Ultrasonic Transducer-Guided Electrochemical Impedance Spectroscopy to Assess Lipid-Laden Plaques

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.