title: Net pressure gradients in aortic prosthetic valves can be estimated by Doppler.
abstract: BACKGROUND
  In aortic prosthetic valves, both the Doppler-estimated gradients and orifice areas are misleading in the assessment of hemodynamic performance. The parameter of major interest is the net pressure gradient after pressure recovery (PR). We, therefore, investigated, in vitro, our ability to predict the net pressure gradient and applied the formulas in a representative patient population with 2 different valve designs.
  
  
  METHODS
  We studied the St Jude Medical (SJM) standard valve (size 19-27) and SJM Biocor (size 21-27) in an in vitro steady-flow model with simultaneous Doppler-estimated pressure and catheter pressure measurements. Using echocardiography, we also studied patients who received the SJM (n = 66) and SJM Biocor (n = 45).
  
  
  RESULTS
  In the SJM, we observed PR both within the prosthesis and aorta, whereas in the SJM Biocor, PR was only present in the aorta. We estimated the PR within the valve and within the aorta separately from echocardiographic in vitro data, combining a regression equation (valve) with an equation on the basis of fluid mechanics theory (aorta). The difference between estimated and catheter-obtained net gradients (mean +/- SD) was 0.6 +/- 1.6 mm Hg in the SJM and -0.2 +/- 1.9 mm Hg in the SJM Biocor. When these equations were applied in vivo, we found that PR had an overall value of 57 +/- 7% of the peak Doppler gradient in the SJM and 33 +/- 9% in the SJM Biocor.
  
  
  CONCLUSIONS
  The in vitro results indicate that it is possible to predict the net pressure gradient by Doppler in bileaflet and stented biologic valves. Our data indicate that important PR is also present in stented biologic valves.
authors.affiliation: Department of Clinical Physiology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. odd.bech-hanssen@vgregion.se
authors.forename: Odd
authors.initials: O
authors.lastname: Bech-Hanssen
authors.forename: Peter
authors.initials: P
authors.lastname: Gjertsson
authors.forename: Erik
authors.initials: E
authors.lastname: Houltz
authors.forename: Bengt
authors.initials: B
authors.lastname: Wranne
authors.forename: Per
authors.initials: P
authors.lastname: Ask
authors.forename: Dan
authors.initials: D
authors.lastname: Loyd
authors.forename: Kenneth
authors.initials: K
authors.lastname: Caidahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001011:Aorta / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002408:Catheters, Indwelling; D015150:Echocardiography, Doppler; D005260:Female; D006350:Heart Valve Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D020127:Recovery of Function / Q000502:physiology; D013223:Statistics as Topic; D016896:Treatment Outcome