Natural History of Non-operative Management in Asymptomatic Patients with 70%-80% Internal Carotid Artery Stenosis by Duplex Criteria

Objective: Treatment of asymptomatic internal carotid artery (ICA) stenosis, particularly for moderate to severe (70%-80%) disease, is controversial. The goal was to assess the clinical course of patients with moderate to severe carotid stenosis. Methods: A single institution retrospective analysis of patients with asymptomatic ICA stenosis identified on duplex ultrasound as moderate to severe (70%-80%) from 2003 to 2018 were analysed. Duplex criteria for 70%-80% stenosis was a systolic velocity of >= 325 cm/s or an ICA:common carotid artery ratio of >= 4, and an end diastolic velocity of <140 cm/s. Asymptomatic status was defined as no stroke/transient ischaemic attack (TIA) within six months of index duplex. Primary outcomes were progression of stenosis to >80%, ipsilateral stroke/TIA without documented progression, and death. Results: In total, 206 carotid arteries were identified in 182 patients meeting the inclusion criteria. Mean patient age was 71.5 years, 57.7% were male, and 67% were white. There were 19 stenoses removed from analysis except for survival analysis as they initially underwent carotid endarterectomy or carotid artery stent based on surgeon/patient preference. Documented progression occurred in 24.1% of stenoses. There were 5.3% of stenoses associated with an ipsilateral stroke/TIA without documented progression, which occurred at a mean of 26.4 months. Kaplan-Meier analysis demonstrated a 60.3% five year freedom from stenosis progression, 92.5% five year freedom from stroke/TIA without documented progression, and 83.7% five year survival. Risk factors associated with stroke/TIA without documented progression at five years were atrial fibrillation (hazard ratio [HR] 14.87, 95% confidence interval [CI] 2.72-81.16; p = .002) and clopidogrel use at index duplex (HR 6.19, 95% CI 1.33-28.83; p = .020). Risk factors associated with death at five years were end stage renal disease (HR 9.67, 95% CI 2.05-45.6; p = .004), atrial fibrillation (HR 7.55, 95% CI 2.48-23; p < .001), prior head/neck radiation (HR 6.37, 95% CI 1.39-29.31; p = .017), non-obese patients (HR 5.49, 95% CI 1.52-20; p = .009), and non-aspirin use at index duplex (HR 3.05, 95% CI 1.12-8.33; p = .030). Conclusion: Patients with asymptomatic moderate to severe carotid stenosis had a low rate of stroke/TIA without documented progression. However, there was a high rate of stenosis progression reinforcing the need to follow these patients closely.