title: The natural history of asymptomatic carotid artery disease.
abstract: OBJECTIVE
  The purpose of this article is to determine the natural history of carotid artery disease among asymptomatic patients with cervical bruits or other risk factors for stroke and to study the value of duplex ultrasonography in predicting future neurologic events.
  
  
  METHODS
  Two hundred forty-two asymptomatic, unoperated patients, referred for evaluation of asymptomatic carotid artery disease, were followed prospectively with duplex ultrasonography.
  
  
  RESULTS
  Fifteen ischemic strokes (6.2%) and 20 transient ischemic attacks (TIA) (8.3%) occurred in 34 patients during a mean follow-up of 27.4 months. Annual stroke, TIA, and combined event rates were 2.7%, 3.6%, and 6.2%, respectively. Although patients with 80% to 99% lesions had a 20.6% annual event rate, most events occurred contralateral to these lesions; the vessel-specific annual event rate for 80% to 99% disease was 5.1%. Only one of 15 strokes occurred ipsilateral to an 80% to 99% stenosis. Echolucent plaques were associated with TIA and stroke (5.7% annual vessel event rate vs 2.4% for echogenic plaques, p = 0.03). Disease progression was highly correlated with TIA and stroke (p < 0.0001), but it usually occurred in association with rather than before ischemic events, thus proving more useful in explaining pathogenesis than in predicting future events. There was no association between aspirin use and TIA, but patients taking aspirin had a threefold higher annual stroke rate (1.6% vs 4.8%, p = 0.027).
  
  
  CONCLUSIONS
  This study, while confirming significant risk for asymptomatic patients with critical stenosis or echolucent plaque, demonstrates the importance of contralateral disease and the absence of orderly progression from minimal disease through high-grade stenosis to symptomatic cerebral ischemia. TIA and stroke commonly occur in association with abrupt, unpredictable, quantum changes in carotid artery disease.
authors.affiliation: Department of Surgery, University of Sydney, Australia.
authors.forename: R W
authors.initials: RW
authors.lastname: Bock
authors.forename: A C
authors.initials: AC
authors.lastname: Gray-Weale
authors.forename: P A
authors.initials: PA
authors.lastname: Mock
authors.forename: M
authors.initials: M
authors.lastname: App Stats
authors.forename: D A
authors.initials: DA
authors.lastname: Robinson
authors.forename: L
authors.initials: L
authors.lastname: Irwig
authors.forename: R J
authors.initials: RJ
authors.lastname: Lusby
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002339:Carotid Arteries / Q000000981:diagnostic imaging; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology; D002561:Cerebrovascular Disorders / Q000453:epidemiology / Q000517:prevention & control; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D015994:Incidence; D002546:Ischemic Attack, Transient / Q000453:epidemiology / Q000517:prevention & control; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D016019:Survival Analysis; D014463:Ultrasonography