A novel technology to measure stenosis severity yields similar results to traditional fractional flow reserve (FFR) without the use of adenosine to induce maximum hyperemia, a new study has shown. Results for instantaneous wave-free ratio (iFR) were presented at the Transcatheter Cardiovascular Therapeutics (TCT) congress in San Francisco, USA.
The study results were presented during a Late Breaking Clinical Trial session at the TCT and have also been accepted for publication in the Journal of the American College of Cardiology.
The ADVISE (Adenosine vasodilation independent stenosis evaluation) trial assessed the ability of the investigational product iFR to provide a measurement of the severity of a coronary stenosis that is similar to FFR, the gold standard for assessing ischaemia, without the need for pharmacologic vasodilation. iFR was developed by physician-scientists at Imperial College London, UK, in partnership with Volcano Corporation.
FFR is only used in 6% or fewer of percutaneous coronary intervention cases in the United States. One of the reasons for the low usage rate is the required use of the drug adenosine, which minimises and stabilises coronary resistance during the test, but is uncomfortable for patients, as well as being time-consuming and expensive, the investigators said.
In ADVISE, 157 stenoses (131 patients) were recruited to this pilot, non-randomised, international, multicentre study. In their investigations, researchers developed a new pressure-based index that does not require adenosine.
Wave intensity analysis identified a period during the normal heart rhythm cycle where intracoronary resistance at rest is similar in variability and magnitude (CV: 0.08±0.06 and 284±147mmHg.s/m) to those during FFR (CV: 0.08±0.06 and 302±315mmHg.s/m, p=NS for both).
The resting ratio of the distal-to-proximal pressure during this period, iFR, correlated closely with FFR (r=0.9, p<0.001) with excellent diagnostic efficiency (receiver operating characteristic area under curve of 93%, at FFR<0.8), specificity, sensitivity, and negative and positive predictive values of 91%, 85%, 85% and 91%, respectively.
“The results of the ADVISE trial indicate that intra-coronary resistance is naturally constant and minimised during the wave-free period. The instantaneous wave-Free Ratio (iFR) calculated over this period produces a drug-free index of stenosis severity that is comparable to FFR,” said ADVISE principal investigator Justin Davies, an interventional cardiologist at National Heart and Lung Institute at Imperial College London.