title: Alterations in left ventricular curvature and principal strains in dilated cardiomyopathy with functional mitral regurgitation.
abstract: OBJECTIVE
  Functional mitral regurgitation (FMR) is increasingly recognized as a left ventricular (LV) disease. Dilated cardiomyopathy (DCM) is commonly accompanied by FMR and reduction of LV torsion. Therapeutic targets for DCM include LV size reduction, altered LV shape, elimination of MR, and increasing LV torsion. It was hypothesized that, in addition to increasing LV size, DCM with FMR would alter normal LV shape and reduce and alter the direction of principal strains across the LV wall. This hypothesis was tested by measuring changes in epicardial and endocardial 2-D principal strains and regional radii of curvature accompanying tachycardia-induced cardiomyopathy in ovine hearts.
  
  
  METHODS
  Radio-opaque marker arrays were implanted into the left ventricle of eight sheep, including one subepicardial triangle and one subendocardial triangle in the anterior wall of the left ventricle. At one week postoperatively, biplane videofluoroscopy was used to determine marker dynamics. Rapid ventricular pacing was then instituted until FMR and signs of heart failure developed, and fluoroscopy was repeated. Circumferential LV radii of curvature were determined from marker triplets.
  
  
  RESULTS
  DCM changed the normal epicardial oval LV cross-section to a more circular configuration. The endocardium maintained its normal circular shape as the left ventricle dilated. Deformations of the triangles from end-diastole to end-systole were determined, and the magnitude and direction of 2-D principal strains calculated. DCM was associated with decreased magnitude of both epicardial (-0.095 +/- 0.055 versus -0.040 +/- 0.032, p = 0.006) and endocardial (-0.117 +/- 0.047 versus -0.073 +/- 0.037, p = 0.023) principal strains. DCM reduced the angle of epicardial but not endocardial principal strain.
  
  
  CONCLUSIONS
  DCM with FMR is associated with LV dilation, circularization of the normally oval equatorial circumferential LV epicardium, transmural reduction in principal strain, and decrease in angle of principal epicardial strain. These changes contribute to a reduction in the net torsional moment and may guide the development of reverse remodeling procedures for the dilated, failing ventricle with FMR.
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Tibayan
authors.forename: David T M
authors.initials: DT
authors.lastname: Lai
authors.forename: Tomasz A
authors.initials: TA
authors.lastname: Timek
authors.forename: Paul
authors.initials: P
authors.lastname: Dagum
authors.forename: David
authors.initials: D
authors.lastname: Liang
authors.forename: Mary K
authors.initials: MK
authors.lastname: Zasio
authors.forename: George T
authors.initials: GT
authors.lastname: Daughters
authors.forename: D Craig
authors.initials: DC
authors.lastname: Miller
authors.forename: Neil B
authors.initials: NB
authors.lastname: Ingels
mesh_terms: D000818:Animals; D006348:Cardiac Surgical Procedures / Q000379:methods*; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000601:surgery*; D004195:Disease Models, Animal; D006334:Heart Function Tests; D006352:Heart Ventricles / Q000503:physiopathology / Q000601:surgery*; D006439:Hemodynamics; D008297:Male; D008944:Mitral Valve Insufficiency / Q000150:complications / Q000175:diagnosis*; D011336:Probability; D011897:Random Allocation; D012016:Reference Values; D018570:Risk Assessment; D012756:Sheep; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000601:surgery*; D020257:Ventricular Remodeling