation should be considered. QFR is measured non-invasively without the need for a pressure wire and vasodilator drugs such as adenosine, which increase blood flow.
QAngio XA 3D/QFR software is installed on a laptop or workstation that is connected to the ICA system. The Digital Imaging and Communication in Medicine (DICOM) data from ICA projections are immediately uploaded and viewable on the connected workstation.
Unlike current techniques for measuring blood flow across a vessel during ICA – such as fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurements – QFR is measured non-invasively without the need for a pressure wire. Unlike FFR, it does not need vasodilator drugs, such as adenosine, to increase blood flow. The QFR results are processed on site and the company claims that the total time for data acquisition and analysis is about 4 to 5 minutes.
The NICE guideline on chest pain recommends further diagnostic testing for people in whom stable angina cannot be excluded by clinical assessment alone. This includes offering 64‑slice or above coronary CT angiography (CCTA) as the first-line diagnostic test when clinical assessment suggests:
typical or atypical angina or
non-anginal chest pain, but 12‑lead resting electrocardiogram (ECG) has been done and shows ST‑T changes or Q waves.
Clinicians can ask for subsequent diagnostic tests, dependent on the CCTA results. NICE's guideline on chest pain recommends offering non-invasive functional imaging for myocardial ischaemia if 64‑slice or above CCTA has shown coronary artery disease of uncertain functional significance, or is non-diagnostic. Non-invasive functional imaging includes:
myocardial perfusion scintigraphy with single-photon emission computed tomography (MPS with SPECT)
first-pass contrast-enhanced MR perfusion
MR imaging for stress-induced wall motion abnormalities.
ICA should be offered as a second-line investigation when the results of non-invasive functional imaging are inconclusive.
When ICA is used to determine the presence and severity of coronary stenosis, it may be combined with the invasive measurement of FFR using a pressure wire. Although the NICE guideline on chest pain does not consider FFR, other guidelines (such as those of the European Society of Cardiology and American College of Cardiology) state that lesions with an FFR of 0.80 or less are functionally significant and revascularisation may be considered.
The company has indicated that the technology would be used as a second-line investigation alongside ICA to avoid invasive FFR measurement, and claimed that is could also be used in selection decisions on what interventional device to use (for example, stent).
The NICE medical technologies guidance on HeartFlow FFRCT recommends it as an option in people with stable, recent-onset chest pain and who are offered CCTA as part of the NICE guideline on chest pain.
The technology would be used by cardiologists in people with chest pain of recent onset during investigative ICA, and in those having a percutaneous coronary intervention (PCI).
The first-year cost for the technology is £23,000; this includes unlimited use of the software over that period. In subsequent years payment is on a per-use basis, with each analysis expected to cost between £150 and £250. The purchase price of the software includes software support and maintenance, usually done remotely from a UK-based support centre. Training is also provided by the company at installation.
The system uses a workstation, which is not included with the purchase of QAngio; the company has indicated, and experts have confirmed, that this is likely to already be in place. Experts have said that in many cases workstations will need to be upgraded or replaced to meet the technical specifications recommended by the company.
The company has said that the cost of an invasive FFR is about £500, with additional costs for adenosine of about £100. Although FFR is recommended by other guideline-producing bodies and appears to be widely used in the NHS, it is not included in the NICE guideline on chest pain.
QAngio 3D/QFR is not currently used in NHS clinical practice but is being used in research.
QAngio 3D/QFR would represent an additional cost compared with standard ICA. It has the potential to reduce costs if it avoids the need for invasive FFR or PCIs.
The technology is designed to be used alongside existing ICA facilities. However, there are likely to be costs to upgrade or replace IT equipment to ensure that existing ICA centres are capable of running the software.