Transcatheter aortic valves inadequately relieve stenosis in small degenerated bioprostheses.

Objectives: Transcatheter aortic valves (TAVs) are a promising treatment for high risk surgical patients suffering from degeneration of previously implanted bioprostheses (valve-in-valve therapy). However, unlike native stenosed aortic valves which have accommodated Edwards SAPIEN transcatheter valves after valvuloplasty, rigid bioprostheses may prevent full TAV stent expansion and disrupt leaflet function. We hypothesized that current 23 mm TAVs would not completely relieve severe stenosis in small bioprosthetic valves. The objective of this study was to study the hemodynamics of TAVs in degenerated bioprostheses.

Methods: Twelve TAVs designed to mimic the 23 mm SAPIEN valve were created. Using a pulse duplicator, hemodynamics of valve-in-valve implantation were measured within 19, 21, and 23 mm Carpentier-Edwards PERIMOUNT degenerated bioprostheses (n=6 each). Bioprosthetic degeneration was simulated using BioGlue to achieve a mean pressure gradient of 50 mmHg.

Results: TAVs significantly reduced the mean pressure gradient (50.9+/-4.7-9.1+/-4.1 mmHg, P<0.001) and total energy loss (870.3+/-157.4-307.8+/-87.3 mJ, P<0.001) in 23 mm degenerated bioprostheses. In 21 mm bioprostheses, the pressure gradient (52.3+/-7.0-19.5+/-5.0 mmHg, P<0.001) and energy loss (785.5+/-128.1-477.8+/-123.2 mJ, P=0.007) were reduced significantly. However, no significant changes in the pressure gradient (57.1+/-4.3-46.5+/-9.3 mmHg, P=0.086) or energy loss (839.3+/-49.3-960.5+/-158.1 mJ, P=0.144) were obtained after TAVI implantation in 19 mm bioprostheses. Incomplete stent expansion resulted in leaflet distortion and central regurgitation when implanted in 19 and 21 mm bioprostheses.

Conclusions: The bioprosthetic annulus and stent posts offered a suitable landing zone for TAVs. However, oversized transcatheter valves were constrained by the rigid bioprostheses resulting in inadequate resolution of bioprosthetic stenosis. Hemodynamics of valve-in-valve intervention was worse than comparable size surgical valve replacements, particularly in 19 and 21 mm valves. Small degenerated bioprostheses require modification of current TAV design to yield acceptable hemodynamics.