Elevated electrochemical impedance in the endoluminal regions with high shear stress: Implication for assessing lipid-rich atherosclerotic lesions

By Yu, Fei; Lee, Juhyun; Jen, Nelson; Li, Xiang; Zhang, Qian; Tang, Rui; Zhou, Qifa; Kim, Eun.S. & Hsiai, Tzung K.
Published in Biosensors and Bioelectronics NULL 2013

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±0.95 dyne/cm2, n=4), but remained unchanged in the normal diet group (baseline: 22.85±0.53 dyn/cm2 vs. 9 weeks: 22.37±0.57 dyne/cm2, 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±55 Ω, n=8 vs. oxLDL-rich lesions: 679±125 Ω, 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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