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. (J Am Coll Cardiol Intv 2012;5:525-32) (C) 2012 by the American College of Cardiology Foundation