Flexible micro sensor for intravascular vulnerable plaque diagnostic with electrical impedance spectroscopy

Studies have shown emerging evidence that rupture of coronary plaque containing a lipid-rich core with subsequent thrombus formation is the most frequent mechanism by which atherosclerosis leads to the acute ischaemic syndromes of unstable angina, acute myocardial infarction, and often times, sudden cardiac death. However, since the lumen is not significantly blocked in these cases, such “vulnerable” plaques show noncritical stenosis in X-ray angiography and Intravascular Ultrasound (IVUS), tools currently available to diagnose coronary artery disease. The ability to distinguish such rupture-prone vulnerable plaques remains largely lacking. Therefore it is of great clinical interest to find improved diagnostic techniques to identify and localize such rupture-prone plaques. On the other hand, lipid has significantly lower electrical impedance than the rest of the vessel components in certain frequency bands [1]. We show in this paper that electrical impedance spectroscopy (EIS) technique can be useful to effectively distinguish plaques with such lipid cores. We include in this paper the design rationale of a four electrode EIS sensor and the measurement results between 1 Hz to 300 KHz of ex-vivo mouse aortas with plaque lesions. The impedance modulus over 200 Hz-100 KHz show consistent elevated values 2-5 times higher than their proximity control sites in all three individual mice. The promising ex-vivo EIS results show promising potential for a reliable unstable plaque diagnostic tool for in-vivo catheter integrated intravascular micro EIS sensors.