Doppler assessment of mechanical aortic valve prostheses: effect of valve design and size of the aorta.
OBJECTIVE
Discrepancies between Doppler and catheter gradients have been reported for bileaflet aortic valve prostheses. Whether modifications in geometric design of newly developed bileaflet valves lead to a different Doppler-catheter gradient relationship has not been evaluated. Variable results have been reported for tilting-disc prostheses. In addition, the effect of aortic size on the Doppler-catheter gradient relationship remains unclear.


METHODS
Various sizes of On-X and Edwards Mira (identical with Sorin Bicarbon) bileaflet valves and Sorin Allcarbon tilting-disc aortic valves (19-25 mm) were studied in a pulsatile flow model. Doppler and catheter gradients were measured simultaneously. Aortic diameters between 1.8 and 4 cm were evaluated.


RESULTS
Correlation between Doppler and catheter gradients was excellent (r = 0.98-0.99 for peak and mean gradients), but in bileaflet valves Doppler significantly overestimated the corresponding catheter gradients as reflected by slopes of the regression lines (1.57-1.8). In the range of relevant gradients > or = 10 mmHg, Doppler exceeded catheter gradients by 40 +/- 17% (peak) and 39 +/- 16% (mean) in Mira valves, and by 46 +/- 19% (peak) and 43 +/- 14% (mean) in On-X valves. In the Sorin tilting-disc valve, Doppler accurately reflected catheter gradients (slopes of regression lines 1.05-1.14). The aortic diameter significantly influenced results in only tilting-disc valves, but in absolute terms the effect was clinically less relevant.


CONCLUSIONS
Discrepancies between Doppler and catheter gradients are common to all bileaflet valves, regardless of their specific geometric design, whereas tilting-disc valves must be considered individually. The influence of aortic size on the Doppler-catheter gradient relationship appears clinically to be less relevant in prosthetic valves.
Department of Cardiology, University of Vienna , Vienna General Hospital, Austria.
Julia
J
Mascherbauer
Heinrich
H
Schima
Gerald
G
Maurer
Helmut
H
Baumgartner
D001011:Aorta; D001021:Aortic Valve; D001696:Biomechanical Phenomena; D001837:Body Weights and Measures; D006328:Cardiac Catheterization; D015150:Echocardiography, Doppler; D006350:Heart Valve Prosthesis; D006801:Humans; D008955:Models, Cardiovascular; D011312:Pressure; D011474:Prosthesis Design; D011673:Pulsatile Flow