title: Temporal changes in interpapillary muscle dynamics as an active indicator of mitral valve and left ventricular interaction in ischemic mitral regurgitation.
abstract: BACKGROUND
  Regional subpapillary myocardial hypokinesis may impair lateral reduction in the interpapillary muscle distance (IPMD) from diastole to systole, and adversely affect mitral valve geometry and tethering.
  
  
  OBJECTIVE
  The goal of this study was to investigate the impact of impaired lateral shortening in the interpapillary muscle distance on mitral valve geometry and function in ischemic heart disease.
  
  
  METHODS
  To quantify ventricular size/shape, regional myocardial contraction, lateral shortening of the IPMD, mitral valve geometry, and severity of mitral regurgitation, 67 patients with ischemic heart disease underwent cardiac magnetic resonance imaging, and a correlation analysis of measured parameters was performed. The impact of reduced IPMD shortening on mitral valve (dys)function was confirmed in swine and in a physiological computational mitral valve model.
  
  
  RESULTS
  Lateral shortening of the IPMD from diastole to systole was severely reduced in patients with moderate/severe ischemic mitral regurgitation (9.6 ± 2.8 mm), but preserved in mild IMR (11.5 ± 3.4 mm). Left ventricular size and ejection fraction did not differ between the groups. In swine with subpapillary infarction and impaired IPMD, mitral regurgitation was evident within 1 week, compared to those pigs with a nonpapillary infarction and preserved IPMD. In the controlled computational valve model, IPMD had the maximal impact on regurgitation, and was exacerbated with additional annular dilation.
  
  
  CONCLUSIONS
  By using cardiac magnetic resonance imaging in humans, we demonstrated that it is the impairment of lateral shortening between the papillary muscles, and not passive ventricular size, that governs the severity of mitral regurgitation. Loss of lateral shortening of IPMD tethers the leaflet edges and impairs their systolic closure, resulting in mitral regurgitation, even in small ventricles. Understanding the lateral dynamics of ventricular-valve interactions could aid the development of new repair techniques for ischemic mitral regurgitation.
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Kanika
authors.initials: K
authors.lastname: Kalra
authors.affiliation: Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Bryant V
authors.initials: BV
authors.lastname: McIver
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Shi
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Guyton
authors.affiliation: Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Sarin
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia.
authors.forename: Vinod H
authors.initials: VH
authors.lastname: Thourani
authors.affiliation: Structural Heart Disease Research and Innovation Laboratory, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University, Atlanta, Georgia. Electronic address: spadala@emory.edu.
authors.forename: Muralidhar
authors.initials: M
authors.lastname: Padala
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000473:pathology* / Q000503:physiopathology; D008944:Mitral Valve Insufficiency / Q000175:diagnosis* / Q000503:physiopathology; D010210:Papillary Muscles / Q000473:pathology* / Q000503:physiopathology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: magnetic resonance imaging; mitral force balance; mitral valve tethering; myocardial infarction; papillary muscles; regional wall motion; regurgitant fraction; tenting area; ventricular imaging