title: Microbubbles associated with mitral valve prostheses in pediatric patients.
abstract: OBJECTIVE
  To assess whether microbubbles are associated with mitral valve prostheses in children and to investigate their relationship to exercise.
  
  
  BACKGROUND
  Bright, highly mobile echoes are seen in left heart chambers of patients with mechanical mitral valve prostheses. The clinical importance of those microbubbles is not yet known but they survive long enough to reach the cerebral circulation. No such studies have been reported in children.
  
  
  METHODS
  There were 20 male and 10 female patients with a mean age of 10.4 years (range 2-16 years). Transthoracic echocardiography with calculation of cardiac output and ejection fraction was performed at baseline and after exercise following mechanical mitral valve replacement. Studies were evaluated for the presence of microbubbles. The mean time from operation to time of study was 18 months (range 0.2-89 months).
  
  
  RESULTS
  Of the 30 children evaluated, 28 (93%) had evidence of microbubbles. Exercise increased the number of microbubbles in 15 of the 26 children. This was positively associated with an increase in cardiac output.
  
  
  CONCLUSIONS
  (1) Microbubbles are commonly observed in children with mechanical mitral prostheses and are augmented by exercise. (2) This phenomenon is of a special concern in children due to their expected longevity with the prosthesis.
authors.affiliation: Division of Cardiology, Red Cross War Memorial Children's Hospital, Cape Town, South Africa.
authors.forename: D
authors.initials: D
authors.lastname: Levy
authors.forename: J
authors.initials: J
authors.lastname: Lawrenson
authors.forename: J
authors.initials: J
authors.lastname: Schulz
authors.forename: S
authors.initials: S
authors.lastname: Milo
authors.forename: S A
authors.initials: SA
authors.lastname: Reisner
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004452:Echocardiography / Q000379:methods / Q000706:statistics & numerical data; D004618:Embolism, Air / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects* / Q000706:statistics & numerical data; D006439:Hemodynamics; D006801:Humans; D015994:Incidence; D008297:Male; D008943:Mitral Valve / Q000000981:diagnostic imaging; D011446:Prospective Studies