title: Coronary Flow Velocity Reserve Assessed by Transthoracic Doppler: The iPOWER Study: Factors Influencing Feasibility and Quality.
abstract: Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography is a noninvasive measure of microvascular function, but it has not achieved widespread use, mainly because of concerns of validity and feasibility. The aim of this study was to describe the feasibility and factors associated with the quality of CFVR obtained in a large prospective study of women suspected of having microvascular disease.
  
  
  
  Women with angina-like chest pain and no obstructive coronary artery disease on coronary angiography (<50% stenosis) were consecutively examined by transthoracic Doppler echocardiography of the left anterior descending coronary artery to measure CFVR (n = 947). Quality was evaluated on the basis of (1) identification of the left anterior descending coronary artery, (2) maintained probe position throughout the examination, (3) visibility and configuration of the left anterior descending coronary artery in two-dimensional color Doppler mode, and (4) gradual, consistent increases of characteristic, well-defined flow velocity curves in pulsed-wave mode.
  
  
  
  The mean age (SD) was 62.1 ± 9.7 years. On the basis of the evaluations, patients were divided into four groups according to quality score: nonfeasible (n = 28 [3%]), low quality (n = 80 [8%]), medium quality (n = 451 [48%]), and high quality (n = 388 [41%]). Quality score was associated with diabetes (P < .01), body mass index (P = .02), waist circumference (P = .05), nonsignificant atherosclerosis on coronary angiography (P = .03), and operator experience (P < .01). Low examination quality was associated with lower CFVR (P = .03), also after multivariate adjustment.
  
  
  
  Transthoracic Doppler echocardiographic measurement of CFVR is highly feasible and of good quality in experienced hands. However, CFVR is possibly underestimated when examination quality is low. Awareness of pitfalls and potential bias may improve the validity and interpretation of the measures obtained.
authors.affiliation: Department of Cardiology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. Electronic address: marie.mide.michelsen@regionh.dk.
authors.forename: Marie M
authors.initials: MM
authors.lastname: Michelsen
authors.affiliation: Department of Cardiology, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Adam
authors.initials: A
authors.lastname: Pena
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Naja D
authors.initials: ND
authors.lastname: Mygind
authors.affiliation: Department of Cardiology, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Daria
authors.initials: D
authors.lastname: Frestad
authors.affiliation: Department of Cardiology, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Ida
authors.initials: I
authors.lastname: Gustafsson
authors.affiliation: Department of Cardiology, Odense University Hospital, Odense, Denmark.
authors.forename: Henrik S
authors.initials: HS
authors.lastname: Hansen
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Kastrup
authors.affiliation: Department of Cardiology, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Bech
authors.affiliation: Department of Cardiology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Nis
authors.initials: N
authors.lastname: Høst
authors.affiliation: Department of Cardiology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva
authors.initials: E
authors.lastname: Prescott
mesh_terms: D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D004452:Echocardiography / Q000379:methods* / Q000592:standards; D015150:Echocardiography, Doppler / Q000379:methods* / Q000592:standards; D005240:Feasibility Studies; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods* / Q000592:standards; D008875:Middle Aged; D015588:Observer Variation; D011785:Quality Assurance, Health Care; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Coronary flow velocity reserve; Coronary microvascular function; Feasibility; Quality; Transthoracic Doppler echocardiography