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Chen M, Neverova N, Xu S, Suwannaphoom K, Lluri G, Tamboline M, Duarte S, Fishbein MC, Luo Y, Packard RRS. Invasive electrochemical impedance spectroscopy with phase delay for experimental atherosclerosis phenotyping. FASEB J 2024; 38:e23700. [PMID: 38787606 DOI: 10.1096/fj.202302544rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 05/07/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024]
Abstract
Distinguishing quiescent from rupture-prone atherosclerotic lesions has significant translational and clinical implications. Electrochemical impedance spectroscopy (EIS) characterizes biological tissues by assessing impedance and phase delay responses to alternating current at multiple frequencies. We evaluated invasive 6-point stretchable EIS sensors over a spectrum of experimental atherosclerosis and compared results with intravascular ultrasound (IVUS), molecular positron emission tomography (PET) imaging, and histology. Male New Zealand White rabbits (n = 16) were placed on a high-fat diet, with or without endothelial denudation via balloon injury of the infrarenal abdominal aorta. Rabbits underwent in vivo micro-PET imaging of the abdominal aorta with 68Ga-DOTATATE, 18F-NaF, and 18F-FDG, followed by invasive interrogation via IVUS and EIS. Background signal-corrected values of impedance and phase delay were determined. Abdominal aortic samples were collected for histology. Analyses were performed blindly. EIS impedance was associated with markers of plaque activity including macrophage infiltration (r = .813, p = .008) and macrophage/smooth muscle cell (SMC) ratio (r = .813, p = .026). Moreover, EIS phase delay correlated with anatomic markers of plaque burden, namely intima/media ratio (r = .883, p = .004) and %stenosis (r = .901, p = .002), similar to IVUS. 68Ga-DOTATATE correlated with intimal macrophage infiltration (r = .861, p = .003) and macrophage/SMC ratio (r = .831, p = .021), 18F-NaF with SMC infiltration (r = -.842, p = .018), and 18F-FDG correlated with macrophage/SMC ratio (r = .787, p = .036). EIS with phase delay integrates key atherosclerosis features that otherwise require multiple complementary invasive and non-invasive imaging approaches to capture. These findings indicate the potential of invasive EIS to comprehensively evaluate human coronary artery disease.
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Affiliation(s)
- Michael Chen
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Natalia Neverova
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Ronald Reagan UCLA Medical Center, Los Angeles, California, USA
- West Los Angeles Veterans Affairs Medical Center, Los Angeles, California, USA
| | - Shili Xu
- Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California, USA
| | - Krit Suwannaphoom
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Gentian Lluri
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Ronald Reagan UCLA Medical Center, Los Angeles, California, USA
| | - Mikayla Tamboline
- Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Sandra Duarte
- Division of Laboratory and Animal Medicine, University of California, Los Angeles, California, USA
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Yuan Luo
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - René R Sevag Packard
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Ronald Reagan UCLA Medical Center, Los Angeles, California, USA
- West Los Angeles Veterans Affairs Medical Center, Los Angeles, California, USA
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California, USA
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, California, USA
- Molecular Biology Institute, University of California, Los Angeles, California, USA
- California NanoSystems Institute, University of California, Los Angeles, California, USA
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Chen M, Neverova N, Xu S, Suwannaphoom K, Lluri G, Tamboline M, Duarte S, Fishbein MC, Luo Y, Packard RRS. Flexible 3-D Electrochemical Impedance Spectroscopy Sensors Incorporating Phase Delay for Comprehensive Characterization of Atherosclerosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558681. [PMID: 37786712 PMCID: PMC10541620 DOI: 10.1101/2023.09.20.558681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Background Distinguishing quiescent from rupture-prone atherosclerotic lesions has significant translational and clinical implications. Electrochemical impedance spectroscopy (EIS) characterizes biological tissues by assessing impedance and phase delay responses to alternating current at multiple frequencies.We evaluated invasive 6-point stretchable EIS sensors over a spectrum of experimental atherosclerosis and compared results with intravascular ultrasound (IVUS), molecular positron emission tomography (PET) imaging, and histology. Methods Male New Zealand White rabbits (n=16) were placed on a high-fat diet for 4 or 8 weeks, with or without endothelial denudation via balloon injury of the infrarenal abdominal aorta. Rabbits underwent in vivo micro-PET imaging of the abdominal aorta with 68 Ga-DOTATATE, 18 F-NaF, and 18 F-FDG, followed by invasive interrogation via IVUS and EIS. Background signal corrected values of impedance and phase delay were determined. Abdominal aortic samples were collected for histological analyses. Analyses were performed blindly. Results Phase delay correlated with anatomic markers of plaque burden, namely intima/media ratio (r=0.883 at 1 kHz, P =0.004) and %stenosis (r=0.901 at 0.25 kHz, P =0.002), similar to IVUS. Moreover, impedance was associated with markers of plaque activity including macrophage infiltration (r=0.813 at 10 kHz, P =0.008) and macrophage/smooth muscle cell (SMC) ratio (r=0.813 at 25 kHz, P =0.026). 68 Ga-DOTATATE correlated with intimal macrophage infiltration (r=0.861, P =0.003) and macrophage/SMC ratio (r=0.831, P =0.021), 18 F-NaF with SMC infiltration (r=-0.842, P =0.018), and 18 F-FDG correlated with macrophage/SMC ratio (r=0.787, P =0.036). Conclusions EIS with phase delay integrates key atherosclerosis features that otherwise require multiple complementary invasive and non-invasive imaging approaches to capture. These findings indicate the potential of invasive EIS as a comprehensive modality for evaluation of human coronary artery disease. GRAPHICAL ABSTRACT HIGHLIGHTS Electrochemical impedance spectroscopy (EIS) characterizes both anatomic features - via phase delay; and inflammatory activity - via impedance profiles, of underlying atherosclerosis.EIS can serve as an integrated, comprehensive metric for atherosclerosis evaluation by capturing morphological and compositional plaque characteristics that otherwise require multiple imaging modalities to obtain.Translation of these findings from animal models to human coronary artery disease may provide an additional strategy to help guide clinical management.
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Abiri P, Luo Y, Huang ZY, Cui Q, Duarte-Vogel S, Roustaei M, Chang CC, Xiao X, Packard R, Cavallero S, Ebrahimi R, Benharash P, Chen J, Tai YC, Hsiai TK. 3-Dimensional electrical impedance spectroscopy for in situ endoluminal mapping of metabolically active plaques. SENSORS AND ACTUATORS. B, CHEMICAL 2022; 354:131152. [PMID: 39391284 PMCID: PMC11466225 DOI: 10.1016/j.snb.2021.131152] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/12/2024]
Abstract
Electrical impedance spectroscopy (EIS) has been recognized to characterize oxidized low-density lipoprotein (oxLDL) in the metabolically active plaque. However, intravascular deployment of 3-D EIS-derived electrical impedance tomography (EIT) for endoluminal mapping of oxLDL-laden arterial walls remains an unmet clinical challenge. To this end, we designed the 6-point microelectrode arrays that were circumferentially configurated onto the balloon catheter for 15 intravascular EIS permutations. In parallel, we created the metabolically active plaques by performing partial ligation of right carotid artery in Yorkshire mini-pigs (n = 6 males), followed by demonstrating the plaque progression at baseline, 8 weeks, and 16 weeks of high-fat diet via computed tomography (CT) angiogram. Next, we deployed the 3-D EIS sensors to the right and left carotid arteries, and we demonstrated 3-D EIS mapping of metabolically active endolumen in the right but not left carotid arteries as evidenced by the positive E06 immunostaining for oxLDL-laden regions. By considering electrical conductivity (σ) and permittivity (ε) properties of collagen, lipid, and smooth muscle presence in the arterial wall, we further validated the 3-D EIS-derived EIT by reconstructing the histology of right and left carotid arteries for the finite element modeling of the oxLDL-laden endolumen, and we accurately predicted 3-D EIS mapping. Thus, we establish the capability of 3-D EIS-derived EIT to detect oxLDL-laden arterial walls with translational implication to predict metabolically active plaques prone to acute coronary syndromes or stroke.
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Affiliation(s)
- Parinaz Abiri
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yuan Luo
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zi-Yu Huang
- Department of Medical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Qingyu Cui
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sandra Duarte-Vogel
- Division of Laboratory Animal Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mehrdad Roustaei
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Chih-Chiang Chang
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xiao Xiao
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Rene Packard
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Susana Cavallero
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ramin Ebrahimi
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Peyman Benharash
- Division of Cardiac Surgery, Department of Surgery, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jun Chen
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yu-Chong Tai
- Department of Medical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Tzung K. Hsiai
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Medical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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Luo Y, Abiri P, Zhang S, Chang CC, Kaboodrangi AH, Li R, Sahib AK, Bui A, Kumar R, Woo M, Li Z, Packard RRS, Tai YC, Hsiai TK. Non-Invasive Electrical Impedance Tomography for Multi-Scale Detection of Liver Fat Content. Theranostics 2018; 8:1636-1647. [PMID: 29556346 PMCID: PMC5858172 DOI: 10.7150/thno.22233] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/01/2017] [Indexed: 12/12/2022] Open
Abstract
Introduction: Obesity is associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). While Magnetic Resonance Imaging (MRI) is a non-invasive gold standard to detect fatty liver, we demonstrate a low-cost and portable electrical impedance tomography (EIT) approach with circumferential abdominal electrodes for liver conductivity measurements. Methods and Results: A finite element model (FEM) was established to simulate decremental liver conductivity in response to incremental liver lipid content. To validate the FEM simulation, we performed EIT imaging on an ex vivo porcine liver in a non-conductive tank with 32 circumferentially-embedded electrodes, demonstrating a high-resolution output given a priori information on location and geometry. To further examine EIT capacity in fatty liver detection, we performed EIT measurements in age- and gender-matched New Zealand White rabbits (3 on normal, 3 on high-fat diets). Liver conductivity values were significantly distinct following the high-fat diet (p = 0.003 vs. normal diet, n=3), accompanied by histopathological evidence of hepatic fat accumulation. We further assessed EIT imaging in human subjects with MRI quantification for fat volume fraction based on Dixon procedures, demonstrating average liver conductivity of 0.331 S/m for subjects with low Body-Mass Index (BMI < 25 kg/m²) and 0.286 S/m for high BMI (> 25 kg/m²). Conclusion: We provide both the theoretical and experimental framework for a multi-scale EIT strategy to detect liver lipid content. Our preliminary studies pave the way to enhance the spatial resolution of EIT as a marker for fatty liver disease and metabolic syndrome.
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Affiliation(s)
- Yuan Luo
- Department of Medical Engineering, California Institute of Technology, Pasadena, California
| | - Parinaz Abiri
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Shell Zhang
- Department of Medical Engineering, California Institute of Technology, Pasadena, California
| | - Chih-Chiang Chang
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California
| | - Amir H. Kaboodrangi
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California
| | - Rongsong Li
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Ashish K. Sahib
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, California
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Alex Bui
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Rajesh Kumar
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, California
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Mary Woo
- School of Nursing, University of California, Los Angeles, California
| | - Zhaoping Li
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - René R. Sevag Packard
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Yu-Chong Tai
- Department of Medical Engineering, California Institute of Technology, Pasadena, California
| | - Tzung K. Hsiai
- Department of Medical Engineering, California Institute of Technology, Pasadena, California
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
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Packard RRS, Luo Y, Abiri P, Jen N, Aksoy O, Suh WM, Tai YC, Hsiai TK. 3-D Electrochemical Impedance Spectroscopy Mapping of Arteries to Detect Metabolically Active but Angiographically Invisible Atherosclerotic Lesions. Am J Cancer Res 2017; 7:2431-2442. [PMID: 28744325 PMCID: PMC5525747 DOI: 10.7150/thno.19184] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 04/18/2017] [Indexed: 11/18/2022] Open
Abstract
We designed a novel 6-point electrochemical impedance spectroscopy (EIS) sensor with 15 combinations of permutations for the 3-D mapping and detection of metabolically active atherosclerotic lesions. Two rows of 3 stretchable electrodes circumferentially separated by 120° were mounted on an inflatable balloon for intravascular deployment and endoluminal interrogation. The configuration and 15 permutations of 2-point EIS electrodes allowed for deep arterial penetration via alternating current (AC) to detect varying degrees of lipid burden with distinct impedance profiles (Ω). By virtue of the distinctive impedimetric signature of metabolically active atherosclerotic lesions, a detailed impedance map was acquired, with the 15 EIS permutations uncovering early stages of disease characterized by fatty streak lipid accumulation in the New Zealand White rabbit model of atherosclerosis. Both the equivalent circuit and statistical analyses corroborated the 3-D EIS permutations to detect small, angiographically invisible, lipid-rich lesions, with translational implications for early atherosclerotic disease detection and prevention of acute coronary syndromes or strokes.
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Gottwald M, Matuschek A, von der Emde G. An active electrolocation catheter system for imaging and analysis of coronary plaques. BIOINSPIRATION & BIOMIMETICS 2017; 12:015002. [PMID: 28129203 DOI: 10.1088/1748-3190/12/1/015002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Coronary artery disease-currently one of the most frequent causes of death-is characterized by atherosclerotic plaques grown in the wall of blood vessels and inhibiting blood flow. Preventive assessment focusses on critical sizes of structural plaque parameters like relative lipid core area and cap thickness to identify high-risk plaques called thin cap fibroatheromas. Although state-of-the-art catheter systems were successfully applied in invasive plaque diagnostics, the high costs induced by these devices inhibit usage in daily clinical practice. To overcome this shortcoming, we follow a biomimetic approach to construct a prospective low-cost catheter system that adapts the active electrolocation principles of weakly electric fish Gnathonemus petersii. Only a few and simple parameters relevant for plaque detection and characterization are estimated from plaque-evoked electric images which are projected on the surface of the catheter. Two prototypical electrolocation catheter systems were tested. The first catheter system featured a ring electrode catheter and was used to obtain dynamic 1D electric images of synthetic plaques in an agarose atherosclerosis model. Our proof of concept showed that synthetic plaques could be reliably detected from 1D electric images. Based on a cluster analysis of selected key image features, synthetic plaques could be categorized into four plaque conditions, predefined from thresholds for critical structural parameters, representing high to low risk plaques. In the second recording approach, plaque-evoked dynamic and static spatial electric images were obtained by a multi-electrode catheter system. Based on these recordings, a synthetic plaque with a critical cap thickness could be detected and localized in a pig coronary artery.
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Affiliation(s)
- Martin Gottwald
- Department of Neuroethology/Sensory Ecology, Institute of Zoology, University of Bonn, Bonn 53115, Germany
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Ma J, Luo Y, Sevag Packard RR, Ma T, Ding Y, Abiri P, Tai YC, Zhou Q, Shung KK, Li R, Hsiai T. Ultrasonic Transducer-Guided Electrochemical Impedance Spectroscopy to Assess Lipid-Laden Plaques. SENSORS AND ACTUATORS. B, CHEMICAL 2016; 235:154-161. [PMID: 27773967 PMCID: PMC5068578 DOI: 10.1016/j.snb.2016.04.179] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Plaque rupture causes acute coronary syndromes and stroke. Intraplaque oxidized low density lipoprotein (oxLDL) is metabolically unstable and prone to induce rupture. We designed an intravascular ultrasound (IVUS)-guided electrochemical impedance spectroscopy (EIS) sensor to enhance the detection reproducibility of oxLDL-laden plaques. The flexible 2-point micro-electrode array for EIS was affixed to an inflatable balloon anchored onto a co-axial double layer catheter (outer diameter = 2 mm). The mechanically scanning-driven IVUS transducer (45 MHz) was deployed through the inner catheter (diameter = 1.3 mm) to the acoustic impedance matched-imaging window. Water filled the inner catheter to match acoustic impedance and air was pumped between the inner and outer catheters to inflate the balloon. The integrated EIS and IVUS sensor was deployed into the ex vivo aortas dissected from the fat-fed New Zealand White (NZW) rabbits (n=3 for fat-fed, n= 5 normal diet). IVUS imaging was able to guide the 2-point electrode to align with the plaque for EIS measurement upon balloon inflation. IVUS-guided EIS signal demonstrated reduced variability and increased reproducibility (p < 0.0001 for magnitude, p < 0.05 for phase at < 15 kHz) as compared to EIS sensor alone (p < 0.07 for impedance, p < 0.4 for phase at < 15 kHz). Thus, we enhanced topographic and EIS detection of oxLDL-laden plaques via a catheter-based integrated sensor design to enhance clinical assessment for unstable plaque.
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Affiliation(s)
- Jianguo Ma
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Yuan Luo
- Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - René R. Sevag Packard
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Teng Ma
- Department of Biomedical Engineering and Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Yichen Ding
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Parinaz Abiri
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Yu-Chong Tai
- Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Qifa Zhou
- Department of Biomedical Engineering and Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Kirk K. Shung
- Department of Biomedical Engineering and Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Rongsong Li
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Tzung Hsiai
- Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, CA 90095, USA
- Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90095, USA
- Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Corresponding Author: Tzung K. Hsiai, M.D., Ph.D., Department of Medicine (Cardiology) and Bioengineering, University of California, Los Angeles, 10833 Le Conte Ave., CHS17-054A, Los Angeles, CA 90095-1679, , Telephone: 310-268-3839
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Two-Point Stretchable Electrode Array for Endoluminal Electrochemical Impedance Spectroscopy Measurements of Lipid-Laden Atherosclerotic Plaques. Ann Biomed Eng 2016; 44:2695-706. [PMID: 26857007 DOI: 10.1007/s10439-016-1559-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/29/2016] [Indexed: 12/28/2022]
Abstract
Four-point electrode systems are commonly used for electric impedance measurements of biomaterials and tissues. We introduce a 2-point system to reduce electrode polarization for heterogeneous measurements of vascular wall. Presence of endoluminal oxidized low density lipoprotein (oxLDL) and lipids alters the electrochemical impedance that can be measured by electrochemical impedance spectroscopy (EIS). We developed a catheter-based 2-point micro-electrode configuration for intravascular deployment in New Zealand White rabbits. An array of 2 flexible round electrodes, 240 µm in diameter and separated by 400 µm was microfabricated and mounted on an inflatable balloon catheter for EIS measurement of the oxLDL-rich lesions developed as a result of high-fat diet-induced hyperlipidemia. Upon balloon inflation, the 2-point electrode array conformed to the arterial wall to allow deep intraplaque penetration via alternating current (AC). The frequency sweep from 10 to 300 kHz generated an increase in capacitance, providing distinct changes in both impedance (Ω) and phase (ϕ) in relation to varying degrees of intraplaque lipid burden in the aorta. Aortic endoluminal EIS measurements were compared with epicardial fat tissue and validated by intravascular ultrasound and immunohistochemistry for plaque lipids and foam cells. Thus, we demonstrate a new approach to quantify endoluminal EIS via a 2-point stretchable electrode strategy.
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Yu F, Lee J, Jen N, Li X, Zhang Q, Tang R, Zhou Q, Kim ES, Hsiai TK. Elevated electrochemical impedance in the endoluminal regions with high shear stress: implication for assessing lipid-rich atherosclerotic lesions. Biosens Bioelectron 2012; 43:237-44. [PMID: 23318546 DOI: 10.1016/j.bios.2012.12.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 11/29/2012] [Accepted: 12/04/2012] [Indexed: 12/19/2022]
Abstract
BACKGROUND Identifying metabolically active atherosclerotic lesions remains an unmet clinical challenge during coronary intervention. Electrochemical impedance (EIS) increased in response to oxidized low density lipoprotein (oxLDL)-laden lesions. We hereby assessed whether integrating EIS with intravascular ultrasound (IVUS) and shear stress (ISS) provided a new strategy to assess oxLDL-laden lesions in the fat-fed New Zealand White (NZW) rabbits. METHODS AND RESULTS A micro-heat transfer sensor was deployed to acquire the ISS profiles at baseline and post high-fat diet (HD) in the NZW rabbits (n=8). After 9 weeks of HD, serum oxLDL levels (mg/dL) increased by 140 fold, accompanied by a 1.5-fold increase in kinematic viscosity (cP) in the HD group. Time-averaged ISS (ISSave) in the thoracic aorta also increased in the HD group (baseline: 17.61±0.24 vs. 9 weeks: 25.22±0.95dyne/cm(2), n=4), but remained unchanged in the normal diet group (baseline: 22.85±0.53dyn/cm(2) vs. 9 weeks: 22.37±0.57dyne/cm(2), n=4). High-frequency intravascular ultrasound (IVUS) revealed atherosclerotic lesions in the regions with augmented ISSave, and concentric bipolar microelectrodes demonstrated elevated EIS signals, which were correlated with prominent anti-oxLDL immuno-staining (oxLDL-free regions: 497±55Ω, n=8 vs. oxLDL-rich lesions: 679±125Ω, n=12, P<0.05). The equivalent circuit model for tissue resistance between the lesion-free and ox-LDL-rich lesions further validated the experimental EIS signals. CONCLUSIONS By applying electrochemical impedance in conjunction with shear stress and high-frequency ultrasound sensors, we provided a new strategy to identify oxLDL-laden lesions. The study demonstrated the feasibility of integrating EIS, ISS, and IVUS for a catheter-based approach to assess mechanically unstable plaque.
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Affiliation(s)
- Fei Yu
- Department of Biomedical Engineering and Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90089, USA
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Yu F, Dai X, Beebe T, Hsiai T. Electrochemical impedance spectroscopy to characterize inflammatory atherosclerotic plaques. Biosens Bioelectron 2011; 30:165-73. [PMID: 21959227 PMCID: PMC3210389 DOI: 10.1016/j.bios.2011.09.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 09/09/2011] [Accepted: 09/09/2011] [Indexed: 11/28/2022]
Abstract
Despite advances in diagnosis and therapy, atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality in the Western world. Predicting metabolically active atherosclerotic lesions has remained an unmet clinical need. We hereby developed an electrochemical strategy to characterize the inflammatory states of high-risk atherosclerotic plaques. Using the concentric bipolar microelectrodes, we sought to demonstrate distinct Electrochemical Impedance Spectroscopic (EIS) measurements for unstable atherosclerotic plaques that harbored active lipids and inflammatory cells. Using equivalent circuits to simulate vessel impedance at the electrode-endoluminal tissue interface, we demonstrated specific electric elements to model working and counter electrode interfaces as well as the tissue impedance. Using explants of human coronary, carotid, and femoral arteries at various Stary stages of atherosclerotic lesions (n=15), we performed endoluminal EIS measurements (n=147) and validated with histology and immunohistochemistry. We computed the vascular tissue resistance using the equivalent circuit model and normalized the resistance to the lesion-free regions. Tissue resistance was significantly elevated in the oxLDL-rich thin-cap atheromas (1.57±0.40, n=14, p<0.001) and fatty streaks (1.36±0.28, n=33, p<0.001) as compared with lesion-free region (1.00±0.18, n=82) or oxLDL-absent fibrous atheromas (0.86±0.30, n=12). Tissue resistance was also elevated in the calcified core of fibrous atheroma (2.37±0.60, n=6, p<0.001). Despite presence of fibrous structures, tissue resistance between ox-LDL-absent fibroatheroma and the lesion-free regions was statistically insignificant (0.86±0.30, n=12, p>0.05). Hence, we demonstrate that the application of EIS strategy was sensitive to detect fibrous cap oxLDL-rich lesions and specific to distinguish oxLDL-absent fibroatheroma.
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Affiliation(s)
- Fei Yu
- Biomedical Engineering and Cardiovascular Medicine, University of Southern California, DRB Suite 140, 1042 Downey Way, Los Angeles, California, USA 90089
| | - Xiaohu Dai
- Biomedical Engineering and Cardiovascular Medicine, University of Southern California, DRB Suite 140, 1042 Downey Way, Los Angeles, California, USA 90089
| | - Tyler Beebe
- Biomedical Engineering and Cardiovascular Medicine, University of Southern California, DRB Suite 140, 1042 Downey Way, Los Angeles, California, USA 90089
| | - Tzung Hsiai
- Biomedical Engineering and Cardiovascular Medicine, University of Southern California, DRB Suite 140, 1042 Downey Way, Los Angeles, California, USA 90089
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