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The instantaneous wave-free ratio (iFR) is a newly developed coronary artery pressure index measured in the wave-free period of diastole in absence of hyperemia. An iFR-guided revascularization strategy was shown to be noninferior to fractional flow reserve (FFR)-guided revascularization strategy in multiple recent randomized controlled trials. The purpose of this study is to evaluate the clinical outcomes with the newly defined threshold of iFR compared to the well established FFR cutoff threshold.
We retrospectively reviewed 1024 intermediate coronary lesions requiring functional evaluation using iFR between January 2015 and June 2016. The threshold cutoff value of 0.89 or less for iFR and 0.80 or less for FFR were used to indicate the presence of hemodynamically important stenosis. We used hybrid iFR-FFR protocol utilizing FFR in lesions with intermediate iFR values between 0.86 to 0.93. Major adverse cardiovascular event (MACE) was defined as composite endpoint of death, myocardial infarction, and target vessel revascularization.
Among 1024 intermediate coronary lesions, 210 lesions (20.5%) had positive iFR (≤0.89) and 814 lesions (79.5%) had negative iFR (>0.89). Hybrid protocol of measuring FFR was done in 451 coronary lesions, including 351 lesions with intermediate iFR range between 0.86 and 0.93. Of those 451 lesions, 104 lesions (23.1%) had positive FFR and 347 lesions (76.9%) had negative FFR. Revascularization done after positive iFR was 155 lesions out of 210 lesions (73.8%) while revascularization was deferred for negative iFR in 92.6% (754 out of 814 lesions). Revascularization rate after positive hybrid approach was 90.1% as opposed to revascularization was deferred for negative hybrid approach in 95.3%. There were no statistically significant differences on MACE between iFR strategy, hybrid protocol, and all lesions that underwent PCI (6.2% vs 5.5% vs 5.1%, p=0.9).
In this single center, real world retrospective study, iFR cutoff value of 0.89 was associated with lower rate of revascularization but similar rate of deferring revascularization. MACE for iFR strategy was similar to hybrid protocol as well as all lesions that underwent PCI.
IMAGING: FFR and Physiologic Lesion Assessment