  The rapid expansion of TAVR to younger, low-risk patients raises concerns
regarding device durability. Necessarily, extended stent lifetime will become
more critical for new generation devices. In vitro methods commonly used for
TAVR stent fatigue testing exclude the effects of the beating heart. We present
a more realistic in silico stent fatigue analysis utilizing a beating heart
model in which TAVR stents experience complex, nonuniform dynamic loading.
Virtual TAVR deployments were simulated in the SIMULIA Living Heart Human Model
of a beating heart using stent models of the self-expandable nitinol 26-mm
CoreValve and Evolut R devices, and a 27-mm PolyV-2. Stent deformation was
monitored over three cardiac cycles, and fatigue resistance was evaluated for
the nitinol stents using finite element analysis via ABAQUS/Explicit. In all
models, there were elements in which strains exceeded fatigue failure. The
PolyV-2 stent had far fewer failing elements since its struts were optimized to
reduce the strain in stent joints, achieving better fatigue resistance in the
stent crown and waist elements. Different stent sections showed markedly
different fatigue resistance due to the varying loading conditions. This study
demonstrates the utility of advanced in silico analysis of devices deployed
within a beating heart that mimics in vivo loading, offering a cost-effective
alternative to human or animal trials and establishing a platform to assess the
impact of device design on device durability. The limited fatigue life of TAVR
stents indicated here highlights a clinical complication that may eventually
develop as younger, lower-risk TAVR patients, age.
