An evaluation of prosthetic aortic valves using transesophageal echocardiography: The double-envelope technique

The conventional continuity equation uses nonsimultaneous measurements of b lood flow velocities through the left ventricular outflow tract and across the aortic valve to calculate aortic valve area (AVA). We have noted that b oth velocities can be simultaneously obtained from continuous wave (CW) Dop pler analysis (double-envelope [DE]). We hypothesize that prosthetic AVA ca n be calculated by using the DE technique, during transesophageal echocardi ography (TEE). Prosthetic AVA was calculated in 41 of 45 patients immediate ly after aortic valve replacement by using the DE/AVA technique. Left ventr icular outflow tract diameter was obtained from an esophageal view, while s ubvalvular (V-1) and valvular (V-2) peak velocities were simultaneously obt ained from transgastric views by using CW Doppler. Prosthetic AVA and V-1/V -2 ratio (Doppler velocity index) were calculated. V-1 was also measured by using pulse wave Doppler, as is conventionally done. Twenty-three Carbomed ic (CM) and 18 Carpentier-Edwards (CE) AVA were evaluated. DE/AVAs for CM a nd CE valves correlated and agreed with that reported by the manufacturer ( CM r(2) = 0.91, mean bias -0.25 cm(2) [SD 0.18]; CE r(2) = 0.73, mean bias -0.02 cm(2) [SD 0.27]). Calculated Doppler velocity index values agree with available data (mean bias 0.03 [SD 0.05]). The V-1 obtained by using the D E method was nearly identical to the V-1 obtained by using pulse wave (r(2) = 0.95, mean bias 0.02 m/s [SD 0.04 m/s]). TEE assessment of prosthetic AV A using the DE technique agrees with data reported by the manufacturer. Obt aining subvalvular and valvular velocities from the same CW Doppler trace m ay simplify the continuity equation and help avoid errors caused by beat-to -beat changes in blood flow. Quantitative prosthetic aortic valve assessmen t can be performed, on-line, with TEE by using the DE technique.