Page 9 - Carotid and peripheral vascular interventions textbook
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                 to cerebrovascular insuff ciency. Three patterns of large    an annual stroke risk of about 2% to 5% for patients
                 vessel injury are described as; 1) intimal damage with   suffering from severe asymptomatic carotid stenosis
                 mural thrombosis occurring within 5 years of therapy,     (ACAS) (3,21). On the opposite side, among symptomatic
                 2) f brotic occlusion presenting within 10 years, as well as     patients (i.e., patients who have had previous stroke or TIA),
                 3) predisposition to development of atheroma together with     the risk of a subsequent stroke increases to 12% - 15%
                 periarterial f brosis that has a latency of about 20 years (20).     during the f rst year and 30% - 35% within 5 years (22).
                 Radiation-induced atheromatous lesions are similar to usual    Besides patient symptoms, annual stroke risk is dependent
                 atherosclerotic lesions. However, the lesions are clearly   on stenosis severity, rate of disease progression, plaque
                 conf ned to irradiated vessel segments, sparing close     morphology, contralateral disease, silent cerebral infarction,
                 nonirradiated segments, which present in unusual locations    collaterals’ extent, and concurrent medical treatment.
                 of atherosclerosis (Fig. 6-9). The specif c process of occlusion     Therefore, the natural history of carotid disease is quite
                 and vascular stenosis after radiation therapy is unknown.   uncertain. Some patients have disease progression and
                                                                 develop a carotid total occlusion without any symptoms,
                 NATURAL HISTORY                                 while other patients may develop a disabling or fatal stroke

                                                                 (23). However, proper treatment of asymptomatic ICA
                     To determine the best preventive therapy for carotid   stenosis, especially for moderate to severe (70% - 80%)
                 artery stenosis, the natural history of stroke in these patients   disease, is still controversial. Although that patient
                 must f rst be elucidated. It is well established that stroke   population usually has a low rate of stroke or TIA, there
                 risk is greater in symptomatic patients compared with   is still a high stenosis progression rate, supporting the
                 asymptomatic patients. Previous studies have published     need to observe those patients closely.

              A   A                                              B  B

                 Figure 6-9. Radiation-induced carotid artery stenosis. Digital subtraction angiography in anteroposterior (A) and lateral (B) views of the right
                 carotid artery showing long diffuse stenoses of the right common carotid artery (black arrows) and involving proximal right subclavian artery
                 (white arrow) with no stenosis of right vertebral artery (yellow arrow).
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