Screening for asymptomatic carotid atherosclerosis

Högberg, D. 2017. Screening for asymptomatic carotid atherosclerosis. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine 1367. 77 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-513-0060-3. Ischemic stroke is the most common cause of handicap in adults and the third most common cause of death in Sweden. Internal carotid artery atherosclerosis is an important cause and accounts for 20% of ischemic strokes. Screening for carotid atherosclerosis has been debated over the past two decades. The aims of this thesis were (I) to study the prevalence of and risk factors associated with carotid artery atherosclerosis among 65 year old men, (II) to evaluate a simplified ultrasound protocol (the grayscale/mosaic method) for the exclusion of significant carotid artery stenosis for screening purpose, (III) to evaluate the required effect of primary preventive therapy in reducing risk of stroke among patients with asymptomatic carotid disease in order for screening to be cost-effective and (IV) to study natural history of carotid atherosclerosis and outcome five years after screening in 65-year old men. The prevalence of atherosclerotic plaques was high (25%), while the prevalence of >50% stenosis was relatively low (2.0%). Smoking, hypertension, diabetes mellitus and coronary artery disease were independent risk factors and individuals with several risk factors had a higher prevalence of stenosis. Most of those at risk were not on any preventive medication. A simplified grayscale/mosaic method was found to have a high negative predictive value for significant carotid stenosis. The minimum stroke risk reduction effect required for preventive intervention to be cost effective was 22%. Carotid atherosclerotic plaque and stenosis 50-79% has a relatively benign development during five years if treated with BMT and risk factor adjustment. Very few progressed to symptomatic disease. More severe stenosis (80-99%) had higher rate of neurological events, and may benefit from additional intervention. In conclusion, prevalence of silent atherosclerotic disease in carotid arteries was common among 65-year-old men. Most of those at risk had no secondary prevention. There is a simple DUS method that could be used for screening purpose. Screening for carotid disease is only cost-effective if the preventive strategy lowers the risk of stroke by 22%. Men with plaques and moderate stenosis have a good prognosis, but among those with severe stenosis there is a need for further intervention.