Response by Ahn and Park to Letter Regarding Article, “Fractional Flow Reserve and Cardiac Events in Coronary Artery Disease: Data From a Prospective IRIS-FFR Registry (Interventional Cardiology Research Incooperation Society Fractional Flow Reserve)”
Authors: Jung-Min Ahn, Seung-Jung Park
Journal: Circulation (2017)

In Response:We thank Drs Jin-Shan and Xue-Bin for their interest and thoughtful questions on our work. 1irst, they asked the indication of fractional flow reserve (FFR) measurement.American practice guideline suggests that FFR measurement is reasonable to assess angiographic intermediate coronary stenosis (50%-70% diameter stenosis).A more recent consensus document has extended FFR use up to 90% diameter stenosis because ≈20% of coronary stenoses with 70% to 90% diameter stenosis are functionally insignificant. 2 In addition, although diameter stenosis is <50%, FFR can be assessed when myocardial ischemia was suspected, particularly in a case of diffuse coronary disease.More important, if there is no objective evidence of ischemia before stenting, FFR should be measured regardless of diameter stenosis except critical stenoses (>90%).Second, they asked another important question about whether coronary revascularization was followed by angiographic stenosis or FFR in cases of "mismatch."Currently, the primary goal of coronary revascularization is the restoration of coronary blood flow.There has been no supportive scientific evidence of preventive coronary stenting on coronary stenosis with an FFR of >0.80 (which means nonischemic coronary flow) even in angiographically tight stenoses. 3In addition, in our registry, among 531 deferred lesions with >70% diameter stenosis, the incidence rate for cardiac death or myocardial infarction was only 0.33% lesion per year; for major adverse cardiac events, 2.81% lesion per year (Figure II in the online-only Data Supplement).Those values appear to be lower than revascularized lesion outcomes from a contemporary stent registry.An ongoing randomized clinical trial to compare preventive coronary intervention with medical treatment for significant angiographic stenosis (>50%) with negative FFR (>0.80) but vulnerable plaque features defined by intracoronary imaging (the PREVENT trial [Preventive Coronary Intervention on Stenosis With Functionally Insignificant Vulnerable Plaque]; URL: http://www.clinicaltrials.gov.Unique identifier: NCT02316886) will answer this question adequately in the future.FFR measurement is more generally accepted in patients without acute coronary syndrome (ACS) because hyperemia may be submaximal in patients with ACS as a result of microvascular injury.In addition, outcomes of deferred lesions in patients with ACS were worse than those in patients with stable coronary artery disease.However, it should be realized that the revascularized lesion outcomes also were worse in patients with ACS.In addition, recent randomized trials showed that compared with angiography-guided percutaneous coronary intervention, FFR-guided percutaneous coronary intervention was associated with better procedural or clinical outcomes in ACS, non-ST-segment-elevation myocardial infarction, and nonculprit lesions of ST-segment-elevation myocardial infarction at the index procedure and at index admission. 4Furthermore, the FFR cutoff value in ACS was 0.78, similar Response by Ahn and Park to