title: Coronary Flow Reserve and Microcirculatory Resistance in Patients With Intermediate Coronary Stenosis.
abstract: BACKGROUND
  The prognostic impact of microvascular status in patients with high fractional flow reserve (FFR) is not clear.
  
  
  OBJECTIVE
  The goal of this study was to investigate the implications of coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients who underwent FFR measurement.
  
  
  METHODS
  Patients with high FFR (>0.80) were grouped according to CFR (≤2) and IMR (≥23 U) levels: group A, high CFR with low IMR; group B, high CFR with high IMR; group C, low CFR with low IMR; and group D, low CFR with high IMR. Patient-oriented composite outcome (POCO) of any death, myocardial infarction, and revascularization was assessed. The median follow-up was 658 days (interquartile range: 503.8 to 1,139.3 days).
  
  
  RESULTS
  A total of 313 patients (663 vessels) were assessed with FFR, CFR, and IMR. Correlation (r = 0.201; p < 0.001) and categorical agreement (kappa value = 0.178; p < 0.001) between FFR and CFR were modest. Low CFR was associated with higher POCO than high CFR (p = 0.034). There were no significant differences in clinical and angiographic characteristics among groups. Patients with high IMR with low CFR had the highest POCO (p = 0.002). Overt microvascular disease (p = 0.008), multivessel disease (p = 0.033), and diabetes mellitus (p = 0.033) were independent predictors of POCO. Inclusion of a physiological index significantly improved the discriminant function of a predictive model (relative integrated discrimination improvement 0.467 [p = 0.037]; category-free net reclassification index 0.648 [p = 0.007]).
  
  
  CONCLUSIONS
  CFR and IMR improved the risk stratification of patients with high FFR. Low CFR with high IMR was associated with poor prognosis. (Clinical, Physiological and Prognostic Implication of Microvascular Status; NCT02186093).
authors.affiliation: Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Joo Myung
authors.initials: JM
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Jung
authors.affiliation: Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Doyeon
authors.initials: D
authors.lastname: Hwang
authors.affiliation: Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Jonghanne
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Cardiology, Xiangtan Central Hospital, Xiangtan, China.
authors.forename: Yongzhen
authors.initials: Y
authors.lastname: Fan
authors.affiliation: Department of Internal Medicine and Emergency Medical Center, Seoul National University Hospital, Seoul, South Korea; Institute of Aging, Seoul National University, Seoul, South Korea.
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Na
authors.affiliation: Department of Medicine, Inje University Ilsan Paik Hospital, Goyang, South Korea.
authors.forename: Joon-Hyung
authors.initials: JH
authors.lastname: Doh
authors.affiliation: Department of Medicine, Keimyung University Dongsan Medical Center, Daegu, South Korea.
authors.forename: Chang-Wook
authors.initials: CW
authors.lastname: Nam
authors.affiliation: Department of Cardiology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Eun-Seok
authors.initials: ES
authors.lastname: Shin
authors.affiliation: Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea; Institute of Aging, Seoul National University, Seoul, South Korea. Electronic address: bkkoo@snu.ac.kr.
authors.forename: Bon-Kwon
authors.initials: BK
authors.lastname: Koo
mesh_terms: D017023:Coronary Angiography; D003326:Coronary Circulation / Q000502:physiology*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D053805:Fractional Flow Reserve, Myocardial / Q000502:physiology*; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014655:Vascular Resistance / Q000502:physiology*
keywords: coronary artery disease; coronary flow reserve; fractional flow reserve; index of microcirculatory resistance; microvascular function