title: Downstream turbulence and high intensity transient signals (HITS) following aortic valve replacement with Medtronic Hall or St. Jude Medical valve substitutes.
abstract: OBJECTIVE
  High intensity transient signals (HITS) representing microembolization to the brain have been found to contribute to cognitive impairment and psychoneurological dysfunction in patients carrying a mechanical aortic valve. It is unknown, whether HITS represent gaseous or solid emboli. This animal study evaluates the impact of valve orientation on HITS for two different mechanical valves with both valves implanted in their best and worst orientation, which has been defined in previous studies with respect to downstream turbulence.
  
  
  METHODS
  In four pigs a rotation device carrying either a Medtronic Hall (MH) or St. Jude Medical (SJM) valve size 23 mm was implanted. The device allowed rotation of the implanted valves without reopening of the aorta. Approximately 30 min after weaning from extracorporeal circulation, a Doppler probe was placed on both common carotid arteries. In different orientations of the implanted valves (best and worst position), HITS were detected by the Doppler probe and recorded for ten min by a transcranial Doppler sonography device (Medilab Inc., Estenfeld, Germany).
  
  
  RESULTS
  HITS showed significant change with rotation for both valve designs. With the major orifice of the MH oriented towards the non-coronary leaflet (optimum position) very low HITS-counts (0.8-1.7/min) were observed. In the worst orientation HITS rose to 43-66/min. For the SJM the HITS count in the optimum position was 23.4-24/min and in the worst orientation 38-48/min.
  
  
  CONCLUSIONS
  Valve orientation has an important impact on microembolization to the brain. In the optimum orientation (large orifice facing the non-coronary leaflet) the Medtronic Hall valve showed negligible incidence of HITS. The St. Jude Medical bileaflet valve showed less variation but demonstrated significant HITS counts at any orientation. As the MH in the worst position shows significantly higher turbulent stresses than the SJM but no higher incidence of HITS, a strong correlation between turbulence and HITS was not demonstrated by this study.
authors.affiliation: Department of Cardio-thoracic Surgery, Herz-Kreislauf-Klinik Bevensen, Bad Bevensen, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Kleine
authors.forename: M
authors.initials: M
authors.lastname: Perthel
authors.forename: J M
authors.initials: JM
authors.lastname: Hasenkam
authors.forename: H
authors.initials: H
authors.lastname: Nygaard
authors.forename: S B
authors.initials: SB
authors.lastname: Hansen
authors.forename: J
authors.initials: J
authors.lastname: Laas
mesh_terms: D000818:Animals; D001021:Aortic Valve; D001672:Biocompatible Materials; D004195:Disease Models, Animal; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D013552:Swine; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D001672:Biocompatible Materials