Background—: Small drifts in intracoronary pressure measurements (±2 mm Hg) can affect stenosis categorization using pressure indices. This has not previously been assessed for fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and whole-cycle distal pressure/proximal pressure (Pd/Pa) indices. Methods and Results—Four hundred forty-seven: stenoses were assessed with FFR, iFR, and whole-cycle Pd/Pa. Cut point values for significance were predefined as ≤0.8, <0.90, and <0.93, respectively. Pressure wire drift was simulated by offsetting the distal coronary pressure trace by ±2 mm Hg. FFR, iFR, and whole-cycle Pd/Pa indices were recalculated and stenosis misclassification quantified. Median (±median absolute deviation) values for FFR, iFR, and whole-cycle Pd/Pa were 0.81 (±0.11), 0.90 (±0.07), and 0.93 (±0.06), respectively. For the cut point of FFR, iFR, and whole-cycle Pd/Pa, 34.6% (155), 50.1% (224), and 62.2% (278) of values, respectively, lay within ±0.05 U. With ±2 mm Hg pressure wire drift, 21% (94), 25% (110), and 33% (148) of the study population were misclassified with FFR, iFR, and whole-cycle Pd/Pa, respectively. Both FFR and iFR had significantly lower misclassification than whole-cycle Pd/Pa ( P <0.001). There was no statistically significant difference between the diagnostic performance of FFR and iFR ( P =0.125). Conclusions—: In a substantial proportion of cases, small amounts of pressure wire drift are enough to cause stenoses to change classification. Whole-cycle Pd/Pa is more vulnerable to such reclassification than FFR and iFR.

Background: There is great degree of interobserver variability in the visual angiographic assessment of left main coronary disease (LMCD). Fractional flow reserve and intravascular ultrasound are often used in this setting. The use of instantaneous wave-free ratio (iFR) for evaluation of LMCD has not been well studied. The aim of this study is to evaluate the use of iFR in the assessment of angiographically intermediate LMCD. Methods: This is an international multicenter retrospective observational study of patients who underwent both iFR and intravascular ultrasound evaluation for angiographically intermediate LMCD. An independent core laboratory performed blinded off-line analysis of all intravascular ultrasound data. A minimum lumen area of 6 mm ² was used as the cutoff for significant disease. Results: One hundred twenty-five patients (mean age, 68.4±9.5 years, 84.8% male) were included in this analysis. Receiver operating curve analysis showed that an iFR of ≤0.89 identified minimum lumen area <6 mm ² with an area under the curve of 0.77 (77% sensitivity, 66% specificity; P <0.0001). Among the 69 patients without ostial left anterior descending artery or left circumflex artery disease, receiver operating curve analysis showed that an iFR of ≤0.89 identified minimum lumen area <6 mm ² with an area under the curve of 0.84 (70% sensitivity, 84% specificity; P <0.0001). The correlation was not significantly different when the body surface area was considered. Conclusions: In this study, in patients with intermediate LMCD, iFR of ≤0.89 correlates with intravascular ultrasound minimum lumen area <6 mm ² regardless of body surface area. The current study supports the use of iFR for the evaluation of intermediate LMCD.

Background: The majority of randomized controlled trials of revascularization decision-making excludes left main coronary artery disease (LMD). Therefore, contemporary clinical outcomes of patients with stable coronary artery disease and LMD with proven ischemia remain poorly understood. The aim of this study was to assess the long-term clinical outcomes of physiologically significant LMD according to the treatment strategies of revascularization versus revascularization deferral. Methods: In this international multicenter registry of stable LMD interrogated with the instantaneous wave-free ratio, patients with physiologically significant ischemia (instantaneous wave-free ratio ≤0.89) were analyzed according to the coronary revascularization (n=151) versus revascularization deferral (n=74). Propensity score matching was performed to adjust for baseline clinical characteristics. The primary end point was a composite of death, nonfatal myocardial infarction, and ischemia-driven target lesion revascularization of left main stem. The secondary end points were as follows: cardiac death or spontaneous LMD-related myocardial infarction; and ischemia-driven target lesion revascularization of left main stem. Results: At a median follow-up period of 2.8 years, the primary end point occurred in 11 patients (14.9%) in the revascularized group and 21 patients (28.4%) in the deferred group (hazard ratio, 0.42 [95% CI, 0.20–0.89]; P =0.023). For the secondary end points, cardiac death or LMD-related myocardial infarction occurred significantly less frequently in the revascularized group (0.0% versus 8.1%; P =0.004). The rate of ischemia-driven target lesion revascularization of left main stem was also significantly lower in the revascularized group (5.4% versus 17.6%; hazard ratio, 0.20 [95% CI, 0.056–0.70]; P =0.012). Conclusions: In patients who underwent revascularization for stable coronary artery disease and physiologically significant LMD determined by instantaneous wave-free ratio, the long-term clinical outcomes were significantly improved as compared with those in whom revascularization was deferred.