title: The aortic reservoir-wave as a paradigm for arterial haemodynamics: insights from three-dimensional fluid-structure interaction simulations in a model of aortic coarctation.
abstract: BACKGROUND
  The reservoir-wave paradigm considers aortic pressure as the superposition of a 'reservoir pressure', directly related to changes in reservoir volume, and an 'excess' component ascribed to wave dynamics. The change in reservoir pressure is assumed to be proportional to the difference between aortic inflow and outflow (i.e. aortic volume changes), an assumption that is virtually impossible to validate in vivo. The aim of this study is therefore to apply the reservoir-wave paradigm to aortic pressure and flow waves obtained from three-dimensional fluid-structure interaction simulations in a model of a normal aorta, aortic coarctation (narrowed descending aorta) and stented coarctation (stiff segment in descending aorta).
  
  
  RESULTS
  We found no unequivocal relation between the intraaortic volume and the reservoir pressure for any of the simulated cases. When plotted in a pressure-volume diagram, hysteresis loops are found that are looped in a clockwise way indicating that the reservoir pressure is lower than the pressure associated with the change in volume. The reservoir-wave analysis leads to very high excess pressures, especially for the coarctation models, but to surprisingly little changes of the reservoir component despite the impediment of the buffer capacity of the aorta.
  
  
  CONCLUSIONS
  With the observation that reservoir pressure is not related to the volume in the aortic reservoir in systole, an intrinsic assumption in the wave-reservoir concept is invalidated and, consequently, also the assumption that the excess pressure is the component of pressure that can be attributed to wave travel and reflection.
authors.affiliation: aIBiTech-bioMMeda, Department of Electronics and Information Systems, iMinds Medical IT bDepartment of Flow, Heat and Combustion Mechanics, Ghent University, Gent, Belgium *Patrick Segers and Liesbeth Taelman contributed equally to the writing of this article.
authors.forename: Patrick
authors.initials: P
authors.lastname: Segers
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Taelman
authors.forename: Joris
authors.initials: J
authors.lastname: Degroote
authors.forename: Joris
authors.initials: J
authors.lastname: Bols
authors.forename: Jan
authors.initials: J
authors.lastname: Vierendeels
mesh_terms: D001011:Aorta / Q000503:physiopathology*; D001017:Aortic Coarctation / Q000503:physiopathology*; D062186:Arterial Pressure / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular