title: Feasibility of cardiovascular magnetic resonance derived coronary wave intensity analysis.
abstract: BACKGROUND
  Wave intensity analysis (WIA) of the coronary arteries allows description of the predominant mechanisms influencing coronary flow over the cardiac cycle. The data are traditionally derived from pressure and velocity changes measured invasively in the coronary artery. Cardiovascular magnetic resonance (CMR) allows measurement of coronary velocities using phase velocity mapping and derivation of central aortic pressure from aortic distension. We assessed the feasibility of WIA of the coronary arteries using CMR and compared this to invasive data.
  
  
  METHODS
  CMR scans were undertaken in a serial cohort of patients who had undergone invasive WIA. Velocity maps were acquired in the proximal left anterior descending and proximal right coronary artery using a retrospectively-gated breath-hold spiral phase velocity mapping sequence with high temporal resolution (19 ms). A breath-hold segmented gradient echo sequence was used to acquire through-plane cross sectional area changes in the proximal ascending aorta which were used as a surrogate of an aortic pressure waveform after calibration with brachial blood pressure measured with a sphygmomanometer. CMR-derived aortic pressures and CMR-measured velocities were used to derive wave intensity. The CMR-derived wave intensities were compared to invasive data in 12 coronary arteries (8 left, 4 right). Waves were presented as absolute values and as a % of total wave intensity. Intra-study reproducibility of invasive and non-invasive WIA was assessed using Bland-Altman analysis and the intraclass correlation coefficient (ICC).
  
  
  RESULTS
  The combination of the CMR-derived pressure and velocity data produced the expected pattern of forward and backward compression and expansion waves. The intra-study reproducibility of the CMR derived wave intensities as a % of the total wave intensity (mean ± standard deviation of differences) was 0.0 ± 6.8%, ICC = 0.91. Intra-study reproducibility for the corresponding invasive data was 0.0 ± 4.4%, ICC = 0.96. The invasive and CMR studies showed reasonable correlation (r = 0.73) with a mean difference of 0.0 ± 11.5%.
  
  
  CONCLUSIONS
  This proof of concept study demonstrated that CMR may be used to perform coronary WIA non-invasively with reasonable reproducibility compared to invasive WIA. The technique potentially allows WIA to be performed in a wider range of patients and pathologies than those who can be studied invasively.
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK. c.raphael@rbht.nhs.uk.|Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK. c.raphael@rbht.nhs.uk.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Raphael
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keegan
authors.affiliation: Department of Bioengineering, Imperial College, London, UK.
authors.forename: Kim H
authors.initials: KH
authors.lastname: Parker
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Simpson
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: Collinson
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Vass
authors.initials: V
authors.lastname: Vassiliou
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Wage
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Drivas
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Strain
authors.affiliation: Liverpool Heart and Chest Hospital, Imperial College Medical School, Liverpool, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Cooper
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Ranil
authors.initials: R
authors.lastname: de Silva
authors.affiliation: Liverpool Heart and Chest Hospital, Imperial College Medical School, Liverpool, UK.
authors.forename: Rod H
authors.initials: RH
authors.lastname: Stables
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Carlo
authors.initials: C
authors.lastname: Di Mario
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Frenneaux
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Dudley J
authors.initials: DJ
authors.lastname: Pennell
authors.affiliation: International Center for Circulatory Health, Imperial College, London, UK.
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
authors.affiliation: Institute of Cardiovascular Science, Faculty of Population Health Sciences, University College London, London, UK.
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Firmin
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Prasad
mesh_terms: D000328:Adult; D001011:Aorta / Q000000981:diagnostic imaging / Q000503:physiopathology; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D062485:Breath Holding; D002138:Calibration; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004739:England; D005240:Feasibility Studies; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results