Page 77 - Libro 2

4 — The Extracranial Duplex Ultrasound Examination
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A
B
For example, the randomized trials that evaluated the efficacy of carotid endarterectomy (CEA) in the 1990s prompted the development of some new inter- pretation criteria.14–16 In the North American Symp- tomatic Carotid Endarterectomy Trial (NASCET), patients with symptomatic internal carotid stenosis of 70% to 99% had dramatic benefit from an end- arterectomy. Based on a detailed review of multiple Doppler waveform parameters, the best criteria for identifying a 70% or greater internal carotid stenosis,
Figure 4-28 Duplex images demonstrating high-grade stenosis of the internal carotid ar- tery. A: A stenosis of 80% to 99% of the proximal internal carotid artery with poststenotic turbulence. B: Calculation of the internal carotid artery (ICA) to the common carotid artery (CCA) ratio.
as defined in the NASCET, was a PSV of 230 cm/s or greater, or an internal carotid to common carotid PSV ratio (ICA/CCA ratio) of 4.0 or greater.17 When calculating the ICA/CCA ratio, it is important to use the highest PSV from the stenotic site for the ICA value and the PSV in a normal mid-to-distal com- mon carotid artery segment (where the imaged arte- rial walls are parallel) for the CCA value (Fig. 4-28). The ICA/CCA ratio is not valid in the presence of significant common carotid artery disease.