title: Direct imaging of bileaflet mechanical valve behavior in the tricuspid position.
abstract: OBJECTIVE
  The optimal orientation of a bileaflet mechanical valve for tricuspid valve replacement (TVR) has not yet been determined. The aim of this study was to use fiberoptic cardioscopy to evaluate the effect of orientation of a mechanical valve implanted in the tricuspid position on bileaflet mechanical valve behavior.
  
  
  METHODS
  Twelve pigs (50-59 kg) underwent TVR with a St. Jude Mechanical Heart Valve (25 mm standard cuff model) after cardioplegic arrest. The mechanical valve was implanted horizontally in six pigs (Group H), and vertically in another six pigs (Group V). The heart was perfused with pellucid Krebs-Henseleit solution in situ and the mechanical valve behavior was observed with a fiberoptic endoscope during different heart rates (HRs) induced by ventricular pacing (60, 90, 120, 150 min(-1)). All images were recorded on a high-speed video system every 4 ms. The closing time lag (CTL) between the valve leaflets was calculated and compared between the two groups.
  
  
  RESULTS
  In Group H, the lower valve leaflet tended to open incompletely and close earlier than the upper leaflet. The calculated CTL was 303+/-60 ms, 65+/-48 ms, 40+/-9 ms, and 40+/-26 ms at pacing HRs of 60, 90, 120, and 150 min(-1), respectively. In contrast to Group H, there was little difference in CTL between the right and left leaflets in Group V. The calculated CTL was 9+/-12 ms, 11+/-10 ms, 1+/-3 ms, and 6+/-7 ms at pacing HRs of 60, 90, 120, and 150 min(-1), respectively. There were significant differences in CLT between the two groups at each ventricular pacing rate (P < 0.01).
  
  
  CONCLUSIONS
  Orientation of an implanted bileaflet valve in the tricuspid position significantly influenced leaflet motion. In a horizontal orientation, the lower valve leaflet opened incompletely and closed earlier than the upper leaflet. These results suggest that the gravity might affect leaflet motion and that bileaflet mechanical valves should be implanted vertically in TVR to prevent abnormal leaflet motion and thrombus formation.
authors: Department of Thoracic and Cardiovascular Surgery, Saga University Faculty of Medicine, 5-1-1 Nabeshima, Saga 849-8501, Japan. ikedaka@cc.saga-u.ac.jp
authors: Kazuyuki
authors: K
authors: Ikeda
authors: Yukio
authors: Y
authors: Okazaki
authors: Kojirou
authors: K
authors: Furukawa
authors: Satoshi
authors: S
authors: Ohtsubo
authors: Junji
authors: J
authors: Yunoki
authors: Masafumi
authors: M
authors: Natsuaki
authors: Tsuyoshi
authors: T
authors: Itoh