The nitinol stent mitral valve implant presents a little-studied failure mode: low-cycle fatigue fracture of a stent post. This phenomenon is related to incomplete expansion of the device during deployment. The analysis of this case has been approached with a 3D pipeline that integrates Materialise Mimics for image segmentation and Ansys for finite element simulations, seeking the mechanical causes of the failure.
3D Pipeline: Segmentation and simulation of structural failure 🔧
The process begins with Materialise Mimics, where the geometry of the stent and surrounding anatomy is reconstructed from CT scans. The model is exported to Ansys for a structural analysis that simulates the cyclic loads of the cardiac cycle. The incomplete expansion condition generates localized stress concentrations at the base of the fractured post. The simulations show that the accumulated plastic deformation, characteristic of low-cycle fatigue, exceeds the material's limit with each heartbeat, leading to premature fracture.
The post that said enough before its time 💥
Sometimes, you think nitinol is a miracle material that never gets tired. But it turns out that if you don't expand it properly, it takes a permanent break. It's like trying to force an umbrella into its case with a hammer: something is going to bend wrong. Low-cycle fatigue doesn't forgive, and the stent post expressed this by fracturing. At least, the failure gave us a perfect excuse to play with Mimics and Ansys, which is more fun than explaining to the patient that their valve said no.