Certain subgroups of patients are at higher risk for CAS. The identification of those patients could improve the decision-making and hence the outcome. This chapter covers factors that are associated with poor outcome during CAS based on the previously reported literature: (1) CAS in female patients, (2) CAS in octogenarians, (3) CAS in patients with difficult aortic arch configuration (type II, III, and bovine arch), (4) CAS in patients who have tortuous common carotid artery (CCA), angulated internal carotid artery (ICA) origin, and/or angulated distal ICA, (5) CAS in high-grade carotid stenosis, (6) CAS for long lesions (≥15 mm), (7) CAS for ostial-centered lesions, (8) CAS in the presence of calcified aortic arch and/or heavily calcified lesions, (9) CAS in the presence of contralateral carotid occlusion, (10) CAS in the presence of vertebral artery occlusion and/or stenosis, and (11) CAS in chronic kidney disease patients
