Should conventional angiography be the gold standard for carotid stenosis?

Purpose: To compare conventional angiography (CA) and rotational angiography (RA) to assess the degree of angiographically-measured stenosis versus cross-sectional area (CSA) stenosis in an in vitro carotid model. Methods: Various grades of stenosis were created by adhering different amounts of silicone rubber sealant onto the inner wall of clear, radiolucent tubes. Following 2- and 3-projection CA and 20-projection RA, the tubes were transected at the actual maximum stenosis. The cross-sectional areas were digitally photographed, and CSA stenosis was calculated using ImageJ planimeter software. The differences among CA, RA, and CSA stenosis measurements were compared statistically. Results: There was no significant difference between RA and CSA stenosis measurements (p=0.46). Conventional angiography with 2 or 3 projections between 0° and 90° underestimated the severity of disease in 19 (63%) of 30 samples. The maximum stenosis percentage was significantly lower in CA versus RA (p<0.0001 in 2-projection, p<0.0003 in 3-projection) and in CA versus CSA stenosis (p<0.0004 in 2-projection, p<0.001 in 3-projection). The maximum stenosis percentages measured by RA were less than CSA stenosis in 5 (71.4%) of 7 tubes (p=NS) containing 50% to 69% stenoses. Eight tubes had mountain-shaped lesions, which was significantly overestimated by RA (11.5%±9.7%, p<0.012). Conclusion: CA with 2 or 3 projections significantly underestimates the maximum stenosis in an in vitro model. RA may overestimate disease in patients with mountain-shaped plaques and may underestimate disease if the stenosis is <70%. Our data suggest that CA should not be the gold standard for the qualification of carotid endarterectomy in asymptomatic patients, nor for vascular laboratory quality assurance analysis.