iFR and FFR Equally Safe for Deferring Revascularization, Pooled Analysis Shows

PARIS, France—Patients whose revascularization is deferred based on the results of physiological assessment fare just as well at 1 year regardless of whether that decision stemmed from instantaneous free-wave ratio (iFR) or fractional flow reserve (FFR) testing, a new analysis shows. One thing that slightly tips the balance, though, is that results for patients deferred under FFR guidance—but not iFR—differ by clinical presentation.

Pooled data from DEFINE-FLAIR and iFR-SWEDEHEART were presented today at EuroPCR 2017. The findings, according to Javier Escaned, MD, PhD (Hospital Clínico San Carlos, Madrid, Spain), help extend the more than 15-year-old message of the DEFER trial into modern practice.

Since DEFER’s 2001 publication, “there have been major changes in clinical practice,” he said in a press briefing. Moreover, the rise of functional assessment means that intervention is being deferred for more and more patients. Given that deferral is more common with iFR than with FFR, “it is even more important to know that deferred patients are safe in the long term,” Escaned commented.

Notably, the 1-year MACE rate seen here—approximately 4%—is “about half of the event rate that was observed in the DEFER study,” he stressed.

Asked by TCTMD what these results add to conversations over physiological assessment, Escaned elaborated on the concerns of clinicians who face patients whose iFR or FFR values are normal. “If I let the patient go and something happens, somebody is going to [ask] me, ‘Why did you not treat that stenosis?’ . . . We have to reaffirm to our colleagues that this is safe.”

ACS Changes the Math

For their meta-analysis, Escaned and colleagues collected data on 4,529 patients from DEFINE-FLAIR and iFR-SWEDEHEART, which were initially released during the American College of Cardiology 2017 Scientific Session. Revascularization was deferred more often when iFR rather than FFR was used to inform treatment decisions (50% vs 45%; P = 0.01).

Among patients whose revascularization was deferred, the 1-year MACE rate (death, nonfatal MI, or unplanned coronary revascularization) was 4.12% with iFR and 4.05% with FFR (P = 0.82). Higher event rates were seen for patients who presented with ACS compared with stable disease (5.9% vs 3.6%; P = 0.04).

Yet outcomes for deferred patients varied according to which tool was used to perform physiological assessment. With FFR deferral, there was a gap in 1-year MACE rates between ACS and stable patients (6.4% vs 3.4%; P = 0.049). But with iFR, the difference by presentation did not reach statistical significance (5.4% vs 3.8%; P = 0.37).

Among patients who underwent treatment, there was no difference in long-term outcome by clinical presentation, Escaned said during his presentation. “This of course raises the hypothesis that the reason for the excess of events in deferred patients with acute coronary syndromes comes from suboptimal decision-making based on physiology.”

To the media, Escaned suggested an explanation for the disparity by clinical presentation seen with FFR but not iFR.

“The hypothesis that some authors have been saying is that in acute coronary syndromes the hyperemic response of the myocardium is blunted,” he said, explaining that this in turn might affect the values obtained by FFR, which measures the pressure gradient across a lesion during hyperemia induced by adenosine. “There is room for improvement in acute coronary syndromes,” Escaned noted, adding, “We have to foster research in this area on how to best investigate stenosis significance in patients who have ACS.”

Panelist Peter Jüni, MD (University of Toronto, Canada), stressed that today’s results merely confirm the main message of the two trials. “The major point here is we shouldn’t forget it’s a randomized comparison of two diagnostic strategies aimed at identifying situations at risk as compared with situations that can be deferred,” he said. At least when it comes to the primary outcome, the analysis shows that “things are okay” for deferred patients, Jüni noted.

Where things get more interesting is ACS, he said. Describing the ACS versus no ACS breakdown as a “phenotype” associated with a doubling in MACE risk, Jüni suggested that clinical presentation in itself might be a strong enough marker for risk stratification and raised the question of whether iFR or FFR are even needed in this group.