Comparison of Preoperative and Postoperative Duplex Ultrasound Evaluation of the Contralateral Carotid Artery

Duplex ultrasound has become the dominant imaging modality used in the evaluation and preoperative planning for carotid artery stenosis. Numerous studies have addressed the impact of contralateral stenoses on the accurate assessment of ipsilateral disease. Several of these investigators have employed arteriography as a standard of comparison, but this technique is less commonly used and often underestimates the degree of plaque bulk and stenosis. The authors therefore used duplex ultrasound to examine the postprocedural effect of carotid endarterectomy (CEA) on contralateral velocity measurements. They retrospectively reviewed the noninvasive laboratory records of all patients who underwent CEA from January 1996 to August 1998. Inclusion criteria required a preoperative and postoperative scan within 6 months of surgery and patency of both internal carotid arteries. Velocities were expressed in centimeters per second (cm/sec). Results were categorized into groups according to severity of the stenosis (0-49%, 50-79%, 80-99%). Peak systolic and end-diastolic velocities were recorded, and the difference between contralateral velocities before and after surgery was determined. Ipsilateral systolic and diastolic velocities were compared with the contralateral differences. Paired Student's t test and correlation coefficients were employed in the statistical analysis with significance assumed for a p value