title: Attenuation of reflected waves in man during retrograde propagation from femoral artery to proximal aorta.
abstract: BACKGROUND
  Wave reflection may be an important influence on blood pressure, but the extent to which reflections undergo attenuation during retrograde propagation has not been studied. We quantified retrograde transmission of a reflected wave created by occlusion of the left femoral artery in man.
  
  
  METHODS
  20 subjects (age 31-83 years; 14 male) underwent invasive measurement of pressure and flow velocity with a sensor-tipped intra-arterial wire at multiple locations distal to the proximal aorta before, during and following occlusion of the left femoral artery by thigh cuff inflation. A numerical model of the circulation was also used to predict reflected wave transmission. Wave reflection was measured as the ratio of backward to forward wave energy (WRI) and the ratio of peak backward to forward pressure (Pb/Pf).
  
  
  RESULTS
  Cuff inflation caused a marked reflection which was largest at 5-10 cm from the cuff (change (Δ) in WRI=0.50 (95% CI 0.38, 0.62); p<0.001, ΔPb/Pf=0.23 (0.18-0.29); p<0.001). The magnitude of the cuff-induced reflection decreased progressively at more proximal locations and was barely discernible at sites>40 cm from the cuff including in the proximal aorta. Numerical modelling gave similar predictions to those observed experimentally.
  
  
  CONCLUSIONS
  Reflections due to femoral artery occlusion are markedly attenuated by the time they reach the proximal aorta. This is due to impedance mismatches of bifurcations traversed in the backward direction. This degree of attenuation is inconsistent with the idea of a large discrete reflected wave arising from the lower limb and propagating back into the aorta.
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK; Cardiovascular Biomedical Research Unit, Royal Brompton Hospital and Imperial College London, London, UK.
authors.forename: A John
authors.initials: AJ
authors.lastname: Baksi
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Nearchos
authors.initials: N
authors.lastname: Hadjiloizou
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Resham
authors.initials: R
authors.lastname: Baruah
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Beth
authors.initials: B
authors.lastname: Unsworth
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Foale
authors.affiliation: Department of Bioengineering, Imperial College London, UK.
authors.forename: Olga
authors.initials: O
authors.lastname: Korolkova
authors.affiliation: Department of Bioengineering, Imperial College London, UK.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Siggers
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, & Imperial College Healthcare NHS Trust, UK.
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.affiliation: Department of Bioengineering, Imperial College London, UK.
authors.forename: Kim H
authors.initials: KH
authors.lastname: Parker
authors.affiliation: Institute of Cardiovascular Sciences, University College London, London WC1E 6BT, UK. Electronic address: alun.hughes@ucl.ac.uk.
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
mesh_terms: D000368:Aged; D001011:Aorta / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001795:Blood Pressure Determination; D017023:Coronary Angiography / Q000379:methods; D005260:Female; D005263:Femoral Artery / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009716:Numerical Analysis, Computer-Assisted / Q000295:instrumentation; D011150:Popliteal Artery / Q000000981:diagnostic imaging; D063177:Pulse Wave Analysis / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology; D013848:Thigh / Q000098:blood supply* / Q000502:physiology; D018608:Ultrasonography, Doppler / Q000379:methods
keywords: Blood pressure; Hemodynamics; Wave reflection