title: Contractile mitral annular forces are reduced with ischemic mitral regurgitation.
abstract: OBJECTIVE
  Forces acting on mitral annular devices in the setting of ischemic mitral regurgitation are currently unknown. The aim of this study was to quantify the cyclic forces that result from mitral annular contraction in a chronic ischemic mitral regurgitation ovine model and compare them with forces measured previously in healthy animals.
  
  
  METHODS
  A novel force transducer was implanted in the mitral annulus of 6 ovine subjects 8 weeks after an inferior left ventricle infarction that produced progressive, severe chronic ischemic mitral regurgitation. Septal-lateral and transverse forces were measured continuously for cardiac cycles reaching a peak left ventricular pressure of 90, 125, 150, 175, and 200 mm Hg. Cyclic forces and their rate of change during isovolumetric contraction were quantified and compared with those measured in healthy animals.
  
  
  RESULTS
  Animals with chronic ischemic mitral regurgitation exhibited a mean mitral regurgitation grade of 2.3 ± 0.5. Ischemic mitral regurgitation was observed to decrease significantly septal-lateral forces at each level of left ventricular pressure (P < .01). Transverse forces were consistently lower in the ischemic mitral regurgitation group despite not reaching statistical significance. The rate of change of these forces during isovolumetric contraction was found to increase significantly with peak left ventricular pressure (P < .005), but did not differ significantly between animal groups.
  
  
  CONCLUSIONS
  Mitral annular forces were measured for the first time in a chronic ischemic mitral regurgitation animal model. Our findings demonstrated an inferior left ventricular infarct to decrease significantly cyclic septal-lateral forces while modestly lowering those in the transverse. The measurement of these forces and their variation with left ventricular pressure contributes significantly to the development of mitral annular ischemic mitral regurgitation devices.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Siefert
authors.forename: Jorge H
authors.initials: JH
authors.lastname: Jimenez
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Koomalsingh
authors.forename: Fernando
authors.initials: F
authors.lastname: Aguel
authors.forename: Dustin S
authors.initials: DS
authors.lastname: West
authors.forename: Takashi
authors.initials: T
authors.lastname: Shuto
authors.forename: Teresa K
authors.initials: TK
authors.lastname: Snow
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gorman
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Gorman
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D008943:Mitral Valve / Q000503:physiopathology*; D008944:Mitral Valve Insufficiency / Q000209:etiology* / Q000503:physiopathology; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000150:complications* / Q000503:physiopathology; D012756:Sheep; D013314:Stress, Mechanical; D013997:Time Factors; D014160:Transducers, Pressure; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
keywords: 24; 28; IMR; LV; LVP; MR; d(LVP)/dt; dF/dt; ischemic mitral regurgitation; left ventricular; left ventricular pressure; mitral regurgitation; peak rate of change of LVP; peak rate of change of force