Ischemic lesion burden and characteristics of aortic atheroma

Imaging Biomarkers and Prevalence of Complex Aortic Plaque in Cryptogenic Stroke: A Systematic Review

BACKGROUND

Complex aortic plaque (CAP) is a potential embolic source in patients with cryptogenic stroke (CS). We review CAP imaging criteria for transesophageal echocardiogram (TEE), computed tomography angiography (CTA), and magnetic resonance imaging and calculate CAP prevalence in patients with acute CS.

METHODS AND RESULTS

PubMed and EMBASE databases were searched up to December 2022 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. Two independent reviewers extracted data on study design, imaging techniques, CAP criteria, and prevalence. The Cochrane Collaboration tool and Guideline for Reporting Reliability and Agreement Studies were used to assess risk of bias and reporting completeness, respectively. From 2293 studies, 45 were reviewed for CAP imaging biomarker criteria in patients with acute CS (N=37 TEE; N=9 CTA; N=6 magnetic resonance imaging). Most studies (74%) used ≥4 mm plaque thickness as the imaging criterion for CAP although ≥1 mm (N=1, CTA), ≥5 mm (N=5, TEE), and ≥6 mm (N=2, CTA) were also reported. Additional features included mobility, ulceration, thrombus, protrusions, and assessment of plaque composition. From 23 prospective studies, CAP was detected in 960 of 2778 patients with CS (0.32 [95% CI, 0.24-0.41], I2=94%). By modality, prevalence estimates were 0.29 (95% CI, 0.20-0.40; I2=95%) for TEE; 0.23 (95% CI, 0.15-0.34; I2=87%) for CTA and 0.22 (95% CI, 0.06-0.54; I2=92%) for magnetic resonance imaging.

CONCLUSIONS

TEE was commonly used to assess CAP in patients with CS. The most common CAP imaging biomarker was ≥4 mm plaque thickness. CAP was observed in one-third of patients with acute CS. However, high study heterogeneity suggests a need for reproducible imaging methods.

Contributing Mechanisms of Aortic Atheroma in Ischemic Cerebrovascular Disease

In recent years, the correlation between aortic atheroma (AA) and the occurrence and recurrence of ischemic cerebrovascular disease (ICVD) has attracted much attention, but the contributory mechanisms remain controversial. This review analyzes related research on the roles of AA in ICVD, and demonstrates the correlation between the formation and development of AA and abnormal metabolism, inflammation, hemodynamic changes, and other contributory factors. The presence of complex aortic plaque (CAP) in the ascending aorta and aortic arch increases the risk of cerebral embolism and degree of injury, while the association between CAP in the descending aorta and cerebral embolism remains ambiguous. AA also functions as an indicator of atherosclerosis burden as well as hypercoagulability, which may further increase the risk of ICVD. Further study on the relationship of AA to ICVD will improve diagnosis and treatment in clinical practice.

Magnetic resonance imaging in acute ischemic stroke treatment

Although intravenous administration of tissue plasminogen activator is the only proven treatment after acute ischemic stroke, there is always a concern of hemorrhagic risk after thrombolysis. Therefore, selection of patients with potential benefits in overcoming potential harms of thrombolysis is of great importance. Despite the practical issues in using magnetic resonance imaging (MRI) for acute stroke treatment, multimodal MRI can provide useful information for accurate diagnosis of stroke, evaluation of the risks and benefits of thrombolysis, and prediction of outcomes. For example, the high sensitivity and specificity of diffusion-weighted image (DWI) can help distinguish acute ischemic stroke from stroke-mimics. Additionally, the lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent potential salvageable tissue by reperfusion therapy. However, the optimal threshold to discriminate between benign oligemic areas and the penumbra is still debatable. Signal changes of fluid-attenuated inversion recovery image within DWI lesions may be a surrogate marker for ischemic lesion age and might indicate risks of hemorrhage after thrombolysis. Clot sign on gradient echo image may reflect the nature of clot, and their location, length and morphology may provide predictive information on recanalization by reperfusion therapy. However, previous clinical trials which solely or mainly relied on perfusion-diffusion mismatch for patient selection, failed to show benefits of MRI-based thrombolysis. Therefore, understanding the clinical implication of various useful MRI findings and comprehensively incorporating those variables into therapeutic decision-making may be a more reasonable approach for expanding the indication of acute stroke thrombolysis.