Test to Fracture of Cardiac Lead Coils in Unidirectional Bending Fatigue

Abstract

Transvenous cardiac leads are a key element of implanted pacing and defibrillation systems, providing the electrical connection between a programmable generator and the heart. Along their pathway, these thin flexible structures are subjected to cyclic in-vivo motion and deformation resulting from patient cardiac contraction, respiration, and arm motion. Medical imaging techniques such as biplane fluoroscopy have shown the in-vivo deformation to be primarily unidirectional cyclic bending.1,2

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.…”

“…In the case of the Fidelis, it has been proposed that the lead fractures J o u r n a l P r e -p r o o f are related to the lead's high flexibility which causes more bending, along with design factors that cause lower fatigue strength 7 . However, there are few published engineering reliability analyses quantifying these factors, and fewer still in the clinical literature [12][13][14][15][16] .…”

“…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 .…”

In silico assessment of biomedical products: The conundrum of rare but not so rare events in two case studies

“…The statistical framework leverages FDA guidance for the use of Bayesian statistics in medical device clinical trials 104 . This approach can have benefits of decreased sample size and trial length while minimizing impact to study endpoints, type I error, and type II error.…”

“…Recent advances in test methods, numerical simulation, and in-vivo imaging have enabled more thorough methods of cardiac lead fracture analysis 103,104 . A Bayesian Network methodology has been developed that integrates in-vivo measurements of device loading with in-vitro measurements of fatigue strength to simulate fatigue lifetime 105 .…”