FFR and iFR Discordance in up to 20% of Cases: Which One Should Inform Our Decisions?

Invasive functional measurement of intermediate lesions has become the gold standard to define revascularization. Due to its favorable long-term prognostic value, fractional flow reserve (FFR) is the reference used to compare all others.

FFR e iFR discordantes hasta en un 20% de los casos ¿con cuál decidimos?

Recently, new nonhyperemic indexes, measured in a specific diastolic period, have emerged. Among them, the one with the most accumulated evidence is instantaneous wave-free ratio (iFR), which is just as helpful as FFR when it comes to decision-making, while being more practical and faster.

When FFR and iFR results match, revascularization is already decided. However, in up to 20% of cases there is a discordance in measurements, leaving the operator with a dilemma.

Multiple studies have compared angiography with FFR, and FFR vs. iFR.

Results from FAME, FAME 2, and DEFER showed a clinical benefit of using FFR vs. angiography for revascularization guidance, as well as the safety of deferring these lesions when their measurement was negative.

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The DEFINE-FLAIR and iFR-SWEDEHEART trials showed noninferiority of iFR vs. FFR for lesion revascularization or deferral.

All of this evidence was compiled in the 2018 European guidelines, which provided a class IA recommendation for both indexes.

Clinical practice pushed iFR because it is faster to measure, cheaper, and presents fewer adenosine adverse events.

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However, FFR and iFR equivalence has been challenged because of the frequent incidence of discordant results.

The 3V FFR-FRIENDS study, recently published in JAHA, compared nonhyperemic indexes vs. FFR at 5 years. This follow-up length seems very reasonable to finally answer these questions about FFR and iFR.

The analysis included 1024 vessels in 435 patients who were measured by FFR and nonhyperemic indexes, such as iFR.

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The study population was divided into three groups: revascularization with FFR ≤0.80; deferred lesions according to negative concordant FFR and iFR, and deferred lesions with discordant FFR and iFR results.

The rates of combined events (cardiac death, vessel-related infarction, and ischemia-driven revascularization) at 5 years were 14.8%, 7.5%, and 14.4% for revascularized patients, concordant deferred patients, and discordant deferred patients, respectively.

Results show a similar prognosis for concordant positive values (≤0.89 or ≤0.80 for iFR or FFR, respectively).

The group of patients deferred with discordant values showed more events than the concordant deferred group. However, these events were less than the number of events in the revascularization group. Deferring based on any index is a reasonable option. Conversely, choosing revascularization does not worsen patient prognosis.

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Original Title: Long-Term Clinical Outcomes of Nonhyperemic Pressure Ratios: Resting Full-Cycle Ratio, Diastolic Pressure Ratio, and Instantaneous Wave-Free Ratio.

Reference: Joo Myung Lee et al. J Am Heart Assoc. 2020;9:e016818. DOI: 10.1161/JAHA.120.016818.

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