In the 1990s the North American Symptomatic Carotid Endarterectomy Trial (NASCET) (1) and European Carotid Surgery Trial (ECST) (2) proved the benefits of performing endarterectomy in those patients with symptomatic high-grade stenosis (70-99%).
In 1995, the Asymptomatic CarotidAtherosclerosis Study (ACAS) (3) also, suggested surgery for high-grade asymptomatic stenosis
The North American Symptomatic Carotid Endarterectomy Trial (NASCET) demonstrated a conclusive benefit for carotid endarterectomy in patients with symptomatic 70-99% ICA stenosis (1)
NASCET was established by angiographic calculation of ICA stenosis percentage using the following formula:
- % ICA stenosis = (1 - [narrowest ICA diameter/diameter normal distal cervical ICA]) x 100
The European Carotid Surgery Trial (ECST) also demonstrated benefits for carotid endarterectomy in patients with symptomatic higher than 80% ICA stenosis (2).
ECST was established by angiographic calculation of ICA stenosis percentage using the following formula:
- % ICA stenosis = (1 - [diameter of the most stenotic part/estimated original diameter at the site of the stenosis]) x 100
Notes:
- conventional angiography has been considered the standard method for evaluating carotid stenosis and the trials published in the 1990s (NASCET, ECST, and ACAS) were based on this method
- however, the introduction and development of ultrasound doppler, CT angiography (CTA) and MRI angiography (MRA) have been replacing angiography for diagnostic purposes
- this has essentially reserved angiography only for endovascular treatment
- doppler ultrasound has become the first choice for carotid stenosis screening, permitting the evaluation of both the macroscopic appearance of plaques as well as flow characteristics (4)
- if there is haemodynamically significant carotid stenosis is usually referred to a further CTA or MRA study
Reference:
- Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N. Engl. J. Med. 1991;325 (7): 445-53.
- Randomised trial of endarterectomy for recently symptomatic carotid stenosis: final results of the MRC European Carotid Surgery Trial (ECST). Lancet. 1998;351 (9113): 1379-87.
- Endarterectomy for asymptomatic carotid artery stenosis. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. JAMA. 1995;273 (18): 1421-8.
- Grant EG, Benson CB, Moneta GL et-al. Carotid artery stenosis: gray-scale and Doppler US diagnosis-Society of Radiologists in Ultrasound Consensus Conference. Radiology. 2003;229 (2): 340-6