title: Left ventricular myocardial contractility is depressed in the borderzone after posterolateral myocardial infarction.
abstract: BACKGROUND
  Contractility in the borderzone (BZ) after anteroapical myocardial infarction (MI) is depressed. We tested the hypothesis that BZ contractility is also decreased after posterolateral MI.
  
  
  METHODS
  Five sheep underwent posterolateral MI. Magnetic resonance imaging (MRI) was performed 2 weeks before and 16 weeks after MI, and left ventricular (LV) volume and regional strain were measured. Finite element (FE) models were constructed, and the systolic material parameter, Tmax, was calculated in the BZ and remote myocardium by minimizing the difference between experimentally measured and calculated LV strain and volume. Sheep were sacrificed 17 weeks after MI, and myocardial muscle fibers were taken from the BZ and remote myocardium. Fibers were chemically demembranated, and isometric developed force, Fmax, was measured at supramaximal [Ca(2+)]. Routine light microscopy was also performed.
  
  
  RESULTS
  There was no difference in Tmax in the remote myocardium before and 16 weeks after MI. However, there was a large decrease (63.3%, p = 0.005) in Tmax in the BZ when compared with the remote myocardium 16 weeks after MI. In addition, there was a significant reduction of BZ Fmax for all samples (18.9%, p = 0.0067). Myocyte cross-sectional area increased by 61% (p = 0.021) in the BZ, but there was no increase in fibrosis.
  
  
  CONCLUSIONS
  Contractility in the BZ is significantly depressed relative to the remote myocardium after posterolateral MI. The reduction in contractility is due at least in part to a decrease in contractile protein function.
authors.affiliation: Department of Medicine, University of California, San Francisco, CA 94121, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Shimkunas
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Wenk
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Soleimani
authors.forename: Michael
authors.initials: M
authors.lastname: Khazalpour
authors.forename: Gabriel
authors.initials: G
authors.lastname: Acevedo-Bolton
authors.forename: Guanying
authors.initials: G
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Saloner
authors.forename: Rakesh
authors.initials: R
authors.lastname: Mishra
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Wallace
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Baker
authors.forename: Julius M
authors.initials: JM
authors.lastname: Guccione
authors.forename: Mark B
authors.initials: MB
authors.lastname: Ratcliffe
mesh_terms: D000818:Animals; D003285:Contractile Proteins / Q000502:physiology; D020342:Finite Element Analysis; D009200:Myocardial Contraction / Q000502:physiology*; D009203:Myocardial Infarction / Q000503:physiopathology*; D012756:Sheep; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D003285:Contractile Proteins