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Asymptomatic high-grade internal carotid artery stenosis: is stratification according to risk factors or duplex
G L Moneta1, D C Taylor, R E Zierler
1Department of Surgery, University of Washington School of Medicine, Seattle.
Insights
High-grade asymptomatic carotid artery stenosis poses a risk for stroke. Duplex scan end-diastolic frequency can identify high-risk patients needing closer monitoring for potential events.
Area of Science:
- Vascular Surgery
- Neurology
- Diagnostic Imaging
Background:
- High-grade asymptomatic internal carotid artery stenosis (80%-99% diameter reduction) is linked to increased neurologic events.
- However, many such lesions remain event-free, necessitating identification of high-risk cases.
Purpose of the Study:
- To compare risk factors and duplex scan findings in patients with high-grade asymptomatic internal carotid artery stenosis.
- To identify predictors of neurologic events or internal carotid artery occlusion in this patient group.
Main Methods:
- Retrospective comparison of two groups: asymptomatic high-grade lesions (Group A, n=33) and those with subsequent neurologic events (Group B, n=26).
- Analysis included patient demographics, comorbidities, contralateral/ipsilateral stenosis, and duplex scan end-diastolic frequencies.
Main Results:
- No significant differences in age, sex, or comorbidities between groups.
- Higher end-diastolic frequencies (>6.5 kHz) on duplex scanning were significantly associated with subsequent neurologic events (p=0.0004).
- End-diastolic frequencies >6.0 kHz correlated with a higher incidence of internal carotid artery occlusion (30% vs. 3.5%, p=0.025).
Conclusions:
- Duplex scan end-diastolic frequency is a valuable tool for risk stratification in high-grade asymptomatic internal carotid artery stenosis.
- This metric may help identify patients at elevated risk for stroke or internal carotid artery occlusion, guiding management decisions.
Abstract:
High-grade (80% to 99% diameter reduction) asymptomatic internal carotid artery stenoses are associated with an increased neurologic event rate (transient ischemic attack, stroke, asymptomatic internal carotid artery occlusion) compared to less severe asymptomatic lesions. However, many do remain free of associated events. To determine which are most dangerous, we compared risk factors and duplex scan results in two groups with asymptomatic high-grade internal carotid artery stenoses. Group A included 31 patients with 33 unoperated high-grade lesions that remained asymptomatic for at least 12 months (mean 30 months). Group B included 25 patients with 26 initially asymptomatic lesions that subsequently were associated with a neurologic event (mean time to event 7.4 months). The groups did not differ significantly in average age, sex, aspirin use, smoking, or prevalence of hypertension, diabetes, or cardiac disease. With respect to the index high-grade lesion, there was no difference in the frequency of a greater than 50% contralateral internal carotid artery stenosis or greater than 50% ipsilateral external carotid stenosis. However, on duplex scanning, high-grade stenoses with greater than 6.5 kHz end-diastolic frequencies were more frequently associated with an event than high-grade lesions with lower end-diastolic frequency (p = 0.0004). Similarly, seven of 23 lesions (30%) with end-diastolic frequency greater than 6.0 kHz were associated with subsequent internal carotid artery occlusion compared to only one of 29 (3.5%) with end-diastolic frequency less than or equal to 6.0 kHz (p = 0.025). Analysis of internal carotid artery end-diastolic frequency may help select a subgroup of patients with asymptomatic high-grade lesions who are at greatest risk for subsequent neurologic symptoms or ICA occlusion or both.