title: Effect of Sex Differences on Invasive Measures of Coronary Microvascular Dysfunction in Patients With Angina in the Absence of Obstructive Coronary Artery Disease.
abstract: OBJECTIVE
  This study investigated sex differences in coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients with angina in the absence of obstructive coronary artery disease.
  
  
  BACKGROUND
  Coronary microvascular dysfunction is associated with worse long-term outcomes, especially in women. Coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) are 2 methods of assessing the coronary microcirculation.
  
  
  METHODS
  We prospectively enrolled 117 women and 40 men with angina in the absence of obstructive coronary artery disease. We performed CFR, IMR, fractional flow reserve, and quantitative coronary angiography in the left anterior descending artery. Coronary flow was assessed with a thermodilution method by obtaining mean transit time (Tmn) (an inverse correlate to absolute flow) at rest and hyperemia.
  
  
  RESULTS
  All patients had minimal atherosclerosis by quantitative coronary angiography (% diameter stenosis: 23.2 ± 12.3%), and epicardial disease was milder in women (fractional flow reserve: 0.88 ± 0.04 vs. 0.87 ± 0.04; p = 0.04). IMR was similar between the sexes (20.7 ± 9.8 vs. 19.1 ± 8.0; p = 0.45), but CFR was lower in women (3.8 ± 1.6 vs. 4.8 ± 1.9; p = 0.004). This was primarily due to a shorter resting Tmn in women (p = 0.005), suggesting increased resting coronary flow, whereas hyperemic Tmn was identical (p = 0.79). In multivariable analysis, female sex was an independent predictor of lower CFR and shorter resting Tmn.
  
  
  CONCLUSIONS
  Despite similar microvascular function in women and men by IMR, CFR is lower in women. This discrepancy appears to be due to differences in resting coronary flow between the sexes. The effect of sex differences should be considered in interpretation of physiological indexes using resting coronary flow.
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: William F
authors.initials: WF
authors.lastname: Fearon
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Honda
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Shigemitsu
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Vedant
authors.initials: V
authors.lastname: Pargaonkar
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Fitzgerald
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: David P
authors.initials: DP
authors.lastname: Lee
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Marcia
authors.initials: M
authors.lastname: Stefanick
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Yeung
authors.affiliation: Stanford Cardiovascular Institute and Stanford University Medical Center, Stanford, California. Electronic address: jtremmel@stanford.edu.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Tremmel
mesh_terms: D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000175:diagnosis / Q000503:physiopathology*; D006328:Cardiac Catheterization; D016009:Chi-Square Distribution; D017023:Coronary Angiography; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D054624:Health Status Disparities; D006801:Humans; D008297:Male; D008833:Microcirculation; D055806:Microvessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012737:Sex Factors; D013815:Thermodilution; D018084:Ultrasonography, Interventional; D014655:Vascular Resistance
keywords: coronary flow reserve; coronary microvascular resistance; physiology; sex