Progression of internal carotid artery stenosis in patients with peripheral arterial occlusive disease

OBJECTIVES: To study the risk factors and rate of progression of asymptomatic carotid stenosis in patients with peripheral arterial occlusive disease. METHODS: Between July 1999 and September 2003, we studied consecutive patients referred to a vascular laboratory for peripheral arterial occlusive disease who had not experienced neurologic symptoms within the previous 3 years. Carotid duplex ultrasound scan (DUS) was performed at baseline and at 6 to 12-month intervals. The internal carotid artery peak systolic velocity (PSV) was used to determine severity of carotid stenosis. Multilevel linear regression modeling (MLM) was used to identify the rate of progression and risk factors for progression. RESULTS: For 614 consecutive patients, median follow-up by DUS was 30 (2-42) months. Patients were 73 +/- 10-years-old, and 62% were men. Mean ankle-brachial index (ABI) was 0.79 +/- 0.24. The baseline prevalence of carotid stenosis >or=50% (PSV >or=125 cm/second) was 22%. During follow-up, ipsilateral amaurosis fugax, transient ischemic attacks, and strokes occurred in 3 (0.4%), 7 (1.1%), and 5 (0.8%) patients, respectively. Overall, there was little progression in carotid stenosis. Female gender, low ABI, and smoking were risk factors for progression of disease regardless of severity of carotid stenosis. Patients with >or=50% carotid stenosis were at greatest risk of progression if they continued smoking and were diabetic. Prediction models for progression of carotid stenosis given a baseline PSV and patient risk factors were constructed. CONCLUSION: There are few neurologic events in patients with asymptomatic carotid stenosis. The average rate of progression of stenosis over 2 years is not significant but greater in diabetic patients with baseline stenosis >50% who continue smoking. Rescreening by serial DUS should be limited to high-grade stenosis and follow-up performed at an interval of 1-2 years.