title: Transthoracic Doppler echocardiography compared with positron emission tomography for assessment of coronary microvascular dysfunction: The iPOWER study.
abstract: BACKGROUND
  Coronary microvascular function can be assessed by transthoracic Doppler echocardiography as a coronary flow velocity reserve (TTDE CFVR) and by positron emission tomography as a myocardial blood flow reserve (PET MBFR). PET MBFR is regarded the noninvasive reference standard for measuring coronary microvascular function but has limited availability. We compared TTDE CFVR with PET MBFR in women with angina pectoris and no obstructive coronary artery disease and assessed repeatability of TTDE CFVR.
  
  
  METHODS
  From a cohort of women with angina and no obstructive coronary artery stenosis at invasive coronary angiography, TTDE CFVR by dipyridamole induced stress and MBFR by rubidium-82 PET with adenosine was successfully measured in 107 subjects. Repeatability of TTDE CFVR was assessed in 10 symptomatic women and in 10 healthy individuals.
  
  
  RESULTS
  MBFR was systematically higher than CFVR. Median MBFR (interquartile range, IQR) was 2.68 (2.29-3.10) and CFVR (IQR) was 2.31 (1.89-2.72). Pearson's correlation coefficient was 0.36 (p<0.01). Limits of agreement (2·standard deviation) assessed by the Bland-Altman (confidence interval, CI) method was 1.49 (1.29;1.69) and unaffected by time-interval between examinations. Results were similar when adjusting for rate pressure product or focusing on perfusion of the left anterior descending artery region. Limits of agreement (CI) for repeated CFVR in 10 healthy individuals and in 10 women with angina was 0.44 (0.21;0.68) and 0.48 (0.22; 0.74), respectively.
  
  
  CONCLUSIONS
  CFVR had a good repeatability, but the agreement between CFVR and MBFR was modest. Divergence could be due to methodology differences; TTDE estimates flow velocities whereas PET estimates myocardial blood flow.
authors.affiliation: Department of Cardiology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. Electronic address: marie.mide.michelsen@regionh.dk.
authors.forename: Marie Mide
authors.initials: MM
authors.lastname: Michelsen
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Naja Dam
authors.initials: ND
authors.lastname: Mygind
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, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Rasmus Huan
authors.initials: RH
authors.lastname: Olsen
authors.affiliation: Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas Emil
authors.initials: TE
authors.lastname: Christensen
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark.
authors.forename: Adam Ali
authors.initials: AA
authors.lastname: Ghotbi
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark.
authors.forename: Philip
authors.initials: P
authors.lastname: Hasbak
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kjaer
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, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Peter Riis
authors.initials: PR
authors.lastname: Hansen
authors.affiliation: Department of Cardiology, Odense University Hospital, University of Southern Denmark, Denmark.
authors.forename: Henrik Steen
authors.initials: HS
authors.lastname: Hansen
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, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Kastrup
authors.affiliation: Department of Cardiology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva
authors.initials: E
authors.lastname: Prescott
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000503:physiopathology; D018618:Echocardiography, Doppler, Color / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017566:Microvascular Angina / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D012189:Retrospective Studies
keywords: Coronary flow velocity reserve; Microvascular angina pectoris; Myocardial blood flow; Myocardial blood flow reserve; Repeatability; Reproducibility