Optimization of intraoperative carotid duplex imaging technique

No clear, consistent guidelines exist on what constitutes an optimal intraoperative duplex ultrasound exam. This study is designed to evaluate such guidelines. Fifty-five random patients who had carotid endarterectomy underwent intraoperative duplex imaging. Abnormal studies were subdivided into Class A (image 40-60% or systolic velocity 110-130 cm/sec), Class B (image 61-80% or systolic velocity >130 cm/sec or internal carotid artery/common carotid artery ratio ≤1.8), Class C (image >80% or end diastolic velocity ≤100 cm/sec), and Class D (external carotid artery or common carotid artery abnormality). Patients had duplex study follow-up short-term (≤6 months, n = 55) and long-term (>6 months, n = 19). Fifty-six studies were performed. Eight studies were technically suboptimal, leaving 48 for evaluation. Forty intraoperative studies were normal; eight were abnormal. Of the 40 normal studies, 16 (40%) became abnormal. Review of intraoperative and postoperative studies revealed no characteristics that predicted the subsequent abnormality in five cases, while four cases revealed technical problems during the intraoperative study. However, seven (45%) involved potentially correctable problems, including four in which scanning was not performed low enough on the CCA or high enough on the ICA, and three in which studies underestimated wall abnormalities by image. Intraoperative techniques must include full evaluation of the common carotid, internal carotid, and clamp sites and close attention must be paid to wall abnormalities on imaging. In this study, such evaluation would have predicted nearly half of all later carotid abnormalities.