Carotid endarterectomy: the mandate for high quality duplex.

Excellent correlation between carotid angiography and duplex scanning has made it possible to perform carotid endarterectomy without angiography. The accuracy of scans from practices without a dedicated vascular laboratory must be validated prior to their use for clinical decisions. Seventy six patients had a carotid duplex performed at an outside institution and were referred for vascular surgery. All patients underwent a repeat study at our dedicated vascular lab. The overall accuracy of our lab was 93.8% for all carotid categories as demonstrated by angiography. Outside carotid duplex reports correlated with repeat exams as follows: occlusions: 10/13 carotids (76.9%); 80%-99% stenoses: 15/39 carotids (38.5%); 50%-79% stenoses: 28/44 carotids (63.6%). If a surgeon's practice is to operate for asymptomatic 80%-99% stenoses by report, then unnecessary surgery might have been performed in 61.5% of these carotids and appropriate surgery denied in 3.6%. Outside duplex velocities consistent with a 60%-99% stenosis correlated in 13/17 carotids (76.5%). If a surgeon's practice is to operate for asymptomatic 60%-99% stenoses based on velocity criteria, then unnecessary surgery might have been performed in 23.5% of these carotids, and appropriate surgery denied in 7.6% placing these patients at increased risk of stroke. Outside scans significantly overestimated the severity of carotid disease (p = 0.003). The weighted kappa analysis for agreement between scans was only 60.2%. Failure to have validated high-quality duplex in labs performing carotid studies can lead to unnecessary angiography or surgery. Carotid endarterectomy without angiography should be performed only when duplex accuracy has been previously validated by angiographic correlation studies. Poor agreement with studies from practices without a dedicated vascular lab makes it mandatory to repeat the duplex on all patients prior to clinical decision making. Reimbursement for such repeat studies should not be denied.