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Hemispheric symptoms and carotid plaque echomorphology
M M Sabetai1, T J Tegos, A N Nicolaides
1Department of Vascular Surgery, Irvine Laboratory for Cardiovascular Investigation , London, United Kingdom.
Insights
Symptomatic carotid plaques are more hypoechoic and stenotic than asymptomatic ones. Amaurosis fugax (AF) plaques are more hypoechoic and stenotic than transient ischemic attack (TIA) or stroke plaques, suggesting different mechanisms.
Area of Science:
- Vascular Surgery
- Neurology
- Radiology
Background:
- Carotid bifurcation disease poses a stroke risk influenced by stenosis severity, symptoms, and plaque echodensity.
- Understanding plaque characteristics is crucial for predicting stroke risk.
Purpose of the Study:
- To investigate the relationship between carotid plaque structure (echodensity, stenosis degree) and symptoms in patients with carotid bifurcation disease.
- To determine if asymptomatic plaques differ structurally from symptomatic ones.
Main Methods:
- Duplex scanning of 295 carotid bifurcation plaques in 264 patients (146 symptomatic, 149 asymptomatic) with >50% stenosis.
- Digitization and normalization of B-mode images to objectively measure plaque echodensity using the gray scale median (GSM).
- Classification of symptomatic plaques by associated events: amaurosis fugax (AF), transient ischemic attacks (TIAs), or stroke.
Main Results:
- Symptomatic plaques exhibited higher stenosis (80.5%) and lower echodensity (mean GSM 13.3) compared to asymptomatic plaques (72.2% stenosis, GSM 30.5).
- Plaques associated with AF showed the lowest echodensity (GSM 7.4) and highest stenosis (85.6%).
- Plaques causing TIAs (GSM 14.9, 79.3% stenosis) and stroke (GSM 15.8, 78.1% stenosis) had similar echodensity and stenosis levels.
Conclusions:
- Hypoechoic carotid plaques are more frequently symptomatic and stenotic than hyperechoic ones.
- The distinct characteristics of AF plaques suggest a different underlying pathophysiology compared to TIAs and strokes.
- Plaque echodensity and stenosis degree are significant indicators of cerebrovascular event risk.
Purpose:
In patients with carotid bifurcation disease, the risk of stroke mainly depends on the severity of the stenosis, the presenting hemispheric symptom, and, as recently suggested, on plaque echodensity. We tested the hypothesis that asymptomatic carotid plaques and plaques of patients who present with different hemispheric symptoms are related to different plaque structure in terms of echodensity and the degree of stenosis.
Methods:
Two hundred sixty-four patients with 295 carotid bifurcation plaques (146 symptomatic, 149 asymptomatic) causing more than 50% stenosis were examined with duplex scanning. Thirty-six plaques were associated with amaurosis fugax (AF), 68 plaques were associated with transient ischemic attacks (TIAs), and 42 plaques were associated with stroke. B-mode images were digitized and normalized using linear scaling and two reference points, blood and adventitia. The gray scale median (GSM) of blood was set to 0, and the GSM of the adventitia was set to 190 (gray scale range, black = 0; white = 255). The GSM of the plaque in the normalized image was used as the objective measurement of echodensity.
Results:
The mean GSM and the mean degree of stenosis, with 95% confidence intervals, for plaques associated with hemispheric symptoms were 13.3 (10.6 to 16) and 80.5 (78.3 to 82.7), respectively; and for asymptomatic plaques, the mean GSM and the mean degree of stenosis were 30.5 (26.2 to 34.7) and 72. 2 (69.8 to 74.5), respectively. Furthermore, in plaques related to AF, the mean GSM and the mean degree of stenosis were 7.4 (1.9 to 12. 9) and 85.6 (82 to 89.2), respectively; in those related to TIA, the mean GSM and the mean degree of stenosis were 14.9 (11.2 to 18.6) and 79.3 (76.1 to 82.4), respectively; and in those related to stroke, the mean GSM and the mean degree of stenosis were 15.8 (10.2 to 21.3) and 78.1 (73.4 to 82.8), respectively.
Conclusion:
Plaques associated with hemispheric symptoms are more hypoechoic and more stenotic than those associated with no symptoms. Plaques associated with AF are more hypoechoic and more stenotic than those associated with TIA or stroke or those without symptoms. Plaques causing TIA and stroke have the same echodensity and the same degree of stenosis. These findings confirm previous suggestions that hypoechoic plaques are more likely to be symptomatic than hyperechoic ones. They support the hypothesis that the pathophysiologic mechanism for AF is different from that for TIA and stroke.