title: High-intensity transient signals due to prosthetic valve obstruction: diagnostic and therapeutic implications.
abstract: BACKGROUND
  High-intensity transient signals (HITS) can be detected by transcranial Doppler ultrasonography (TCD) in patients carrying a mechanical prosthetic valve. The HITS counts and a frequency analysis were evaluated in patients with prosthetic valve obstruction in the aortic position.
  
  
  METHODS
  Simultaneous echocardiographic, cineradiographic, and TCD evaluations for a St. Jude Medical valve were performed in 108 patients. All patients were asymptomatic and had no significant stenosis of the carotid artery. The HITS were identified according to criteria established by consensus of the International Cerebral Hemodynamics Symposium.
  
  
  RESULTS
  The HITS counts in 69 patients with normal prosthetic valve function were 2.2 +/- 4.4, and the counts in 39 patients with prosthetic valve obstruction (group D) were 8.3 +/- 10.8. This difference was significant (p = 0.0002). In 2 patients of group D who had a greater rate of less than 400 Hz HITS, which were produced by solid microemboli, thrombolysis resulted in a mitigation of restricted leaflet movement equal to or greater than 10(o). The total number of HITS decreased and the rate of less than 400 Hz HITS also markedly decreased after thrombolysis in these 2 patients. On the other hand, 4 patients who obtained no improvement of leaflet movement by thrombolysis had lower rates of less than 400 Hz HITS than did the 2 patients.
  
  
  CONCLUSIONS
  These results suggest that measurement of HITS counts is useful for detection of prosthetic valve obstruction, and that a frequency analysis of HITS may be valuable to clarify the cause of the obstructed prosthetic valves.
authors.affiliation: Department of Surgery, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Hiratsuka
authors.forename: Shuji
authors.initials: S
authors.lastname: Fukunaga
authors.forename: Eiki
authors.initials: E
authors.lastname: Tayama
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Takagi
authors.forename: Koichi
authors.initials: K
authors.lastname: Arinaga
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shojima
authors.forename: Hideki
authors.initials: H
authors.lastname: Teshima
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Aoyagi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve; D002933:Cineradiography; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis* / Q000188:drug therapy; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015912:Thrombolytic Therapy; D017585:Ultrasonography, Doppler, Transcranial