Intravascular sensors to assess unstable plaques and their compositions: a review

Atherosclerosis and its thrombotic complications plague developed countries. The rupture of vulnerable atherosclerotic plaques contributes to acute cardiovascular events and sudden cardiac deaths. Historically, coronary angiography has proved an invaluable tool for the detection and treatment of coronary stenoses that may cause myocardial ischemia; however, the method lacks the capacity to provide thorough information about properties of the lesion (i.e. whether it is lipid-rich, fibrotic, or calcified). Recent advances in electronics, biomaterials and microfabrication techniques have enabled novel multimodality catheters for the assessment of atherosclerotic plaques, such as the integration of intravascular ultrasound with photoacoustic microscopy or optical coherence tomography as well as the utilization of stretchable electrodes for electrochemical impedance spectroscopy. These technologies enable the identification of the complexity and composition of potentially unstable plaques as well as investigations of stenosis severity, plaque formation, and remodeling in both humans and studied animal models. However, real-time detection of vulnerable atherosclerotic lesions prepared for clinical trials remains an unmet challenge. In this context, this review highlights existing and newly-emerged intravascular sensors to assess unstable plaques and their compositions. Advantages and limitations, as well as further development and potential clinical applications, will be thoroughly discussed.