CM&S Innovators Circle: Credible Modeling for Cardiovascular Device Fatigue Assessment

Fatigue evaluation of implantable cardiovascular devices conventionally uses demonstration testing (or “test-to-success”), in which full devices must survive a prescribed number of cycles under representative physiological loading. Survival establishes that the device meets a reliability requirement but provides no information about its proximity to fracture.

The ASTM F3211 fatigue-to-fracture (FtF) methodology augments demonstration testing by loading specimens at hyper-physiological conditions to induce fractures across a range of strain amplitudes. The resulting fracture and run-out data are used to construct a device-specific strain-life diagram. Finite element analysis (FEA) is critical to both approaches.

When surrogates or coupons are used in place of full devices, FEA provides evidence that the strain distribution in the specimen matches that in the device under the relevant loading. FEA additionally guides selection of FtF test levels that produce clinically relevant fractures within a practical number of cycles. It is also used to predict the device strain amplitude at worst-case physiological conditions, which is combined with the strain-life diagram from FtF to calculate the fatigue safety factor. Given this reliance on FEA, credible computational models are required for fatigue evaluation of cardiovascular devices.

This CM&S Innovators Circle will describe research to advance the use of credible computational modeling and simulation (CM&S) for fatigue assessment of cardiovascular devices. The session will begin by introducing a collaborative project applying FtF and FEA to evaluate the fatigue resistance of an implantable nitinol inferior vena cava filter. The approach uses device surrogates that reproduce the strain distribution in the fatigue-prone fillet region of the device. The project is establishing the credibility of the FEA through rigorous verification, validation, and uncertainty quantification following ASME V&V 40 and the FDA CM&S Credibility Guidance.

This combined approach yields a prediction of the fatigue safety factor with an uncertainty estimate that accounts for input uncertainty from material properties and manufacturing tolerances, numerical uncertainty from discretization error, and model form uncertainty quantified by a validation metric. Taken together, this work provides an end-to-end example of how credible CM&S can be used to support fatigue assessment of a cardiovascular device in a regulatory application.