Flow characteristics of the SAPIEN aortic valve: the importance of recognizing in-stent flow acceleration for the echocardiographic assessment of valve function

Background: The percutaneously implanted Edwards SAPIEN valve (Edwards Lifesciences, Irvine, CA) consists of cusps mounted within a stent. The individual impact of the stent and cusps on transvalvular flow and its implications for the echocardiographic assessment of valve function have not been previously reported.

Methods: The study group consisted of 40 patients who underwent successful implantation with the SAPIEN valve. Pulsed Doppler was recorded with sample volumes immediately proximal to the stent (prestent), within the stent but proximal to the cusps (in-stent precusp), and distal to the cusps (in-stent postcusp). The Doppler velocity index and effective orifice area were calculated using both prestent and in-stent precusp velocities to represent "subvalvular" flow and continuous-wave recordings of the left ventricular outflow tract and aortic valve to represent postvalvular flow.

Results: In all patients, there was flow acceleration at two levels: in-stent precusp and in-stent postcusp. The mean in-stent precusp peak velocities were significantly higher than the prestent values (1.5 ± 0.2 vs 1.0 ± 0.2 m/sec, P < .0001). Effective orifice area and Doppler velocity index calculated using the prestent versus in-stent precusp velocities were also significantly different (1.79 ± 0.34 vs 2.54 ± 0.46 cm(2), P < .0001, and 0.48 ± 0.12 vs 0.73 ± 0.13, P < .0001, respectively).

Conclusions: The SAPIEN valve demonstrates flow acceleration at two levels, representing contributions of both the stent and valve cusps to the total valve gradient. Failure to recognize this phenomenon may result in inappropriate selection of the in-stent precusp pulsed Doppler spectrum to represent "subvalvular" flow, thereby overestimating the effective orifice area and Doppler velocity index.