SCREENING FOR ASYMPTOMATIC INTERNAL CAROTID-ARTERY STENOSIS - DUPLEX CRITERIA FOR DISCRIMINATING 60-PERCENT TO 99-PERCENT STENOSIS

Purpose: The Asymptomatic Carotid Atherosclerosis Study (ACAS) showed that carotid endarterectomy reduces stroke risk in symptom-free patien ts with 60% or greater internal carotid artery (ICA) stenosis. This wi ll surely lead to the performance of an increased number of screening duplex examinations. Assuming that positive study results will lead to arteriography or endarterectomy and keeping in mind the modest benefi t for prophylactic endarterectomy demonstrated by ACAS (absolute risk reduction for ipsilateral stroke of 5.8% at 5 years), duplex criteria for 60% or greater ICA stenosis must have high positive predictive val ues (PPV). Determining criteria for 60% or greater stenosis, which emp hasized high accuracy and PPV, forms the basis for this study. Methods : Stenoses detected by angiography in 352 ICAs were blindly compared w ith those detected by duplex scanning. Duplex criteria were determined for highest overall accuracy in detection of 60% or greater ICA steno sis and for 95% or greater PPV. Results: Maximal accuracy for detectio n of 60% or greater stenosis was 90%. This was achieved by the combina tion of a peak systolic velocity of 260 cm/sec or greater and an end d iastolic velocity of 70 cm/sec or greater (sensitivity 84%, specificit y 94%, PPV 92%). The 95% PPV for 60% or greater stenosis results from combining Peak systolic velocity of 290 cm/sec or greater and end dias tolic velocity of 80 cm/sec or greater. Conclusions: With use of these criteria duplex scanning accurately detects with high PPVs the thresh old level of ICA stenosis defined in ACAS as receiving stroke reductio n benefit from prophylactic carotid endarterectomy. These criteria sho uld be useful for carotid artery screening and minimizing unneeded int ervention.