title: Influence of microvascular resistance on fractional flow reserve after successful percutaneous coronary intervention.
abstract: OBJECTIVE
  Increased microvascular resistance may impair hyperemic coronary flow by limiting the maximal and constant vasodilation, resulting in increased fractional flow reserve (FFR) due to the underestimation of the translesional pressure gradient. We examined whether microvascular resistance affects FFR after successful percutaneous coronary intervention (PCI).
  
  
  RESULTS
  We measured FFR and the index of microcirculatory resistance (IMR) in 104 coronary arteries of 98 patients after successful elective stenting. FFR values were compared according to the quartiles of the IMR values. Coronary flow was assessed using the hyperemic mean transit time (Tmn ). The IMR values for the interquartile ranges of 8.5-11.3, 13.9-16.3, 20.9-24.5, and 34.2-61.6 were 10.2, 15.1, 22.8, and 38.2, respectively. Both FFR and Tmn values differed significantly across the IMR quartiles (P < 0.001). The angiographic and intravascular ultrasound findings and post-PCI cardiac troponin levels showed no significant difference across the IMR quartiles. Multivariate logistic regression analysis revealed that the left anterior descending artery lesion location (odds ratio [OR] 0.17, 95% confidence interval [CI] 0.06-0.49, P = 0.001), IMR (OR 1.05, 95% CI 1.01-1.09, P = 0.012), and minimal cross-sectional lumen area (OR 1.49, 95% CI 1.03-2.17, P = 0.036) were independent predictors of increased FFR.
  
  
  CONCLUSIONS
  Increased microvascular resistance may reduce coronary flow and increase FFR after successful elective PCI.
authors.affiliation: Department of Cardiology, Tsuchiura Kyodo General Hospital, Tsuchiura, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Murai
authors.forename: Tetsumin
authors.initials: T
authors.lastname: Lee
authors.forename: Taishi
authors.initials: T
authors.lastname: Yonetsu
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Isobe
authors.forename: Tsunekazu
authors.initials: T
authors.lastname: Kakuta
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D016009:Chi-Square Distribution; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D007564:Japan; D016015:Logistic Models; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D062645:Percutaneous Coronary Intervention / Q000009:adverse effects / Q000295:instrumentation; D012189:Retrospective Studies; D012307:Risk Factors; D015607:Stents; D013997:Time Factors; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional; D014655:Vascular Resistance
keywords: coronary flow; coronary physiology; fractional flow reserve; microcirculation; percutaneous coronary intervention