title: The influence of prosthesis size and design on exercise dynamics after aortic valve replacement.
abstract: OBJECTIVE
  Residual gradient following aortic valve replacement (AVR) may adversely affect clinical outcome. The size and design of the valve may influence these characteristics. The study aim was to determine the influence of prosthesis physical size and leaflet design on hemodynamic performance after mechanical AVR.
  
  
  METHODS
  After AVR, two patient groups with a range of valve sizes were studied. Group 1 patients (n=19) each received a monoleaflet valve; group 2 patients (n=18) each received a bileaflet valve. Transthoracic echocardiography was performed at rest and after graded bicycle ergometry to assess prosthetic valve parameters, including mean and peak transvalvular gradient and effective orifice area (EOA).
  
  
  RESULTS
  Transprosthetic gradients (mean and peak) measured at rest, maximum exercise and 3-min recovery were related to indexed geometric orifice area (IGOA) by an exponential decay function, with no significant advantage for either valve design. However, in valve sizes < or =25 mm the bileaflet valves demonstrated lower gradients, both at rest and under exercise conditions (mean gradient during exercise, bileaflet versus monoleaflet 19.9 +/- 7.2 mmHg versus 25.6 +/- 6.3 mmHg, p = 0.01). Similarly, EOAs were larger in the bileaflet group when equivalent GOAs < or =2.5 cm2 were compared (EOA: bileaflet versus monoleaflet 1.51 +/- 0.33 cm2 versus 1.14 +/- 0.26 cm2, p = 0.018). The total work performed correlated with prosthesis diameter (r2 = 0.81, p = 0.037) and was not influenced by valve design.
  
  
  CONCLUSIONS
  The hemodynamic performance of mechanical aortic valves, including transprosthetic gradient and maximum exercise work performed, related principally to the prosthesis physical size. However, within the smaller valve sizes, the bileaflet design appeared to offer hemodynamic advantages.
authors.affiliation: Departments of Cardiac Surgery, Royal Victoria Hospital, Belfast, Northern Ireland.
authors.forename: Niaz F
authors.initials: NF
authors.lastname: Ali
authors.forename: Vinod S
authors.initials: VS
authors.lastname: Mahadevan
authors.forename: Andrew
authors.initials: A
authors.lastname: Muir
authors.forename: Christine
authors.initials: C
authors.lastname: Maguire
authors.forename: David
authors.initials: D
authors.lastname: Young
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Campalani
authors.forename: Norman P S
authors.initials: NP
authors.lastname: Campbell
authors.forename: Mark H D
authors.initials: MH
authors.lastname: Danton
mesh_terms: D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000601:surgery*; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D004452:Echocardiography; D019544:Equipment Failure Analysis; D005080:Exercise Test; D006350:Heart Valve Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D016896:Treatment Outcome