Background and Importance Symptomatic carotid stenosis accounts for approximately 10% of all strokes. Currently, CT angiography (CTA) is the main diagnostic modality, based on which, patients are referred to either carotid angioplasty and stenting thorugh digital substraction angiography (DSA) or endarterectomy. CTA accuracy is relatively low and fasle-positive CTA results may expose patients to unnecessary procedural complications. In this study, we aim to assess the correlation of CTA to DSA in carotid stenosis and characterize patients referred for intervention based on CTA who did not require it based on DSA.

Methods We retrospectively reviewed 186 patients who underwent carotid angioplasty and stenting (DSA) following pre-procedural diagnostic CT angiogram (CTA) at Thomas Jefferson University Hospital from April 2017 to December 2022. The degree of carotid stenosis was compared between CTA and DSA. DSA was measured from the lateral projection, while CTA was measured minimal axial luminal diameter, per usual practice. Patients with discordant degree of stenosis with less than 50% on DSA (discordant group, +CTA - DSA) were compared with patients with concordant degree of stenosis on DSA and CTA (concordant group, +CTA +DSA). Chi-square test was used for categorical variables. Bland-Altman plots and linear regression were used for comparing degree of stenosis from DSA and CTA.

Results Twenty-one of 186 patients (11.2%) were found to have less than 50% carotid stenosis on DSA (discordant group). No clinical covariate was found to be associated with a discordant degree of stenosis, but severe plaque calcification on CTA was associated with a discordant degree of stenosis on DSA (LR+ = 7.4). Among all 186 patients, agreement between the%stenosis from CTA and DSA was weak-moderate (r²= 0.27, p <0.01). When discordant DSA were discarded, we found moderate-strong agreement between CTA and DSA (adj r²=0.37)(p<0.0001). Of 186 patients, 127 patients had CTA stenosis of ≥70%, and 59 had CTA of 50-69%. Correlation between CTA and DSA in severe CTA stenosis was weak (r²=0.11, p <0.01), and correlation between CTA and DSA in moderate CTA stenosis did not reach significance.

Conclusion Of patients with stenosis found on CTA, over 88% also had stenosis on DSA, with this PPV in line with previous studies. The percent-stenosis value from CTA and DSA was weakly correlated, likely due to measurement technicalities, but does not affect clinical judgement of stenosis overall. Severe calcification found on CTA may potentially indicate non-stenosis on DSA.

Disclosures R. Abbas: None. W. Chong: None. Y. Hai: None. K. El Naamani: None. M. Gooch: 2; C; Medtronic. S. Tjoumakaris: 2; C; microvention. A. Flanders: None. P. Jabbour: 2; C; Medtronic.