title: Invasive minimal Microvascular Resistance Is a New Index to Assess Microcirculatory Function Independent of Obstructive Coronary Artery Disease.
abstract: Coronary microcirculatory dysfunction portends a poor cardiovascular outcome. Invasive assessment of microcirculatory dysfunction by coronary flow reserve (CFR) and hyperemic microvascular resistance (HMR) is affected by coronary artery disease (CAD). In this study we propose minimal microvascular resistance (mMR) as a new measure of microcirculatory dysfunction and aim to determine whether mMR is influenced by CAD.
  
  
  
  We obtained 482 simultaneous measurements of intracoronary Doppler flow velocity and pressure. The mMR is defined as the ratio between distal coronary pressure and flow velocity during the hyperemic wave-free period. Measurements were divided into 2 cohorts. Cohort 1 was a paired analysis involving 81 pairs with a vessel with and without CAD to investigate whether HMR, CFR, and mMR are modulated by CAD. CFR was lower, and HMR was higher, in vessels with CAD than in vessels without CAD: 2.12±0.79 versus 2.56±0.63 mm Hg·cm-1·s, P<0.001, and 2.61±1.22 versus 2.31±0.89 mm Hg·cm-1·s, P=0.04, respectively. mMR was equal in vessels with and without CAD: 1.54±0.77 versus 1.53±0.57 mm Hg·cm-1·s, P=0.90. Differences for CFR occurred when FFR was 0.60 to 0.80 or ≤0.60 but not when FFR ≥0.80. For HMR, the difference occurred only when FFR ≤0.60. For mMR, no difference was observed in any FFR stratum. Cohort 2 was used for validation and showed significant relationships for CFR and HMR with FFR: Pearson r=0.488, P<0.001 and -0.159, P=0.03, respectively; mMR had no association with FFR: Pearson r=0.055; P=0.32.
  
  
  
  mMR is a novel index to assess microcirculatory dysfunction and is not modified by the presence of obstructive CAD.
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Guus A
authors.initials: GA
authors.lastname: de Waard
authors.affiliation: Imperial College London, London, United Kingdom.
authors.forename: Sukhjinder S
authors.initials: SS
authors.lastname: Nijjer
authors.affiliation: Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: Martijn A
authors.initials: MA
authors.lastname: van Lavieren
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Nina W
authors.initials: NW
authors.lastname: van der Hoeven
authors.affiliation: Imperial College London, London, United Kingdom.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Petraco
authors.affiliation: Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: Tim P
authors.initials: TP
authors.lastname: van de Hoef
authors.affiliation: Hospital General ISSSTE, Querétaro, México.
authors.forename: Mauro
authors.initials: M
authors.lastname: Echavarría-Pinto
authors.affiliation: Imperial College London, London, United Kingdom.
authors.forename: Sayan
authors.initials: S
authors.lastname: Sen
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Peter M
authors.initials: PM
authors.lastname: van de Ven
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Knaapen
authors.affiliation: Cardiovascular Institute, Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Escaned
authors.affiliation: Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Piek
authors.affiliation: Imperial College London, London, United Kingdom.
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands n.vanroyen@vumc.nl.
authors.forename: Niels
authors.initials: N
authors.lastname: van Royen
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D015331:Cohort Studies; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015150:Echocardiography, Doppler; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D014655:Vascular Resistance
keywords: coronary flow; microcirculation; microvascular dysfunction; resistance