Patients With Asymptomatic Severe Carotid Artery Stenosis May Need to Be Considered for Early Intervention and Not Medical Therapy Alone

In an important paper, “Natural History of Asymptomatic Severe Carotid Artery Stenosis” presented at the 2013 Vascular Annual Meeting of the Society for Vascular Surgery (May 30 to June 1), Conrad et al from the Division of  Vascular and Endovascular Surgery at Massachusetts General Hospital stated that 6% of Americans over the age of 65 have asymptomatic severe carotid artery stenosis. 

Dr. Conrad further noted that stenosis over 50% is responsible for 12% to 20% of anterior cerebral circulation infarcts and went on to say that “the superiority of carotid endarterectomy over medical management for the prevention of stroke in patients with stenosis greater than 70% is supported by level-1 evidence and practice guidelines from the Society for Vascular Surgery and other societies. It is clear that the addition of statins to medical therapy has improved outcomes when it comes to stroke, and this has translated into a decrease in the stroke risk for the general population over time. It is suggested that the benefit of endarterectomy in the asymptomatic trials is secondary to inadequate medical therapy in the medical therapy arm rather than the benefit of carotid endarterectomy itself.”

Dr. Conrad cited a meta-analysis published in 2009 advancing the notion that medical intervention alone was best for prevention of stroke associated with asymptomatic severe carotid stenosis and that the rate of stroke with medical intervention alone has fallen since the 1980s. “However, this meta-analysis is flawed as it included patients with moderate stenosis for whom no intervention is indicated,” he said. 

The objective of this study was to determine the natural history of medically treated patients with asymptomatic severe (>70%) carotid artery stenosis. Asymptomatic severe carotid artery stenosis patients were identified by duplex ultrasound and included if they were treated with medical therapy. Patients were excluded if they had a carotid intervention within six months of the index diagnostic study. Aspirin and statin use was recorded for each patient. The study endpoints included ipsilateral neurologic symptoms (stroke, transient ischemic attack, and amaurosis fugax referable to the ipsilateral carotid artery) and death. The investigators identified 126 carotid arteries in 115 patients (mean age 73.5 years). Eighty-eight patients (70%) had severe stenosis (70% to 89%) and 38 (30%) had very severe stenosis (90% to 99%). Eighty-six percent of patients were on a statin and 89% were on aspirin. 

At 60-month follow-up, 31 patients (24.6%) developed ipsilateral neurologic symptoms. Most of the symptoms (71%) occurred in the first 12 months. Forty-five percent of the symptoms (14) were strokes. Freedom from symptoms at 60 months was 80% for patients with 70% to 89% stenosis and 45% for patients with 90% to 99% stenosis (P=.003). The use of statins showed no difference in the incidence of symptoms (P=.98). At 5 years, 41 patients (33%) died without revascularization, 44 (34%) remain alive on medical therapy, and 41 (33%) underwent carotid revascularization (32 had endarterectomy and 9 had carotid artery stenting). The reason for revascularization was ipsilateral neurologic symptoms in 56% of the cases and plaque progression in 44%. Multivariate predictors of death included age, chronic obstructive pulmonary disease, diabetes, and high-risk stenosis.

Dr. Conrad concluded that ipsilateral neurologic symptoms are frequent and, in this study, occurred mainly within the first year of follow-up. Diabetes, chronic kidney disease, and chronic obstructive pulmonary disease predict poor prognosis in the asymptomatic population. He noted that, “although there is a general agreement that future trials should include a medical arm, these data show a prohibitively high neurological event rate in patients with >90% stenosis that is not seen in patients with moderate (50% to 69%) disease.”