title: Undersized Mitral Annuloplasty Increases Strain in the Proximal Lateral Left Ventricular Wall.
abstract: BACKGROUND
  Recurrence of mitral regurgitation (MR) after undersized mitral annuloplasty (MA) for ischemic MR is as high as 60%, with the recurrence rate likely due to continued dilation of the left ventricle (LV). To better understand the causes of recurrent MR, we studied the effect of undersized MA on strain in the LV wall. We hypothesize that the acute change in ventricular shape induced by MA will cause increased strain in regions nearest the mitral valve.
  
  
  METHODS
  Finite element models were previously reported, based on cardiac magnetic resonance images of 5 sheep with mild to moderate ischemic MR. A 24-mm saddle-shaped rigid annuloplasty ring was modeled and used to simulate virtual MA. Longitudinal and myofiber strains were calculated at end-diastole and end-systole, with preoperative early diastolic geometry as the reference state.
  
  
  RESULTS
  The undersized MA significantly increased longitudinal strain at end-diastole in the lateral LV wall. The effect was greatest in the proximal-lateral endocardial surface, where longitudinal strain after MA was approximately triple the preoperative strain (11.17% ± 2.15% vs 3.45% ± 0.92%, p = 0.0057). In contrast, postoperative end-diastolic fiber strain decreased in this same region (2.53% ± 2.14% vs 7.72% ± 1.79%, p = 0.0060). There were no significant changes in either strain type at end-systole.
  
  
  CONCLUSIONS
  Undersized MA increased longitudinal strain in the proximal lateral LV wall at end-diastole. This procedure-related strain at the proximal-lateral LV wall may foster continued LV enlargement and subsequent recurrence of mitral regurgitation.
authors.affiliation: University of California, San Francisco, San Francisco, California.
authors.forename: Joe Luis
authors.initials: JL
authors.lastname: Pantoja
authors.affiliation: East Bay Surgical Residency, University of California, San Francisco, San Francisco, California.
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Morgan
authors.affiliation: Department of Cardiothoracic Surgery, New York University, New York, New York; New York Harbor Veterans Affairs Medical Center, New York, New York.
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Grossi
authors.affiliation: Department of Biomedical Engineering, University of Arkansas, Fayetteville, Arkansas.
authors.forename: Morten O
authors.initials: MO
authors.lastname: Jensen
authors.affiliation: Departments of Medicine (Cardiology) and Radiology, Weill Cornell Medicine, New York, New York.
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Weinsaft
authors.affiliation: Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Levine
authors.affiliation: Department of Surgery, University of California, San Francisco, San Francisco, California; Department of Bioengineering, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.affiliation: Department of Surgery, University of California, San Francisco, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California. Electronic address: mark.ratcliffe@med.va.gov.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Ratcliffe
mesh_terms: D000818:Animals; D006352:Heart Ventricles; D058386:Mitral Valve Annuloplasty / Q000009:adverse effects*; D008944:Mitral Valve Insufficiency / Q000209:etiology*; D012008:Recurrence; D012756:Sheep; D013314:Stress, Mechanical