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Li L, Jiang C, Wang H, Xie H, Li L. A mechanical analysis informed fractography study on load-specific fatigue behaviors of Pt-Ir coils used in implantable medical leads. J Mech Behav Biomed Mater 2021; 116:104364. [PMID: 33545415 DOI: 10.1016/j.jmbbm.2021.104364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/14/2021] [Accepted: 01/22/2021] [Indexed: 11/26/2022]
Abstract
Fatigue fracture is a major threaten to implantable medical coils such as platinum-iridium (Pt-Ir) coils used in deep brain stimulation leads. The fractography under bending and torsion fatigue was studied in comparison with mechanical analysis to grasp load-specific fatigue characteristics and understand the mechanisms. Mechanical analysis of the coil under bending and torsion was conducted with both analytical and numerical methods. Pt-Ir coils were experimentally fatigued at roughly paralleled bending and torsional load levels. The fatigue life was recorded and the fracture morphology was observed and analyzed. It is revealed that the helical structure of the coil turns bending and torsion loads into different locally distributed stresses, which mainly determine the fatigue behaviors. Features of fracture morphology, such as ratchet mark and fatigue striation, are identifiable to differentiate load types and stress levels. Both bending and torsion may play important roles in fatigue fractures of the coil. The study proposes an effective approach to study load-specific fatigue characteristics of medical coils which provides fundamental knowledge for medical lead design and clinical fracture diagnosis.
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Affiliation(s)
- Linze Li
- National Engineering Laboratory for Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China
| | - Changqing Jiang
- National Engineering Laboratory for Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China.
| | - Hanchen Wang
- National Engineering Laboratory for Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China
| | - Huimin Xie
- AML, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China
| | - Luming Li
- National Engineering Laboratory for Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China; Precision Medicine & Healthcare Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, 518071, China; IDG/McGovern Institute for Brain Research at Tsinghua University, Beijing, 100084, China; Institute of Epilepsy, Beijing Institute for Brain Disorders, Beijing, 100093, China.
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Viceconti M, Cobelli C, Haddad T, Himes A, Kovatchev B, Palmer M. In silico assessment of biomedical products: The conundrum of rare but not so rare events in two case studies. Proc Inst Mech Eng H 2017; 231:455-466. [PMID: 28427321 DOI: 10.1177/0954411917702931] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In silico clinical trials, defined as "The use of individualized computer simulation in the development or regulatory evaluation of a medicinal product, medical device, or medical intervention," have been proposed as a possible strategy to reduce the regulatory costs of innovation and the time to market for biomedical products. We review some of the the literature on this topic, focusing in particular on those applications where the current practice is recognized as inadequate, as for example, the detection of unexpected severe adverse events too rare to be detected in a clinical trial, but still likely enough to be of concern. We then describe with more details two case studies, two successful applications of in silico clinical trial approaches, one relative to the University of Virginia/Padova simulator that the Food and Drug Administration has accepted as possible replacement for animal testing in the preclinical assessment of artificial pancreas technologies, and the second, an investigation of the probability of cardiac lead fracture, where a Bayesian network was used to combine in vivo and in silico observations, suggesting a whole new strategy of in silico-augmented clinical trials, to be used to increase the numerosity where recruitment is impossible, or to explore patients' phenotypes that are unlikely to appear in the trial cohort, but are still frequent enough to be of concern.
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Affiliation(s)
- Marco Viceconti
- 1 Department of Mechanical Engineering, INSIGNEO Institute for in silico Medicine, The University of Sheffield, Sheffield, UK
| | - Claudio Cobelli
- 2 Department of Information Engineering, University of Padova, Padova, Italy
| | | | | | - Boris Kovatchev
- 4 Center for Diabetes Technology, The University of Virginia, Charlottesville, VA, USA
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Zhou L, Bar-Cohen Y, Peck RA, Chirikian GV, Harwin B, Chmait RH, Pruetz JD, Silka MJ, Loeb GE. Analytical Modeling for Computing Lead Stress in a Novel Epicardial Micropacemaker. Cardiovasc Eng Technol 2017; 8:96-105. [PMID: 28070867 DOI: 10.1007/s13239-017-0292-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 01/02/2017] [Indexed: 12/01/2022]
Abstract
Implantation and maintenance of a permanent cardiac pacing system in children remains challenging due to small patient size, congenital heart defects and somatic growth. We are developing a novel epicardial micropacemaker for children that can be implanted on the epicardium within the pericardial space via a minimally-invasive technique. The key design configurations include a novel open-coiled lead in which living tissue replaces the usual polymeric support for the coiled conductor. To better understand and be able to predict the behavior of the implanted lead, we performed a radiographic image-based modeling study on a chronic animal test. We report a pilot study in which two mechanical dummy pacemakers with epicardial leads were implanted into an adult pig model via a minimally invasive approach. Fluoroscopy was obtained on the animal on Post-Operative Days #9, #35 and #56 (necropsy). We then constructed an analytic model to estimate the in vivo stress conditions on the open-coil lead based on the analysis of orthogonal biplane radiographic images. We obtained geometric deformation data of the implanted lead including elongation magnitudes and bending radii from sequenced films of cardiac motion cycles. The lead stress distribution was investigated on each film frame and the point of maximum stress (Mean Stress = 531.4 MPa; Alternating Stress = ± 216.4 MPa) was consistently where one of the leads exited the pericardial space, a deployment that we expected to be unfavorable. These results suggest the modeling approach can provide a basis for further design optimization. More animal tests and modeling will be needed to validate whether the novel lead design could meet the requirements to withstand ~200 million cardiac motion cycles over 5 years.
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Affiliation(s)
- Li Zhou
- Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA.
| | - Yaniv Bar-Cohen
- Division of Cardiology, Department of Pediatrics, Keck School of Medicine, Children's Hospital Los Angeles, University of Southern California, 4650 Sunset Blvd, Los Angeles, CA, 90027, USA
| | - Raymond A Peck
- Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA
| | - Giorgio V Chirikian
- Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA
| | - Brett Harwin
- Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA
| | - Ramen H Chmait
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, 1300 North Vermont Avenue, Suite 710, Los Angeles, CA, 90027, USA
| | - Jay D Pruetz
- Division of Cardiology, Department of Pediatrics, Keck School of Medicine, Children's Hospital Los Angeles, University of Southern California, 4650 Sunset Blvd, Los Angeles, CA, 90027, USA
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, 1300 North Vermont Avenue, Suite 710, Los Angeles, CA, 90027, USA
| | - Michael J Silka
- Division of Cardiology, Department of Pediatrics, Keck School of Medicine, Children's Hospital Los Angeles, University of Southern California, 4650 Sunset Blvd, Los Angeles, CA, 90027, USA
| | - Gerald E Loeb
- Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA
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Liu L, Wang J, Yang W, Chen SJ. In Vivo Stress Analysis of a Pacing Lead From an Angiographic Sequence. J Biomech Eng 2011; 133:041004. [DOI: 10.1115/1.4003524] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this paper, a method is presented to analyze the mechanical stress distribution in a pacing lead based on a sequence of paired 2D angiographic images. The 3D positions and geometrical shapes of an implanted pacemaker lead throughout the cardiac cycle were generated using a previously validated 3D modeling technique. Based on the Frenet–Serret formulas, the kinematic property of the lead was derived and characterized. The distribution of curvature and twist angle per unit length in the pacing lead was calculated from a finite difference method, which enabled a rapid and effective computation of the mechanical stress in the pacing lead. The analytical solution of the helix deformation geometry was used to evaluate the accuracy of the proposed numerical method, and an excellent agreement in curvature, twist angle, and stresses was achieved. As demonstrated in the example, the proposed technique can be used to analyze the complex movement and deformation of the implanted pacing lead in vivo. The information can facilitate the future development of pacing leads.
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Affiliation(s)
- L. Liu
- Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843
| | - J. Wang
- Department of Engineering Technology and Industrial Distribution, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843
| | - W. Yang
- Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843
| | - S. J. Chen
- Department of Medicine/Cardiology, Department of Bioengineering, University of Colorado Denver, Aurora, CO 80045
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