title: Pressure recovery in aortic stenosis: an in vitro study in a pulsatile flow model.
abstract: OBJECTIVE
  This study was designed to study pressure recovery in various models of aortic valve stenosis by performing hemodynamic measurements under physiologic conditions in a pulsatile aortic flow circuit. The results were used to validate calculations of pressure recovery based on theoretic considerations derived from fluid dynamics.
  
  
  BACKGROUND
  Pressure recovery in aortic stenosis has not been systematically analyzed.
  
  
  METHODS
  Stenoses varying in size, shape (circular, Y-shaped, slitlike) and inlet configuration (sharp-edged, nozzle-shaped inlet, artificially stenosed bioprostheses) were used. Aortic pressures were measured at multiple sites distal to the stenotic orifice to determine pressure gradients and recovery.
  
  
  RESULTS
  With decreasing orifice area (2, 1.5, 1 and 0.5 cm2) pressure recovery increased (5, 7, 10 and 16 mm Hg, respectively) and the index pressure recovery to maximal peak to peak gradient decreased (56%, 37%, 24% and 14%, respectively). For a given orifice size of 0.5 cm2, this index ranged between 12% for a Y-shaped orifice and 15% for a circular orifice with a nozzle (cardiac output 4 liters/min). Increasing the cardiac output increased pressure recovery, whereas the ratio of pressure recovery to maximal pressure gradient remained constant.
  
  
  CONCLUSIONS
  The index pressure recovery to transvalvular pressure gradient, which expresses the hemodynamic relevance of pressure recovery, decreases with increasing severity of aortic stenosis but is independent of transvalvular flow. Thus, pressure recovery is of minor importance in severe aortic stenosis but may account for discrepancies between Doppler and manometric gradients observed in patients with mild to moderate aortic stenosis or a prosthetic valve in the aortic position.
authors.affiliation: Helmholtz Institute for Biomechanical Engineering Aachen University of Technology, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Voelker
authors.forename: H
authors.initials: H
authors.lastname: Reul
authors.forename: T
authors.initials: T
authors.lastname: Stelzer
authors.forename: A
authors.initials: A
authors.lastname: Schmidt
authors.forename: K R
authors.initials: KR
authors.lastname: Karsch
mesh_terms: D001024:Aortic Valve Stenosis / Q000473:pathology / Q000503:physiopathology*; D001705:Bioprosthesis / Q000592:standards; D001794:Blood Pressure; D015150:Echocardiography, Doppler; D005069:Evaluation Studies as Topic; D006350:Heart Valve Prosthesis / Q000592:standards; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D015203:Reproducibility of Results; D012720:Severity of Illness Index