Neurological outcome of conservative versus endovascular treatment of patients with asymptomatic high-grade carotid artery stenosis: A propensity score-adjusted analysis

\ Purpose: To report a propensity score-adjusted analysis of the long-term risks for stroke after carotid artery stenting (CAS) compared to medical therapy in patients with asymptomatic high-grade carotid artery stenosis. Methods: A total of 946 consecutive patients (605 men; median age 73 years) with asymptomatic high-grade carotid artery stenoses ( >= 70%) identified in a single center registry were treated either medically (n=525) or with CAS (n=421). A propensity score-adjusted analysis was performed to test the hypothesis that long-term neurological outcome might be better after CAS than after medical treatment, depending on the baseline degree of carotid stenosis and the patient's medical status. Baseline degree of stenosis was classified as 70% to 79% (n=307), 80% to 89% (n=366), and 90% to 99% (n=272) by duplex ultrasound. Surgical risk was estimated by the American Society of Anesthesiologists (ASA) score (I to IV). Results: Stroke-free survival rates at 1, 3, and 5 years were 97%, 93%, and 89% after conservative treatment versus 94%, 93%, and 91% after CAS (p=0.56), respectively. Compared to conservatively treated patients with 70% to 79% stenoses, the adjusted hazard ratios for stroke were 2.36 (p=0.044) for conservatively treated patients with 80% to 89% and 3.17 (p=0.026) for those with 90% to 99% stenoses. For CAS patients with 70% to 79%, 80% to 89%, and 90% to 99% stenoses, the adjusted hazard ratios for stroke were 1.32 (p=0.63), 0.91 (p=0.84), and 0.98 (p=0.98) irrespective of the ASA score, the propensity to undergo CAS, and other potential confounders. Thus, the risk of stroke increased in parallel with the degree of stenosis in conservatively treated patients, but remained unchanged in patients undergoing CAS. Conclusions: Patients with asymptomatic severe carotid narrowing ( >= 80%) might benefit from CAS with respect to stroke-free survival. Randomized controlled trials are needed to confirm these findings.