The Reproducibility of a Proposed Standard Fatigue Test for Cardiac Device Leads

Abstract

The Transvenous Cardiac Leads Working Group of the Cardiac Rhythm Management Devices Committee of the Association for the Advancement of Medical Instrumentation is developing a fatigue performance standard for cardiac device leads. The proposed standard would calculate a figure-of-merit (FOM) that is based on a life prediction using a Bayesian framework. The framework uses distributions for bending fatigue strength, patient age, patient activity level, and in vivo bending. The benchtop fatigue testing portion of the standard is based on the unsupported bending of the lead at multiple alternating curvature levels to generate fatigue fracture data in low-cycle and high-cycle regimes. To estimate the interlaboratory reproducibility of the benchtop testing methodology, a lead mock-up was constructed from a bifilar 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 FOM Manuscript received May 2, 2018; accepted for publication July 24, 2018. National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, USA T. P. Q. http://orcid.org/0000-0001-7731-0128 Medtronic, 8200 Coral Sea St. NE, Mounds View, MN 55112, USA A. H. http://orcid.org/0000-0002-68834840 Boston Scientific, 4100 Hamline Ave. North, St. Paul, MN 55112, USA ASTM Fourth Symposium on Fatigue and Fracture of Metallic Medical Materials and Devices, on May 22–23, 2018 in San Diego, CA, USA This work is not subject to copyright law. ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. FOURTH SYMPOSIUM ON FATIGUE AND FRACTURE OF METALLIC MEDICAL MATERIALS AND DEVICES 85 STP 1616, 2019 / available online at www.astm.org / doi: 10.1520/STP161620180033 that is proposed for the standard was calculated using initial in vivo curvature data of a well-performing lead. The reproducibility standard deviation of the FOM across the four laboratories was 0.17 % of the grand mean.