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

Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

“…Recognition of phenomena associated with the fatigue properties of particular materials will allow sensor researchers and manufacturers to choose materials that best suit the purpose of their particular sensor. Additionally, the development of standards for the fatigue testing of wearable sensors [40,74,187] is needed and will allow for consistent reporting of testing methodologies and output. The development of standards will ultimately improve the ability of researchers, manufacturers, health professionals, and consumers to perform head-to-head comparisons of wearable sensing technologies.…”

“…Liu et al [ 73 ] found that the stresses placed on the lead in vivo could be determined by applying classic mechanical principles to a model created from 3D images rendered from angiograms and argue that this method can facilitate fatigue-life predictions of the leads. Recently, due to the ongoing high incidence of failure, standard protocols for the fatigue testing of ICD leads have been proposed [ 74 ]. The proposed method involves the application of a buckling or a bending force at a rate of 5 Hz to 12 samples per four curvature amplitudes of 0.78 cm −1 , 1.11 cm −1 , 2.12 cm −1 , and 2.45 cm −1 ( n = 48).…”

In vitro modeling accurately predicts cardiac lead fracture at 10 years

“…Fatigue data consists of a bending stress level and the number of cycles to fracture at that stress level. Our bench test for lead fatigue strength has been described previously 12,13,18,19 and is designed to replicate the millions of bending cycles a lead may experience over a 10 year timeframe for the patient (Figure 2, supplementary video). This allows us to determine how long a lead can survive without fracture.…”

“…The modeling framework used for fracture free survival was based on Monte Carlo simulation methods, previously described in detail in 12,18 . Briefly, individual patients were J o u r n a l P r e -p r o o f simulated to have a random lead curvature, activity level, and lead fatigue strength, all from random distributions based on clinical and bench measurements described above.…”

“…Pre-market human clinical studies are an important source of evidence, but there is value in identifying a potentially unreliable lead even before the first human implant. Recently, advances have been made in engineering methods for preclinical evaluation of conductor fracture on the bench 13,17 including predictive models for fracture free survival in a population 12,18 based on incorporation of in vivo use conditions 16 . This approach is currently being used in the development of a new standard for lead conductor fractures developed through the Association for the Advancement of Medical Instrumentation Cardiac Rhythm Management Device Committee 19 .…”