title: The effect of the fiber curvature gradient on break excitation in cardiac tissue.
abstract: BACKGROUND
  Break excitation has been hypothesized as a mechanism for the initiation of reentry in cardiac tissue. One way break excitation can occur is by virtual electrodes formed due to a curving fiber geometry. In this article, we are concerned with the relationship between the peak gradient of fiber curvature and the threshold for break stimulation and the initiation of reentry.
  
  
  METHODS
  We calculate the maximum gradient of fiber curvature for different scales of fiber geometry in a constant tissue size (20x20 mm), and also examine the mechanisms by which reentry initiation fails.
  
  
  RESULTS
  For small peak gradients, reentry fails because break excitation does not occur. For larger peak gradients, reentry fails because break excitation fails to develop into full-scale reentry. For strong stimuli above the upper limit of vulnerability, reentry fails because the break excitation propagates through the hyperpolarized region and then encounters refractory tissue, causing the wave front to die.
authors.affiliation: Department of Physics, Oakland University, Rochester, Michigan 48309, USA.
authors.forename: Deborah Langrill
authors.initials: DL
authors.lastname: Beaudoin
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Roth
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D016880:Anisotropy; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D003198:Computer Simulation; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000502:physiology*