Change in Peak Systolic Velocity Estimation in Internal Carotid Artery Following Contralateral Near Occlusive Carotid Endarterectomy

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Carotid artery stenosis (CAS) is one of the main causes of stroke, as the internal carotid artery (ICA) is a major source of cerebral blood supply. A common surgical intervention for CAS is carotid endarterectomy (CEA), which carries a high risk of stroke and mortality. CEA is indicated for 50% to 99% stenosis in symptomatic patients and 60% to 99% stenosis in asymptomatic patients. Carotid duplex ultrasound is frequently used to estimate peak systolic velocity (PSV), end diastolic velocity (EDV), and ICA/common carotid artery (CCA) ratio to determine the extent of stenosis. This does not account for other factors that can artificially change PSV and EDV, such as a contralateral carotid artery near occlusion with >90% stenosis. Although >70% contralateral stenosis has been previously studied, limited research exists on the impact of ICA near occlusions. We hypothesize that the degree of stenosis in an ipsilateral patent vessel can be more accurately estimated by examining the change in PSV pre- vs post-CEA of the contralateral ICA near occlusion. A retrospective study was conducted on 239 patients, at least 18 years of age, who underwent standard, routine carotid duplex ultrasound at a single institution. Patients who qualified for the study had bilateral carotid stenosis with ICA near occlusive disease on at least one side and underwent CEA. Near occlusion was determined by either a carotid duplex ultrasound >70% with one of the following criteria: PSV >400, EDV >140, or ratio of ICA/CCA >6, or a carotid computed tomography angiography showing near occlusion interpreted by a physician. Preoperative duplex velocities contralateral to the CEA were recorded and compared postoperatively. Interestingly, in the presence of contralateral >50% ICA stenosis, the PSV, EDV, and ICA/CCA ratio in the unoperated artery increased significantly following contralateral CEA (P < .001). In greater than 70% contralateral ICA occlusion, PSV, EDV, and ICA/CCA ratio increased to a greater extent compared with >50% contralateral ICA stenosis (P < .001). In detecting ≥70% stenosis of the patent vessel pre-CEA, PSV ≥250 cm/s had 87.2% sensitivity. In predicting ≥70% stenosis of the patent vessel pre-CEA, PSV >300 cm/s had 96.0% sensitivity. The present study deviates from the current theoretical model and shows that ultrasound PSV, EDV, ICA/CCA ratios can be significantly elevated in the patent vessel pre-CEA and post-CEA of the contralateral ICA near occlusion. This study provides novel insight into customized duplex ultrasound criteria for estimation of stenosis and to avoid unnecessary high-risk surgery.