Author + information
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 recent randomized controlled trials. The purpose of this study is to evaluate 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 in 837 patients referred for coronary angiography 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. Additional FFR measurement and revascularization was performed at the discretion of the operator.
Among 1024 intermediate coronary lesions, 210 lesions (20.5%) had positive iFR (≤0.89) and 814 lesions (79.5%) had negative iFR (>0.89). Patients with positive iFR were older (67+11 vs 65+10, p=0.034), less predominantly male (53.8% vs 61.5%, p=0.035), higher comorbidities such as diabetes mellitus (49.5% vs 36.5%, p=0.001), hyperlipidemia (91.0% vs 83.2%, p=0.005), history of PCI (40.5% vs 33.2%, p=0.047), and more LAD lesions (90.5% vs 57.4%, p<0.001). 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 (similar rate was observed for intermediate iFR range with 27.1% and 72.9% respectively). The mean iFR value corresponding to positive FFR was 0.88 while the mean iFR for negative FFR was 0.92. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of positive iFR to predict positive result with hybrid protocol were 79.6%, 93.5%, 74.1%, 95.1%, 90.9% respectively. Multiple regression analysis revealed that older age, diabetes mellitus, acute coronary syndrome, and LAD lesion were independent predictors of positive iFR (Odds ratio 1.02, 1.76, 1.72, 7.36 respectively).
In this single center, real world retrospective study, iFR cutoff value of 0.89 showed high specificity and negative predictive value compared to hybrid protocol. Older age, diabetes mellitus, acute coronary syndrome, and LAD lesion were independent predictors of positive iFR in intermediate coronary lesions.
IMAGING: FFR and Physiologic Lesion Assessment