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WASHINGTON — The instantaneous wave-free ratio (iFR) was just as good as fractional flow reserve (FFR) to parse which patients should get revascularization for their coronary artery disease, two studies reported here at the American College of Cardiology meeting and online in the New England Journal of Medicine.

The first, the DEFINE-FLAIR trial, showed that the 1-year risk of all-cause death, nonfatal MI, or unplanned revascularization was 6.8% for iFR versus 7.0% for FFR (HR 0.95, 95% CI 0.68-1.33; P<0.001 for noninferiority).

The iFR group had fewer adverse procedural unpleasant sensations such as a difficulty breathing and chest pain (3.1% versus 30.8%, P<0.001) and a shorter median procedural time (40.5 versus 45.0 minutes, P=0.001), according to , of London’s Hammersmith Hospital, and colleagues.

DEFINE-FLAIR was a blinded trial that had 2,492 patients with coronary artery disease randomized to iFR- or FFR-guided revascularization.

In addition to the trial, a registry study also suggested that iFR was a better experience for patients while being on par with FFR in terms of 1-year outcomes.

iFR as a measure of severity of coronary artery stenosis was non-inferior to FFR in terms of the composite endpoint of all-cause death, nonfatal MI, and unplanned revascularization within a year of the index percutaneous coronary intervention (PCI, 6.7% versus 6.1%, HR 1.12, 95% CI 0.79-1.58; P=0.007 for noninferiority).

"It will be interesting to see if this increases the use of physiological assessment. I hope it does. It may shift people from doing FFR to iFR because they can avoid the use of adenosine,” said panelist , of Stanford University Medical Center, Calif.

Similarly, at a press conference, , commented: “There’s been a real push to do physiological assessment to identify patients [for] PCI. FFR has been that standard. Clinically there’s been some reluctance to jump on the FFR bandwagon and the idea that a technology can be quicker and as safe as the established FFR is very enticing to a clinician.”

The finding remained robust across all major subgroups. Moreover, there were no differences between groups in terms of the individual outcomes of MI, target lesion revascularization, restenosis, and stent thrombosis, according to , of Skane University Hospital in Sweden, and co-investigators of the iFR-SWEDEHEART study.

This was multicenter study of enrollees in the Swedish Coronary Angiography and Angioplasty Registry. Included were 2,037 participants with stable angina or an acute coronary syndrome.

More patients in the FFR group reported chest discomfort during the procedure (68.3% versus 3.0, P<0.001), as iFR evaluates the hemodynamic severity of a lesion without requiring a vasodilator such as adenosine.

As in DEFINE-FLAIR, stenting had been deferred if iFR and FFR were above 0.89 and 0.80, respectively.

“We should be reminded that this study and the previous one do not provide any info on which patients we need to apply physiological assessment,” said panelist , of University Hospital in Lille, France. “Should we use it in all acute coronary syndrome patients? We don’t have an important group: patients managed without physiology.”

“Despite strong data in its favor, the use of FFR remains low. One major reason is that in order to induce a hyperemic state (which simulates exercise), a vasodilator such as adenosine is administered. Adenosine may cause bradycardia or heart block and result in termination of the procedure,” , of Brigham and Women’s Hospital in Boston, wrote in an accompanying editorial in NEJM.

“Increased procedural time and cost associated with FFR, as well as patient discomfort from chest pain and dyspnea caused by adenosine, are also issues to be considered.”

iFR “might be expected to lower health care costs, assuming that the price of the guidewire used for iFR measurement is not higher than the price of the guidewire used for FFR measurement,” the editorialist suggested.

Calling the results “remarkably concordant,” he concluded that “there will always be patients in the catheterization laboratory who have a coronary stenosis of intermediate severity on angiography. FFR has been the evidence-based standard for invasive evaluation of such lesions, but it now appears that iFR may be the new standard.”

However, he noted, “[i]t is important to note that the results of these two trials do not apply to the evaluation of presumed culprit lesions in patients with acute coronary syndromes; for such lesions, current evidence favors early catheterization and revascularization guided by an anatomical assessment of lesion severity.”