The Reproducibility of a Proposed Standard Fatigue Test for Cardiac Device Leads
Timothy P. Quinn, Jolene D. Splett, Joseph D. McColskey, James Dawson, David Smith, Adam Himes, Daniel Cooke
The Transvenous Cardiac Leads Working Group of the Cardiac Rhythm Management Devices Committee of The Association for the Advancement of Medical Instrumentation (AAMI CRMD WG1) is developing a fatigue performance standard for cardiac device leads. The proposed standard would calculate a figure- of-merit that is based on a life prediction made from a Bayesian statistical model. The model uses distributions for bending fatigue strength, patient age, patient activity level, and in-vivo bending. The bench-top fatigue testing portion of the standard is based on the unsupported bending of the lead at multiple stress levels to generate fatigue fracture data in low-cycle and high-cycle regimes. To measure the inter-laboratory reproducibility of the bench-top testing methodology, a lead mock-up was constructed from a bi-filar MP35N coil in a thin-walled polyurethane tube. Four laboratories each tested 48 specimens and produced fatigue life curves based on the results. To compare the data, the figure-of-merit that is proposed for the standard was calculated using initial in- vivo curvature data of a well-performing lead. The standard deviation of the figure-of-merit across the four laboratories was less than 0.1%.