The Natural History of Asymptomatic Carotid Stenosis: Assessing the Risk and Rate of Disease Progression

Abstract

Recent studies have found that asymptomatic patients with more severe carotid stenosis have an increased risk of stroke. Patients with mild disease (<50%) have a low risk of stroke and a 3-4% annual risk of disease progression. Those with moderate (50-79%) or severe (>80%) stenosis are at higher risk of progression (3-11% per year) and subsequent neurologic symptoms. In all patients, progression is associated with a 5- 20-fold increase in the risk of transient ischemic attack (TIA) or stroke. An elevated peak systolic velocity (PSV >175 cm/sec) on duplex scan, contralateral carotid stenosis, and systolic hypertension have been associated with an increased risk of disease progression. In most studies, gender, smoking, and other cardiovascular risk factors have not been correlated with progression. Based on the studies reviewed in this report, asymptomatic patients with bilateral carotid stenosis < 50% do not warrant a follow up duplex scan for ≥2 years, while patients with moderate disease or severe contralateral stenosis should undergo at least annual examinations. Individuals with a PSV > 175 and contralateral stenosis >80% or contralateral occlusion are at the highest risk of progression and should be studied every 6 months.