1.1 There is not enough evidence to recommend using QAngio XA 3D quantitative flow ratio (QAngio QFR) and CAAS vessel fractional flow reserve (CAAS vFFR) during invasive coronary angiography to assess coronary stenosis in stable angina. QAngio QFR's diagnostic accuracy is considered acceptable for assessing coronary stenosis during invasive coronary angiography, but its clinical effectiveness is uncertain. CAAS vFFR's diagnostic accuracy and clinical effectiveness is uncertain. Further research is recommended in both diagnostic-only catheter labs and interventional catheter labs.
1.2 Further research is recommended (see section 5) on:
people's experiences of QAngio QFR and CAAS vFFR compared with the reference standard of FFR or instantaneous wave‑free ratio (iFR)
test failure rates of QAngio QFR and CAAS vFFR in clinical practice and how these affect whether revascularisation is done
the clinical benefit of using QAngio QFR and CAAS vFFR
the diagnostic accuracy of CAAS vFFR.
Why the committee made these recommendations
FFR or iFR can be used with invasive coronary angiography to assess coronary stenosis. However, they can have unpleasant side effects and increase the risk of adverse events, such as damage to the artery.
CAAS vFFR and QAngio QFR use X‑ray images taken during an invasive coronary angiography to construct a 3D image of the artery. This image is used to estimate the effect of coronary stenosis on blood flow through the artery without the side effects and risk of adverse events of FFR or iFR.
Published evidence shows that the diagnostic accuracy of QAngio QFR is similar to FFR, but the diagnostic accuracy of CAAS vFFR is very uncertain. Whether QAngio QFR or CAAS vFFR affect clinical outcomes and improve quality of life is also uncertain. Also, in clinical practice the quality of the images varies depending on if they are done in a diagnostic‑only centre or one that offers interventional procedures. Poor image quality might mean the tests fail.
The cost‑effectiveness estimates for CAAS vFFR and QAngio QFR are uncertain but suggest that they are more cost effective than invasive coronary angiography alone. The estimates suggest that, compared with FFR and iFR, CAAS vFFR is less cost effective and QAngio QFR is slightly cheaper but less clinically effective.
There are multiple tests in use that assess coronary stenosis and it is not clear what clinical benefits QAngio QFR and CAAS vFFR offer over these. Therefore, QAngio QFR and CAAS vFFR are not recommended for use in the NHS, and further research is recommended.