title: Geometric perturbations in multiheaded papillary tip positions associated with acute ovine ischemic mitral regurgitation.
abstract: BACKGROUND
  Novel surgical approaches are focusing on the "ventricular disease" of ischemic mitral regurgitation (IMR), to correct altered papillary muscle (PM) tip positions (apical displacement) and ameliorate leaflet tethering. Due to the anatomic complexity of the subvalvular apparatus, however, the precise geometric perturbations of the multiheaded PM tips associated with IMR remain uncharacterized.
  
  
  METHODS
  In 6 adult sheep, we implanted 3 markers on each PM. To specifically identify distinct PM tips, 1 marker was placed on the PM origin of the dominant chord to the anterior, posterior, and commissural leaflets. Nine markers were placed on the edge of the posterior mitral leaflet, and 5 on the edge of the anterior mitral leaflet. Eight markers were sewn around the mitral annulus. Animals were studied immediately postoperatively, with biplane videofluoroscopy and transesophageal echocardiography, before and during acute snare occlusion of the proximal left circumflex coronary artery, to induce IMR. Papillary muscle tip and leaflet edge geometry was expressed as the orthogonal distance of each respective marker to the least-squares mitral annulus plane at end-systole. In addition, the distance from each PM tip marker to the mitral annulus "saddle horn" was calculated.
  
  
  RESULTS
  Acute left circumflex occlusion significantly increased mitral regurgitation from a baseline of 0.7 ± 0.3 to 2.5 ± 0.5 (P < .05). The IMR was associated with posterior leaflet restriction near the central leaflet edge, with simultaneous prolapse of both leaflets near the posterior commissure. No apical displacement of PM tips was observed during IMR, although the posterior PM moved farther away from the midseptal annulus.
  
  
  CONCLUSIONS
  During acute ischemia, no apical displacement of any PM tip was observed. Posterior PM movement away from the annular saddle horn, and toward the annulus, was associated with IMR and leaflet prolapse near the posterior commissure, and with restriction near the valve center. These data may help guide development of surgical interventions aimed at PM repositioning.
authors.affiliation: Meijer Heart and Vascular Institute at Spectrum Health, Grand Rapids, Mich.
authors.forename: Tomasz A
authors.initials: TA
authors.lastname: Timek
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif.
authors.forename: David T
authors.initials: DT
authors.lastname: Lai
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bothe
authors.affiliation: Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, Calif.
authors.forename: David
authors.initials: D
authors.lastname: Liang
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif; Department of Cardiovascular Physiology and Biophysics, Research Institute of the Palo Alto Medical Foundation, Palo Alto, Calif.
authors.forename: George T
authors.initials: GT
authors.lastname: Daughters
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif; Department of Cardiovascular Physiology and Biophysics, Research Institute of the Palo Alto Medical Foundation, Palo Alto, Calif.
authors.forename: Neil B
authors.initials: NB
authors.lastname: Ingels
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif. Electronic address: dcm@stanford.edu.
authors.forename: D Craig
authors.initials: DC
authors.lastname: Miller
mesh_terms: D000208:Acute Disease; D000818:Animals; D008297:Male; D055641:Mathematical Concepts; D008944:Mitral Valve Insufficiency / Q000150:complications / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000150:complications / Q000503:physiopathology*; D010210:Papillary Muscles / Q000503:physiopathology*; D012756:Sheep
keywords: ischemic mitral regurgitation; mitral valve; mitral valve repair