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.