Validation and Characterization of Transcatheter Aortic Valve Effective Orifice Area Measured by Doppler Echocardiography
OBJECTIVES: The objectives were to compare different Doppler echocardiographic methods for the measurement of prosthetic valve effective orifice area (EOA) following transcatheter aortic valve implantation (TAVI) and to determine the factors influencing the EOA of transcatheter balloon expandable valves. Previous studies have used different methods for the measurement of the valve EOA following TAVI. Factors influencing
the EOA of transcatheter valves are unknown.
METHODS: A total of 122 patients underwent TAVI with the use of the Edwards-SAPIEN valve (Edwards Lifesciences, Irvine, California). The EOA was measured by transthoracic echocardiography at hospital discharge, 6 months and 1 year after TAVI with the use of 2 methods as described in previous studies. In Method #1 (EOA(1)), LVOT diameter (LVOTd) entered in the continuity equation was measured at the base of prosthesis cusps whereas, in Method #2 (EOA(2)), LVOTd was measured immediately proximal to the prosthesis stent.
RESULTS: The average EOA(2) (1.57 ± 0.41 cm(2)) was larger (p < 0.01) than the EOA(1) (1.21 ± 0.38 cm(2)). Accordingly, incidence of severe PPM (indexed EOA ≤0.65 cm(2)/m(2)) was 3-fold lower with the use of EOA(2) than with EOA(1) (9% vs. 33%; p < 0.001). Mean transprosthetic gradient correlated better (p = 0.03) with indexed EOA(2) (r = -0.70, p < 0.0001) than with indexed EOA(1) (r = -0.58, p < 0.0001). Intraobserver and interobserver variability were lower for EOA(2) compared to EOA(1) (intra: 5% vs. 7%, p = 0.06; inter: 6% vs. 14%; p < 0.001). Aortic annulus size was the sole independent determinant (p = 0.01) of prosthetic valve EOA(2). The average EOA varied from 1.37 ± 0.23 cm(2) for aortic annulus size <19 mm up to 1.90 ± 0.17 cm(2) for size >23 mm.
CONCLUSIONS: When estimating the EOA of Edwards-SAPIEN valves by Doppler-echocardiography, it is recommended to use the LVOT diameter and velocity measured immediately proximal to the stent. The main determinant of the EOA of transcatheter valves is the patient’s annulus size and these valves provide excellent hemodynamics even in patients with a small aortic annulus.
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