OCT in Endovascular Recanalization of Chronic Carotid Artery Occlusion

Overview

Chronic carotid artery occlusion is an important cause of ischemic stroke. Even with best medical therapy, patients with symptomatic disease may continue to have recurrent ipsilateral transient ischemic attack or ischemic stroke and may have a substantial burden of cognitive decline. Advances in guidewires, microcatheters, distal protection devices, and endovascular techniques have improved the technical success of CCAO recanalization; however, the overall clinical benefit of endovascular therapy appears highly dependent on patient selection and intra-procedural decision-making. During endovascular recanalization, once the guidewire crosses the occluded segment, the operator often must determine whether intraluminal thrombus, dissection, plaque debris, or other lesions are present. Digital subtraction angiography is essential for lumen and flow assessment but cannot reliably characterize the tissue composition or age of intraluminal filling defects. OCT provides high-resolution intraluminal imaging and may improve thrombus identification and lesion assessment in this setting.

OCT is one of the highest-resolution intravascular imaging modalities, with axial resolution in the range of approximately 10-20 um. Compared with intravascular ultrasound, OCT can more clearly demonstrate vessel wall layering, plaque components, thrombus surface morphology, signal attenuation, and intraluminal structural detail. In carotid intervention, published clinical experience suggests that OCT may help define thrombus boundaries, characterize thrombus morphology, guide stent landing zones, inform use of protection devices, and support peri-procedural antithrombotic decisions. The clinical value of OCT thrombus typing remains incompletely established. Coronary OCT studies have reported good discrimination of thrombus type using image attenuation, backscatter, and grayscale parameters, whereas other studies comparing acute OCT findings with histopathology have not confirmed reliable prediction of thrombus composition or freshness. These conflicting data indicate that OCT thrombus classification should be validated prospectively within the specific clinical context of CCAO recanalization rather than extrapolated from coronary studies or isolated case reports.