title: Is cerebral microembolism in mechanical prosthetic heart valves clinically relevant?
abstract: OBJECTIVE
  High-intensity transient signals (HITS) are frequently detected by transcranial Doppler (TCD) ultrasound in patients with mechanical prosthetic heart valves (PHVs), but published data about their clinical relevance are controversial. This study was undertaken to determine the clinical relevance of HITS in patients with mechanical PHVs.
  
  
  METHODS
  The authors prospectively studied patients with mechanical PHVs using TCD monitoring for microemboli detection with and without O2 inhalation. The cognitive testing of patients included the Mini-Mental State Examination, the Dementia Rating Scale, and MicroCog.
  
  
  RESULTS
  The authors studied 36 patients (20 women, aged 58 +/- 13 years). HITS were detected in 72% of patients, with a nonsignificant increase of HITS rate in the aortic valve group (P = .07). There was no significant difference in HITS rate between asymptomatic and symptomatic patients. In a multiple linear regression model, HITS rate was predicted only by younger age (P = .024). No correlation was found between HITS rate and the cognitive performance of patients. There was a significant decrease in HITS rate after 100% O2 inhalation compared to baseline levels (32.8 +/- 40.2 vs 6.1 +/- 11.3, P = .011). Subgroup analysis in asymptomatic patients confirmed this finding (P = .017), but in symptomatic patients, decreased HITS rate was not statistically significant (P = .18).
  
  
  CONCLUSIONS
  Only age was a significant predictor of HITS in patients with mechanical PHVs. The lack of association between HITS, clinical symptoms, and cognitive functioning suggests that most of these signals represent harmless epiphenomena, and only HITS detected after O2 inhalation have any clinical relevance.
authors.affiliation: Stroke Research Unit, Division of Neurology, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Canada. nadareishviliz@ninds.nih.gov
authors.forename: Zurab G
authors.initials: ZG
authors.lastname: Nadareishvili
authors.forename: Vadim
authors.initials: V
authors.lastname: Beletsky
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Black
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Fremes
authors.forename: Morris
authors.initials: M
authors.lastname: Freedman
authors.forename: David
authors.initials: D
authors.lastname: Kurzman
authors.forename: Larry
authors.initials: L
authors.lastname: Leach
authors.forename: John W
authors.initials: JW
authors.lastname: Norris
mesh_terms: D000704:Analysis of Variance; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D016009:Chi-Square Distribution; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D006801:Humans; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000209:etiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010102:Oxygen Inhalation Therapy; D011446:Prospective Studies; D012307:Risk Factors; D017585:Ultrasonography, Doppler, Transcranial