Is the percentage of stenosis of the internal carotid artery a reliable measure of the risk of ischemic storke? A morphometric study by duplex ultrasound of aortic arch branches in 500 normal adults

Backgrond. The percentage of stenosis has been considered for the last 20 years, and still continues to be, the main criterion of choice between a surgical and a medical treatment of atherosclerotic lesions of the aortic arch branches, particularly as regards the internal carotid artery. On the other side, it has been demonstrated that the risk of adverse acute cerebrovascular events, besides being related to the characteristics of the plaque, such as softness, subintimal haemorrhage or surface ulcer, is strictly related to the actual residual lumen of the internal carotid artery. The pre-eminent role of the percentage of stenosis in the choice of the treatment, hence, presumes a narrow range of variation of the original calibre of the vessel, yet to be proven. Methods. Five-hundred normal adults underwent the measurement of the internal calibre of the aortic arch branches by duplex ultrasound in order to find out their actual range of variation. Results. The range of variation of the internal calibre of the aortic arch branches, expressed as the ratio between the maximum and the minimum value found for each vessel, was very wide in all cases (from 180% for the right common carotid artery to 340% for the right vertebral artery). With reference to the internal carotid arteries, the range of variation was 219% for the right internal carotid artery and 241% for the left internal carotid arteries. Conclusions. Due to the wide range of variation of the original calibre of the aortic arch branches, the percentage of stenosis alone cannot be considered an accurate measure of the severity of the stenosis, and hence a reliable criterion of choice of the treatment.