Instantaneous Wave-free Ratio

Instantaneous Wave-free Ratio (iFR) is a new technique for the evaluation of coronary stenosis severity. Since it was first commercialised by Volcano Corporation / Philips in 2013 (CE Mark) and 2014 (FDA approval) it is being used in over 3000 catheter laboratories globally and has rapidly become one of the main coronary physiological assessment techniques.

It was developed by Dr Justin Davies, a clinical academic at Hammersmith Hospital. He has more than 15 patents either granted / pending on this technique which can evaluate the abnormal narrowing of the coronary arteries which can result in a heart attack. Imperial BRC supported the core clinical academic salaries, specific project funding and clinical research infrastructure such as the Imperial Clinical Trials Unit (ICTU).

By using mathematical algorithms to detect the best phase of the cardiac cycle to measure stenosis severity, iFR removes the need for the administration of powerful vasodilator drugs such as adenosine, which improves patient comfort and reduces costs.

Much of the success of iFR is due to the simplicity of the technique and potential for costs savings and improved patient experience. Two very large randomised clinical studies DEFINE-FLAIR (n=2500), and iFR SwedeHeart (n=2000) are now near completion of recruitment.

DEFINE-FLAIR is an investigator-led National Institute for Health Research (NIHR) adopted study run at the Imperial College Healthcare NHS Trust in collaboration with the Oxford Biomedical Research Centre and RB&HT Biomedical Research Unit. It is the largest physiological study ever performed in the field, with investigators in Australia, Asia, Africa, Middle East and North America.

iFR is already included in the 2015 European Society of Cardiology (ESC) coronary revascularisation guidelines. Reporting in 2016, the DEFINE-FLAIR and iFR-SwedeHeart studies will aim to extend guideline indications to become standard of care for revascularisation decision making.

  • Dr Justin Davies
    Dr Justin Davies
    Senior Reserch Fellow / Consultant Cardiologist
  • Imperial Clinical Trials Unit
  • NIHR Oxford Biomedical Research Centre
  • NIHR Royal Brompton Cardiovascular Biomedical Research Unit