title: Prevalence and characteristics of intracranial microemboli signals in patients with different types of prosthetic cardiac valves.
abstract: OBJECTIVE
  Transcranial Doppler detection of microemboli is widely described, but there is no clear evidence of the clinical significance or nature of the embolic material in vivo. Thromboembolism is a major cause of morbidity in patients with prosthetic cardiac valves. We undertook this study to evaluate the prevalence and the acoustic characteristics of microembolic signals in three groups of patients with different prosthetic valves.
  
  
  METHODS
  One hundred seventy-nine patients with prosthetic cardiac valves (85 Björk-Shiley, 56 Medtronic-Hall, and 38 Carpentier-Edwards) and 25 normal subjects were examined using transcranial Doppler. Monitoring time was 30 minutes over the right middle cerebral artery.
  
  
  RESULTS
  The prevalence and numbers of embolic signals were significantly higher in patients with Björk-Shiley compared with those with Medtronic-Hall and Carpentier-Edwards valves (89% versus 50% and 53%, respectively; P < .001, chi 2; 156 [112, 204] versus 2 [1, 4] and 2 [1, 4] signals/h, respectively; median [95% nonparametric confidence interval], both P < .001, multiple comparisons, Bonferroni correction). The signal intensity was significantly higher in patients with Björk-Shiley and Medtronic-Hall valves than patients with Carpentier-Edwards valves (2435 [2345, 2527] and 2120 [1745, 2483] versus 225 [184, 287] power units, median [95% confidence interval], both P < .001). No correlation was found between embolic signal numbers and clinical parameters including history of neurological deficit, cardiac rhythm, duration of artificial valve, previous cardiac operations, or intensity of anticoagulation. Embolic signals were not detected in any of the control subjects.
  
  
  CONCLUSIONS
  Our data showed that the prevalence, quantity, and acoustic characteristics of Doppler embolic signals differ in patients having three different types of prosthetic heart valves. However, no correlation with clinical parameters was identified.
authors.affiliation: University Department of Medicine, Western Infirmary, Glasgow, UK.
authors.forename: D
authors.initials: D
authors.lastname: Georgiadis
authors.forename: D G
authors.initials: DG
authors.lastname: Grosset
authors.forename: A
authors.initials: A
authors.lastname: Kelman
authors.forename: A
authors.initials: A
authors.lastname: Faichney
authors.forename: K R
authors.initials: KR
authors.lastname: Lees
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000925:Anticoagulants / Q000627:therapeutic use; D002536:Cerebral Arteries / Q000000981:diagnostic imaging; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D014463:Ultrasonography
chemical_list: D000925:Anticoagulants