title: Effects of ischemia on epicardial deformation in the passive rabbit heart.
abstract: BACKGROUND
  Surgically induced ischemia in the arrested heart can result in changes in the mechanical properties of the myocardium. Regions of ischemia may be characterized based on the amount of epicardial deformation for a given load. Computer aided speckle interferometry (CASI), which tracks the movement of clusters of particles, is developed as a technique for measuring epicardial deformation, thereby determining the perfusion status of the passive heart.
  
  
  METHODS
  Silicone carbide particles and retroreflective beads were dispersed randomly onto the epicardial surface of 11 isolated rabbit hearts to form speckle images. The hearts were arrested with hyperkalemic Krebs-Henseleit buffered solution. Each heart was then exposed to a series of intracavitary pressures, and at each pressure speckle images were acquired with a charge-coupled device (CCD) camera. Nine hearts were exposed to global ischemia, and two hearts were exposed to regional ischemia by occluding the second diagonal branch of the left anterior descending artery (LAD). The hearts were again loaded and the speckle images were acquired. CASI was used to determine the distribution of deformation field.
  
  
  RESULTS
  CASI was able to determine displacements with a spatial resolution of about 50 microns. Global ischemia resulted in a significant increase in the maximum principle strain and the first invariant of the 2-D strain tensor. In the regionally ischemic heart, a large difference in deformation between the ischemic and perfused regions was clearly observed.
  
  
  CONCLUSIONS
  Based on epicardial deformation, CASI is able to distinguish between perfused and ischemic myocardium, with a spatial resolution of 50 microns.
authors.affiliation: Department of Biomedical Engineering, Institute of Molecular Cardiology, State University of New York at Stony Brook, Stony Brook, NY, USA.
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Gaudette
authors.forename: Irvin B
authors.initials: IB
authors.lastname: Krukenkamp
authors.forename: Evren U
authors.initials: EU
authors.lastname: Azeloglu
authors.forename: Adam E
authors.initials: AE
authors.lastname: Saltman
authors.forename: Miriam
authors.initials: M
authors.lastname: Lense
authors.forename: Joseph
authors.initials: J
authors.lastname: Todaro
authors.forename: Fu-Pen
authors.initials: FP
authors.lastname: Chiang
mesh_terms: D000818:Animals; D004548:Elasticity; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D066298:In Vitro Techniques; D007368:Interferometry / Q000379:methods*; D009068:Movement; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology*; D010496:Pericardium / Q000503:physiopathology*; D051381:Rats