Optical Coherence Tomography Evaluation of Carotid Artery Stenosis and Stenting in Patients With Previous Cervical Radiotherapy

Heavy macrophage infiltration identified by optical coherence tomography relates to plaque rupture

OBJECTIVE

Risk stratification plays a critical role in patients with asymptomatic carotid atherosclerotic stenosis. Heavy macrophage infiltration (HMC) is an important factor of plaque destabilization. However, in vivo imaging technologies and screening criteria for HMC remain limited. We aimed to (i) introduce algorithms for in vivo detection of macrophage infiltrations using optical coherence tomography (OCT) and (ii) to investigate the threshold of HMC and its association with plaque vulnerability.

METHODS

Ex vivo OCT images were co-registered with histopathology in 282 cross-sectional pairs from 19 carotid endarterectomy specimens. Of these, 197 randomly selected pairs were employed to define the parameters, and the remaining 85 pairs were used to evaluate the accuracy of the OCT-based algorithm in detecting macrophage infiltrations. Clinical analysis included 93 patients receiving carotid OCT evaluation. The prevalence and burden of macrophage infiltration were analyzed. Multivariable and subgroup analysis were performed to investigate the association between HMC and plaque rupture.

RESULTS

The sensitivity and specificity of algorithm for detecting macrophage infiltration were 88.0% and 74.9%, respectively. Of 93 clinical patients, ruptured plaques exhibited higher prevalence of macrophage infiltration than nonruptured plaques (83.7% [36/43] vs 32.0% [16/50], p < 0.001). HMC was identified when the macrophage index was greater than 60.2 (sensitivity = 74.4%, specificity = 84.0%). Multivariable analysis showed that HMC and multiple calcification were independent risk factors for non-lipid-rich plaque rupture.

INTERPRETATION

This study provides a novel approach and screening criteria for HMC, which might be valuable for atherosclerotic risk stratification.

Optical Coherence Tomography in the Evaluation of Suspected Carotid Webs

BACKGROUND

Carotid web (CaW) is a subtype of fibromuscular dysplasia that predominantly involves the intimal layer of the arterial wall and is commonly overlooked as a separate causative entity for recurrent strokes. CaW is defined as a shelf-like lesion at the carotid bulb, although different morphological features have been reported. Optical coherence tomography (OCT) has been described in the literature as a useful microscopic and cross-sectional tomographic imaging tool. This study aimed to evaluate the potential utility of OCT in characterizing the wall structure features of patients with suspected CaW.

METHODS

Retrospective analysis of patients with suspected CaW who underwent digital subtraction angiography (DSA) coupled with OCT of the carotid bulb from 2018 to 2021 in a single comprehensive stroke center.

RESULTS

Sixteen patients were included. The median age was 56 years (IQR 46-61) and 50% were women. OCT corroborated the diagnosis of CaW in 12/16 (75%) cases and ruled it out in 4/16 (25%) patients in whom atherosclerotic disease was demonstrated. Five of the 12 lesions demonstrated a thick fibrotic ridge consistent with CaW but also showed atherosclerotic changes in the vicinity of the carotid bulb (labeled as "CaW+"). In 4/16 (25%) patients, microthrombi adhered to the vessel wall were noted on OCT (inside the CaW pocket or just distal to the web), none of which were observed on CT angiography or DSA.

CONCLUSIONS

OCT may have value as a complementary imaging tool in the investigation of patients with suspected CaW and atypical morphological features. Further studies are warranted.

Novel Imaging-Based Biomarkers for Identifying Carotid Plaque Vulnerability

Carotid artery disease has traditionally been assessed based on the degree of luminal narrowing. However, this approach, which solely relies on carotid stenosis, is currently being questioned with regard to modern risk stratification approaches. Recent guidelines have introduced the concept of the "vulnerable plaque," emphasizing specific features such as thin fibrous caps, large lipid cores, intraplaque hemorrhage, plaque rupture, macrophage infiltration, and neovascularization. In this context, imaging-based biomarkers have emerged as valuable tools for identifying higher-risk patients. Non-invasive imaging modalities and intravascular techniques, including ultrasound, computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy, have played pivotal roles in characterizing and detecting unstable carotid plaques. The aim of this review is to provide an overview of the evolving understanding of carotid artery disease and highlight the significance of imaging techniques in assessing plaque vulnerability and informing clinical decision-making.

Detecting vulnerable carotid plaque and its component characteristics: Progress in related imaging techniques

Carotid atherosclerotic plaque rupture and thrombosis are independent risk factors for acute ischemic cerebrovascular disease. Timely identification of vulnerable plaque can help prevent stroke and provide evidence for clinical treatment. Advanced invasive and non-invasive imaging modalities such as computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy can be employed to image and classify carotid atherosclerotic plaques to provide clinically relevant predictors used for patient risk stratification. This study compares existing clinical imaging methods, and the advantages and limitations of different imaging techniques for identifying vulnerable carotid plaque are reviewed to effectively prevent and treat cerebrovascular diseases.