Structural integrity of balloon-expandable stents after transcatheter aortic valve replacement: assessment by multidetector computed tomography.

OBJECTIVES: This study sought to evaluate the structural integrity of balloon-expandable stents used in transcatheter aortic valve replacement.
BACKGROUND: Underexpansion, deformation, or fracture of stent frames may affect transcatheter heart valve (THV) function and durability.
METHODS: Patients >1 year after transcatheter aortic valve replacement underwent multidetector computed tomography. Geometry of the stent frame was assessed for circularity; eccentricity; minimum and maximum external diameter; and expansion at the inflow, mid-stent, and outflow levels, as well as for stent fracture. THV noncircularity was defined as stent eccentricity >10% (1 - minimum diameter/maximum diameter) and THV underexpansion when expansion <90% (multidetector computed tomography derived external valve area/nominal external valve area). Echocardiography was performed after implantation and annually.
RESULTS: Fifty patients underwent multidetector computed tomography at an average of 2.5 ± 0.9 years after transcatheter aortic valve replacement (35 Sapien, 8 Sapien XT, and 7 Cribier-Edwards valves [all Edwards Lifesciences, Irvine, California). The mean external diameter for the 23- and 26-mm valves was 23.3 ± 0.9 mm and 25.9 ± 0.9 mm, respectively. Circularity was present in 96% (48 of 50) and median eccentricity was 2.0% (interquartile range: 1.2% to 3.0%). Mean THV expansion was 104.1 ± 7.4%, which increased from stent inflow to outflow (100.8 ± 7.6% vs. 108.1 ± 6.9%, p < 0.001). Stent fracture was not observed. Underexpanded valves (8% [4 of 50]) and noncircular valves (4% [2 of 50]) demonstrated stable hemodynamic function on annual echocardiography.
CONCLUSIONS: Balloon-expandable aortic valves have excellent rates of circularity with low eccentricity and maintain full expansion without stent fracture at an average 2.5 years after implantation.