Net pressure gradients in aortic prosthetic valves can be estimated by Doppler.
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.
Bech-Hanssen
Odd
O
Department of Clinical Physiology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. odd.bech-hanssen@vgregion.se
Gjertsson
Peter
P
Houltz
Erik
E
Wranne
Bengt
B
Ask
Per
P
Loyd
Dan
D
Caidahl
Kenneth
K
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