Although immaturity of neointimal smooth muscle cells (SMCs) in coronary arteries has recently been demonstrated to be associated with acute coronary syndrome, the carotid arterial counterpart has not been investigated. We hypothesized that the same investigation of carotid endarterectomy specimens might contribute to living patients. Carotid endarterectomy specimens from 33 Asian males who underwent a 5-year follow-up were examined. Age, atherosclerotic risk factors, and percentage stenosis were investigated. Histologically, the fibrous cap/lipid core ratio was measured. Maturation of SMCs was assessed by the h-caldesmon/smooth muscle actin (SMA) ratio by immunohistochemistry in 3 different regions (luminal, medial, and opposite side of lipid core) in the neointima. Associations of these factors with preoperative symptoms along with postoperative systemic atherogenic cardiovascular events were analyzed. It was revealed that fibrous cap/lipid core ratio was significantly lower in symptomatic than in asymptomatic patients, while the h-caldesmon/SMA ratio was significantly lower in patients with than without postoperative systemic atherogenic cardiovascular events by the Student's t-test (P<0.05). Logistic regression model demonstrated that younger age and a lower h-caldesmon/SMA ratio were associated with postoperative systemic atherogenic cardiovascular events (P<0.05). This result was not different when 3 different regions were each analyzed instead. Immaturity of neointimal SMCs shown by a lower h-caldesmon/SMA ratio by immunohistochemistry was associated with systemic atherogenic cardiovascular events. Thus, this finding may be predictive of these events after carotid endarterectomy. Uniform results among different neointimal regions suggest that immaturity of neointimal SMCs causes plaque instability and does not occur secondarily to plaque instability.
Keywords: Carotid endarterectomy; differentiation; immunohistochemistry; prognosis; smooth muscle.